GB2376513A

GB2376513A - Heat transfer element

Info

Publication number: GB2376513A
Application number: GB0114578A
Authority: GB
Inventors: Rd Niels Lieng
Original assignee: BUNDY AS
Current assignee: BUNDY AS
Priority date: 2001-06-15
Filing date: 2001-06-15
Publication date: 2002-12-18
Also published as: WO2002103258A2; GB0114578D0; AU2002321715A1; WO2002103258A3

Abstract

A heat transfer element (601) for use within a refrigeration system comprising heat transfer tubing (602) comprising an inlet portion (603) for receiving a refrigerant, a heat transfer portion (604) comprising an oblong cross-section and an outlet portion (605). In the preferred embodiment the heat transfer tubing (603) is fabricated from an aluminium alloy, and the inlet portion (603) and the outlet portion (604) comprise a connection member fabricated from copper. In the preferred embodiment the heat transfer element (601) comprises a serpentine shape (606). In alternative embodiments the heat transfer tubing (603) is fabricated from aluminium, steel or copper. Associated methods of manufacturing a heat transfer element (601) are disclosed.

Description

Heat Transfer Element Field of the Invention The present invention relates to a heat transfer element for use within a refrigeration system.

Introduction Refrigeration systems comprising one or more heat transfer elements are known. Refrigeration systems operate to maintain a temperature below the temperature of the surroundings within a refrigeration cavity in which, for example, food may be preserved. Such a refrigeration system may be found in a domestic refrigeration unit or a commercial refrigeration unit, for example, an ice cream freezer or a bottle cooler. In such a refrigeration unit, heat is absorbed from the refrigeration cavity and rejected to the surrounding environment.

Different refrigeration systems such as a vapour-compression refrigeration system and a gas refrigeration system are known. These refrigeration systems comprise tubing and heat transfer elements through which a working fluid, known as a refrigerant, may flow. The heat transfer elements within these refrigeration systems function to transfer heat to or from the refrigerant as the refrigerant flows around the refrigeration system which operates a refrigeration cycle. When designing a refrigeration system, the stages of the refrigeration cycle are considered alone and with respect to the complete refrigeration system in order to maximise the performance of the refrigeration unit into which the refrigeration system will be integrated.

According to performance, efficiency and design specifications, heat transfer elements may be mounted inside the refrigeration cavity or within the walls defining the refrigeration cavity within a refrigeration unit. For example, a refrigeration unit may contain a visible heat transfer element contained within the refrigeration cavity to maximise performance and efficiency.

Alternatively, for aesthetic reasons, a potential customer may prefer a refrigeration unit comprising a refrigeration system that is hidden from view.

Brief Summary of the Invention According to a first aspect of the present invention, there is provided a heat transfer element for a refrigeration system comprising heat transfer tubing comprising an inlet portion for receiving a refrigerant, a heat transfer portion comprising an oblong cross-section and an outlet portion, wherein said heat transfer tubing is aluminium, aluminium alloy, copper or steel.

Oblong is herein defined as a geometrical shape being longer than broad.

The preferred oblong cross-section is a geometrical shape being longer than broad, having substantially parallel long plane sides and rounded ends.

Brief Description of the Several Views of the Drawings According to a second aspect of the present invention the inlet portion and the outlet portion of the heat transfer element comprise a copper connection member.

The invention will now be described by way of example only, with reference to the accompanying drawings in which; Figure 1 shows a schematic of a typical vapour-compression refrigeration system ;

Figure 2 shows a refrigeration unit; Figure 3 illustrates the prior art wrap-around construction of a heat transfer element; Figure 4 shows tubing typically used in the wrap-around construction of a prior art heat transfer element ; Figure 5 shows in plan cross-section the prior art wrap-around construction of a heat transfer element ; Figure 6 shows a heat transfer element according to the present invention; Figure 7 shows a heat transfer element according to the present invention installed within a refrigeration unit; Figure 8 shows heat transfer tubing according to the present invention; Figure 9 shows a plan cross-section and a side cross-section of heat transfer tubing according to the present invention; Figure 10 shows a flow chart comprising the steps of manufacturing a heat transfer element according to the preferred embodiment of the present invention; Figure 11 illustrates the inlet portion and the outlet portion of a heat transfer element according to the preferred embodiment of the present invention ; Figure 12 shows a flow chart comprising the steps of installing a heat transfer element according to the present invention into the refrigeration cavity walling of a refrigeration cavity within a refrigeration unit.

