SHELL-AND-TUBE HEAT EXCHANGER, OPERATION METHOD THEREFOR, AND REFRIGERATION DEVICE PROVIDED THEREWITH

Abstract

 A shell-and-tube heat exchanger of the present disclosure includes: a shell 201; a plurality of heat transfer tubes 202 disposed parallel to each other in the shell 201; and a nozzle 204 for spraying a liquid phase refrigerant from an inlet side of the plurality of heat transfer tubes 202 through which a heat medium flows into the plurality of heat transfer tubes 202 toward an outlet side of the plurality of heat transfer tubes 202 through which the heat medium flows out of the plurality of heat transfer tubes 202, the nozzle 204 being disposed on the inlet side of the plurality of heat transfer tubes 202. One example of the shell-and-tube heat exchanger is an evaporator 101.

Description

TECHNICAL FIELD

[0001] The present invention relates to a shell-and-tube heat exchanger, a method for operating the shell-and-tube heat exchanger, and a refrigeration apparatus including the shell-and-tube heat exchanger.

BACKGROUND ART

[0002] A technique for cooling a refrigerant inside a heat transfer tube by sprinkling cooling water toward the heat transfer tube has been known. A conventional evaporative condenser described in Patent Literature 1 includes a plurality of water spraying nozzles for spraying cooling water toward condenser coils. Through heat exchange between the cooling water and a refrigerant flowing in the condenser coils, the cooling water evaporates and the refrigerant is cooled and condensed.

CITATION LIST

Patent Literature

[0003] Patent Literature 1: WO 2017/073367

SUMMARY OF INVENTION

Technical Problem

[0004] It is desirable that a shell-and-tube heat exchanger to which the configuration described in Patent Literature 1 is applied have an improved heat exchange efficiency. The present disclosure provides a technique suitable for improvement in heat exchange efficiency of a shell-and-tube heat exchanger.

Solution to Problem

[0005] A shell-and-tube heat exchanger of the present disclosure includes:

a shell;

a plurality of heat transfer tubes disposed parallel to each other in the shell; and

a first nozzle for spraying a liquid phase refrigerant on the plurality of heat transfer tubes from an inlet side of the plurality of heat transfer tubes through which a heat medium flows into the plurality of heat transfer tubes toward an outlet side of the plurality of heat transfer tubes through which the heat medium flows out of the plurality of heat transfer tubes, the first nozzle being disposed on the inlet side of the plurality of heat transfer tubes.

[0006] A shell-and-tube heat exchanger operation method of the present disclosure is a method for operating the above shell-and-tube heat exchanger of the present disclosure, the method including:

allowing the heat medium to flow into the plurality of heat transfer tubes;

spraying the liquid phase refrigerant from the first nozzle toward the plurality of heat transfer tubes to cause heat exchange between the heat medium and the liquid phase refrigerant; and

adjusting a spray pressure of the liquid phase refrigerant sprayed from the first nozzle so that an edge of a flow of the liquid phase refrigerant sprayed from the nozzle reaches a position a given distance away from outlets of the plurality of heat transfer tubes toward inlets of the plurality of heat transfer tubes.

[0007] A refrigeration apparatus of the present disclosure includes the above shell-and-tube heat exchanger of the present disclosure as at least one of an evaporator and a condenser.

Advantageous Effects of Invention

[0008] The present disclosure can provide a technique suitable for improvement in heat exchange efficiency of a shell-and-tube heat exchanger.

BRIEF DESCRIPTION OF DRAWINGS

[0009] 

FIG. 1 shows a configuration of an absorption refrigeration apparatus according to Embodiment 1 of the present disclosure.

FIG. 2 is a longitudinal cross-sectional view of an evaporator of the absorption refrigeration apparatus shown in FIG. 1.

FIG. 3 is a top view showing a positional relation between a heat transfer tube and a nozzle in the evaporator shown in FIG. 2.

FIG. 4 is a property diagram showing a relation between a distance from an inlet of a heat transfer tube and a temperature difference ΔT between temperatures of a heat medium and a refrigerant.

FIG. 5 is a longitudinal cross-sectional view of an evaporator according to Embodiment 2.

FIG. 6 is a longitudinal cross-sectional view of an evaporator according to Embodiment 3.

FIG. 7A shows a spray pattern of a liquid phase refrigerant sprayed from a nozzle.

FIG. 7B shows a spray pattern of a liquid phase refrigerant sprayed from a nozzle.

FIG. 8 is a longitudinal cross-sectional view of the evaporator shown in FIG. 6 along an A-A line.

FIG. 9 shows how a liquid phase refrigerant is sprayed and flows.

DESCRIPTION OF EMBODIMENTS

(Findings on which the present disclosure is based)

[0010] Before the present inventor conceived the present disclosure, a refrigerant sprayed on a heat transfer tube from a nozzle did not always reach a portion far away from the nozzle due to, for example, an air current in a shell, the air current changing depending on a variation in load or operation conditions. In other words, dryout of the surface of a heat transfer tube was an issue. The term "dryout" refers to a phenomenon forming a large dry region on the surface of a heat transfer tube. An increase in spray pressure of a nozzle allows a refrigerant to reach a farther place. However, an increase in spray pressure can damage a heat transfer tube by erosion. An increase in the number of nozzles increases the cost. Moreover, an increase in the number of nozzles increases the amount of a refrigerant sprayed, increasing the thickness of a liquid film on the surface of a heat transfer tube. The thicker the liquid film is, the lower the heat exchange efficiency is.

[0011] Meanwhile, a difference between the temperature of a heat medium flowing inside a heat transfer tube and that of a refrigerant on the surface of the heat transfer tube is small near an outlet of a heat exchanger. That is, a wet condition of the heat transfer tube near the outlet of the heat exchanger has a small influence on the performance of the heat exchanger. Moreover, even if the spray pressure is so low that a refrigerant cannot directly reach an end of a heat transfer tube, inertia extends a spray distance of a liquid film made of the refrigerant in the case where the flow of the refrigerant has a velocity component parallel to a longitudinal direction of the heat transfer tube.

[0012] On the basis of these findings, the present inventor has configured the subject matter of the present invention.

[0013] Embodiments will be described below in detail with reference to the drawings. An unnecessarily detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same components may be omitted. This is for avoiding unnecessary redundancy of the description given below and for helping persons skilled in the art easily understand the description.

[0014] The accompanying drawings and the description given below are provided for allowing persons skilled in the art to sufficiently understand the present disclosure, and there is no intention to limit the subject matter in the claims.

(Embodiment 1)

[0015] Embodiment 1 will be described hereinafter with reference to FIGS. 1 to 4.

[1-1. Configuration of absorption refrigeration apparatus]

[0016] FIG. 1 shows a configuration of an absorption refrigeration apparatus 100 according to Embodiment 1. The absorption refrigeration apparatus 100 includes an evaporator 101, an absorber 102, a regenerator 103, and a condenser 104. These are mutually connected by paths 110a, 110b, 11 0c, 110d, and 209. A refrigerant and an absorbing liquid for the absorption refrigeration apparatus 100 are, for example, water and a lithium bromide solution. Other examples of the refrigerant and the absorbing liquid are ammonia and water.

