GB2508842A

GB2508842A - Double wall tube heat exchanger

Info

Publication number: GB2508842A
Application number: GB1222359.0A
Authority: GB
Inventors: Thomas Zenon Zakrzewski; Andreas Richard Hilgert; Markus Angelo Ullrich; Ralph Peter Merkel
Original assignee: Eaton Industrial IP GmbH and Co KG
Current assignee: Eaton Industrial IP GmbH and Co KG
Priority date: 2012-12-12
Filing date: 2012-12-12
Publication date: 2014-06-18
Also published as: GB201222359D0

Abstract

A double wall tube heat exchanger comprises a hose 22 and an inner tube 23 arranged inside the hose thereby defining a clearance between the hose and the inner tube, the inner tube forming an inner channel (24, fig 2) and the clearance forming an outer channel (25). The hose may be made from flexible heat insulating rubber and the inner tube from a heat conducting material such as aluminium, brass or alloys thereof. The inner tube may be a spiral or convoluted tube or may have an outer helical groove winding around the inner tube and extending the longitudinal direction. A low temperature low pressure refrigerant may communicate through the inner channel in one direction and a high temperature high pressure refrigerant through the outer channel in an opposite direction (i.e. the refrigerants communicate through the inner and outer channels in counterflow).

Description

A double-wall-tube heat exchanger The present invention relates to a doube-wa1I-tube heat exchanger, in partiefflar for an air conditioning system of a motor vehicle.

A conventional refrigeration system for use in a car includes a compressor, a condenser, an evaporator and an expansion valve serving as pressure reducing device. A major aim in the automotive industry is to reduce fiicl consumption and C02-cmissions. In this regard it is im-portant to increase the efficiency of car air conditioning systems. For this reason it is already well known to use internal heat exchanger for a thermal exchange between the air condition-ing systems suction lines and liquid lines. Using internal heat exchanger the cold vapor from the evaporator is used to cool the hot liquid before it enters the expansion valve. Following the expansion, more liqnid refrigerant is available for absorbing heat in the evaporator and, hence, increasing the efficiency ofthe air conditioning system.

Internal heat exchangers are well known in the art. US (5 883 601 B2, for instance, discloses an internal heat exchanger tube that includes a central channel surrounded by a plurality of outer channels arranged concentric to the central channel. The high-temperature high-pressure refrigerant from the compressor and the condenser flows through the central channel and the low-temperature low-pressure refrigerant from the evaporator flows through the outer chan- nels. Between the central channel and the outer channels there takes place a thermal ex-change.

Other internal heat exchangers are disclosed in US 2009/0166019 Al and US 7 866 378 B2.

When the air conditioning system is installed in the engine compartment of a car these well known internal heat exchangers have to be bent to fit with the other systems and components.

In addition, flexible tubes (hoses) have to be provided between the internal heat exchanger and the other air conditioning system components in order to equalize tolerances in length and position. However, due to the restricted packaging room in engine compartments it is neces-sary to avoid any additional components.

The object of the present invention is to provide an internal heat exchanger with the ability to equalize tolerances in length and/or position.

The object is solved by a double-wall-tube heat exchanger comprising a hose, and an inner tube forming an inner channel said inncr tubc being arranged inside the hose defining a clear-ance bctwccn the hose and the inner tube, said clearance forming an outer channel.

The hose can be bent elastically without ductile deformation so that the hose can equalize tolerances in length and position between two components of an air conditioning system. It is not ncccssary to provide thrthcr components to equalize tolerances. A further advantage is thc noise reducing ability of the hose so that the complete internal heat exchanger has a very low noise level.

In a preferred embodiment the hose is made of a heat insulating material. The insulating mate-rial avoids a heat exchange with the ambient air so that the efficiency of the air conditioning system can be further improved. Preferably the hose is made of a rubber material or any other suitable flcxible material.