Best Mode for Carrying Out the Invention A preferred embodiment and method according to the present invention will now be described by way of example only with reference to the

accompanying drawings identified above.

Figure 1 Figure 1 shows a schematic of a typical vapour-compression refrigeration system 101. In practice, this system comprises tubing through which refrigerant may flow.

Refrigerant enters compressor 102 as saturated vapour flowing in the direction of arrow 103 towards condenser 104. As the refrigerant flows through the compressor 102, it is compressed to the pressure of the condenser 104. During this compression, the temperature of the refrigerant increases above the temperature of the surrounding environment. The refrigerant enters condenser 104 as superheated vapour. In the condenser 104, the refrigerant condenses to a saturated liquid. During this process, the refrigerant rejects heat to the surrounding environment. On leaving condenser 104, the refrigerant still has a temperature above the temperature of the surrounding environment, and flows in the direction of arrow 105 towards capillary tube 106. As the refrigerant flows through capillary tube 106 in the direction of arrow 107, the refrigerant is throttled to the pressure of evaporator 108. During this process, the temperature of the refrigerant decreases below the temperature of the refrigeration cavity, entering evaporator 108 as a saturated mixture. The refrigerant absorbs heat from within the refrigeration cavity and evaporates to form a saturated vapour before flowing from the evaporator 108 in the direction of arrow 109 to

compressor 102. The refrigerant re-enters compressor 102 and the refrigeration cycle is completed.

Practical refrigeration systems differ from thermodynamically ideal refrigeration systems in respect of irreversibilities. In summary, an irreversibility represents energy available within a stage of a system, that is not converted into work. Irreversibilities have a degrading effect of the performance of a refrigeration system.

A source of irreversibility in vapour-compression refrigeration cycle 101 results from pressure differentials caused by fluid friction. A second source of irreversibility arises from undesired heat transfer to or from the surrounding environment. Heat transfer between surfaces is proportional to the contact area between the surfaces.

An object of the present invention is to provide a heat transfer element wherein the associated irreversibilities are minimised.

As the efficiency of practical refrigeration systems deviates from that of the ideal refrigeration cycle, refrigeration systems contain a pre-determined volume of refrigerant that will provide for a minimum performance specification to be achieved in individual refrigeration units.

Figure 2 A refrigeration unit 201 in which vapour-compression refrigeration system 101 may operate is shown in Figure 2. In this example, refrigeration unit 201 is a chest freezer comprising a refrigeration cavity 202 defined by refrigeration cavity walling 203.

Refrigeration cavity walling 203 comprises inner liner 301 and outer liner 302 as shown in Figure 3. As is known in industry, refrigeration unit 201

may comprise a refrigeration system incorporated within refrigeration cavity walling 203. This arrangement is known as a hot wall skin refrigeration system, incorporating heat transfer elements constructed using a technology known as wrap-around technology.

Evaporator 303 comprises evaporator tubing 304 having a coiled structure and is shown in position around inner liner 301. Similarly, condenser 305 comprises condenser tubing 306 having a coiled structure and is shown in position around the inner of outer liner 302. Thermal paste 307 functions to increase the desired heat transfer between evaporator 303 and inner liner 301, and between condenser 306 and outer liner 302.

Insulation 308 functions to minimise the undesired heat transfer between evaporator 304 and condenser 305.

Figure 4 Figure 4 shows tubing typically used in the construction of heat transfer elements by the described prior art wrap-around construction, for example, evaporator tubing 304 or condenser tubing 305.

In prior art refrigeration systems the diameter of the tubing is typically in the region of 8mm for the construction of an evaporator and typically in the range 4.7 to 6.4mm for the construction of a condenser. The diameter of the tubing differs according to the difference in the volume of the refrigerant in a vapour phase compared to the volume of refrigerant in a liquid phase, wherein the former is greater.

Tubing 401, shown in contact with liner 402, comprises a circular cross-section having a cross-sectional area a. With this arrangement, heat can be directly transferred between the contacting surfaces through a single

point contact only.