[0017] The evaporator 101 is constituted of a shell-and-tube heat exchanger according to Embodiment 1. The evaporator 101 includes a heat transfer tube 202 and a circulation circuit 205. A heat medium such as water flows inside the heat transfer tube 202. The circulation circuit 205 includes a pump 206. A nozzle 204 is provided at a downstream end of the circulation circuit 205. An upstream end of the circulation circuit 205 is connected to a bottom portion of the evaporator 101. A liquid phase refrigerant is stored in the bottom portion of the evaporator 101. The liquid phase refrigerant circulates in the circulation circuit 205 by the action of the pump 206. Specifically, the liquid phase refrigerant is transferred to the nozzle 204 by the pump 206, and is sprayed from the nozzle 204 toward the heat transfer tube 202. Heat exchange occurs between the heat medium in the heat transfer tube 202 and the sprayed liquid phase refrigerant, and thereby cold energy is taken out of the refrigerant. The refrigerant is heated on the surface of the heat transfer tube 202 to evaporation. An outlet of the evaporator 101 is connected to the absorber 102 via the path 209.

[0018] The absorber 102 is constituted, for example, of a shell-and-tube heat exchanger. The absorber 102 includes a heat transfer tube 121 and a sprinkling tray 107. A heat medium such as water flows inside the heat transfer tube 121. The absorbing liquid is sprinkled from the sprinkling tray 107 toward the heat transfer tube 121. The absorbing liquid is cooled on the surface of the heat transfer tube 121, and, simultaneously, a gas phase refrigerant is absorbed by the absorbing liquid. An outlet of the absorber 102 is connected to an inlet of the regenerator 103 by the path 110a. The path 110a includes a pump 106.

[0019] The regenerator 103 includes a heater 123 for heating the absorbing liquid. The heater 123 may be a boiler itself, or may be a circuit in which a heat medium heated in a boiler circulates. A bottom portion of the regenerator 103 is connected to the spray tray 107 of the absorber 102 by the path 110d. Since the internal pressure of the regenerator 103 is higher than that of the absorber 102, the absorbing liquid is transferred to the sprinkling tray 107 from the bottom portion of the regenerator 103 by the pressure difference. An outlet of the regenerator 103 is connected to an inlet of the condenser 104 by the path 110b.

[0020] The condenser 104 is constituted, for example, of a shell-and-tube heat exchanger. The condenser 104 is a heat exchanger for cooling and liquefying the refrigerant heated and vaporized in the regenerator 103. The condenser 104 includes, for example, a heat transfer tube 124. A heat medium such as water flows inside the heat transfer tube 124. The refrigerant is cooled on the surface of the heat transfer tube 124 to be liquefied. An outlet of the condenser 104 is connected to an inlet of the evaporator 101 by the path 110c.

[0021] The path 110a and the path 110b are vapor paths. The path 110c and the path 110d are liquid paths. Each path is formed of at least one metal tube.

[1-2. Behavior of absorption refrigeration apparatus]

[0022] A behavior and an action of the absorption refrigeration apparatus 100 configured as above will be described hereinafter.

[0023] In the evaporator 101, the liquid phase refrigerant is pumped by the pump 206 to the nozzle 204 through the circulation circuit 205, and sprayed in the form of mist on the heat transfer tube 202 from the nozzle 204. The sprayed liquid phase refrigerant exchanges heat with the heat medium flowing inside the heat transfer tube 202 on the surface of the heat transfer tube 202 to evaporate. A low-temperature and low-pressure gas phase refrigerant is thus generated. The gas phase refrigerant is absorbed into the absorber 102 through the path 209. In the absorber 102, the gas phase refrigerant is absorbed by the absorbing liquid dropped from the sprinkling tray 107. At this time, the absorbing liquid absorbs the gas phase refrigerant on the surface of the heat transfer tube 121 while being cooled by the heat transfer tube 121. Then, the absorbing liquid runs down to a bottom portion of the absorber 102, and is transferred to the regenerator 103 through the path 110a. Just before flowing into the regenerator 103, the absorbing liquid is a liquid mixture of an absorbing agent and the refrigerant. After flowing into the regenerator 103, the absorbing liquid is heated by the heater 123. A refrigerant component having a low boiling point is vaporized by the heating to be separated as a high-temperature gas phase refrigerant. The absorbing liquid is transferred to the sprinkling tray 107 through the path 110d. The separated high-temperature gas phase refrigerant is transferred to the condenser 104 through the path 110b. The high-temperature gas phase refrigerant is cooled by the heat transfer tube 124 to be condensed. A liquid phase refrigerant is thus generated. The liquid phase refrigerant is transferred to the evaporator 101 through the path 110c. This cycle repeats.

[0024] The absorption refrigeration apparatus 100 is applied, for example, to a business-use or home-use air conditioner. A heat medium cooled by the evaporator 101 is supplied into a room and used for cooling of the room. Alternatively, a heat medium heated by the condenser 104 is supplied into a room and used for heating of the room. The heat medium is, for example, water. However, the application of the absorption refrigeration apparatus 100 is not limited to an air conditioner, and may be another apparatus such as a chiller and a heat storage device.

[1-3. Configuration of evaporator]

[0025] FIG. 2 is a longitudinal cross-sectional view of the evaporator 101 of the absorption refrigeration apparatus 100 shown in FIG. 1. The evaporator 101 is constituted of a shell-and-tube heat exchanger. The evaporator 101 is also called a spray evaporator. The evaporator 101 includes a shell 201, a plurality of the heat transfer tubes 202, and the nozzle 204. In FIG. 2, the Z axis represents an axis parallel to the vertical direction. The X axis represents an axis parallel to the horizontal direction. The direction perpendicular to the page is the Y axis (not illustrated).

[0026] The shell 201 is, for example, a container having a rectangular or circular cross-sectional shape. The container may be a pressure-resistant container. The shell 201 has a flow inlet 201a and a flow outlet 201b. The path 110c is connected to the flow inlet 201a. The absorber 102 is connected to the flow outlet 201b via the path 209. The liquid phase refrigerant flows from the outside into the shell 201 through the flow inlet 201a. The gas phase refrigerant generated on the surfaces of the plurality of heat transfer tubes 202 is led to the outside of the shell 201 through the flow outlet 201b.

[0027] The plurality of heat transfer tubes 202 are arranged parallel to each other in the shell 201. The plurality of heat transfer tubes 202 each include an inlet 202p and an outlet 202q. The heat transfer tube 202 is, for example, a heat transfer tube having a circular cross-sectional shape. The heat transfer tube 202 is made of a metal such as copper and stainless steel, and is typically a copper tube. In the present embodiment, the plurality of heat transfer tubes 202 are arranged in three tiers in the vertical direction. The heat transfer tubes 202 are arranged also in a plurality of columns in the direction perpendicular to the page.

[0028] The nozzle 204 is disposed on an inlet side of the plurality of heat transfer tubes 202 through which the heat medium flows into the plurality of heat transfer tubes 202. From the inlet side of the plurality of heat transfer tubes 202 through which the heat medium flows into the plurality of heat transfer tubes 202 toward an outlet side of the plurality of heat transfer tubes 202 through which the heat medium flows out of the plurality of heat transfer tubes 202, the liquid phase refrigerant is sprayed on the plurality of heat transfer tubes 202 from the nozzle 204. The liquid phase refrigerant is, for example, a liquid water.

[0029] In a longitudinal direction of the heat transfer tube 202, the nozzle 204 is located between a middle position of the heat transfer tube 202 and the inlet 202p. The nozzle 204 may be disposed as near as possible to the inlet 202p. In that case, the liquid phase refrigerant can be sprayed also on a portion near the inlet 202p of the heat transfer tube 202.

