TECHNICAL FIELD
[0001] The present disclosure relates to a refrigeration cycle apparatus.
BACKGROUND ART
[0002] In recent years, it has been required to use refrigerant having a low GWP (Global
Warming Potential). However, it is difficult to reduce the GWP while keeping the performance,
and use of a refrigerant mixture of two or more kinds of refrigerants has been studied,
in order to compensate for a disadvantage of a refrigerant with an advantage of another
refrigerant. In the case of a non-azeotropic refrigerant mixture that is a mixture
of refrigerants different in boiling point from each other, it is known that the isotherm
is inclined in a two-phase region on a p-h chart.
[0003] Japanese Patent Laying-Open No. 2018-21721 (PTL 1) discloses a refrigeration cycle apparatus for which a non-azeotropic refrigerant
mixture is used, with a reduced deviation of the temperature distribution for the
entire evaporator.
CITATION LIST
PATENT LITERATURE
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0005] For example, for a low-temperature high-humidity heating operation performed at an
outside air temperature of around 2°C, there is a concern that the heating capacity
may be lowered due to frosting. Therefore, for introducing an air conditioning system,
generally the system is designed such that the maximum capacity that can be exhibited
in a non-frosted state under a low-temperature high-humidity condition is sufficient.
When a frost is formed, the operating frequency of the compressor is increased so
as to increase the amount of circulating refrigerant, thereby avoiding deterioration
of the heating capacity due to frosting.
[0006] Defrosting operation is performed when the compressor frequency reaches the maximum
frequency and the capacity is deteriorated due to frosting. During this operation,
there is a problem that low-temperature refrigerant flows into the load side to lower
the temperature, which impairs comfort of the load side. There is also a problem that
shortening of the total period, i.e., defrosting period, which is the sum of the time
of a single heating operation and a subsequent defrosting time, results in deterioration
of the integrated heating capacity and reduction of the average coefficient of performance
(COP). During heating operation under low-temperature high-humidity condition, the
evaporation temperature of refrigerant is lower than the outside air and frosting
is unavoidable, and therefore, a technique for extending the defrosting period while
suppressing frosting is required.
[0007] An object of the present disclosure is to provide a refrigeration cycle apparatus
that enables extension of the defrosting period while suppressing frosting.
SOLUTION TO PROBLEM
[0008] The present disclosure relates to a refrigeration cycle apparatus. The refrigeration
cycle apparatus comprises: a refrigerant circuit in which a compressor, a condenser,
a first expansion valve, and an evaporator are connected by a refrigerant pipe; and
a non-azeotropic refrigerant that flows through the refrigerant pipe. When the non-azeotropic
refrigerant passes through the evaporator, a temperature difference occurs between
an inlet and an outlet of the evaporator. The evaporator comprises: a group of fins
that are stacked at intervals; and a heat transfer tube that extends through the group
of fins in a stacking direction of the group of fins and allows the non-azeotropic
refrigerant to flow inside the heat transfer tube. The group of fins comprises: a
first fin part to which frost can adhere in a humid environment; and a second fin
part to which no frost adheres to ensure ventilation.
ADVANTAGEOUS EFFECTS OF INVENTION
[0009] The refrigeration cycle apparatus of the present disclosure enables suppression of
frosting and extension of the defrosting period during low-temperature high-humidity
heating operation, to thereby enable improvement in the comfort of the load side.
BRIEF DESCRIPTION OF DRAWINGS
[0010]
Fig. 1 is shows a configuration of a refrigeration cycle apparatus according to Embodiment
1.
Fig. 2 is a p-h diagram of a refrigeration cycle apparatus in a reference example
using an azeotropic refrigerant.
Fig. 3 shows a frost region of an outdoor heat exchanger in a reference example using
an azeotropic refrigerant.
Fig. 4 is a p-h diagram of the refrigeration cycle apparatus of the present embodiment
using a non-azeotropic refrigerant.
Fig. 5 shows a configuration of an outdoor heat exchanger and a frost region of the
present embodiment using a non-azeotropic refrigerant.
Fig. 6 is a front view of the outdoor heat exchanger shown in Fig. 5.
Fig. 7 illustrates a difference in defrosting period between a refrigeration cycle
apparatus in a reference example and the refrigeration cycle apparatus of the present
embodiment.
Fig. 8 shows a configuration of a refrigeration cycle apparatus according to Embodiment
2.
Fig. 9 illustrates arrangement of a temperature sensor 111.
Fig. 10 illustrates how the position where temperature sensor 111 is to be attached
is determined.
Fig. 11 is a flowchart for illustrating a process performed by a controller according
to Embodiment 2.
Fig. 12 is a p-h diagram for illustrating a change in refrigeration cycle according
to Embodiment 2.
Fig. 13 shows a configuration of a refrigeration cycle apparatus according to Embodiment
3.
Fig. 14 is a flowchart for illustrating a process performed by a controller according
to Embodiment 3.
Fig. 15 is a p-h diagram for illustrating a change in refrigeration cycle according
to Embodiment 3.
Fig. 16 shows a configuration of a refrigeration cycle apparatus according to Embodiment
4.
Fig. 17 is a flowchart for illustrating a process performed by a controller according
to Embodiment 4.
Fig. 18 is a p-h diagram for illustrating a change in refrigeration cycle according
to Embodiment 4.
Fig. 19 shows a configuration of a refrigeration cycle apparatus according to Embodiment
5.
Fig. 20 is a flowchart for illustrating a process performed by a controller according
to Embodiment 5.
Fig. 21 is a p-h diagram for illustrating a change in refrigeration cycle according
to Embodiment 5.
Fig. 22 shows a configuration of a refrigeration cycle apparatus according to Embodiment
6.