D-shaped tubing 403, typically made by a rolling process, comprises flat surface 404 and rounded surface 405. By positioning D-shaped tubing 403 such that the flat surface 404 faces the plane surface of liner 402, an increased area of contact may be achieved. However, D-shaped tubing 403 may only be bent in a direction perpendicular to flat surface 404, and therefore the scope of applications for which this type of tubing is suitable is limited.

Tubing 401 and D-shaped tubing 403 are typically fabricated from steel or copper. In comparison, greater heat transfer can be achieved using copper. However, copper is generally more expensive than steel and hence fabricating refrigeration components from copper may increase the cost of the refrigeration system, which may correspondingly increase the cost of the refrigeration unit comprising the refrigeration system.

Figure 5 A plan view of refrigeration unit 201 comprising a prior art hot wall skin refrigeration system is shown in Figure 5.

The integration of heat transfer elements constructed by the described prior art wrap-around construction into a prior art hot wall skin refrigeration system is problematic and awkward. A particular problem occurs during the application of thermal paste and tube fixings as it is necessary for the installation engineer to reach into refrigeration cavity walling 203. In doing this, an installation engineer is at risk of physical strain. Physical strain may be experienced at or after the time of installation and may be accumulative.

In particular, back strain is a problem.

The present invention provides a heat transfer element and an associated method of installation, wherein the installation process is facilitated by the features of the heat transfer element. An object of the present invention is to address the problem of physical strain experienced by installation engineers through installing a heat transfer element within a refrigeration unit.

Figure 6 Figure 6 illustrates a heat transfer element 601 according to the present invention. Heat transfer element 601 comprises heat transfer tubing 602 comprising an inlet portion 603 for receiving a refrigerant, a heat transfer portion 604 and an outlet portion 605. According to the preferred embodiment of the present invention, heat transfer portion 604 comprises an oblong cross-section. Oblong is herein defined as a geometrical shape being longer than broad, having substantially parallel long sides and rounded ends.

According to the preferred embodiment, heat transfer 601 comprises at least one substantially planar face and further comprises a serpentine shape 606.

Alternatively, heat transfer element 601 may comprise any desired shape.

An object of the present invention is to ease the installation of heat transfer element 601 into a refrigeration unit such as refrigeration unit 201.

According to the preferred embodiment of the present invention, heat transfer element 601 comprises a serpentine shape 606 in two dimensions.

The size and the weight distribution of the preferred embodiment facilitates the manoeuvrability of heat transfer element 601. Therefore, an installation engineer may experience less physical strain installing heat transfer element 601 than when installing a heat transfer element constructed by the

described prior art wrap-around construction.

In comparison with the described prior art wrap-around construction, heat transfer element 601 has smaller dimensions which corresponds to a lower mass. Thus, the risk of physical strain that may be experienced by the installation engineer when installing the heat transfer element 601 is minimised by these features. This is particularly advantageous when heat transfer element 601 is to be installed by the preferred method of installation, wherein heat transfer element 601 is lowered into position within refrigeration cavity walling 203 from a height above refrigeration unit 201.

According to the preferred embodiment of the present invention, heat transfer element 601 is configured to be installed on a single wall within refrigeration cavity walling 203. Alternatively, heat transfer element 601 may be sited in any desired location.

In the preferred embodiment, heat transfer element 601 comprises a serpentine shape 606 having inlet portion 603 positioned adjacent to outlet portion 605 such that when the heat transfer element 601 is lowered into the refrigeration cavity walling 203, the inlet portion 603 and the outlet portion 605 are positioned towards the upper of the refrigeration cavity walling 203 and are consequently easily accessible by the installation engineer. An object of this feature is to reduce the risk of physical strain that may be experienced by an installation engineer during the application of tube fixings to inlet portion 603 and outlet portion 605. Preferably, inlet portion 603 and outlet portion 605 of heat transfer element 601 are positioned vertically when installed, to minimise awkward movements during the application of tube fixings.

In addition, the structure of the preferred embodiment of the present invention provides for an increased visibility of heat transfer element 601 during installation. This feature facilitates the alignment of heat transfer element 601 with other refrigeration components. Furthermore, according to the preferred embodiment, the alignment process is facilitated by inlet portion 603 being positioned adjacent, preferably parallel to outlet portion 605, such that alignment of one will in effect pre-align the other. These features provide for a less complex and less time consuming method of installation of heat transfer element 601.