In order to avoid a reduction of the clearance between the inner tube and the hose during elas-tically bending the internal heat exchanger the inner tube can be formed as a spiral tube with an outer helical groove winding around the inncr tube and extending the longitudinal direc-tion. As a result, the clearance is always at least provided between by the helical grooves and the hose. Further, the length of the flow path in the outer channel is thereby increased provid-ing a better heat exchange over an increased flow path. The inner tube can also be provided in the form of a convoluted tube in order to enhance flexibility, wherein the convoluted tube has a plurality of annular ring-shaped grooves over its length.

For providing a high elastic flexibility of the internal heat exchanger also the inner tube is flexible. Flexible means, that the inner tube can be bent elastically without ductile defor-mation. However, generally the inner tube can also be made of material which can be easily bent in a ductile manner as long as the force for bending the inner tube is low enough to allow an elastic bending of the hose.

The inner tube is made of a heat conducting material in order to enhance heat exchanging abilities. For example, the inner tube can be made of aluminium, brass or alloys thereof In order to have a suitable flexibility of the inner tube it should be made of a soft metal. Alterna-tively, also non-metal materials can be used for the inner tube as long as these materials have enough heat conducting ability and are flexible.

The low-temperature low-pressure refrigerant can be disposed within the inner channel and the high-temperature and high-pressure refrigerant can be disposed within the outer channel.

Typically, the refrigerant in the inner channel and the refrigerant in the outer channel have opposite flow directions in regard to the longitudinal direction or axis of the internal heat ex-changer.

It shall be emphasized, that the claimed heat exchanger is not limited to an application in an air conditioning system. The heat exchanger according to this invention can also be used in other applications where an efficient heat exchange is necessary.

The above and other objects, features and advantages of the present invention will be come more apparent from the following detailed description of an preferred embodiment made with reference to the accompanying drawings.

Figure 1 is a schematic view of an automotive air conditioning system; Figure 2 is a side view of a double-wall-tube heat exchanger and Figure 3 is a sectional view of area III of the heat exchanger according to Figure 2.

Figure 1 depicts a schematic view of an air conditioning system 1 for a motor vehicle. The air conditioning system I comprises a compressor 2 driven, for instance, by the engine of the motor vehicle. The compressor 2 has an outlet 3 and an inlet 4.

While gaseous refrigerant is led through the inlet 4 into the compressor 2, compressed refrig-erant is output at the outlet 3. From the outlet 3 a pressure line S leads to a condenser 6, in which the high-temperature high-pressure refrigerant is condensed. The high-temperature high-pressure refrigerant is output at an outlet 7 of the condenser 6 to another pressure line 8 that leads to a high-pressure inlet of heat exchanger 10. This heat exchanger is a double-wall-tube heat exchanger according to the invention. The heat exchanger 10 has a high-pressure outlet connccted to an cxpansion valvc 13 via a pressure linc 12. Downstream of the expan-sion valve 13 the refrigerant is fed into an evaporator 14. Here, the refrigerant evaporates by rccciving hcat from thc ambicnt air in ordcr to cool ambicnt air. From the evaporator 14 thc gascous low-tempcrat-urc ow-prcssurc rcfrigcrant is cd through a ow-prcssurc linc 15 to a low-pressure inlet 16 of the heat exchanger 10. The low-temperature low-pressure refrigerant flows through the heat exchanger 10 in an opposite flow direction to the high-temperature high-pressure refrigerant. In this way, the low-temperature low-pressure refrigerant passes the high-temperature high-pressure rcfrigerant and thereby cooling the high-temperature high-pressure refrigerant. From the heat exchanger thc low-temperature low-prcssure refrigcrant is fed through a low-pressure line 18 to the inlet 4 of the compressor 2.

Figures 2 and 3 depict a double-wall-tube heat exchanger 10 according to Figure 1. The dou-ble-wall-tube heat exchanger 10 comprises a double-wall-tube 19 connected at one end to a first fitting 20 and at a second end to a second fitting 21. The first fitting 20 comprises the high-pressurc inlct 9 for thc high-tcmpcrature high-prcssurc rcfrigcrant. The rcfrigcrant fcd into the high-prcssure inlct 9 flows through thc double-wall-tubc 20 to the high-prcssurc out- let 11 arranged at the second fitting 21. The second fitting 21 ifirther comprises the low-pressure inlet 16 for gaseous low-temperature low-pressure refrigerant which is fed into the low-pressure inlet 16, through the double-wall tube 19 to the low-pressure outlet 17 which is arranged at the first fitting 20.