[0030] The shape of a flow of the liquid phase refrigerant sprayed from the nozzle 204 is, for example, a conical shape.

[0031] FIG. 3 is a top view showing a positional relation between the heat transfer tube 202 and the nozzle 204 in the evaporator 101 shown in FIG. 2. In FIG. 3, the X axis and the Y axis each represent an axis parallel to the horizontal direction. Dotted lines represent edges E1 and E2 of the flow of the sprayed liquid phase refrigerant, the edges being defined in plan view. The nozzle 204 has a spray axis Am. The spray axis Am is a central axis of the nozzle 204, and is an axis passing through a center of an opening of the nozzle 204. The spray axis Am passes through a center of the flow of the sprayed liquid phase refrigerant. A nozzle hole is located at a center of the nozzle 204. The flow of the sprayed liquid phase refrigerant is in the shape of a sector having a spray angle α in plan view. The spray angle α is, for example, 90 degrees or more and 120 degrees or less. The spray angle α is typically 105 degrees.

[0032] The spray axis Am is parallel to a plane (XY plane) including a central axis Bx of the heat transfer tube 202. The central axis Bx is an axis being parallel to the longitudinal direction of the heat transfer tube 202 and passing through a center of a cross-section of the heat transfer tube 202. The spray axis Am is inclined to the Y axis perpendicular to the longitudinal direction of the heat transfer tube 202 and is inclined to the central axis Bx of the heat transfer tube 202. An angle θ made by the central axis Bx and the spray axis Am is, for example, 30 degrees or more and 50 degrees or less. The angle θ is typically 45 degrees. The angle θ is an acute angle made by a heading direction of the liquid phase refrigerant along the spray axis Am of the nozzle 204 and a direction that is in parallel to the longitudinal direction of the heat transfer tube 202 and that is from the inlet 202p of the heat transfer tube 202 toward the outlet 202q of the heat transfer tube 202.

[0033] As can be understood from FIG. 3, "spraying the liquid phase refrigerant on the plurality of heat transfer tubes 202 from the inlet side of the plurality of heat transfer tubes 202 through which the heat medium flows into the plurality of heat transfer tubes 202 toward the outlet side of the plurality of heat transfer tubes 202 through which the heat medium flows out of the plurality of heat transfer tubes 202" indicates that the angle θ is an acute angle. This configuration allows the liquid phase refrigerant to reach a vicinity of the outlet 202q of the heat transfer tube 202.

[0034] A spray pressure of the nozzle 204 can be adjusted so that the sprayed liquid phase refrigerant directly reaches a position P1. The edge E1 of the flow of the liquid phase refrigerant and the heat transfer tube 202 intersect at the position P1. The position P1 is a position located a distance L ahead from the outlet 202q of the heat transfer tube 202 toward the inlet 202p thereof. That is, the flow of the liquid phase refrigerant (liquid phase refrigerant mist) does not directly reach a portion near the outlet 202q of the heat transfer tube 202. However, the flow of the liquid phase refrigerant has a velocity component parallel to the longitudinal direction of the heat transfer tube 202. Therefore, the liquid phase refrigerant spreads by inertial force. Hence, heat exchange is performed also in the portion near the outlet 202q.

[0035] In the present embodiment, the liquid phase refrigerant is sprayed also from a direction perpendicular to the longitudinal direction of the heat transfer tube 202 (namely, a direction parallel to the Y axis) toward a direction inclined to the inlet side of the heat transfer tube 202. This configuration allows the liquid phase refrigerant to be sprayed also on a vicinity of the inlet 202p of the heat transfer tube 202, and that makes dryout less likely to occur in the vicinity of the inlet 202p of the heat transfer tube 202. The flow of the liquid phase refrigerant shown in FIG. 3 is formed by adjusting the orientation of the nozzle 204 and the spray pressure thereof.

[0036] That is, the liquid phase refrigerant is sprayed from the nozzle 204 toward the plurality of heat transfer tubes 202 to cause heat exchange between the heat medium and the liquid phase refrigerant. The spray pressure of the liquid phase refrigerant sprayed from the nozzle 204 is adjusted so that the edge E1 of the flow of the liquid phase refrigerant sprayed from the nozzle 204 reaches the position the given distance L away from the outlets 202q of the plurality of heat transfer tubes 202 toward the inlets 202p of the plurality of heat transfer tubes 202.

[0037] As shown in FIG. 2, the evaporator 101 further includes a flow path cover 207, a flow path cover 208, and the circulation circuit 205. The configuration of the circulation circuit 205 is as described with reference to FIG. 1. The nozzle 204 is provided at a downstream end of the circulation circuit 205. The flow path cover 207 includes a flow inlet 211 through which the heat medium flows in. The flow path cover 207 is attached to the shell 201 to cover the inlets 202p of the plurality of heat transfer tubes 202. The flow path cover 208 includes a flow outlet 212 through which the heat medium flows out. The flow path cover 208 is attached to the shell 201 to cover the outlets 202q of the plurality of heat transfer tubes 202. The heat medium flows into the heat transfer tube 202 through the flow path cover 207 and flows out of the heat transfer tube 202 to the outside through the flow path cover 208.

[0038] In the present embodiment, flow directions (from left to right) of the heat medium in the plurality of heat transfer tubes 202 are the same. That is, the number of passes in the evaporator 101 is one.

[1-4. Behavior of evaporator]

[0039] A behavior and an action of the evaporator 101 configured as above will be described hereinafter.

[0040] In the evaporator 101, the liquid phase refrigerant is pumped by the pump 206 to the nozzle 204 through the circulation circuit 205, and sprayed in the form of mist on the heat transfer tube 202 from the nozzle 204.

[0041] The heat medium such as water flows into the flow path cover 207 through the flow inlet 211 and flows into the heat transfer tube 202 through the flow path cover 207. Then, the heat medium flows through the heat transfer tube 202 from left to right, and flows out through the flow outlet 212 via the flow path cover 208.

[0042] As shown in FIG. 3, from the inlet side of the plurality of heat transfer tubes 202 through which the heat medium flows into the plurality of heat transfer tubes 202 toward the outlet side thereof, the liquid phase refrigerant is sprayed from the nozzle 204. The flow of the liquid phase refrigerant is a flow having the spray angle α. The sprayed liquid phase refrigerant exchanges heat with the heat medium on the surface of the heat transfer tube 202 and evaporates. The flow of the liquid phase refrigerant does not reach the outlet 202q of the heat transfer tube 202, but reaches the position P1 the distance L away from the outlet 202q. The liquid phase refrigerant is likely to spread by inertial force, but the amount of the sprayed liquid phase refrigerant is small in a region between the position P1 and the outlet 202q.

[0043] FIG. 4 is a property diagram showing a relation between a distance from the inlet 202p of the heat transfer tube 202 and a temperature difference ΔT. The horizontal axis represents the distance from the inlet 202p of the heat transfer tube 202. The vertical axis represents the temperature difference ΔT. The temperature difference ΔT is a difference between temperatures of the heat medium and the refrigerant. The temperature difference ΔT is largest at the inlet 202p of the heat transfer tube 202, decreases toward the outlet 202q, and is smallest at the outlet 202q. Heat exchange between the heat medium and the refrigerant is almost complete at a vicinity of the outlet 202q of the heat transfer tube 202. Therefore, an amount of heat exchange is small in a region (a region extending over the distance L) between the position P1 and the outlet 202q. According to the present embodiment, a sparse region where the amount of the sprayed liquid phase refrigerant is small can be formed in a region where the amount of heat exchange is small, and therefore dryout is less likely to occur.