An object of the present invention is to provide a heat transfer element 601 configured to be easily integrated into existing refrigeration system designs.

Figure 7 Figure 7 shows a plan view of heat transfer element 601 installed on a single wall within refrigeration cavity walling 203 within refrigeration unit 201.

With this arrangement, heat transfer is installed as a condenser.

From this figure it can be observed that heat transfer element 601 occupies less volume within refrigeration cavity walling 203 than evaporator 304 which has been constructed by the described prior art wrap-around construction method.

The structure of the preferred embodiment of the present invention provides for a width b of refrigeration cavity walling 203 comprising the prior art heat transfer element only, which is less than width c of refrigeration cavity walling 203 comprising both heat transfer elements. An advantage provided by the preferred embodiment of the present invention in comparison with the

prior art wrap-around construction, is that for a refrigeration unit 201 comprising outer liner 302 having pre-existing dimensions, the volume of refrigeration cavity 202 can be increased. Thus, the present invention effectively utilises the internal volume of refrigeration unit 201.

However, in comparison with the described prior art wrap-around construction, the preferred embodiment of the present invention provides a shorter available length of tubing through which refrigerant may flow, and through which heat may be transferred to or from the refrigerant. A reduction in the length of tubing corresponds to a reduction in the amount of thermal paste 307 that will be applied between the tubing and the adjacent surface between which heat is to be transferred. This provides a financial advantage, in particular because thermal paste 307 is expensive.

As previously stated, an object of the present invention is to provide a heat transfer element 601 configured to be easily integrated into existing refrigeration system designs. Therefore, it is a further object of the present invention to provide a heat transfer element 601 that provides a performance efficiency in the magnitude of that provided by heat transfer elements constructed by the described prior art wrap-around construction.

The preferred embodiment comprises a serpentine shape 606 that increases the available length of tubing, and the effective length along which heat may be transferred to or from the refrigerant, within a heat transfer element 601 having pre-determined dimensions. According to the present invention, heat transfer element 601 may comprise a serpentine shape 606 in two or three dimensions.

As previously stated, undesired heat transfer to and from the surroundings is a source of irreversibility within a refrigeration system.

Undesired heat transfer decreases the overall efficiency of a refrigeration system, and may increase the operating and maintenance costs of a refrigeration system and associated refrigeration unit.

In a refrigeration system such as vapour-compression refrigeration system 101 operating under normal conditions, a stabilised amount of heat is absorbed and released by the refrigerant.

One way in which the present invention provides for a decrease in undesirable heat transfer is by providing for an increase in desired heat transfer. To increase the performance of the preferred embodiment, the present invention provides for an increase in heat transfer associated with heat transfer tubing 602 forming heat transfer portion 604 within heat transfer element 601.

Figure 8 Figure 8 shows a section of heat transfer tubing 602 from heat transfer portion 604 of heat transfer element 601 according to the preferred embodiment, wherein heat transfer element 601 is installed as a condenser within vapour-compression system 101. Refrigerant 801 is shown to have condensed to a liquid phase. Refrigerant 801 may be isobutane or propane, and is preferably R134a, more preferably R600a or any suitable refrigerant, for example, R404 or R290.

According to the preferred embodiment of the present invention, heat transfer tubing 602 forming heat transfer portion 604 comprises an oblong cross-section having a cross-sectional area d, a perimeteral area p and a wall thickness w.

As previously indicated, heat transfer is proportional to the contact area between the heat releasing surface and the heat receiving surface. The oblong cross-section comprises substantially parallel long sides providing an increase in contact area between heat transfer element 601 and liner 802, and thus providing for an increase in heat transfer. This feature provides for a reduction in the amount of thermal paste 307 that will be applied between the tubing and the adjacent surface between which heat is to be transferred. More preferably, the application of thermal paste 307 may be eliminated by the present invention.

As previously stated, an object of the present invention is to provide a heat transfer element 601 configured to be easily integrated into existing refrigeration system designs.

According to the preferred embodiment of the present invention, cross-sectional area d is equal to cross-sectional area a provided by prior art tubing 701 comprising a circular cross-section. This is advantageous in that heat transfer tubing 602 can accommodate a similar volumetric flow rate of refrigerant 801 received by equivalent heat transfer tubing within existing refrigeration systems. Furthermore, the present invention provides for an improved utilisation of material resources, thus providing a financial and logistical advantage.