Fig. 23 is a flowchart for illustrating a process performed by a controller according
to Embodiment 6.
Fig. 24 is a p-h diagram for illustrating a change in refrigeration cycle according
to Embodiment 6.
DESCRIPTION OF EMBODIMENTS
[0011] Embodiments of the present invention are hereinafter described in detail with reference
to the drawings. In the following, a plurality of embodiments are described, and it
is originally intended that characteristics described in connection with respective
embodiments are combined as appropriate. In the drawings, the same or corresponding
parts are denoted by the same reference characters, and a description thereof is not
herein repeated. In the following drawings, the relation in size between components
may be different from the actual relation in size therebetween.
Embodiment 1
[0012] Fig. 1 shows a configuration of a refrigeration cycle apparatus according to Embodiment
1. Refrigeration cycle apparatus 100 includes a refrigerant circuit 80 including a
compressor 10, an indoor heat exchanger 20, an expansion valve LEV1, an outdoor heat
exchanger 40, pipes 51 to 56, and a four-way valve 50. Four-way valve 50 has ports
P1 to P4.
[0013] Pipe 51 is connected between a discharge outlet of compressor 10 and port P1 of four-way
valve 50. Pipe 52 is connected between port P3 of four-way valve 50 and port P1 of
indoor heat exchanger 20. Pipe 53 is connected between indoor heat exchanger 20 and
expansion valve LEV1. Pipe 54 is connected between LEV1 and outdoor heat exchanger
40.
[0014] Pipe 55 is connected between port P2 of outdoor heat exchanger 40 and port P4 of
four-way valve 50. Pipe 56 is connected between a suction inlet of compressor 10 and
port P2 of four-way valve 50.
[0015] Compressor 10 is configured to change the operating frequency based on a control
signal received from a controller (not shown). Specifically, compressor 10 has a drive
motor incorporated therein, the rotational speed of the drive motor is a variable
under inverter control, and changing of the operating frequency causes the rotational
speed of the drive motor to change. The output of compressor 10 is adjusted by changing
the operating frequency of compressor 10. Any of various types of compressors, such
as rotary type, reciprocating type, scroll type, screw type and like may be employed
as compressor 10.
[0016] Four-way valve 50 is controlled to be set in either a cooling operation state or
a heating operation state by a control signal received from a controller (not shown).
In the heating operation state, port P1 communicates with port P3 and port P2 communicates
with port P4, as shown by a solid line. In the cooling operation state, ports P1 and
P4 communicate with each other and ports P2 and P3 communicate with each other, as
shown by a broken line,.
[0017] In the heating operation state, compressor 10 is operated to cause refrigerant to
circulate in the refrigerant circuit in the order of compressor 10, indoor heat exchanger
20, LEV1, outdoor heat exchanger 40, and compressor 10. In the cooling operation state,
compressor 10 is operated to cause refrigerant to circulate in the refrigerant circuit
in the order of compressor 10, outdoor heat exchanger 40, LEV1, indoor heat exchanger
20, and compressor 10.
[0018] Fig. 2 is a p-h line diagram of a refrigeration cycle apparatus in a reference example
using an azeotropic refrigerant. Fig. 3 shows a frost region of an outdoor heat exchanger
in a reference example using an azeotropic refrigerant.
[0019] As shown in Fig. 2, when azeotropic refrigerant is used, there is no temperature
rise in the two-phase region, and therefore, the front surface of outdoor heat exchanger
40 exposed to air sucked into the heat exchanger during low-temperature high-humidity
heating operation is uniformly frosted. In such a case, the frost causes an air passage
to be narrowed, and thus the amount of air blown out of outdoor heat exchanger 40
decreases. It is therefore necessary to frequently perform defrosting before the air
passage is blocked, and thus the defrosting period is short.
[0020] Fig. 4 is a p-h diagram of the refrigeration cycle apparatus of the present embodiment
using a non-azeotropic refrigerant. Fig. 5 shows a configuration of an outdoor heat
exchanger and a frost region of the present embodiment using a non-azeotropic refrigerant.
Fig. 6 is a front view of the outdoor heat exchanger shown in Fig. 5.
[0021] As shown in the p-h diagram of Fig. 4, when the non-azeotropic refrigerant is used,
the isotherm is inclined in the two-phase region, and therefore, the temperature of
a refrigerant outlet of outdoor heat exchanger 40 can be set to 0.5°C during heating
operation even when the temperature of a refrigerant inlet of outdoor heat exchanger
40 is -5°C. This means that the temperature of a part of outdoor heat exchanger 40
can be set to 0°C or more. In the present embodiment, the refrigeration cycle apparatus
is operated so as to have a temperature distribution as shown in Fig. 4 during low-temperature
high-humidity heating operation performed at an outside air temperature of around
2°C.
[0022] As shown in Fig. 5, the refrigerant flows from pipe 54 into outdoor heat exchanger
40, and the refrigerant flows from outdoor heat exchanger 40 into pipe 55. Supposing
that the side from which air is sucked is the front side of outdoor heat exchanger
40, a group of fins L1 in the first row is disposed on the front side and a group
of fins L2 in the second row is disposed on the rear side. A pipe serving as a refrigerant
flow path and made up of six pipes is arranged for each of respective groups of fins
L1 and L2, and these pipes are arranged in parallel and connected together on each
lateral side. The six pipes for fin group L1 are herein referred to as heat transfer
tubes R1 to R6 in order from the top, and the six pipes for fin group L2 are herein
referred to as heat transfer tubes R7 to R12 in order from the bottom.
[0023] As shown in Figs. 5 and 6, refrigerant flows from the right side of heat transfer
tube R1 which is the top one in fin group L1 in the first row, flows from right to
left through heat transfer tube R1, then flows through a connection pipe C12, and
the refrigerant flows from left to right through heat transfer tube R2, thus completing
a single go-and-return passage.
