WO2006065186A1

WO2006065186A1 - Improved air conditioning system

Info

Publication number: WO2006065186A1
Application number: PCT/SE2004/001928
Authority: WO
Inventors: Ulf BJÖRKERUD
Original assignee: Volvo Lastvagnar Ab
Priority date: 2004-12-16
Filing date: 2004-12-16
Publication date: 2006-06-22

Abstract

A heat exchange device combined in an accumulator or receiver/drier wherein the heat exchange is done between an outer compartment and an inner compartment together forming a twin walled heat exchanging unit.

Description

Improved air conditioning system

Field of the invention

The present invention relates to a cooling system in vehicles and in particular to a cooling system comprising a heat exchange function using a double walled vessel.

Background of the invention

It is an increasing demand from regulatory authorities to increase the efficiency of cooling (air conditioning) systems in vehicles and reduce risks for introducing environmentally unfriendly substances outside of closed loop air conditioning systems. This demand has been actualized due to growing environmental concerns.

Conventional cooling systems comprise mainly four major components: an evaporator for absorbing heat from the inside of a vehicle, a condenser for radiating heat from the cooling substance, a compressor for circulating the cooling substance within the system, and an accumulator for storing and drying the cooling substance (depending on the type of cooling system this part is sometimes replaced with a receiver-drier). The operation of air condition systems are well known in the art.

In order to control the flow of the liquid entering the evaporator mainly two different components are used: in some systems an orifice tube is used for controlling the flow of the cooling substance and in other systems a thermal expansion valve is used for regulating the flow of the refrigerant substance.

The operation of a standard air condition system may be as follows with an orifice tube system as an example:

1. The compressor pumps the cooling substance around the system, it takes the gas from the low pressure side and outputs higher pressure gas.

2. The cooling substance (in gas phase) enters the condenser which condenses the gas into a liquid phase.

3. An orifice tube reduces the pressure of the liquid and thus lowers the temperature, as may be understood by the well known Carnot cycle. 4. The cold liquid is entered into an evaporator, and the cold liquid is made to boil by absorbing heat from the vehicle compartment. The vehicle compartment is then cooled (air condition). 5. The cooling substance (in gas phase mostly) is outputted from the evaporator and entered into an accumulator, which allows for a controlled delivery of gas to the compressor and at the same time makes sure no cooling substance in liquid phase reaches the compressor. The compressor may be damaged if subjected to cooling substance in liquid phase and/or will operate in a non optimal manner.

6. The process cycle now starts over again.

In order to increase the efficiency of the air condition system it is sometimes suggested to sub-cool the liquid substance from the condenser before entering the evaporator directly or via regulating components. Sub cooling of the liquid cooling substance means cooling of the liquid, at a constant pressure, below the point at which it was condensed. This may be done in a separate heat exchanger exchanging heat between high pressure liquid line between the condenser and orifice tube, and the low pressure gas line between the accumulator and compressor for an orifice tube system.

However, increasing the number of components increases the possibility for faulty connections, parts that may brake down, and the number of operation during assembly increases. It is therefore of interest to find solutions where it is possible to combine components.

One such solution is found in US 6463757 wherein an accumulator is designed to reduce flooding (slugging) while incorporating an internal heat exchanger for better system performance. The high pressure condensate from the condenser is circulated in tubing spiraling around the low pressure gas (with liquid mixed in) in the accumulator. The tubing comprises a complex structure and has drawbacks in assembly and production due to the complex structure.

Summary of the invention

Accordingly the present invention according to a preferred embodiment preferably seeks to mitigate, alleviate or eliminate one or more of the above-mentioned disadvantages singly or in any combination.

In an embodiment of the present invention, a heat exchange device for use in an air conditioning system in a vehicle is provided, the device is arranged for receiving and heat-exchanging between a cooling substance at a first temperature (Tl) from a condenser and cooling substance having a second temperature (T2) from an evaporator, characterized by that the device is formed as a first and second vessels, the second vessel being arranged inside the first vessel and forming a twin walled heat exchanging unit comprising:

- an outer compartment between the first and second vessel,

- an inner compartment inside the second vessel,

- an outer wall of the second vessel separating the first and second vessel and providing a heat conducting wall, - a first inlet and a first outlet through which one of the first or second cooling substances can flow through the outer compartment,

- a second inlet and a second outlet through which one of the first or second cooling substances can flow through the inner compartment.

The outer compartment may surround the inner compartment concentrically.

The inner compartment is an accumulator or a receiver/drier.

The outer compartment may further comprise a flow steering structure, such as a spiraling structure.

The cooling substance of a first temperature may comprise high pressure cooling substance in liquid phase from the condenser and the cooling substance of a second temperature may comprise low pressure cooling substance in liquid or gas phase from the evaporator.

The cooling substance of a first temperature may comprise low pressure cooling substance in gas or liquid phase from the evaporator and the cooling substance of a second temperature may comprise high pressure cooling substance in liquid or gas phase from the condenser.

In another embodiment of the present invention, an air conditioning system for use in a vehicle is provided, comprising:

- an evaporator; - a condenser;

- an orifice tube or thermostatic expansion valve; and - a heat exchange device for receiving and heat-exchanging between a cooling substance at a first temperature (Tl) from a condenser and cooling substance having a second temperature (T2) from an evaporator, characterized by that the device is formed as a first and second vessels, the second vessel being arranged inside the first vessel and forming a twin walled heat exchanging unit comprising: o an outer compartment between the first and second vessel, o an inner compartment inside the second vessel, o an outer wall of the second vessel separating the first and second vessel and providing a heat conducting wall, o a first inlet and a first outlet through which one of the first or second cooling substances can flow through the outer compartment, o a second inlet and a second outlet through which one of the first or second cooling substances can flow through the inner compartment.