When flowing through heat transfer tubing 602, refrigerant 801 condenses on the inner surface of heat transfer tubing 602 An oblong cross-section having a cross-sectional area a advantageously provides an increase in internal surface area in comparison with a circular cross-section also having a cross-sectional area a. This increase in the internal surface area of heat transfer tubing 602 provides for

an increase in the rate at which refrigerant 801 condenses.

As refrigerant 801 changes phase from a vapour phase to a liquid phase, the velocity of refrigerant 801 decreases, resulting in a pressure loss.

As previously stated, pressure differentials, resulting from fluid friction, are a source of irreversibility within a refrigeration system. It is an object of the present invention to minimise pressure loss within heat transfer element 601.

An increase in the rate of condensation of refrigerant 801 within heat transfer element 601 provides for a decrease in the pressure loss between inlet portion 603 and outlet portion 605. This is advantageous in that this decrease in pressure loss provides for an increase in the overall performance of the vapour-compression refrigeration system 101.

Furthermore, according to the geometry of the oblong cross-section and the preferred orientation of the tubing against liner 401, wherein a substantially long side of the oblong cross-section is adjacent to liner 401, refrigerant 801 flows in closer proximity to liner 401. This feature facilitates the rejection of heat into the surrounding environment as refrigerant 801 condenses, and thus further provides for an increase in condensation rate, and for a reduction in pressure loss.

Figure 9 Figure 9 shows in plan cross-section 901 and side cross-section 902 heat transfer tubing 602 adjoining inlet portion 603 of heat transfer element 601 according to the preferred embodiment. Heat transfer tubing 602 comprises an oblong cross-section and a height h.

Height h is one of a plurality of variables that determine the performance of heat transfer element 601 and consequently, the performance of the overall refrigeration system. In the preferred embodiment, heat transfer tubing 602 has a height h of 3.5 mm and has an outer width measurement of 10.6 mm comprising a flat surface of 7.1 mm.

A second variable determining the performance of heat transfer element 601 and consequently, the performance of the overall refrigeration system, is the radius of curvature of heat transfer tubing 602. Preferably, the radius of curvature is in the range of twenty to fifty millimetres. In the preferred embodiment of the present invention, the radius of curvature is twenty-five millimetres.

Heat transfer tubing 602 is preferably fabricated from aluminium, more preferably aluminium alloy or may be fabricated from copper or steel. Aluminium provides heat transfer characteristics in the range defined by the values provided by steel and copper, and is more easily formed, thus facilitating the manufacture of heat transfer element 601. In addition, aluminium is advantageously resistant to corrosion. The preferred aluminium alloy is Al 3103.

Aluminium has a lower density in comparison with steel and copper.

Correspondingly, the mass of the preferred embodiment of the present invention is reduced when heat transfer tubing 602 is fabricated from aluminium or aluminium alloy. This feature provides for a reduction in the risk of physical strain that may be experienced by an installation engineer through the installation of heat transfer element 601 into a refrigeration unit such a refrigeration unit 201.

To interface heat transfer element 601 and the connecting tubing of the refrigeration system into which heat transfer element 601 will be installed, inlet portion 603 and/or outlet portion 605 may comprise a connection member. Inlet portion 603, outlet portion 605 and any connection members may comprise a plurality of different cross-sections and/or wall thicknesses, in order to accommodate refrigeration components having different physical dimensions, and furthermore may be fabricated from any material or combination of materials.

Connection members may be in connection with the outer circumference, the inner circumference or the perimeteral area p of the crosssection of the inlet portion 603 or the outlet portion 605 comprising the

connection member.

Figure 10 Figure 10 shows the preferred method of manufacturing heat transfer element 601 according to the preferred embodiment of the present invention.

Advantageously, a heat transfer element 601 suitable for use as a condenser, or alternatively, a heat transfer element 601 suitable for use as an evaporator may be manufactured by this method.

At step 1001, heat transfer tubing 602, fabricated from aluminium, or more preferably aluminium alloy, comprising a circular cross-section is received in the form of a coil. The diameter of heat transfer tubing 602 received will correlate to the function of the manufactured heat transfer element 601.