[0024] The refrigerant flowing out from heat transfer tube R2 flows through a connection
pipe C23, and flows from right to left through heat transfer tube R3. Then, the refrigerant
flows through a connection pipe C34, and flows from left to right through heat transfer
tube R4, thus completing a further single go-and-return passage.
[0025] The refrigerant flowing out from heat transfer tube R4 flows through a connection
pipe C45, and flows from right to left through heat transfer tube R5. Then, the refrigerant
flows through a connection pipe C56, and flows from left to right through heat transfer
tube R6, thus completing a further single go-and-return passage.
[0026] Through heat transfer tubes R7 to R12 shown in Fig. 5 as well, refrigerant similarly
flows through three go-and-return passages in the left-right direction in Fig. 6.
Heat transfer tubes R7 to R12, however, differ from heat transfer tubes R1 to R6 in
that the refrigerant flows in order from the lower stage toward the upper stage.
[0027] Specifically, refrigerant flowing out from heat transfer tube R6 flows through a
connection pipe C67, and flows through heat transfer tube R7 from right to left in
Fig. 6. Then, the refrigerant flows through a connection pipe, and flows from left
to right through heat transfer tube R8, thus completing a further single go-and-return
passage.
[0028] The refrigerant flowing out from heat transfer tube R8 flows through a connection
pipe C89, and flows through heat transfer tube R9 from right to left in Fig. 6. Then,
the refrigerant flows through a connection pipe, and flows from left to right through
heat transfer tube R10, thus completing a further single go-and-return passage.
[0029] The refrigerant flowing out from heat transfer tube R10 flows through a connection
pipe C1011, and flows through heat transfer tube R11 from right to left in Fig. 6.
Then, the refrigerant flows through a connection pipe, flows from left to right through
heat transfer tube R12, thus completing a further single go-and-return passage, and
flows to pipe 55.
[0030] When non-azeotropic refrigerant is applied to outdoor heat exchanger 40 having such
a configuration as described above, a frost region A1 where frost can adhere and a
non-frost region A2 where frost does not adhere can be distinguished from each other,
in low-temperature high-humidity heating operation performed at an outside air temperature
of around 2°C. Therefore, even if the volume of blown air decreases in frost region
A1, an adequate volume of blown air can be ensured in non-frost region A2. Thus, the
defrosting period can be extended by causing unbalanced frosting on outdoor heat exchanger
40.
[0031] Fig. 7 illustrates a difference in defrosting period between a reference example
and the refrigeration cycle apparatus of the present embodiment. Fig. 7 shows capacity
J0, compressor frequency F0, and amount of frost G0 of the refrigeration cycle apparatus
in the comparative example shown in Figs. 2 and 3, and capacity 11, compressor frequency
F1, and amount of frost G1 of the refrigeration cycle apparatus in the present embodiment
shown in Figs. 4 to 6.
[0032] As in the comparative example, the amount of frost, if formed on the entire surface,
satisfies G0 > G1 for time t0 to t1. Moreover, in order to ensure a required capacity,
compressor frequency F0 reaches the maximum frequency (upper limit frequency) at time
t1. Therefore, for time t1 to t3, with the increase of amount of frost G0, capacity
J0 decreases earlier and defrosting becomes necessary and started at time t3.
[0033] In contrast, in the present embodiment, amount of frost G1 is smaller than amount
of frost G0, and compressor frequency F1 reaches the upper limit at time t2 later
than time 11. Therefore, capacity J1 has decreased to reach a value at which start
of defrosting is required at time t4 later than time t3. The subsequent defrosting
time is substantially constant in both the comparative example and the present embodiment,
and therefore, the defrosting period of the present embodiment, in which the heating
operation time is longer, is longer than that of the comparative example. Therefore,
the refrigeration cycle apparatus of the present embodiment has the extended defrosting
period, which provides improvement in the comfort for the load, as well as improvement
in the average COP.
Embodiment 2
[0034] Fig. 8 shows a configuration of a refrigeration cycle apparatus according to Embodiment
2. Refrigeration cycle apparatus 110 shown in Fig. 8 further includes a controller
90 and a temperature sensor 111, in addition to the components of refrigeration cycle
apparatus 100 in Fig. 1. The description of the other components is given above in
connection with Fig. 1, and therefore, the description thereof is not herein repeated.
[0035] Controller 90 includes a CPU (Central Processing Unit) 91, a memory 92 (ROM (Read
Only Memory) and RAM (Random Access Memory)), and an input/output buffer (not shown),
for example. CPU 91 deploys and executes, on the RAM for example, a program stored
in the ROM. The program stored in the ROM is a program in which a processing procedure
for controller 90 is specified. Controller 90 controls each device in refrigeration
cycle apparatus 110 in accordance with these programs. This control is not limited
to processing by software, but may also be performed by dedicated hardware (electronic
circuit). In particular, controller 90 is configured to control LEV1 based on an output
of temperature sensor 111.
[0036] Fig. 9 illustrates arrangement of temperature sensor 111. Fig. 9 shows temperature
sensor 111 disposed in outdoor heat exchanger 40 shown in Fig. 5. The description
of outdoor heat exchanger 40 is given above in connection with Figs. 4 to 6, and therefore,
the description thereof is not herein repeated.
[0037] Temperature sensor 111 is disposed at the boundary between a portion intended to
serve as frost region A1 of outdoor heat exchanger 40 and a portion intended to serve
as non-frost region A2 thereof. The refrigeration cycle apparatus is controlled in
such a manner that the temperature detected by temperature sensor 111 is 0°C, so that
frost is formed in frost region A1 and no frost is formed in non-frost region A2 during
low-temperature high-humidity heating operation, so that ventilation in non-frost
region A2 can be ensured and the defrosting period can be extended appropriately.