[1-5. Effect, etc.]

[0044] As described above, in the present embodiment, the nozzle 204 is disposed on the inlet side of the plurality of heat transfer tubes 202 through which the heat medium flows into the plurality of heat transfer tubes 202, and the liquid phase refrigerant is sprayed on the plurality of heat transfer tubes 202 from the nozzle 204 from the inlet side of the plurality of heat transfer tubes 202 through which the heat medium flows into the plurality of heat transfer tubes 202 toward the outlet side thereof.

[0045] According to this configuration, the liquid phase refrigerant is sprayed from the nozzle 204 toward the axial direction of the heat transfer tube 202. The heat transfer tube 202 includes a portion near the nozzle 204 and a portion far from the nozzle 204. The liquid phase refrigerant easily reaches the portion near the nozzle 204. Therefore, the portion near the nozzle 204 is a dense region where the amount of the sprayed liquid phase refrigerant is large. On the other hand, the liquid phase refrigerant does not easily reach the portion far from the nozzle 204. Therefore, the portion far from the nozzle 204 is a sparse region where the amount of the sprayed liquid phase refrigerant is small. In addition, the nozzle 204 is disposed on the inlet side of the heat transfer tube 202. Therefore, the temperature difference ΔT between the temperatures of the liquid phase refrigerant and the heat medium in the heat transfer tube 202 is large in the dense region. On the other hand, in the sparse region, the temperature difference ΔT between the temperatures of the refrigerant and the heat medium is small since heat exchange between the refrigerant and the heat medium has already made sufficient progress. Since the sparse region where the amount of the sprayed liquid phase refrigerant is small can be formed in a region where the temperature difference ΔT and the amount of heat exchange are small, dryout is less likely to occur. For these reasons, even in a region that is far from the nozzle 204 and where the amount of the sprayed liquid phase refrigerant is small, dryout can be avoided without increasing the spray pressure of the nozzle 204. According to the technique of the present disclosure, erosion can be avoided to increase the reliability of the evaporator 101, and the heat exchange efficiency of the evaporator 101 can be improved.

[0046] Moreover, in the present embodiment, the angle θ made by the heading direction of the liquid phase refrigerant along the spray axis Am of the nozzle 202 and the direction that is in parallel to the longitudinal direction of the heat transfer tube 202 and that is from the inlet 202p of the heat transfer tube 202 toward the outlet 202q of the heat transfer tube 202 may be an acute angle. This configuration allows the liquid phase refrigerant to reach a vicinity of the outlet 202q of the heat transfer tube 202.

(Embodiment 2)

[0047] Embodiment 2 will be described hereinafter with reference to FIG. 5. The same components as those in Embodiment 1 are denoted by the same reference characters, and detailed descriptions thereof are omitted.

[2-1. Configuration of evaporator]

[0048] FIG. 5 is a longitudinal cross-sectional view of an evaporator 301 according to Embodiment 2. In the evaporator 301 of the present embodiment, the plurality of heat transfer tubes 202 include a first heat transfer tube group 202a and a second heat transfer tube group 202b. The first heat transfer tube group 202a is a heat transfer tube group including one of the heat transfer tubes 202, the one being located in a top tier in the shell 201. The second heat transfer tube group 202b is a heat transfer tube group located below the first heat transfer tube group 202a and adjacent to the first heat transfer tube group 202a. A flow direction of the heat medium in the first heat transfer tube group 202a is opposite to that of the heat medium in the second heat transfer tube group 202b. Specifically, the flow direction of the heat medium in the first heat transfer tube group 202a is 180 degrees opposite to that of the heat medium in the second heat transfer tube group 202b. The heat medium flows in the second heat transfer tube group 202b and the first heat transfer tube group 202a in this order. The term "heat transfer tube group" means a group of the heat transfer tubes 202 in which heat media having temperatures in the same temperature range flow.

[0049] In the present embodiment, the nozzle 204 described in Embodiment 1 is defined as a first nozzle 204a. The first nozzle 204a is a nozzle for spraying the liquid phase refrigerant on the first heat transfer tube group 202a. It should be noted that the liquid phase refrigerant not evaporated on the first heat transfer tube group 202a drops down to the second heat transfer tube group 202b. The first heat transfer tube group 202a is a top-tier heat transfer tube group including the heat transfer tube 202 located in the top tier; therefore, even when the liquid phase refrigerant sprayed from the first nozzle 204a fails to directly reach a vicinity of an outlet of the first heat transfer tube group 202a, the failure does not have a large effect on the heat exchange efficiency of the evaporator 301.

[0050] The evaporator 301 further includes a second nozzle 204b. The second nozzle 204b is disposed at a position on an outlet side of the second heat transfer tube group 202b through which the heat medium flows out of the second heat transfer tube group 202b, the position being shifted from a position of the first nozzle 204a to an outlet side of the first heat transfer tube group 202a through which the heat medium flows out of the first heat transfer tube group 202a. The liquid phase refrigerant is sprayed on the second heat transfer tube group 202b from the second nozzle 204b. The outlet side of the first heat transfer tube group 202a through which the heat medium flows out of the first heat transfer tube group 202a is an inlet side of the second heat transfer tube group 202b through which the heat medium flows into the second heat transfer tube group 202b. An inlet side of the first heat transfer tube group 202a through which the heat medium flows into the first heat transfer tube group 202a is the outlet side of the second heat transfer tube group 202b through which the heat medium flows out of the second heat transfer tube group 202b. In a direction parallel to the longitudinal direction of the heat transfer tube 202, a distance between the first nozzle 204a and the second nozzle 204b is, for example, equal to the distance L described in Embodiment 1.

[0051] The second nozzle 204b is a nozzle for spraying the liquid phase refrigerant on the second heat transfer tube group 202b from the outlet side of the second heat transfer tube group 202b through which the heat medium flows out of the second heat transfer tube group 202b toward the inlet side of the second heat transfer tube group 202b through which the heat medium flows into the second heat transfer tube group 202b. The second nozzle 204b can increase the amount of heat exchange on the second heat transfer tube group 202b.

[0052] In the present embodiment, a spray direction of the second nozzle 204b coincides with a spray direction of the first nozzle 204a. In other words, a spray axis of the second nozzle 204b is parallel to the spray axis Am (FIG. 3) of the first nozzle 204a. According to this configuration, the liquid phase refrigerant sprayed from the first nozzle 204a drops down from the first heat transfer tube group 202a to the second heat transfer tube group 202b, and therefore the liquid phase refrigerant can also reach a region where the liquid phase refrigerant sprayed from the second nozzle 204b does not reach.

[0053] The evaporator 301 includes only the first nozzle 204a as a nozzle for spraying the liquid phase refrigerant on the first heat transfer tube group 202a. This configuration can decrease the cost of the evaporator 301. The second nozzle 204b is the only nozzle for directly spraying the liquid phase refrigerant on the second heat transfer tube group 202b. However, the liquid phase refrigerant sprayed from the first nozzle 204a also drops down to the second heat transfer tube group 202b.

[0054] The configuration and the properties of the first nozzle 204a are the same as, for example, those of the second nozzle 204b. That is, nozzles that are the same product can be used as the first nozzle 204a and the second nozzle 204b. That can decrease the cost of the evaporator 301.