Heat transfer tubing 602 is straightened and cut to the desired length at step 1002. At step 1003, heat transfer tubing 602 is formed into a

serpentine shape 606.

At step 1004, heat transfer tubing 602 is processed such that following processing, heat transfer tubing 602 forming heat transfer portion 604 comprises an oblong cross-section having height h. Preferably, this is achieved by a suitable hydraulic press comprising limiting guides to ensure the consistency of height h between individual heat transfer elements.

Alternatively, the oblong cross-section may be achieved using a suitable roller. Height h of heat transfer tubing 602 will correspond to the function of the manufactured heat transfer element 601, and will typically be smaller for a condenser than for an evaporator.

To eliminate any convex deformation of heat transfer tubing 602 during processing, step 1004 is preferably performed under an air pressure greater than atmospheric air pressure, preferably nine bar.

The mechanical processing at step 1004 work hardens transfer tubing 602, consequently increasing the rigidity of heat transfer element 601. This is advantageous in decreasing the risk of deformation of heat transfer element 601 that may occur during transportation. In addition, an increase in rigidity facilitates the installation and operation of heat transfer element 601.

At stage 1005, inlet portion 603 and outlet portion 605 are fitted with a connection member fabricated from copper and comprising a circular crosssection. Preferably, the connection members are assembled onto heat transfer element 601 by means of a brazing process. The interfacing connection between heat transfer element 601 and the connection members may be achieved by a flame soldering process using cesium as a flux agent and zinc as a brazing alloy.

At stage 1006, heat transfer element 601 is safety tested in accordance with regulations in current enforcement. Heat transfer element 601 is preferably tested using a known helium leak testing technique. This technique detects leakage levels of refrigerant 801.

According to an alternative method, heat transfer tubing 602 may be received at step 1001 in the form of individual lengths that are preferably straightened prior to step 1003. According to a second alternative method, step 1005, which corresponds to the assembly of a first connection member onto inlet portion 603 and a second connection member onto outlet portion 605, may be performed prior to step 1004.

According to a second alternative embodiment and associated method, heat transfer tubing 602 comprising an oblong cross-section may be received at step 1001 in the form of a coil or as individual lengths.

According to a further alternative embodiment of the present invention, heat transfer tubing 602 may be fabricated from copper or steel.

In contrast to the described prior art wrap-around construction, a single heat transfer element 601 design can be integrated into a plurality of refrigeration units having different physical dimensions. This effective use of design and manufacturing resources provides a financial advantage and logistical advantage. Furthermore, in contrast to the described prior art wraparound construction, heat transfer element 601 is not sensitive to minor variations in the physical dimensions of individual refrigeration units.

According to the preferred embodiment of the present invention, heat transfer element 601 is configured in such a way that a plurality of heat transfer elements according to the same embodiment may be stacked together in a way that makes economical use of space. Thus, the present invention advantageously provides for a financial advantage through a reduction in transportation costs. Furthermore, the present invention provides a heat transfer element 601 requiring less storage space than a heat transfer

element constructed by the described prior art wrap-around construction.

Figure 11 Figure 11 shows inlet portion 603 and outlet portion 605 of heat transfer element 601 manufactured by the process shown in Figure 10. According to step 1005, inlet portion 603 comprises a connection member 1101 and outlet portion 605 comprises a connection member 1102.

Connection member 1101 functions to interface inlet portion 603 and connecting tubing 1103. Similarly, connection member 1102 functions to interface outlet portion 605 with connecting tubing 1104. As previously indicated, inlet portion 603, outlet portion 605, connection member 1101 and connection member 1102 may comprise a plurality of different cross-sections and/or wall thicknesses, in order to achieve the accommodation of different refrigeration system components, which may have different physical dimensions.

According to the preferred embodiment, connection member 1101 and connection member 1102 are fabricated from copper and comprise a circular cross-section. This feature facilitates the integration of heat transfer element 601 into existing refrigeration system designs that typically comprise

connecting tubing fabricated from copper. The similarity of the materials facilitates the preferred method of interfacing heat transfer element 601 with other refrigeration system components. Thus, the present invention provides for a financial advantage through providing a less complex and less timeconsuming method of installation.