The boundary between frost region A1 and non-frost region A2 can be determined experimentally
in advance so as to be appropriate for performing low-load heating under a low-temperature
low-humidity condition.
[0038] Fig. 10 illustrates how the position where temperature sensor 111 is to be attached
is determined. As shown by the solid line in Fig. 10, the relation between the area
of frost and the capacity at the maximum frequency under a low-temperature high-humidity
operating condition is determined in advance. The position where temperature sensor
111 is to be attached is determined, such that the area of frost region A1 is equal
to an area of frost S (A1) with which the capacity required during low-temperature
high-humidity operation is exhibited.
[0039] Fig. 11 is a flowchart for illustrating a process performed by the controller according
to Embodiment 2. Controller 90 determines whether or not temperature Tsen detected
by temperature sensor 111 attached to outdoor heat exchanger 40 is lower than frosting
temperature Tfro (step S1). Frosting temperature Tfro may for example be set to 0°C.
[0040] While Tsen < Tfro is not satisfied (NO in S1), controller 90 repeats the process
in step S1. When Tsen < Tfro is satisfied (YES in S1), controller 90 increases the
degree of opening of LEV1 such that Tsen ≥ Tfro is satisfied (S2).
[0041] Fig. 12 is a p-h diagram for illustrating a change in a refrigeration cycle according
to Embodiment 2. When the degree of opening of LEV1 is increased in step S2, the degree
of subcooling at the outlet of the load-side heat exchanger decreases, so that the
refrigeration cycle changes from the state indicated by solid line CY1 to the state
indicated by broken line CY2 on the p-h diagram.
[0042] At this time, until compressor frequency F reaches maximum value Fmax (NO in S3),
controller 90 adjusts compressor frequency F such that heating capacity Q reaches
target heating capacity Qtar (S5), and then performs the process from step S1 again.
[0043] In contrast, when compressor frequency F reaches maximum value Fmax (YES in S3),
the target capacity has not been reached, and controller 90 determines whether or
not defrosting is necessary. Whether or not defrosting is necessary can be determined
based on the time for which heating operation is continued, and/or an allowable ratio
of decrease in capacity during heating (decrease of refrigerant pressure in low-pressure
portion), for example.
[0044] When defrosting is unnecessary (NO in S4), controller 90 performs the process again
from step S1. When defrosting is necessary (YES in S4), controller 90 starts defrosting
operation.
[0045] As described above, the refrigeration cycle apparatus according to Embodiment 2 increases,
during low-temperature high-humidity heating operation, the enthalpy at the refrigerant
inlet of outdoor heat exchanger 40 and increases the temperature using the temperature
gradient of non-azeotropic refrigerant. In this way, only a partial region of outdoor
heat exchanger 40 is frosted, and the defrosting period is extended. In particular,
temperature sensor 111 is disposed at the boundary between the frost region and the
non-frost region of outdoor heat exchanger 40, and therefore, the frost region can
be controlled accurately.
Embodiment 3
[0046] Fig. 13 shows a configuration of a refrigeration cycle apparatus according to Embodiment
3. In refrigeration cycle apparatus 120 shown in Fig. 13, refrigerant circuit 80 further
includes an internal heat exchanger 121 and an expansion valve LEV2, in addition to
the components of refrigeration cycle apparatus 110 in Fig. 8. A part of refrigerant
flowing through pipe 53 is branched into a bypass flow path 61, reduced in pressure
by expansion valve LEV2, and returned to compressor 10. While the refrigerant is returned
to an intermediate pressure port of compressor 10 in Fig. 13, the bypass flow path
may be formed to cause the refrigerant to be returned to a suction inlet of compressor
10. Internal heat exchanger 121 is configured to exchange heat between the refrigerant
flowing out from indoor heat exchanger 20 and the refrigerant after being reduced
in pressure by expansion valve LEV2 in bypass flow path 61. The description of the
other components is given above in connection with Fig. 8, and therefore, the description
thereof is not herein repeated.
[0047] Fig. 14 is a flowchart for illustrating a process performed by a controller according
to Embodiment 3. The process in the flowchart of Fig. 14 includes step S12 instead
of step S2 of the process in the flowchart shown in Fig. 11. The description of the
other features of the process is given above in connection with Fig. 11, and therefore,
step S12 is described here.
[0048] While the process in Fig. 11 increases the degree of opening of LEV1 such that Tsen
≥ Tfro detected by temperature sensor 111 is satisfied (S2), the process in Fig. 14
decreases the degree of opening of LEV2 such that Tsen ≥ Tfro is satisfied (S12),
when Tsen < Tfro is satisfied (YES in S1).
[0049] Fig. 15 is a p-h diagram for illustrating a change in refrigeration cycle according
to Embodiment 3. When the degree of opening of LEV2 is decreased in step S12, the
degree of subcooling at the outlet of internal heat exchanger 121 decreases, so that
the refrigeration cycle changes from the state indicated by solid line CY11 to the
state indicated by broken line CY12 on the p-h diagram.
[0050] In this way, Embodiment 3 changes the degree of opening of LEV2 so as to keep, at
around 0°C, the portion where temperature sensor 111 is disposed, and keep the boundary
as intended between frost region A1 and non-frost region A2.
[0051] When compressor frequency F reaches maximum value Fmax during operation and the target
capacity is not reached, the defrosting operation is started after the determination
of whether or not defrosting is necessary (S4).
[0052] By employing the configuration and control like those in Embodiment 3 as well, only
a partial region of outdoor heat exchanger 40 can be frosted and the defrosting period
can be extended.