[0055] During the operation of the evaporator 301, a spray pressure of the first nozzle 204a may be the same or different from that of the second nozzle 204b. In the present embodiment, a circuit for supplying the liquid phase refrigerant to the first nozzle 204a is used also as a circuit for supplying the liquid phase refrigerant to the second nozzle 204b. That is, the first nozzle 204a and the second nozzle 204b share the circulation circuit 205. Therefore, when a pressure loss in the circulation circuit 205 is excluded, the spray pressure of the first nozzle 204a is equal to that of the second nozzle 204b.

[0056] In the present embodiment, the plurality of heat transfer tubes 202 further include a third heat transfer tube group 202c, a fourth heat transfer tube group 202d, and a fifth heat transfer tube group 202e. Each heat transfer tube group includes the plurality of heat transfer tubes 202 arranged in three tiers in the vertical direction. The flow directions of the heat medium in the odd-numbered heat transfer tube groups are the same. The flow directions of the heat medium in the even-numbered heat transfer tube groups are the same. The flow direction of the heat medium in the odd-numbered heat transfer tube group is opposite to the flow direction of the heat medium in the even-numbered heat transfer tube group. Each heat transfer tube group is provided with one nozzle 204. The nozzle 204 for spraying the liquid phase refrigerant toward the odd-numbered heat transfer tube group is the first nozzle 204a. The nozzle 204 for spraying the liquid phase refrigerant toward the even-numbered heat transfer tube group is the second nozzle 204b. The first nozzles 204a and the second nozzles 204b are alternately disposed in a staggered pattern along the vertical direction. Positions of the plurality of first nozzles 204a in the longitudinal direction of the heat transfer tube 202 are the same. Positions of the plurality of second nozzles 204b in the longitudinal direction of the heat transfer tube 202 are the same.

[0057] Under the flow path cover 207, one partition plate 210 is disposed to separate the second heat transfer tube group 202b and the third heat transfer tube group 202c, and the other partition plate 210 is disposed to separate the fourth heat transfer tube group 202d and the fifth heat transfer tube group 202e. Under the flow path cover 208, one partition plate 210 is disposed to separate the first heat transfer tube group 202a and the second heat transfer tube group 202b, and the other partition plate 210 is disposed to separate the third heat transfer tube group 202c and the fourth heat transfer tube group 202d. Hence, the heat medium flows in the fifth heat transfer tube group 202e, the fourth heat transfer tube group 202d, the third heat transfer tube group 202c, the second heat transfer tube group 202b, and the first heat transfer tube group 202a in this order. The flow direction of the heat medium is reversed under the flow path cover 207 and the flow path cover 208. After flowing under the flow path cover 207, the heat medium flows in a bottom-tier heat transfer tube group (the fifth heat transfer tube group 202e) including the heat transfer tube 202 located in a bottom tier and meanders toward the top-tier heat transfer tube group (the first heat transfer tube group 202a). After flowing through the top-tier heat transfer tube group, the heat medium flows to the outside via the flow path cover 208.

[0058] The flow path cover 207 allows communication between an inlet of the first heat transfer tube group 202a through which the heat medium flows into the first heat transfer tube group 202a and an outlet of the second heat transfer tube group 202b through which the heat medium flows out of the second heat transfer tube group 202b. The flow path cover 207 also allows communication between an inlet of the third heat transfer tube group 202c through which the heat medium flows into the third heat transfer tube group 202c and an outlet of the fourth heat transfer tube group 202d through which the heat medium flows out of the fourth heat transfer tube group 202d. The flow path cover 208 allows communication between an inlet of the second heat transfer tube group 202b through which the heat medium flows into the second heat transfer tube group 202b and an outlet of the third heat transfer tube group 202c through which the heat medium flows out of the third heat transfer tube group 202c. The flow path cover 208 also allows communication between an inlet of the fourth heat transfer tube group 202d through which the heat medium flows into the fourth heat transfer tube group 202d and an outlet of the fifth heat transfer tube group 202e through which the heat medium flows out of the fifth heat transfer tube group 202e. The flow direction of the heat medium can be smoothly changed by means of the flow path cover 207 and the flow path cover 208.

[0059] In the present embodiment, each heat transfer tube group is provided with only one nozzle. In the vertical direction, there is only one first nozzle 204a disposed at a height where the first nozzle 204a overlaps the first heat transfer tube group 202a. In the vertical direction, there is only one second nozzle 204b disposed at a height where the second nozzle 204b overlaps the second heat transfer tube group 202b. This configuration is applicable to the third heat transfer tube group 202c, the fourth heat transfer tube group 202d, and the fifth heat transfer tube group 202e. An increase in the number of nozzles makes it easy to spray the liquid phase refrigerant on the whole of each heat transfer tube 202. However, an excessive amount of the sprayed liquid phase refrigerant makes the liquid film on the surface of the heat transfer tube 202 too thick. On the contrary, in this case, the heat exchange efficiency may decrease. An increase in the number of nozzles increases the cost. The present embodiment is suitable for a case where limiting of the total number of the nozzles 204 and maximizing of the heat exchange efficiency are both desired. Moreover, since the present embodiment can decrease the number of the nozzles 204, the present embodiment is suitable for reduction in cost of the evaporator 301 and miniaturization of the evaporator 301.

[2-2. Behavior of evaporator]

[0060] A behavior and an action of the evaporator 301 configured as above will be described hereinafter.

[0061] The liquid phase refrigerant is sprayed from the first nozzle 204a toward the axial direction of the heat transfer tube 202. Specifically, the liquid phase refrigerant is sprayed toward the first heat transfer tube group 202a from the first nozzle 204a. The liquid phase refrigerant easily reaches a portion near the first nozzle 204a. Therefore, the portion near the first nozzle 204a is a dense region A1 where the amount of the sprayed liquid phase refrigerant is large. On the other hand, the liquid phase refrigerant does not easily reach a portion far from the first nozzle 204a. Therefore, the portion far from the first nozzle 204a is a sparse region B1 where the amount of the sprayed liquid phase refrigerant is small.

[0062] The heat medium meanders from the bottom-tier heat transfer tube group tier toward the top-tier heat transfer tube group. The first nozzle 204a for spraying the liquid phase refrigerant on the first heat transfer tube group 202a being the top-tier heat transfer tube group is disposed on the inlet side of the first heat transfer tube group 202a. Therefore, a portion near the outlet of the first heat transfer tube group 202a is the sparse region B1 where the amount of the sprayed liquid phase refrigerant is small. In the sparse region B1, dryout is less likely to occur since heat exchange between the refrigerant and the heat medium has already made sufficient progress.

[0063] Meanwhile, the second nozzle 204b is disposed at a position shifted from the position of the first nozzle 204a to the outlet side of the first heat transfer tube group 202a through which the heat medium flows out of the first heat transfer tube group 202a. An amount of the shift of the second nozzle 204b with respect to the position of the first nozzle 204a is equal to a length, namely, the distance L, of the sparse region B1 in the longitudinal direction of the heat transfer tube 202. The liquid phase refrigerant sprayed from the second nozzle 204b sufficiently reach a vicinity of the inlet of the second heat transfer tube group 202b. A portion near the inlet of the second heat transfer tube group 202b is a dense region B2 where the amount of the sprayed liquid phase refrigerant is large. A portion near the outlet of the second heat transfer tube group 202b is located behind the second nozzle 204b. Therefore, the liquid phase refrigerant sprayed from the second nozzle 204b barely reaches the portion near the outlet of the second heat transfer tube group 202b. The portion near the outlet of the second heat transfer tube group 202b is a sparse region A2 where the amount of the sprayed liquid phase refrigerant is small. However, the dense region A1 is located above the sparse region A2. Hence, the liquid phase refrigerant drops down from the dense region A1 toward the sparse region A2. Consequently, the heat transfer tube 202 in the sparse region A2 is wetted with the liquid phase refrigerant. The same phenomenon repeats for the third heat transfer tube group 202c, the fourth heat transfer tube group 202d, and the fifth heat transfer tube group 202e. The whole third heat transfer tube group 202c, the whole fourth heat transfer tube group 202d, and the whole fifth heat transfer tube group 202e are thereby sufficiently wetted with the liquid phase refrigerant.