Figure 3 shows an enlarged part longitudinal section in the area III according to Figure 2. The doubic-wall tube 19 comprises an elastic flcxible hose 22, preferably made of a rubbcr matc- rial, and an inner tubc 23. The inner tube 23 forms an inner channcl for feeding gaseous low-temperature low-pressure refrigerant. The inner tube is arranged inside the hose defining a radial clearance between a circumferential outer surface 26 of the inner tube 23 and a circum-fcrential inncr surfacc 27 of the hosc 22. The clcarancc defincs an outcr channel which is, viewed in a cross section, ring shaped around the inner tube 23. The outer channel 25 serves as flow path for high-temperature high-pressure liquid refrigerant.

The first fitting 20 is tube like and has a first connection portion 28 and a second connection portion 29. The first connection portion 28 is arranged at one end of the hose 22, surrounding an outer surface 30 of the hose 22 and is bonded to the outer surface 30 of the hose 22.

The inner tube 23 projects out of the hose 22. A second connection portion 29 surrounds the projecting end of the inner tube 23 and is bonded to the outer surface 26 of the inner tube 23.

The second connection portion extends into the tube like low-pressure outlet 17.

Between the first connection portion 28 and the second connection portion 29 a port portion 31 is arranged which surrounds the outer surface 26 of the inner tube 23 with a radial clear-ance and extends into the high-pressure inlet 9 hydraulically connecting the high-pressure inlet 9 to the outer channel 25.

The second fitting 21 is formed identical to the first fitting 20.

Reference numerals I air conditioning system 2 compressor 3 outlet 4 inlet pressure line 6 condenser 7 outlet 8 pressure line 9 high-pressure inlet heat exchanger 11 high-pressure outlet 12 pressure line 13 expansion valve 14 evaporator low-pressure line 16 low-pressure inlet 17 low-pressure outlet 18 low-pressure line 19 double-wall tube first fitting 21 second fitting 22 hose 23 innertubc 24 inner channel outer channel 26 outer surface (of inner tube) 27 inner surface (of hose) 28 first connection portion 29 second connection portion outer surface (of hose) 31 port portion

Claims

Claims 1. A double-wall-tube heat exchanger (10) comprising a hose (22), and an inner tube (23) forming an inner channel (24) said inner tube (23) being arranged inside the hose (22) defin-ing a clearance between thc hosc (22) and thc inner tube (23) said clearance forming an outcr channel (25).
2. A double-wall-tube heat cxchangcr (10) according to claim 1, in which thc hosc (22) is made of a heat insulating material.
3. A double-wall-tube heat exchanger (10) according to any onc of the preccding claims, in which the hose (22) is made of a rubber material.
4. A double-wall-tube heat exchanger (10) according to any one of the preceding claims, in which the inner tube (23) is a spiral tube or a convoluted tube.
5. A double-wall-tube heat exchanger (10) according to any one of the preceding claims, in which the inner tube (23) has an outer helical groove winding around the inner tube (23) and extending the longitudinal direction.
6. A double-wall-tube heat exchanger (10) according to any one of the preceding claims, in which the inner tube (23) is flexible.
7. A double-wall-tube heat exchanger (10) according to any one of the preceding claims, in which the inner tube (23) is made of a heat conducting material, e.g. aluminium, brass or al-loys thereof.
8. A double-wall-tube heat exchanger (10) according to any one of the preceding claims, in which a low-temperature low-pressure refrigerant being disposed within the inner channel (24) and a high-temperature high-pressure refrigerant being disposed within the outer channel (25).
9. A double-wall-tube heat exchanger (10) according to claim 8, in which the refrigerant in the inner channel (24) and the refrigerant in the outer channel (25) have opposite flow direc-tions.