The invention relates to a heat exchanger, in particular to a heat exchanger which may be used in a refrigerated sales furniture and which operates efficiently under low charge conditions.
Refrigerated sales furnitures usually are equipped with a refrigeration circuit, configured for cooling a refrigerated sales space of the refrigerated sales furniture and including in the direction of flow of a circulating refrigerant: a compressor, a heat rejecting heat exchanger (condenser/gas cooler), an expansion device and a heat receiving heat exchanger (evaporator).
In order to reduce the energy consumption of the refrigeration circuit, it would be beneficial to improve the efficiency of the refrigeration circuit, in particular by providing an improved heat receiving heat exchanger, which operates efficiently even under low charge conditions, i.e. when only a relatively small amount of refrigerant is circulating within the refrigeration circuit.
A heat exchanger according to the invention comprises the features of claim 1.
According to exemplary embodiments of the invention, a heat exchanger comprises a gas flow path extending from a gas inlet side to an opposing gas outlet side and at least one heat exchange coil extending through the gas flow path, the at least one heat exchange coil being configured for allowing heat exchange between a fluid flowing through the at least one heat exchange coil and a gas, in particular air, flowing through the gas flow path. The at least one heat exchange coil comprises: a refrigerant inlet portion with an inlet terminal; a refrigerant outlet portion with an outlet terminal; and a heat exchange portion, which is fluidly connected between the refrigerant inlet portion and the refrigerant outlet portion for allowing a fluid refrigerant to flow from the refrigerant inlet portion through the heat exchange portion into the refrigerant outlet portion. The refrigerant inlet portion, the heat exchange portion and the refrigerant outlet portion are arranged within the gas flow path so that gas entering at the gas inlet side will first pass the refrigerant outlet portion, then the refrigerant inlet portion and finally the heat exchange portion of the heat exchange coil before leaving the gas flow path at the gas outlet side. The refrigerant inlet portion is provided by a single tube section. The heat exchange portion and the refrigerant outlet portion are respectively provided by at least two tubes sections connected in parallel, and the volume ratio between the volume of the refrigerant inlet portion and the sum of the volumes of the heat exchange portion and of the refrigerant outlet portion is in a range of 1:3 to 1:7, in particular in a range of 1:4 to 1:6.
A heat exchanger with such a configuration may be operated very efficiently even under low charge conditions, i.e. when only a relatively small amount of refrigerant is circulating within the refrigeration circuit. In consequence, such heat exchanger in particular is very suitable to be employed in a refrigeration circuit using a flammable refrigerant, as in this case the maximum amount of refrigerant circulating within the refrigeration circuit is limited by safety requirements.
In the following, exemplary embodiments of the invention will be described in more detail with reference to the enclosed figures, wherein
The heat exchanger 3 comprises a gas inlet side 4, which is configured for receiving a relatively warm gas flow W, in particular warm return air, and an opposing gas outlet side 6, which is configured for delivering a relatively cold gas flow C, which has been cooled by the heat exchanger 3.
In the configuration shown in
Two outer endplates 31a, 32b and a plurality of fins 30, which are arranged between the two endplates 31a, 32b, extend parallel to direction of the gas flow between the gas inlet side 4 and the gas outlet side 6.
The heat exchanger 3 further comprises a heat exchange coil 8 meandering through the heat exchanger 3. The heat exchange coil 8 comprises, in the direction of flow of the refrigerant, a refrigerant inlet portion 10 with an inlet terminal 12 for receiving the refrigerant, a heat exchange portion 18, which is arranged downstream of the refrigerant inlet portion 10, and a refrigerant outlet portion 14, which is arranged downstream of the heat exchange portion 18. The refrigerant outlet portion 14 has an outlet terminal 16 for discharging the refrigerant after it has passed the heat exchange coil 8.