[0064] As described above, the whole second heat transfer tube group 202b is wetted with the liquid phase refrigerant sprayed from the second nozzle 204b and the liquid phase refrigerant dropping from the first heat transfer tube group 202a. Eventually, a region where the amount of the sprayed liquid phase refrigerant is small and the liquid phase refrigerant is not likely to drop from the above is the sparse region B1 only. The sparse region B1 is a region where the temperature difference ΔT between the temperatures of the refrigerant and the heat medium is smallest in the evaporator 301 and where the amount of heat exchange is small. A wet condition of the sparse region B1 has a small influence on the heat exchange performance of the evaporator 301.

[2-3. Effect, etc.]

[0065] As described above, in the present embodiment, the evaporator 301 further includes the second nozzle 204b disposed at a position on the outlet side of the second heat transfer tube group 202b through which the heat medium flows out of the second heat transfer tube group 202b, the position being shifted from the position of the first nozzle 204a to the outlet side of the first heat transfer tube group 202a through which the heat medium flows out of the first heat transfer tube group 202a. According to this configuration, the sparse region B1 can be formed only near the outlet of the first heat transfer tube group 202a being the top-tier heat transfer tube group even in a large-capacity evaporator including a plurality of heat transfer tube groups. The whole second heat transfer tube group 202b being the heat transfer tube group located below the first heat transfer tube group 202a can be wetted with the liquid phase refrigerant. Therefore, dryout can be avoided without increasing the spray pressures of the first nozzle 204a and the second nozzle 204b. According to the technique of the present disclosure, erosion can be avoided to increase the reliability of the evaporator 301, and the heat exchange efficiency of the evaporator 301 can be improved.

[0066] Moreover, in the present embodiment, the evaporator 301 may further include the second nozzle 204b disposed at a position on the outlet side of the second heat transfer tube group 202b through which the heat medium flows out of the second heat transfer tube group 202b, the position being shifted from the position of the first nozzle 204a to the outlet side of the first heat transfer tube group 202a through which the heat medium flows out of the first heat transfer tube group 202a, the second nozzle 204b being for spraying the liquid phase refrigerant on the second heat transfer tube group 202b. Using the second nozzle 204b, the liquid phase refrigerant is sufficiently sprayed on the second heat transfer tube group 202b.

[0067] Moreover, in the present embodiment, the liquid phase refrigerant may be sprayed on the second heat transfer tube group 202b from the second nozzle 204b from the outlet side of the second heat transfer tube group 202b through which the heat medium flows out of the second heat transfer tube group 202b toward the inlet side of the second heat transfer tube group 202b through which the heat medium flows into the second heat transfer tube group 202b. The second nozzle 204b can increase the amount of heat exchange on the second heat transfer tube group 202b.

[0068] Moreover, in the present embodiment, the spray direction of the second nozzle 204b may coincide with the spray direction of the first nozzle 204a. According to this configuration, the liquid phase refrigerant sprayed from the first nozzle 204a drops down from the first heat transfer tube group 202a to the second heat transfer tube group 202b, and therefore the liquid phase refrigerant can reach a region where the liquid phase refrigerant sprayed from the second nozzle 204b does not reach.

[0069] Moreover, in the present embodiment, the evaporator 301 may include only the first nozzle 204a as a nozzle for spraying the liquid phase refrigerant on the first heat transfer tube group 202a. This configuration can decrease the cost of the evaporator 301.

[0070] Moreover, in the present embodiment, the evaporator 301 may further include the flow path cover 207 allowing communication between the inlet of the first heat transfer tube group 202a through which the heat medium flows into the first heat transfer tube group 202a and the outlet of the second heat transfer tube group 202b through which the heat medium flows out of the second heat transfer tube group 202b. The flow direction of the heat medium can be smoothly changed by means of the flow path cover 207.

(Embodiment 3)

[0071] Embodiment 3 will be described hereinafter with reference to FIGS. 6 to 9. The same components as those in Embodiment 1 or 2 are denoted by the same reference characters, and detailed descriptions thereof are omitted.

[3-1. Configuration of evaporator]

[0072] FIG. 6 is a longitudinal cross-sectional view of an evaporator 401 according to Embodiment 3. The difference between the evaporator 401 of the present embodiment and the evaporator 301 (FIG. 5) of Embodiment 2 is the shape of the flow of the liquid phase refrigerant sprayed from the nozzle 204. Except for this point, the configuration of the evaporator 401 is the same as the configuration of the evaporator 301. In the present embodiment, the flow of the liquid phase refrigerant sprayed from the nozzle 204 has a flat shape.

[0073] FIG. 7A and FIG. 7B each show a spray pattern of the liquid phase refrigerant sprayed from the nozzle 204. The liquid phase refrigerant is sprayed from the nozzle 204 in a flat spray pattern having the spray axis Am. As shown in FIG. 7A, the liquid phase refrigerant sprayed from the nozzle 204 forms a sector-shaped spray region M. A spray region S appearing when the spray pattern is projected on a plane H perpendicular to the spray axis Am has a flat shape. The liquid phase refrigerant sprayed in such a spray pattern passes between the heat transfer tubes 202.

[0074] FIG. 8 is a longitudinal cross-sectional view of the evaporator 401 shown in FIG. 6 along an A-A line. In the example shown in FIG. 8, twelve heat transfer tubes 202 are arranged in the Y-axis direction. However, the number of the heat transfer tubes 202 in the Y-axis direction is not limited to a specific value. The liquid phase refrigerant is sprayed from the nozzle 204 such that the spray axis Am passes between a pair of the heat transfer tubes 202 nearest to the nozzle 204 in the direction (Y-axis direction) perpendicular to the longitudinal direction of the heat transfer tube 202 and that the spray region S passes between the pair of the heat transfer tubes 202. For example, the spray axis Am extends horizontally.

[0075] The nozzle 204 is, for example, disposed only on one side in the Y-axis direction, and is not disposed on the other side in the Y-axis direction. Therefore, at a plane (YZ plane) perpendicular to the longitudinal direction of the heat transfer tube 202, the liquid phase refrigerant is sprayed from the nozzle 204, for example, in a positive Y-axis direction.

[0076] FIG. 9 shows how the liquid phase refrigerant is sprayed from the nozzle 204 and flows. The plurality of heat transfer tubes 202 include a first tier 22a and a second tier 22b. The first tier 22a includes a plurality of the heat transfer tubes 202 arranged along a first plane. The second tier 22b includes a plurality of the heat transfer tubes 202 arranged along a second plane parallel to the first plane, and is adjacent to the first tier 22a in a direction (Z-axis direction) perpendicular to the first plane. The first plane and the second plane are planes parallel to the XY plane.

