WO1993001459A1

WO1993001459A1 - Heat pumping system with flow restricting tube in inner cavity of suction conduit

Info

Publication number: WO1993001459A1
Application number: PCT/DK1992/000215
Authority: WO
Inventors: Lasse Lykke Espersen
Original assignee: Maskinfabrikken Derby A/S
Priority date: 1991-07-05
Filing date: 1992-07-03
Publication date: 1993-01-21
Also published as: AU2349192A

Abstract

A heat pumping system comprises a compressor (12), a condenser (13) communicating with the outlet of the compressor, and an evaporator (19) communicating with the inlet of the compressor through a suction conduit (18), while a flow restricting metal tube (17) interconnecting the condenser and the evaporator extends along at least part of its length axially through the inner cavity or bore of the suction conduit (18), so as to form a tube assembly (16). The compressor (12) and the condenser (13) are arranged in a compressor unit (14), and the evaporator (19) is arranged in a separate cooling unit (10). Thus, separate units (10, 14) are interconnected by the tube assembly (16) which is flexible so that the mutual positions of the compressor unit and the cooling unit may be changed.

Description

HEAT PUMPING SYSTEM WITH FLOW IffiS-_RINCTING TUBE IN INNER CAVITY OF SUCTION C-ONDUIT

The present invention relates to a heat pumping system comprising a compressor having an inlet and an outlet, a condenser communicating with the outlet of the compressor, an evaporator communicating with the inlet of the compres¬ sor through a suction conduit, and a flow restricting metal tube interconnecting the condenser and the evaporator and extending along at least part of its length axially through the inner cavity or bore of the suction conduit (18) , so as to form a tube assembly.

In conventional heat pumping systems of the above type the suction conduit as well as the flow restricting tube are tubes made from metal. Normally, the diameter of the flow restricting tube is smaller than that of the suction con- duit and the flow restricting tube may then extend axially within the suction tube. The flow restricting tube may comprise one or more restrictions or may be a capillary tube, whereby a pressure difference may be obtained between the condenser and the evaporator when a usual refrigerant is circulated through the system by means of the compres¬ sor.

In the known heat pumping systems of the above type, the various components, such as the compressor, the condenser, and the evaporator are arranged in one and the same unit or at mutually fixed positions, and the tube assembly, which interconnects the condenser and the eva¬ porator and comprises a pair of coaxial metal tubes, is rather stiff.

The present invention provides a heat pumping system of the above type having an improved utility.

The heat pumping system according to the invention is characterized in a compressor unit comprising the compres¬ sor and the condenser, and a separate cooling comprising the evaporator, the separate compressor and cooling units being interconnected by the tube assembly, which is flex¬ ible so as to allow substantial changes of the mutual positions of said units. This means, that the compressor unit and the cooling unit may be placed at different posi¬ tions, which are the most convenient in each single case. Thus, the units may be placed on top of each other or separated from each other. As an example the cooling unit may comprise a display container which is arranged at a location where it is important that it occupies the smal¬ lest possible space and is as noiseless as possible. In such case the more noisy compressor unit may be arranged at a remote location, and because of the flexible nature of the suction conduit and the flow restricting metal tube interconnecting the cooling and compressor units it is possible to move the unit to some extent in relation to each other.

The inner diameter of the suction conduit substantially exceeds the outer diameter of the flow restricting tube so that the refrigerant may flow from the evaporator to the inlet of the compressor through an annular space defined within the suction conduit around the- flow restricting tube arranged therein.

The outer suction conduit may, for example, be made from a flexible material, such as plastic material, and may be cylindrical. Alternatively, the suction conduit may be a peripherally corrugated metal tube and may then be rather flexible even when it is made from steel or any other hard metal. The inner flow restricting metal tube may function as a stiffening member preventing the suction conduit from being sharply bent. On the other hand the outer suction conduit may protect the thinner flow restricting metal tube against breakage and other mechanical damage.

While the suction conduit and the flow restricting metal tube may co-extend for a certain distance, their end por- tions are to be connected to different parts of the evapo¬ rator on one hand and the compressor and the condenser on the other hand. Therefore, opposite end portions of the flow restricting tube may be arranged outside the suction conduit while the intermediate part of the flow restricting tube is arranged inside the suction conduit, the flow restricting tube passing sealingly through the wall of the suction conduit.