Inlet portion 603 and outlet portion 605 are shown positioned on the Inner of outer liner 302 of refrigeration unit 201 in alignment with connecting tubing 1103 and connecting tubing 1104 respectively. The alignment of heat transfer element 601 with connecting tubing of a refrigeration system corresponds to step 1201 of the preferred installation process shown in Figure 12, and described with reference to heat transfer element 601 installed as a condenser within vapour-compression refrigeration system 101 integrated into refrigeration unit 201.

Figure 12 Inlet portion 603 and outlet portion 605 are connectedly interfaced with connecting tubing 1103 and 1104 respectively at step 1202. This is preferably achieved by means of a brazing process, which forms a continuous seam between the refrigeration components. A continuous seam is of particular significance in refrigeration systems containing a refrigerant 801 comprising a hazardous substance, wherein the elimination of any leakage of refrigerant 801 is desired. The interfacing connection may be achieved by a flame soldering process using cesium as a flux agent and zinc as a brazing alloy. Alternatively, the interfacing connection may be achieved by any other suitable fixing means, for example, a chemical fixing means.

Once heat transfer element 601 is secured into position on the inner of outer liner 302 by the preceding steps, a covering is applied over heat transfer element 601 onto the inner of outer liner 302 at step 1203. This covering preferably comprises adhesive foil and preferably covers all exposed surfaces of heat transfer element 601. The covering functions to prevent insulation 308 introduced at step 1204 from insulating heat transfer tubing 602. Preferably insulation 308 comprises a suitable foam insulator and is injected into refrigeration cavity walling 203 within refrigeration unit 201.

The present invention provides for the omission of the application of thermal paste 307, which according to an alternative method of installation, is applied between heat transfer tubing 602 and outer liner 302 prior to step 1203. To achieve this, a suitable thermal paste 307, may be applied to heat transfer tubing 602 and/or outer liner 302 or may be in the form of a separate component.

The present invention provides for a less complex, less time consuming and less expensive method of installation, and effectively utilises human resources.

An object of the present invention is to increase desired heat transfer through decreasing undesired heat transfer, to improve the efficiency of a refrigeration system comprising heat transfer element 601. Referring to Figure 6, insulation 308 functions to prevent undesired heat leakage from heat transfer element 601 to refrigeration cavity 202 within refrigeration unit 201.

According to the prior art wrap-around construction, heat leakage through insulation 308 may occur through all the surfaces of inner liner 301. According to the preferred embodiment of the present invention, heat

leakage from heat transfer element 601 may occur through only one wall of inner liner 301, more specifically, through the wall opposite to the one wall to which heat transfer element 601 is mounted on outer liner 302. Thus, in this embodiment, insulation 308 for heat transfer element 601 is required within one wall of refrigeration cavity walling 203 only.

As previously indicated, the present invention provides for an effective utilisation of the internal volume within refrigeration unit 201. Through providing for a decrease in the amount of insulation 308 required within refrigeration cavity walling 203, the present invention allows for an increase in the internal volume of refrigeration cavity 202, and further allows for additional insulation to be introduced into refrigeration cavity walling 203 without necessitating a reduction in the internal volume of refrigeration cavity 202. The present invention provides for an increase in the efficiency of refrigeration unit 201 through minimising undesired heat transfer. This decrease in undesired heat transfer provides for an increase in the performance efficiency of the refrigeration system comprising heat transfer element 601, and further provides for a decrease in the operation costs of the refrigeration unit 201 comprising the refrigeration system.

Claims

1. A heat transfer element for a refrigeration system comprising heat transfer tubing comprising an inlet portion for receiving a refrigerant, a heat transfer portion comprising an oblong cross-section and an outlet portion, wherein said heat transfer tubing is aluminium.

2. A heat transfer element for a refrigeration system comprising heat transfer tubing comprising an inlet portion for receiving a refrigerant, a heat transfer portion comprising an oblong cross-section and an outlet portion, wherein said heat transfer tubing is aluminium alloy.

3. A heat transfer element for a refrigeration system comprising heat transfer tubing comprising an inlet portion for receiving a refrigerant, a heat transfer portion comprising an oblong cross-section and an outlet portion, wherein said heat transfer tubing is copper.