Embodiment 4
[0053] Fig. 16 shows a configuration of a refrigeration cycle apparatus according to Embodiment
4. In refrigeration cycle apparatus 130 shown in Fig. 16, refrigerant circuit 80 further
includes a bypass flow path 62 and an expansion valve LEV3, in addition to the components
of refrigeration cycle apparatus 110 in Fig. 8. A part of discharged gas refrigerant
flowing through pipe 51 is branched into bypass flow path 62 at a branch point BP2,
adjusted in flow rate by expansion valve LEV3, and merged into refrigerant in pipe
54 at a merging point MP2. The description of the other components is given above
in connection with Fig. 8, and therefore, the description thereof is not be herein
repeated.
[0054] Fig. 17 is a flowchart for illustrating a process performed by a controller according
to Embodiment 4. The process in the flowchart of Fig. 17 includes step S22 instead
of step S2 of the process in the flowchart shown in Fig. 11. The description of the
other features of the process is given above in connection with Fig. 11, and therefore,
step S22 is described here.
[0055] While the process in Fig. 11 increases the degree of opening of LEV1 such that Tsen
≥ Tfro detected by temperature sensor 111 is satisfied (S2), the process in Fig. 17
increases the degree of opening of LEV3 such that Tsen ≥ Tfro is satisfied (S22),
when Tsen < Tfro is satisfied (YES in S1).
[0056] Fig. 18 is a p-h diagram for illustrating a change in the refrigeration cycle according
to Embodiment 4. In step S22, the degree of opening of LEV3 is increased, which increases
refrigerant in bypass flow path 62 that merges into two-phase refrigerant flowing
into outdoor heat exchanger 40, so that the temperature at the inlet of outdoor heat
exchanger 40 increases. In the refrigeration cycle, as shown by arrows CY21 and CY22
on the p-h diagram shown in Fig. 18, a part of the discharged gas merges into the
refrigerant, and accordingly, the specific enthalpy of the refrigerant at the inlet
of outdoor heat exchanger 40 also increases.
[0057] In this way, Embodiment 4 changes the degree of opening of LEV3 so as to keep, at
around 0°C, the portion where temperature sensor 111 is disposed, and keep the boundary
as intended between frost region A1 and non-frost region A2.
[0058] When compressor frequency F reaches maximum value Fmax during operation and the target
capacity is not reached, the defrosting operation is started after the determination
of whether or not defrosting is necessary (S4).
[0059] By employing the configuration and control like those in Embodiment 4 as well, only
a partial region of outdoor heat exchanger 40 can be frosted and the defrosting period
can be extended.
Embodiment 5
[0060] Fig. 19 shows a configuration of a refrigeration cycle apparatus according to Embodiment
5. In refrigeration cycle apparatus 140 shown in Fig. 19, refrigerant circuit 80 further
includes a heater 141, in addition to the components of refrigeration cycle apparatus
110 in Fig. 8. Heater 141 is capable of heating refrigerant flowing in pipe 54. The
description of the other components is given above in connection with Fig. 8, and
therefore, the description thereof is not be herein repeated.
[0061] Fig. 20 is a flowchart for illustrating a process performed by a controller according
to Embodiment 5. The process in the flowchart of Fig. 20 includes step S32 instead
of step S2 of the process in the flowchart shown in Fig. 11. The description of the
other features of the process is given above in connection with Fig. 11, and therefore,
step S32 is described here.
[0062] While the process in Fig. 11 increases the degree of opening of LEV1 such that Tsen
≥ Tfro detected by temperature sensor 111 is satisfied (S2), the process in Fig. 20
increases the amount of heat generated by heater 141 such that Tsen ≥ Tfro is satisfied
(S32), when Tsen < Tfro is satisfied (YES in S1).
[0063] Fig. 21 is a p-h diagram for illustrating a change in the refrigeration cycle according
to Embodiment 5. In step S32, the amount of heat generated by heater 141 is increased,
which raises the temperature of refrigerant flowing into outdoor heat exchanger 40,
so that the temperature at the inlet of outdoor heat exchanger 40 increases. The refrigeration
cycle changes from CY31 to CY32 on the p-h diagram shown in Fig. 21, and the specific
enthalpy of refrigerant at the inlet of outdoor heat exchanger 40 also increases as
shown by an arrow in the drawing.
[0064] In this way, Embodiment 5 changes the amount of heat generated by heater 141, so
as to keep, at around 0°C, the portion where temperature sensor 111 is disposed, and
keep the boundary as intended between frost region A1 and non-frost region A2.
[0065] When compressor frequency F reaches maximum value Fmax during operation and the target
capacity is not reached, the defrosting operation is started after the determination
of whether or not defrosting is necessary (S4).
[0066] By employing the configuration and control like those in Embodiment 5 as well, only
a partial region of outdoor heat exchanger 40 can be frosted and the defrosting period
can be extended.
Embodiment 6
[0067] Fig. 22 shows a configuration of a refrigeration cycle apparatus according to Embodiment
6. In refrigeration cycle apparatus 150 shown in Fig. 22, refrigerant circuit 80 further
includes, in addition to the components of refrigeration cycle apparatus 110 in Fig.
8, a three-way valve 152 and an internal heat exchanger 151. Three-way valve 152 is
a flow-path switching device that is provided on pipe 51 and switches, in accordance
with a control signal from controller 90, the flow path to convey refrigerant discharged
from compressor 10 directly to port P1 of the four-way valve, or to convey the refrigerant
through internal heat exchanger 151 to port P1. Internal heat exchanger 151 is configured
to exchange heat between refrigerant flowing through pipe 54 and refrigerant conveyed
from compressor 10 through three-way valve 152. The description of the other components
is given above in connection with Fig. 8, and therefore, the description thereof is
not be herein repeated.