The refrigerant inlet portion 10, the heat exchange portion 18 and the refrigerant outlet portion 14 are respectively limited by the endplates 31a, 32b and extend basically orthogonally to the fins 30 and the direction of the gas flows W, C. The heat exchange coil 8 further comprises connecting portions 11 extending outside the endplates 31a, 32b basically parallel to the fins 30 and fluidly connecting the refrigerant inlet portion 10, the heat exchange portion 18 and the refrigerant outlet portion 14 with each other.
The heat exchange portion 18 comprises two sub-portions 17, 19 extending parallel to each other between the endplate 31a, 32b. Further connecting portions 11 extending outside the endplates 31a, 32b basically parallel to the fins 30 fluidly connect the sub-portions 17, 19 with each other. The number of two sub-portions 17, 19 shown in
The refrigerant inlet portion 10, the heat exchange portion 18 and the refrigerant outlet portion 14 are arranged along the flow path of the gas so that gas entering at the gas inlet side 4 first passes the refrigerant outlet portion 14 (overheating portion) for overheating the refrigerant before it leaves the heat exchange coil 8 via the outlet terminal 16. After having passed the refrigerant outlet portion 14, the gas will pass the refrigerant inlet portion 10 and finally the heat exchange portion 18 of the heat exchange coil 8 before leaving the gas flow path of the heat exchanger 3 at the gas outlet side 6.
The refrigerant inlet portion 10 is formed by a single inlet tube section 9.
The heat exchange portion 18 is provided by two heat exchange tube sections 20, 22 fluidly connected in parallel and extending basically parallel to each other. A refrigerant inlet side of each of the two heat exchange tube sections 20, 22 is fluidly connected with the inlet tube section 9.
On a refrigerant outlet side each of the two heat exchange tube sections 20, 22 turns into a corresponding outlet tube section 24, 26, respectively extending through the gas inlet side 4 of the heat exchanger 3.
The outlet tube sections 24, 26 merge downstream of the heat exchanger 3 providing a common outlet terminal 16.
The two tube sections 20, 22, 24, 26 pairwise extending basically parallel to each other may be arranged next to each other in the direction of the gas flow, as shown in
A volume ratio R between the volume Vin of the refrigerant inlet portion 10 formed by the inlet tube section 9 and the volume Vex of the heat exchange portion 18, which is provided by the combined volumes of the heat exchange tube sections 20, 22 (Vex = V20 + V22), plus the volume Vout of the refrigerant outlet portion 14, which is provided by the combined volumes of the outlet tube sections 24, 26 (Vout = V24 + V26), in particular is between 1:3 and 1:7, i.e. R = Vin : (Vex + Vout).
It is noted that the volume of the connecting portions 11 is not considered when calculating the volume ratio R.
A heat exchanger 2 with such a design has been found to allow for a very efficient transfer of heat from the gas passing the heat exchanger 2 with the refrigerant flowing through the heat exchange coil 8, in particular under low charge conditions, i.e. when only a comparatively small amount of refrigerant is circulating within the refrigeration circuit.
As only a single inlet tube section 9 is used and therefore the cross section of the inlet tube section 9 is considerably smaller than the combined cross section of the heat exchange tube sections 20, 22, the flowing speed of the refrigerant within the inlet tube 9 section is relatively high. As a result, a comparable large amount of refrigerant flowing through the inlet tube section 9 is turned into gas by the warm air flow W flowing into the heat exchanger 3. Generating a large amount of gas in the refrigerant inlet portion 10 is beneficial for enhancing the efficiency of the heat exchanger 3 in particular when the heat exchanger is operated with a low refrigerant charge.
Further heat exchange portions 18, which are not depicted in the Figure, may be present. Such further heat exchange portions 18 may be part of additional meandering heat exchange coils 8 of one or more further heat exchangers.
Two heat exchange tube sections 20, 22 and two outlet tube sections 24, 26 are depicted in
The heat exchangers 3 according to the first exemplary embodiment also may be modified to comprise more than one heat exchange coil 8.