As mentioned above, the flow restricting tube may contain one or more restrictions permitting the establishment of a pressure difference between the condenser and the evapora¬ tor. In the preferred embodiment, however, the flow re¬ stricting tube is a capillary tube, which may, for example, be made from aluminum, copper or their alloys or from steel.

When the suction tube is made from plastic material at least the inner surface of the conduit should be made from a refrigerant resistant material, such as polyamide. Thus, the suction conduit may be made from one and the same refrigerant resistant plastic material, or it may be made from a plastic laminate comprising an inner layer of a refrigerant resistant material, such as polyamide. The laminate may further comprise an outer or intermediate layer of a material, such as polyethylene, for preventing moisture or water vapour from permeating through the walls of the suction conduit and into the refrigerant flowing therethrough. The outer or intermediate tubular layer of polyethylene is preferably substantially thicker than the inner tubular layer of polyamide. The laminated suction conduit may be made by an extrusion process, and the vari¬ ous tubular layers of the conduit may then be extruded successively by a multi step extruding process. The suction conduit may further comprise an outer tubular casing, which may, for example, be made from polyvinylchloride. The compressor unit may comprise an electric driving motor, and therefore, the compressor unit is preferably arranged adjacent to an electric outlet or socket from which elec¬ trical power may be supplied. The cooling unit may comprise control devices, such as a thermostat for controlling the function of the compressor. Furthermore, the cooling unit may comprise electrically powered devices, such as light sources, fans, etc. All such devices may be connected to the compressor unit or to an electrical outlet by electri- cal conductor means. In such case the suction conduit may comprise an outer tubular casing surrounding the suction conduit, electrical conductor means, which extend between the cooling unit and the compressor unit and which are arranged between the outer casing and an adjacent layer or embedded in the outer casing, which may, for example, be made from polyvinylchloride. The compressor and cooling units may then be interconnected by a unitary, cable-like tube assembly.

The present invention also relates to a tube assembly for use in a heat pumping system of the type described above and comprising a suction conduit and a flow restricting tube extending along at least part of its length axially through the inner cavity or bore of the suction conduit, and the tube assembly according to the invention is charac- terized in that it is flexible and that the suction conduit comprises tubular members made from flexible plastic mate¬ rial and/or a flexible, corrugated metal tube.

The invention will now be further described with reference to the drawings, wherein Fig. 1 is a perspective view of a refrigerator system according to the invention,

Fig. 2 is a longitudinal sectional view of a flexible tube assembly according to the invention shown in an enlarged scale, Fig. 3 is a cross-sectional view of the tube assembly of

Fig. 2 shown in a further enlarged scale, Fig. 4 is a longitudinal sectional view of another embodi¬ ment of the tube assembly according to the invention shown in a further enlarged scale, and

Fig. 5 is a cross-sectional view of the suction tube shown in a further enlarged scale.

Fig. 1 shows a refrigerated display container 10, which is provided with a hinged lid 11 of a transparent material. The display container 10 is cooled by means of a heat pumping system according to the invention comprising an evaporator defining the inner side wall surfaces of ar¬ ranged within the bottom of the display container 10, a compressor 12 and a condenser 13. The compressor and the condenser are arranged within a separate compressor unit 14 to which electrical power may be supplied from an electri- cal power source (not shown) through an electrical cable 15. The display container or display unit 10 and the sepa¬ rate compressor unit 14 are interconnected by means of a flexible tube assembly 16 which is shown in more detail in Figs. 2-5.

The display container, which may contain products which need to be kept under cool conditions, may be positioned in department stores or shops so that the products are easily accessible to the costumers. It may, however, be desirable to position the noisy and heat generating compressor unit at a remote, retracted position, where it is not visible. The flexible tube assembly permits the compressor unit 14 and the display container 10 to be arranged in almost any desired relative positions and also permits change of the position of the display container, when the compressor unit is kept stationary.