[0068] Fig. 23 is a flowchart for illustrating a process performed by a controller according
to Embodiment 6. The process in the flowchart of Fig. 23 includes step S42 instead
of step S2 of the process in the flowchart shown in Fig. 11. The description of the
other features of the process is given above in connection with Fig. 11, and therefore,
step S42 is described here.
[0069] While the process in Fig. 11 increases the degree of opening of LEV1 such that Tsen
≥ Tfro detected by temperature sensor 111 is satisfied (S2), the process in Fig. 20
switches three-way valve 152 such that refrigerant discharged from compressor 10 flows
through internal heat exchanger 151 (S42), when Tsen < Tfro is satisfied (YES in S1).
Accordingly, the state of refrigerant circuit 80 becomes a state where Tsen ≥ Tfro
is satisfied, or becomes closer to such a state.
[0070] Fig. 24 is a p-h diagram for illustrating a change in the refrigeration cycle according
to Embodiment 6. In step S42, three-way valve 152 is switched so as to introduce the
discharged refrigerant into internal heat exchanger 151, and then, the refrigeration
cycle changes from CY41 to CY42 on the p-h diagram shown in Fig. 24. Specifically,
as shown by CY42, refrigerant discharged from compressor 10 releases heat as shown
by arrow CY42A until the refrigerant flows into indoor heat exchanger 20. The refrigerant
having passed through LEV1 receives heat as indicated by arrow CY42B, and therefore,
the temperature of the refrigerant flowing into outdoor heat exchanger 40 increases.
[0071] In this way, Embodiment 6 changes the destination of the discharged refrigerant so
as to cause the refrigerant to flow through internal heat exchanger 151 so as to keep,
at around 0°C, the portion where temperature sensor 111 is disposed, and keep the
boundary as intended between frost region A1 and non-frost region A2.
[0072] When compressor frequency F reaches maximum value Fmax during operation and the target
capacity is not reached, the defrosting operation is started after the determination
of whether or not defrosting is necessary (S4).
[0073] By employing the configuration and control like those in Embodiment 6 as well, only
a partial region of outdoor heat exchanger 40 can be frosted and the defrosting period
can be extended.
(Summary)
[0074] The above embodiments are now summarized again with reference to the drawings.
[0075] The present disclosure relates to refrigeration cycle apparatus 100. Refrigeration
cycle apparatus 100 shown in Fig. 1 includes: refrigerant circuit 80 in which compressor
10, indoor heat exchanger 20 (condenser), first expansion valve LEV1, and outdoor
heat exchanger 40 (evaporator) are connected by refrigerant pipes 51 to 56; and a
non-azeotropic refrigerant that flows through refrigerant pipes 51 to 56. When the
non-azeotropic refrigerant passes through outdoor heat exchanger 40 (evaporator),
a temperature difference occurs between the inlet and the outlet of outdoor heat exchanger
40 (evaporator). As shown in Figs. 5 and 6, outdoor heat exchanger 40 (evaporator)
includes: groups of fins L1, L2 that are stacked at intervals; and heat transfer tubes
R1 to R12 that extend through groups of fins L1, L2 in a stacking direction of groups
of fins L1, L2 and allow the non-azeotropic refrigerant to flow inside the heat transfer
tubes. Groups of fins L1, L2 each include: a first fin part (frost region A1) to which
frost can adhere in a humid environment; and a second fin part (non-frost region A2)
to which no frost adhere to ensure ventilation.
[0076] Preferably, refrigeration cycle apparatus 100 further includes controller 90 configured
to control refrigerant circuit 80. As described above in connection with Figs. 4 and
5, controller 90 is configured to control refrigerant circuit 80 such that the non-azeotropic
refrigerant flowing in the heat transfer tubes (heat transfer tubes R1 to R3) extending
through the first fin part has a temperature of 0°C or lower and the non-azeotropic
refrigerant flowing in the heat transfer tubes (heat transfer tubes R4 to R12) extending
through the second fin part has a temperature of 0°C or higher.
[0077] Preferably, as shown in Figs. 8 and 9, the first fin part is disposed in predetermined
frost region A1 in outdoor heat exchanger 40 (evaporator). The second fin part is
disposed in predetermined non-frost region A2 in outdoor heat exchanger 40 (evaporator).
Refrigeration cycle apparatus 110 further includes temperature sensor 111 disposed
at a boundary between frost region A1 and non-frost region A2 in outdoor heat exchanger
40 (evaporator). Controller 90 is configured to control the degree of opening of first
expansion valve LEV1 based on an output of temperature sensor 111 such that the temperature
of the boundary between frost region A1 and non-frost region A2 is 0°C.
[0078] Preferably, in refrigeration cycle apparatus 120 shown in Fig. 13, refrigerant circuit
80 further includes: bypass flow path 61 that branches at branching point BP1 from
refrigerant pipe 53 connecting indoor heat exchanger 20 (condenser) to first expansion
valve LEV1, to return refrigerant to compressor 10; second expansion valve LEV2 disposed
in bypass flow path 61; and internal heat exchanger 121 configured to exchange heat
between refrigerant flowing from indoor heat exchanger 20 (condenser) toward branching
point BP1 and refrigerant having passed through second expansion valve LEV2.
[0079] Preferably, as shown in Figs. 8 and 9, the first fin part is disposed in predetermined
frost region A1 in outdoor heat exchanger 40 (evaporator). The second fin part is
disposed in predetermined non-frost region A2 in outdoor heat exchanger 40 (evaporator).