[0077] There is an imaginary plane between the first tier 22a and the second tier 22b, the imaginary plane not intersecting a tangible object from one end of the first tier 22a to the other end thereof. The one end and the other end are determined in a direction in which the heat transfer tubes 202 in the first tier 22a are arranged.

[0078] The plurality of heat transfer tubes 202 in the first tier 22a and the plurality of heat transfer tubes 202 in the second tier 22b form a rectangular grid, a square grid, or a parallelogram grid on a third plane perpendicular to the longitudinal direction (X-axis direction) of the heat transfer tube 202. The third plane is a plane parallel to the YZ plane.

[0079] The spray axis Am of the spray pattern of the liquid phase refrigerant sprayed from the nozzle 204 passes between a first end portion 22j of each of the heat transfer tubes 202 in the first tier 22a and a second end portion 22k of each of the heat transfer tubes 202 in the second tier 22b. The first end portion 22j is an end portion close to the second tier 22b in the direction (Z-axis direction) perpendicular to the first plane. The second end portion 22k is an end portion close to the first tier 22a in the direction (Z-axis direction) perpendicular to the first plane. The spray pattern of the liquid phase refrigerant sprayed from the nozzle 204 passes between the first tier 22a and the second tier 22b.

[0080] The second tier 22b is, for example, disposed below the first tier 22a in the vertical direction. The plurality of heat transfer tubes 202 include, for example, a lower heat transfer tube group 22c. The lower heat transfer tube group 22c includes a plurality of the heat transfer tubes 202, and is disposed below the second tier 22b in the vertical direction. Each of the heat transfer tubes 202 of the lower heat transfer tube group 22c is disposed, for example, directly below any of the plurality of heat transfer tubes 202 in the second tier 22b.

[0081] For example, the plurality of heat transfer tubes 202 of the lower heat transfer tube group 22c and the plurality of heat transfer tubes 202 in the second tier 22b form a rectangular grid or a square grid on the third plane.

[3-2. Behavior of evaporator]

[0082] A behavior and an action of the evaporator 401 configured as above will be described hereinafter.

[0083] As shown in FIG. 8, the liquid phase refrigerant is sprayed from the nozzle 204 toward a space between two tiers of the heat transfer tubes 202 adjacent to each other in the Z-axis direction. The liquid phase refrigerant is sprayed in a spray pattern having the spray axis Am extending between the two tiers. The sprayed liquid phase refrigerant adheres to the surfaces of the heat transfer tubes 202. Through heat exchange between the heat medium inside the heat transfer tube 202 and the liquid phase refrigerant adhering to the surface of the heat transfer tube 202, the liquid phase refrigerant evaporates and a gas phase refrigerant is generated. The liquid phase refrigerant that remains unevaporated flows along the surfaces of the heat transfer tubes 202, and drops toward the heat transfer tubes 202 disposed below.

[0084] As shown in FIG. 9, the liquid phase refrigerant sprayed from the nozzle 204 passes between the heat transfer tubes 202 in the first tier 22a and the heat transfer tubes 202 in the second tier 22b, which are disposed to form a rectangular grid, a square grid, or a parallelogram grid on the third plane. A member, such as a heat transfer tube, capable of directly hindering advance of the liquid phase refrigerant sprayed from the nozzle 204 is not present between the first tier 22a and the second tier 22b. Therefore, the liquid phase refrigerant sprayed from the nozzle 204 easily flows straight between the first tier 22a and the second tier 22b. Meanwhile, a part of the liquid phase refrigerant sprayed from the nozzle 204 comes into contact with the first end portion 22j of the heat transfer tube 202 in the first tier 22a and the second end portion 22k of the heat transfer tube 202 in the second tier 22b. A part of the liquid phase refrigerant in contact with the heat transfer tube 202 in the first tier 22a flows in a positive Z-axis direction along a front part of the heat transfer tube 202, the front part being defined with respect to the flow of the liquid phase refrigerant. A part of the liquid phase refrigerant in contact with the heat transfer tube 202 in the second tier 22b flows in a negative Z-axis direction along the front part of the heat transfer tube 202. In addition, another part of the liquid phase refrigerant flows in the negative Z-axis direction along a rear part of the heat transfer tube 202 in the second tier 22b. Such flows of the liquid phase refrigerant occur around the heat transfer tubes 202 of each column in the first tier 22a and the second tier 22b.

[0085] As shown in FIG. 9, in an upper heat transfer tube group 22m composed of the first tier 22a and the second tier 22b, heat transfer involving forced convection is caused by direct contact of the liquid phase refrigerant with the surfaces of the heat transfer tubes 202, promoting heat exchange between the liquid phase refrigerant and the heat medium.

[0086] On the surfaces of the heat transfer tubes 202 in the second tier 22b, the liquid phase refrigerant forms a liquid film while flowing in the negative Y-axis direction, and a part of the liquid phase refrigerant forming the liquid film evaporates. An unevaporated liquid phase refrigerant that failed to evaporate in the upper heat transfer tube group 22m drops down from a lowermost portion of the heat transfer tube 202 in the second tier 22b toward the heat transfer tube 202 of the lower heat transfer tube group 22c. The dropped liquid phase refrigerant flows downward while forming a liquid film on the surface of the heat transfer tube 202; a part of the liquid phase refrigerant evaporates, and another part of the liquid phase refrigerant further drops down toward the heat transfer tube 202 disposed below. Such flows and dropping occur around the heat transfer tubes 202 of each column in the lower heat transfer tube group 22c. As described above, the liquid phase refrigerant sprayed from the nozzle 204 drops from the heat transfer tubes 202 of the upper heat transfer tube group 22m, and is thus indirectly supplied around the heat transfer tubes 202 of the lower heat transfer tube group 22c. The liquid phase refrigerant that remains after the dropping is stored at a bottom portion of the shell 201.

[0087] The liquid phase refrigerant sprayed from the nozzle 204 is directly supplied around the heat transfer tubes 202 of the upper heat transfer tube group 22m to generate forced convection. The liquid phase refrigerant is sprayed from the nozzle 204 in a flat spray pattern having the spray axis Am, so that the liquid phase refrigerant is likely to flow straight between the first tier 22a and the second tier 22b. Thus, in the upper heat transfer tube group 22m, forced convection of the liquid phase refrigerant is likely to be generated also around the heat transfer tubes 202 far from the nozzle 204. Therefore, the surfaces of the heat transfer tubes 202 far from the nozzle 204 are likely to be wetted with the liquid phase refrigerant, and dryout is less likely to occur on the surfaces of the far heat transfer tubes 202.

[0088] In addition, the liquid phase refrigerant drops down from the heat transfer tubes 202 of the upper heat transfer tube group 22m toward the lower heat transfer tube group 22c. Therefore, in the lower heat transfer tube group 22c, a liquid film of the liquid phase refrigerant is likely to be formed also on the surfaces of the heat transfer tubes 202 far from the nozzle 204. Hence, the surfaces of the heat transfer tubes 202 located far from the nozzle 204 are likely to be wetted with the liquid phase refrigerant, and dryout is less likely to occur on the surfaces of the far heat transfer tubes 202.

[3-3. Effect, etc.]