For the clarity of the illustration, the two heat exchange coils 8a, 8b shown in
The inlet terminal 12a and the outlet terminal 16a of a first heat exchange coil 8a are arranged on a first (left) lateral side 7a of the heat exchanger 5, and the inlet terminal 12b and the outlet terminal 16b of a second heat exchange coil 8b are arranged on an opposite second (right) lateral side 7b of the heat exchanger 5. As a result, the refrigerant is flowing in a counterflow arrangement through the first and second heat exchange coils 8a, 8b, in particular in the refrigerant inlet portions 10a, 10b and the refrigerant outlet portions 14a, 14b. This results in a nearly homogeneous distribution of the heat within the heat exchanger 5 and in particular avoids that, in operation, one lateral side 7a, 7b of the heat exchanger 5 becomes considerably warmer than the other lateral side 7b, 7a. As a result, the heat transfer within the heat exchanger 5 is enhanced and the efficiency of the heat exchanger 5 is optimized.
Although only two heat exchange coils 8a, 8b are shown in
Additional heat exchange coils or heat exchange portions 18 of heat exchange coils 8a, 8b in particular may be arranged above or below the sectional planes represented by
In case an even number of heat exchange coils 8a, 8b is provided, it is beneficial to respectively provide the same number of inlet terminals 12a, 12b and outlet terminals 16a, 16b on both sides of the heat exchanger 5 for generating a nearly homogeneous distribution of the heat between the first and second lateral sides 7a, 7b of the heat exchanger 5, as it has been described before.
In case an odd number of heat exchange coils 8a, 8b is provided, the difference between the number of inlet terminals 12a, 12b and the difference between the numbers of outlet terminals 16a, 16b on both sides of the heat exchanger 5 may be chosen to be one in order to cause a distribution of the heat between the first and second lateral sides 7a, 7b of the heat exchanger 5 which is as homogeneous as possible.
The heat exchange tube sections 20, 22 are arranged in a rectangular matrix arrangement comprising columns extending perpendicular to the direction of the gas flow F, i.e. vertically in
The distance B of the heat exchange tube sections 20, 22 along the (vertical) columns is different from the distance A of the heat exchange tube sections 20, 22 along the (horizontal) rows. The ratio of the distance A along the rows with respect to the distance B along the columns may be between 0.7 and 1.0, in particular between 0.8 and 0.9.
The distance A of the heat exchange tube sections 20, 22 along the rows may be between 35 mm and 45 mm, in particular between 38 mm and 42 mm and the distance B of the heat exchange tube sections 20, 22 along the columns is between 45 mm and 55 mm, in particular between 48 mm and 52 mm.
The diameter D of the tube sections 20, 22 in particular may be in the range of 7 mm to 9.52 mm. In particular, the inner diameter D of the tube sections 20, 22 may be 7 mm and the outer diameter of the tube sections 20, 22 may be 9.52 mm.
When each of the fins 30 is (mentally) divided into a plurality of equally sized fin areas X, and each fin area X is assigned to one of the tube sections 20, 22, the ratio of the circumference πD of the tube sections 20, 22 with respect to the size of the fin areas X may be in the range of 1.0 mm/cm2 to 2.5 mm/cm2, in particular between 1.5 mm/cm2 and 2.0 mm/cm2, for allowing an efficient transfer of heat between the gas flowing through the heat exchanger and the refrigerant flowing through the heat exchange coil 8.
A number of optional features are set out in the following. These features may be realized in particular embodiments, alone or in combination with any of the other features.
In an embodiment the refrigerant inlet portion, the heat exchange portion and the refrigerant outlet portion respectively extend between opposing endplates. The endplates in particular support the refrigerant inlet portion, the heat exchange portion and the refrigerant outlet portion for providing a rigid structure of the heat exchanger. The endplates further define the volumes of the refrigerant inlet portion, the heat exchange portion and the refrigerant outlet portion which are to be considered when calculating the volume ratio.
In an embodiment the heat exchange portion comprises at least two sub-portions extending parallel to each other and being fluidly connected by connecting portions. Providing a heat exchange portion comprising plurality of sub-portions allows to increase the capacity of the heat exchanger.