The tube assembly 16 comprises an inner capillary tube 17, which may, for example, be made from copper, aluminum or steel, and an outer suction tube or hose 18, which may, for example, be made from or comprise a refrigerant resistant plastic material, such as polyamide. The inner diameter of the suction tube 18 substantially exceeds the outer diame¬ ter of the capillary tube 17 so as to define an annular space between the outer surface of the capillary tube and the inner surface of the suction tube. The capillary tube 17 interconnects the condenser 13 and the evaporator 19, while the suction tube 18 extends between the evaporator 19 and the inlet of the compressor 12. Therefore, the capil¬ lary tube 17 may be passed sealingly through the wall of the suction tube or hose 18 as shown in Figs. 1 and 2. Furthermore, the suction tube 18 may be divided in two or more sections and adjacent sections may be interconnected by means of releasable tube connectors 20.

The display unit 10 may contain electrical devices, such as a fan, a lamp, etc., and control devices, such as a ther- mostat. Such devices may be connected to the electrical power supply cable and/or to control devices, such as switches arranged within the compressor unit 14, by means of conductors or conduits 21 extending axially within an annular space defined between the outer peripheral surface of the suction tube or hose 18 and the inner peripheral surface of an outer tubular casing 22, which is made from plastic material, such as polyethylene.

It should be understood that the inner capillary metal tube 17 of the tube assembly 16 serves as a stiffening member for stiffening the plastic suction hose 18, whereby it is prevented from being sharply bent so that the passage therethrough is more or less obstructed. On the other hand, the suction tube or hose 18 and the outer tubular casing 22 protect the capillary metal tube from breakage and other mechanical damaging.

Fig. 4 shows a modified embodiment of the tube assembly 16. In this embodiment the suction tube 18 comprises a flexible tube 23, which may be made from stainless steel or another metal, and which is provided with peripherally extending corrugations 26. These corrugations may be formed like a screw. The inner diameter of the outer tubular casing 22, which is made from plastic material, exceeds the maximum outer diameter of the flexible metal tube 23 so as to define a space in which electrical conductors may be ar- ranged.

Fig. 5 shows a laminated suction tube 18 having an inner tubular layer 25 of a refrigerant resistant and refrigerant impenetrable material, such as polyamide. The suction tube further comprises a thicker intermediate layer 24 of a material, which is impenetrable to moisture or water va¬ pour, such as polyethylene, and an outer protective tubular layer or casing 22 of a plastic material, such as poly¬ vinylchloride, in which electrical conductors 21 are em¬ bedded. The laminated suction tube 18 shown in Fig. 5 may be made by simultaneous extrusion of the various layers of the tube.

EXAMPLE

A tube assembly as that shown in Fig. 3 comprises an inner capillary tube, which is made from copper, with an inner diameter of 0.9-1.2 mm and an outer diameter of 2.2-2.5 mm. The capillary tube is arranged within a suction hose which is made from polyamide. The inner diameter of the suction hose is 6 mm, and the outer diameter is 8 mm. The suction hose is surrounded by an outer tubular casing or hose which is made from plastic material which is reinforced by means of a helically wound metal member. The inner diameter of the outer casing is 14 mm and the outer diameter is 16 mm. Longitudinally extending electrical conductors are arranged within the space defined between the outer peripheral surface of the suction hose and the inner peripheral sur¬ face of the outer casing. This tube assembly was found to be sufficiently flexible to allow substantial relative movement between a compressor unit and a display unit interconnected by the tube assembly. In the suction tube shown in Fig. 5 the inner diameter of the tube 25, which is made from polyamide, is 6 mm. The wall thickness of the tubular layer 25 is 1 mm. The inner and outer diameters of the intermediate layer 24, which is made from polyethylene, are 8 mm and 13 mm, respectively, which means that the wall thickness of the tubular layer 24 is 2.5 mm. The outer diameter of the outer protective casing 22, which is made from polyvinylchloride, is 15 mm, and the wall thickness of the tubular casing 22 is 1 mm. The cross-sectional area or each of the conductors 21, which are made from copper, is 0.5 mm².

It should be understood that the tube assembly described above could be used in connection with any kind of heat pumping system, whether the evaporator is moveable in rela- tion to the compressor and the condenser or not. The heat pumping system could be used in any kind of apparatus or plant, such as in any kind of cooling or freezing system or any kind of heating system in which a heating pump is used.