Refrigeration cycle apparatus 120 shown in Fig. 13 further includes temperature sensor
111 disposed at a boundary between frost region A1 and non-frost region A2 in outdoor
heat exchanger 40 (evaporator). Controller 90 is configured to control the degree
of opening of second expansion valve LEV2 based on an output of temperature sensor
111, as shown in Fig. 14, such that the temperature of the boundary between frost
region A1 and non-frost region A2 is 0°C.
[0080] Preferably, in refrigeration cycle apparatus 130 shown in Fig. 16, refrigerant circuit
80 further includes: bypass flow path 62 that branches from the refrigerant pipe between
a discharge outlet of compressor 10 and indoor heat exchanger 20 (condenser) and merges
into the refrigerant pipe connecting first expansion valve LEV1 to outdoor heat exchanger
40 (evaporator); and expansion valve LEV3 serving as a flow rate adjustment valve
disposed in bypass flow path 62.
[0081] More preferably, as shown in Figs. 8 and 9, the first fin part is disposed in predetermined
frost region A1 in outdoor heat exchanger 40 (evaporator). The second fin part is
disposed in predetermined non-frost region A2 in outdoor heat exchanger 40 (evaporator).
Refrigeration cycle apparatus 130 shown in Fig. 16 further includes temperature sensor
111 disposed at a boundary between frost region A1 and non-frost region A2 in outdoor
heat exchanger 40 (evaporator). Controller 90 is configured to control the degree
of opening of LEV3 based on an output of temperature sensor 111, as shown in Fig.
17, such that the temperature of the boundary between frost region A1 and non-frost
region A2 is 0°C.
[0082] Preferably, in refrigeration cycle apparatus 140 shown in Fig. 19, refrigerant circuit
80 further includes heater 141 configured to heat refrigerant flowing in refrigerant
pipe 54 connecting first expansion valve LEV1 to outdoor heat exchanger 40 (evaporator).
[0083] More preferably, as shown in Figs. 8 and 9, the first fin part is disposed in predetermined
frost region A1 in outdoor heat exchanger 40 (evaporator). The second fin part is
disposed in predetermined non-frost region A2 in outdoor heat exchanger 40 (evaporator).
Refrigeration cycle apparatus 140 shown in Fig. 19 further includes temperature sensor
111 disposed at a boundary between frost region A1 and non-frost region A2 in outdoor
heat exchanger 40 (evaporator). Controller 90 is configured to control the amount
of heat generated by heater 141 based on an output of temperature sensor 111, as shown
in Fig. 20, such that the temperature of the boundary between frost region A1 and
non-frost region A2 is 0°C.
[0084] Preferably, in refrigeration cycle apparatus 150 shown in Fig. 22, refrigerant pipe
51, which is a part of the refrigerant pipe connecting the discharge outlet of compressor
10 to indoor heat exchanger 20 (condenser), includes a first flow path 51A and a second
flow path 51B disposed in parallel with first flow path 51A. Refrigerant circuit 80
further includes: internal heat exchanger 151 configured to exchange heat between
refrigerant flowing from first expansion valve LEV1 toward outdoor heat exchanger
40 (evaporator), and refrigerant flowing in second flow path 51B; and three-way valve
152 configured to switch to allow refrigerant discharged from compressor 10 to flow
in first flow path 51A or flow in second flow path 51B.
[0085] More preferably, as shown in Figs. 8 and 9, the first fin part is disposed in predetermined
frost region A1 in outdoor heat exchanger 40 (evaporator). The second fin part is
disposed in predetermined non-frost region A2 in outdoor heat exchanger 40 (evaporator).
Refrigeration cycle apparatus 150 shown in Fig. 22 further includes temperature sensor
111 disposed at a boundary between frost region A1 and non-frost region A2 in outdoor
heat exchanger 40 (evaporator). Controller 90 is configured to control three-way valve
152 based on an output of temperature sensor 111 as shown in Fig. 23, such that the
temperature of the boundary between frost region A1 and non-frost region A2 is 0°C.
[0086] Preferably, refrigeration cycle apparatus 100 further includes a four-way valve 50
capable of interchanging the discharge outlet and the suction inlet of compressor
10 to connect the discharge outlet and the suction inlet to refrigerant circuit 80.
Four-way valve 50 is capable of switching to allow refrigerant to flow through refrigerant
circuit 80 in a first direction in which refrigerant flows in the order of compressor
10, indoor heat exchanger 20 (condenser), first expansion valve LEV1, and outdoor
heat exchanger 40 (evaporator), or a second direction in which refrigerant flows in
the order of compressor 10, outdoor heat exchanger 40 (evaporator), first expansion
valve LEV1, and indoor heat exchanger 20 (condenser).
[0087] The above configuration provide unbalanced frosting to enable extension of the defrosting
period, which also provides improvement in comfort for the load. Further, the integrated
heating capacity increases, which improves the average COP.
[0088] It should be construed that the embodiments disclosed herein are given by way of
illustration in all respects, not by way of limitation. It is intended that the scope
of the present disclosure is defined by claims, not by the above description of the
embodiments, and encompasses all modifications equivalent in meaning and scope to
the claims.
REFERENCE SIGNS LIST
[0089] 10 compressor; 20, 40, 121, 151 heat exchanger; 50 four-way valve; 51-56 pipe; 51A
first flow path; 51B second flow path; 61, 62 bypass flow path; 80 refrigerant circuit;
90 controller; 91 CPU; 92 memory; 100, 110, 120, 130, 140, 150 refrigeration cycle
apparatus; 111 temperature sensor; 141 heater; 152 three-way valve; A1 frost region;
A2 non-frost region; BP1, BP2 branching point; C12, C23, C34, C45, C56, C67, C89,
C1011 connection pipe; L1, L2 group of fins; LEV1, LEV2, LEV3 expansion valve; P1,
P2, P3, P4 port; R1-R12 heat transfer tube
1. A refrigeration cycle apparatus comprising:
a refrigerant circuit in which a compressor, a condenser, a first expansion valve,
and an evaporator are connected by a refrigerant pipe; and
a non-azeotropic refrigerant that flows through the refrigerant pipe, wherein
when the non-azeotropic refrigerant passes through the evaporator, a temperature difference
occurs between an inlet and an outlet of the evaporator,
the evaporator comprises:
a group of fins that are stacked at intervals; and
a heat transfer tube that extends through the group of fins in a stacking direction
of the group of fins and allows the non-azeotropic refrigerant to flow inside the
heat transfer tube, and
the group of fins comprises:
a first fin part to which frost can adhere in a humid environment; and
a second fin part to which no frost adheres to ensure ventilation.