4. A heat transfer element for a refrigeration system comprising heat transfer tubing comprising an inlet portion for receiving a refrigerant, a heat transfer portion comprising an oblong cross-section and an outlet portion, wherein said heat transfer tubing is steel.

5. A method of manufacturing a heat transfer element comprising heat transfer tubing comprising an inlet portion for receiving a refrigerant, a heat transfer portion and an outlet portion comprising the steps of

a) forming heat transfer tubing into a desired shape; b) applying processing means to said heat transfer tubing such that said heat transfer tubing comprises an oblong cross-section; wherein said heat transfer tubing is aluminium, aluminium alloy copper or steel.

6. A method of manufacturing a heat transfer element comprising heat transfer tubing comprising an inlet portion for receiving a refrigerant, a heat transfer portion and an outlet portion comprising the step of a) forming heat transfer tubing comprising an oblong cross-section into a desired shape wherein said heat transfer tubing is aluminium, aluminium alloy, copper or steel.

7. A method of manufacturing a heat transfer element comprising heat transfer tubing comprising an inlet portion for receiving a refrigerant, a heat transfer portion and an outlet portion comprising the steps of a) forming heat transfer tubing into a desired shape; b) connecting a copper connection member to said inlet portion and/or said outlet portion; wherein said heat transfer tubing is aluminium, aluminium alloy, copper or steel.

8. A heat transfer element according to any of claims 1 to 7 wherein said inlet portion comprises a circular cross-section.

9. A heat transfer element according to any of claims 1 to 7 wherein said inlet portion comprises an oblong cross-section.

10.

10. A heat transfer element according to any of claims 1 to 9 wherein said outlet portion comprises a circular cross-section.

11. A heat transfer element according to any of claims 1 to 9 wherein said outlet portion comprises an oblong cross-section.

12. A heat transfer element according to any of claims 1 to 11 wherein said inlet portion comprises a connection member.

13. A heat transfer element according to any of claims 1 to 12 wherein said outlet portion comprises a connection member.

14. A heat transfer element according to claim 12 or claim 13 wherein said connection member comprises copper.

15. A heat transfer element according to any of claims 7 and 12 to 14 wherein said connection member comprises a circular cross-section.

16. A heat transfer element according to any of claims 7 and 12 to 15 wherein said connection member is integral to said heat transfer element.

17. A heat transfer element according to any of claims 7 and 12 to 15 wherein said connection member is fixedly attached to said heat transfer element.

18. A heat transfer element according to any of claims 1 to 17 wherein said heat transfer element is an evaporator.

19. A heat transfer element according to any of claims 1 to 17 wherein said heat transfer element is a condenser.

20. A heat transfer element according to any of claims 1 to 19 wherein said heat transfer element comprises a serpentine shape.

21. A method according to claim 5 or 7 wherein said heat transfer tubing initially comprises a substantially circular cross-section.

22. A method according to claim 5 to 7 or 21 further comprising the step of cutting the heat transfer tubing into individual lengths prior to step a).

23. A method according to any of claims 5 to 7,21 or 22 further comprising the step of straightening the heat transfer tubing prior to step a).

24. A method according to any of claims 5 and 6 or 21 to 23 dependent on claim 5 or claim 6 further comprising the step of assembling a connection member to said inlet portion.

25. A method according to any of claims 5,6 or 21 to 24 dependent on claim 5 or claim 6 further comprising the step of assembling a connection member to said outlet portion.

26. A method according to any of claims 5,6 or claims 21 to 25 dependent on claim 5 or claim 6 wherein said processing means comprises a hydraulic press.

27. A method according to any of claims 5, 6 or claims 21 to 25 dependent on claim 5 or claim 6 wherein said processing means comprises a roller.

28. A refrigeration system comprising a heat transfer element according to any of claims 1 to 4, or 8 to 20 dependent on any of claims 1 to 4.

29. A refrigeration system comprising a heat transfer element manufactured according to any of claims 5 to 7, or 21 to 27 dependent on any of claims 5 to 7.

30. A refrigeration system according to claim 28 or claim 29 wherein said refrigeration system comprises a vapour-compression refrigeration system.

31. A heat transfer element substantially as herein described with

reference to and as shown in, or in a combination of Figure 6, Figure 9 or Figure

11.

32. A method of manufacturing a heat transfer element substantially as herein described with reference to and as shown in Figure