Claims

1. A heat pumping system comprising a compressor (12) having an inlet and an outlet, a condenser (13) communicat¬ ing with the outlet of the compressor, an evaporator (19) communicating with the inlet of the compressor through a suction conduit (18) , and a flow restricting metal tube (17) interconnecting the condenser and the evaporator ex¬ tending along at least part of its length axially through the inner cavity or bore of the suction conduit (18) , so as to form a tube assembly, c h a r a c t e r i z e d in a compressor unit (14) com¬ prising the compressor (12) and the condenser (13) , and a separate cooling unit (10) comprising the evaporator (19) , the separate compressor and cooling units (10, 14) being interconnected by the tube assembly which is flexible so as to allow substantial changes of the mutual positions of said units (10, 14) .

2. A heat pumping system according to claim 1, wherein the suction conduit (18) is made from a flexible material, such as plastic material.

3. A heat pumping system according to claim 1, wherein the suction conduit (18) is a flexible metal tube having peri¬ pherally extending corrugations (26) .

4. A heat pumping system according to any of the claims 1- 3, wherein the cooling unit comprises a display container

(10).

5. A heat pumping system according to any of the claims 1- 4, wherein opposite end portions of the flow restricting tube (17) are arranged outside the suction conduit (18) while the intermediate part of the flow restricting tube is arranged inside the suction conduit, the flow restricting tube passing sealingly through the wall of the suction conduit.

6. A heat pumping system according to any of the claims 1-5, wherein the flow restricting tube is a capillary metal tube (17) .

7. A heat pumping system according to any of the claims 1-6, wherein the suction conduit (18) is made from a plas¬ tic laminate (22, 24, 25) comprising an inner layer (25) of refrigerant resistant material.

8. A heat pumping system according to claim 7, wherein the suction conduit (18) comprises an inner tubular layer of polyamide (25) and a surrounding tubular layer of polyethy¬ lene (24) .

9. A heat pumping system according to any of the claims 1- 8, wherein the tube assembly further comprises an outer tubular casing (22) surrounding the suction conduit (18) , and electrical conductor means (21) which extend between the cooling unit (10) and the compressor unit (14) , and which are arranged between the outer casing and an adjacent layer or embedded in the outer casing.

10. A heat pumping system according to claim 9, wherein the outer casing (22) is made from polyvinylchloride.

11. A tube assembly for use in a heat pumping system ac¬ cording to any of the claims 1-10, and comprising a suc¬ tion conduit (18) and a flow restricting tube (17) extend¬ ing along at least part of its length axially through the inner cavity or bore of the suction conduit, c h a r a c t e r i z e d in that it is flexible and that the suction conduit (18) comprises tubular members made from flexible plastic material and/or a flexible, corruga¬ ted metal tube.

12. A tube assembly according to claim 11, wherein the suction conduit (18) is a flexible tube having peripherally extending corrugations (26) .

13. A tube assembly according to claim 11 or 12, wherein the opposite end portions of the flow restricting tube (17) are arranged outside the suction conduit (18) , while the intermediate part of the flow restricting tube is arranged inside the suction conduit, the flow restricting tube passing sealingly through the wall of the suction conduit.

14. A tube assembly according to any of the claims 11-13, wherein the flow restricting tube (17) is a capillary metal tube.

15. A tube assembly according to any of the claims 11-14, wherein the suction conduit (18) comprises a tubular inner layer of a refrigerant resistant plastic material, such as polyamide.

16. A tube assembly according to claim 15, wherein the suction conduit (18) is made from a plastic laminate (22, 24, 25) further comprising a tubular layer (24) of polyet¬ hylene.

17. A tube assembly according to any of the claims 11-16, further comprising an outer tubular casing (22) and elec- trical conductor means (21) extending along at least part of the length of the suction conduit (18) , the electrical conductor means being arranged between the suction conduit and the tubular casing (22) or being embedded in the lat¬ ter.

18. A tube assembly according to claim 17, wherein the outer casing (22) is made from polyvinylchloride.