[0089] As described above, in the present embodiment, the nozzle 204 may have the spray axis Am passing between the first end portion 22j of each of the plurality of heat transfer tubes 202 in the first tier 22a and the second end portion 22k of each of the plurality of heat transfer tubes 202 in the second tier 22b and the nozzle 204 may be for spraying the liquid phase refrigerant in a flat spray pattern to pass between the first tier 22a and the second tier 22b, the first end portion 22j being close to the second tier 22b in the direction perpendicular to the first plane, the second end portion 22k being close to the first tier 22a in the direction perpendicular to the first plane. The spray axis Am passes between the first end portion 22j of each of the heat transfer tubes 202 in the first tier 22a and the second end portion 22k of each of the heat transfer tubes 202 in the second tier 22b. The first end portion 22j is an end portion of each of the heat transfer tubes 202 in the first tier 22a, the end portion being close to the second tier 22b in the direction perpendicular to the first plane. The second end portion 22k is an end portion of each of the heat transfer tubes 202 in the second tier 22b, the end portion being close to the first tier 22a in the direction perpendicular to the first plane.

[0090] Thus, since the liquid phase refrigerant is sprayed from the nozzle 204 in a flat spray pattern having the spray axis Am, the liquid phase refrigerant is likely to flow straight between the first tier 22a and the second tier 22b. Therefore, in the first tier 22a and the second tier 22b, forced convection of the liquid phase refrigerant is likely to be generated also around the heat transfer tubes 202 far from the nozzle 204. As a result, the surfaces of the heat transfer tubes 202 far from the nozzle 204 are likely to be wetted with the liquid phase refrigerant, and dryout is less likely to occur on the surfaces of the far heat transfer tubes 202.

[0091] The effect described in Embodiment 2 is also obtained according to the present embodiment. That is, even in the case where the heat transfer tubes 202 are arranged in multiple columns and multiple tiers in the horizontal direction and the perpendicular direction, the sparse region B1 can be formed only near the outlet of the first heat transfer tube group 202a being the top-tier heat transfer tube group. The whole second heat transfer tube group 202b being the heat transfer tube group located below the first heat transfer tube group 202a can be wetted with the liquid phase refrigerant. Therefore, dryout can be avoided without increasing the spray pressures of the first nozzle 204a and the second nozzle 204b. According to the technique of the present disclosure, erosion can be avoided to increase the reliability of the evaporator 401, and the heat exchange efficiency of the evaporator 401 can be improved.

INDUSTRIAL APPLICABILITY

[0092] The shell-and-tube heat exchanger disclosed in the present specification is useful as an evaporator of an absorption refrigeration apparatus. The shell-and-tube heat exchanger may be used not only as an evaporator but also as a condenser. The shell-and-tube heat exchanger of the present disclosure can also be included in non-absorption refrigeration apparatuses, such as centrifugal chillers and vapor-compression refrigeration apparatuses. Applications of the refrigeration apparatuses are not limited to particular applications, and examples thereof include domestic-use and business-use air conditioners, chillers, apparatuses for process cooling, and heat storage apparatuses.

Claims

1. A shell-and-tube heat exchanger, comprising:

a shell;

a plurality of heat transfer tubes disposed parallel to each other in the shell; and

a first nozzle for spraying a liquid phase refrigerant on the plurality of heat transfer tubes from an inlet side of the plurality of heat transfer tubes through which a heat medium flows into the plurality of heat transfer tubes toward an outlet side of the plurality of heat transfer tubes through which the heat medium flows out of the plurality of heat transfer tubes, the first nozzle being disposed on the inlet side of the plurality of heat transfer tubes.

2. The shell-and-tube heat exchanger according to claim 1, wherein an angle θ made by a heading direction of the liquid phase refrigerant along a spray axis of the first nozzle and a direction that is in parallel to a longitudinal direction of the heat transfer tube and that is from an inlet of the heat transfer tube toward an outlet of the heat transfer tube is an acute angle.

3. The shell-and-tube heat exchanger according to claim 1 or 2, wherein

the plurality of heat transfer tubes comprise a first heat transfer tube group and a second heat transfer tube group,

the first heat transfer tube group is a heat transfer tube group comprising one of the heat transfer tubes, the one being located in a top tier in the shell,

the second heat transfer tube group is a heat transfer tube group located below and adjacent to the first heat transfer tube group,

a flow direction of the heat medium in the first heat transfer tube group is opposite to a flow direction of the heat medium in the second heat transfer tube group,

the heat medium flows in the second heat transfer tube group and the first heat transfer tube group in this order, and

the first nozzle is a nozzle for spraying the liquid phase refrigerant on the first heat transfer tube group.

4. The shell-and-tube heat exchanger according to claim 3, further comprising a second nozzle for spraying the liquid phase refrigerant on the second heat transfer tube group, the second nozzle being disposed at a position on an outlet side of the second heat transfer tube group through which the heat medium flows out of the second heat transfer tube group, the position being shifted from a position of the first nozzle to an outlet side of the first heat transfer tube group through which the heat medium flows out of the first heat transfer tube group.

5. The shell-and-tube heat exchanger according to claim 4, wherein the second nozzle is for spraying the liquid phase refrigerant on the second heat transfer tube group from the outlet side of the second heat transfer tube group through which the heat medium flows out of the second heat transfer tube group toward an inlet side of the second heat transfer tube group through which the heat medium flows into the second heat transfer tube group.

6. The shell-and-tube heat exchanger according to claim 4 or 5, wherein a spray direction of the second nozzle coincides with a spray direction of the first nozzle.

7. The shell-and-tube heat exchanger according to any one of claims 3 to 6, wherein the shell-and-tube heat exchanger comprises only the first nozzle as a nozzle for spraying the liquid phase refrigerant on the first heat transfer tube group.

8. The shell-and-tube heat exchanger according to any one of claims 1 to 7, wherein

the plurality of heat transfer tubes comprise a first tier and a second tier, the first tier comprising a plurality of heat transfer tubes arranged along a first plane, the second tier comprising a plurality of heat transfer tubes arranged along a second plane parallel to the first plane, the second tier being adjacent to the first tier in a direction perpendicular to the first plane,

the first nozzle comprises a spray axis passing between a first end portion of each of the plurality of heat transfer tubes in the first tier and a second end portion of each of the plurality of heat transfer tubes in the second tier, the first end portion being close to the second tier in the direction perpendicular to the first plane, the second end portion being close to the first tier in the direction perpendicular to the first plane, and

the first nozzle is for spraying the liquid phase refrigerant in a flat spray pattern to pass between the first tier and the second tier.

9. The shell-and-tube heat exchanger according to any one of claims 1 to 8, further comprising a flow path cover allowing communication between an inlet of the first heat transfer tube group through which the heat medium flows into the first heat transfer tube group and an outlet of the second heat transfer tube group through which the heat medium flows out of the second heat transfer tube group.

10. A method for operating the shell-and-tube heat exchanger according to any one of claims 1 to 9, the method comprising:

allowing the heat medium to flow into the plurality of heat transfer tubes;

spraying the liquid phase refrigerant from the first nozzle toward the plurality of heat transfer tubes to cause heat exchange between the heat medium and the liquid phase refrigerant; and

adjusting a spray pressure of the liquid phase refrigerant sprayed from the first nozzle so that an edge of a flow of the liquid phase refrigerant sprayed from the nozzle reaches a position a given distance away from outlets of the plurality of heat transfer tubes toward inlets of the plurality of heat transfer tubes.

11. A refrigeration apparatus comprising the shell-and-tube heat exchanger according to any one of claims 1 to 9 as at least one of an evaporator and a condenser.

Drawing