In an embodiment the heat exchanger comprises at least two heat exchange coils extending through the gas flow path. Providing two or more heat exchange coils increases the capacity of the heat exchanger.
In an embodiment the heat exchanger comprises a first group of heat exchange coils and a second group of heat exchange coils. The inlet terminals of the first group of heat exchange coils are arranged on a first lateral side of the heat exchanger and the inlet terminals of the second group of heat exchange coils are arranged on an opposing second lateral side of the heat exchanger. In consequence, the direction of refrigerant flow through the refrigerant inlet portions of the first group of heat exchange coils is opposite to the direction of refrigerant flow through the refrigerant inlet portions of the second group of heat exchange coils. As a result, the heat transfer is distributed more homogeneously over the whole width of the heat exchanger and, in consequence, the efficiency of the heat transfer is enhanced.
In an embodiment the outlet terminals of the first group of heat exchange coils are arranged on a first lateral side of the heat exchanger, and the outlet terminals of the second group of heat exchange coils are arranged on an opposing second lateral side of the heat exchanger. In consequence, the direction of refrigerant flow through the refrigerant outlet portions of the first group of heat exchange coils is opposite to the direction of refrigerant flow through the refrigerant outlet portions of the second group of heat exchange coils. As a result, the heat transfer is distributed more homogeneously over the whole width of the heat exchanger and, in consequence, the efficiency of the heat transfer and the superheating of the refrigerant within the refrigerant outlet portions are enhanced.
In an embodiment the inner diameter of the tube sections is more than 6 mm, in particular at least 7 mm. In an embodiment the outer diameter of the tube sections is less than 10 mm, in particular not more than 9.52 mm. In an embodiment the inner diameter of the tube sections is 7 mm, the outer diameter of the tube sections is 9.52 mm. Tube sections having these diameters have been found as allowing an efficient heat transfer.
In an embodiment the heat exchange tube sections are arranged in columns and rows forming a rectangular matrix, wherein the distance of the heat exchange tube sections along the columns differs from the distance of the heat exchange tube sections along the rows. The ratio of the distance of the heat exchange tube sections along the rows with respect to the distance of the heat exchange tube sections along the columns in particular may be between 0.7 and 1.0, in particular between 0.8 and 0.9. Such a configuration has been found as allowing an efficient heat transfer between gas flowing through the heat exchanger and fluid refrigerant flowing through the tube sections.
In an embodiment the distance of the tube sections in the direction parallel to the gas flow is smaller than the distance of the tube sections in a direction orthogonal to the gas flow. Such a configuration has been found as allowing an efficient heat transfer between gas flowing through the heat exchanger and refrigerant flowing through the tube sections.
In an embodiment the distance of the heat exchange tube sections along the rows is between 35 mm and 45 mm, and/or the distance of the heat exchange tube sections along the columns is between 45 mm and 55 mm.
In an embodiment the heat exchanger further comprises a plurality of fins extending basically parallel to the the gas flow path and/or orthogonally to the inlet tube sections, to the outlet tube sections and/or to the heat exchange tube sections. The fins direct the flow of gas flowing through the heat exchanger and enhance the transfer of heat between the flow of gas and the refrigerant flowing through the inlet tube sections, through the outlet tube sections and through the heat exchange tube sections.
In an embodiment the ratio of the circumference of the tube sections with respect to a fin area, which is assigned to each tube section by mentally dividing the area of each fin into a plurality of equally sized fin areas, each of the fin areas being centered at one of the tube sections, is in the range of 1.0 mm/cm2 to 2.5 mm/cm2, in particular between 1.5 mm/cm2 and 2.5 mm/cm2. Such a configuration has been found as allowing an efficient transfer of heat between gas flowing through the heat exchanger and refrigerant flowing through the tube sections.
In an embodiment the heat exchanger is configured for flowing R290 through the at least one heat exchange coil. Using R290 as a refrigerant allows a very efficient and economic operation of the refrigeration circuit.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition many modifications may be made to adopt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention include all embodiments falling within the scope of the claims.
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.