2. The refrigeration cycle apparatus according to claim 1, further comprising a controller
configured to control the refrigerant circuit, wherein
the controller is configured to control the refrigerant circuit such that, when air
exchanging heat with the evaporator has a temperature of 0°C or higher, the non-azeotropic
refrigerant flowing in the heat transfer tube extending through the first fin part
has a temperature of 0°C or lower and the non-azeotropic refrigerant flowing in the
heat transfer tube in the second fin part has a temperature of 0°C or higher and lower
than or equal to the temperature of the air.
3. The refrigeration cycle apparatus according to claim 2, wherein
the first fin part is disposed in a predetermined frost region in the evaporator,
the second fin part is disposed in a predetermined non-frost region in the evaporator,
the refrigeration cycle apparatus further comprises a temperature sensor disposed
at a boundary between the frost region and the non-frost region in the evaporator,
and
the controller is configured to control a degree of opening of the first expansion
valve based on an output of the temperature sensor such that a temperature of the
boundary is 0°C.
4. The refrigeration cycle apparatus according to claim 2, wherein
the refrigerant circuit further comprises:
a bypass flow path that branches at a branching point from the refrigerant pipe connecting
the condenser to the first expansion valve, to return refrigerant to the compressor,
a second expansion valve disposed in the bypass flow path, and
an internal heat exchanger configured to exchange heat between refrigerant flowing
from the condenser toward the branching point and refrigerant having passed through
the second expansion valve.
5. The refrigeration cycle apparatus according to claim 4, wherein
the first fin part is disposed in a predetermined frost region in the evaporator,
the second fin part is disposed in a predetermined non-frost region in the evaporator,
the refrigeration cycle apparatus further comprises a temperature sensor disposed
at a boundary between the frost region and the non-frost region in the evaporator,
and
the controller is configured to control a degree of opening of the second expansion
valve based on an output of the temperature sensor such that a temperature of the
boundary is 0°C.
6. The refrigeration cycle apparatus according to claim 2, wherein
the refrigerant circuit further comprises
a bypass flow path that branches from the refrigerant pipe between a discharge outlet
of the compressor and the condenser and merges into the refrigerant pipe between the
first expansion valve and the evaporator, and
a flow rate adjustment valve disposed in the bypass flow path.
7. The refrigeration cycle apparatus according to claim 6, wherein
the first fin part is disposed in a predetermined frost region in the evaporator,
the second fin part is disposed in a predetermined non-frost region in the evaporator,
the refrigeration cycle apparatus further comprises a temperature sensor disposed
at a boundary between the frost region and the non-frost region in the evaporator,
and
the controller is configured to control a degree of opening of the flow rate adjustment
valve based on an output of the temperature sensor such that a temperature of the
boundary is 0°C.
8. The refrigeration cycle apparatus according to claim 2, wherein the refrigerant circuit
further comprises a heater configured to heat refrigerant flowing in the refrigerant
pipe connecting the first expansion valve to the evaporator.
9. The refrigeration cycle apparatus according to claim 8, wherein
the first fin part is disposed in a predetermined frost region in the evaporator,
the second fin part is disposed in a predetermined non-frost region in the evaporator,
the refrigeration cycle apparatus further comprises a temperature sensor disposed
at a boundary between the frost region and the non-frost region in the evaporator,
and
the controller is configured to control an amount of heat generated by the heater
based on an output of the temperature sensor such that a temperature of the boundary
is 0°C.
10. The refrigeration cycle apparatus according to claim 2, wherein
a part of the refrigerant pipe connecting a discharge outlet of the compressor to
the condenser comprises:
a first flow path; and
a second flow path disposed in parallel with the first flow path, and
the refrigerant circuit further comprises:
an internal heat exchanger configured to exchange heat between refrigerant flowing
from the first expansion valve toward the evaporator, and refrigerant flowing in the
second flow path, and
a flow path switching device configured to switch to allow refrigerant discharged
from the compressor to flow in the first flow path or flow in the second flow path.
11. The refrigeration cycle apparatus according to claim 10, wherein
the first fin part is disposed in a predetermined frost region in the evaporator,
the second fin part is disposed in a predetermined non-frost region in the evaporator,
the refrigeration cycle apparatus further comprises a temperature sensor disposed
at a boundary between the frost region and the non-frost region in the evaporator,
and
the controller is configured to control the flow path switching device based on an
output of the temperature sensor such that a temperature of the boundary is 0°C.
12. The refrigeration cycle apparatus according to any one of claims 1 to 11, further
comprising a four-way valve configured to interchange a discharge outlet and a suction
inlet of the compressor to connect the discharge outlet and the suction inlet to the
refrigerant circuit, wherein
the four-way valve is configured to switch to allow refrigerant to flow through the
refrigerant circuit in a first direction or a second direction, the refrigerant flowing
in order of the compressor, the condenser, the first expansion valve, and the evaporator
in the first direction, the refrigerant flowing in order of the compressor, the evaporator,
the first expansion valve, and the condenser in the second direction.