In yet another embodiment of the present invention, a method of heat exchange in an air condition system for use in a vehicle is provided, comprising the steps of:

- providing cooling substance at a first temperature in a first compartment;

- providing cooling substance of a second temperature in a second compartment surrounding the first compartment;

- wherein heat is exchanged through a wall separating the two compartments, together forming a twin walled heat exchanging unit.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

Brief description of the drawings

In the following the invention will be described in a non-limiting way and in more detail with reference to exemplary embodiments illustrated in the enclosed drawings, in which:

Fig. 1 illustrates schematically a cooling system according to one embodiment of to the present invention.

Fig. 2 illustrates schematically a cooling system according to a second embodiment of the present invention. Fig. 3 illustrates schematically an accumulator according to the first embodiment of to the present invention.

Fig. 4 illustrates schematically a receiver/drier according to the second embodiment of the present invention.

Detailed description of the invention

The present invention will now be described in detail with reference to the drawings. Fig. 1 illustrates a first embodiment of the present invention with an accumulator 1 and an orifice tube 4, which is one of two standard versions of air conditioning or cooling systems. A compressor 2 pumps a cooling substance around the cooling system 10. A condenser 3 removes heat from the cooling substance which condenses into a liquid phase. An orifice tube 4 is used to regulate the flow of the cooling substance and reduces the pressure and the temperature of the cooling substance. An evaporator 5 removes heat from the vehicle compartment by bringing the cooling substance into a boil. Cold liquid/gas leaves the evaporator 3 and is transferred to the accumulator 1. The accumulator 1 is used for storing and drying the cooling substance. The main purpose of the accumulator 1 is to stop cold liquid from entering the compressor 2 since the efficiency of compressor 2 is reduced if it is made to pump liquid substance or it may actually be destroyed.

In the present invention the cooling substance is after the condenser 3 guided through the accumulator in an outer compartment around the inner accumulator compartment in order to pre cool the cooling substance before going to the orifice tube. At the same time the cold liquid/gas coming from the evaporator 5 is slightly heated before continuing to the compressor 2. This ensures that the risk of pumping cold liquid (so called slugs) through the compressor is reduced. The sub cooling of the cooling substance before the orifice tube 4 by using the heat exchange process in the accumulator increases the coefficient of performance (COP).

The present invention according to the first embodiment comprises an accumulator 300 provided with a combined heat exchanger as may be seen in Fig. 3. The device 300 comprises an outer wall 301 surrounding an inner wall 302 forming an outer compartment 303 there between. The inner wall 302 forms an inner compartment

309. The outer compartment has one inlet tubing 316 and one outlet tubing 317, where between cooling substance can flow. The device 300 further comprises a block 313 through which inlet tubing 307 and outlet tubing 308 is arranged. The outlet tubing 308 may further comprise a U-shaped part 314 and an oil return hole

310. Above an inlet part 318 of the U-shaped tubing 314 a splash guard 311 may be located. The reference numeral 312 represents a level of liquid cooling substance.

The accumulator/heat exchanger 300 is designed so as to have double walls 301 and 302, which may be called a twin walled heat exchange unit, where the cold cooling substance in liquid or gas phase from the evaporator 5 is contained inside the inner compartment 309 and the hot liquid from the condenser is contained in the outer compartment 303 of the accumulator.

The operation of the combined accumulator/heat exchanger 300 is as follows. Cold liquid/gas 305 from the evaporator enters into the accumulator 300 through a tube 307 and slightly heated cooling substance 306 in gas phase is sucked out through a second tube 308 to a compressor. This tube 308 may be formed as a U-shape 314 in the flask in order to catch lubrication residues (such as oil) in the cooling substance. These lubrication residues may be brought out through an oil return hole 310. The cold liquid/gas contained in the accumulator 300 is slightly heated by the surrounding outer compartment 303 containing hot liquid 315 from the condenser. The hot liquid 315 from the condenser enters via a tube 316 from the condenser into the outer compartment 303 and sub-cooled liquid 304 exits via a tube 317 to the orifice tube.

An optional splash guard 311 may be installed in order to stop cold liquid entering into the inner compartment 309 from being led into the U-shaped tube 314 by mistake since this could cause liquid cooling substance to reach the compressor.

Since the warm liquid from the condenser surrounds the cold liquid/gas from the evaporator inside the accumulator the heat exchange works to level out the temperature difference between the two parts. This has two advantages: it ensures that the cold liquid/gas is slightly warmer and thus the risk of transferring liquid phase cooling substance to the compressor is reduced and the warm liquid from the condenser is slightly cooled (sub-cooled) before reaching the orifice tube 4, which increases the efficiency of the cooling process in the end.

In another embodiment of the present invention, as seen in Fig. 2, an air condition system 20 uses a thermostatic expansion valve (TXV) 26 and receiver/drier vessel 27. The compressor 22 pumps the cooling substance around the air condition system 20 and hot gas enters a condenser 25 which condenses the gas into liquid phase. The liquid cooling substance is entered into a receiver/drier 27 that removes moisture and is used to store and filter liquid cooling substance.

A thermostatic expansion valve may be used to expand the warm high pressure liquid substance into cold low pressure liquid substance which enters into an evaporator 23 and removes heat from the vehicle compartment. Cooling substance is outputted from the evaporator 23 and in the present invention is used for sub cooling the liquid from the condenser 25 in the receiver/drier 27. The cooling substance, now in gas phase, is then brought to the compressor 22 and the cooling cycle starts over again.

In the second embodiment, illustrated in Fig. 4, of the present invention a receiver/drier 400 has a similar function of heat exchange as the accumulator in the first embodiment of the present invention. The device 400 comprises an outer wall 401 surrounding an inner wall 402 forming an outer compartment 417 there between. The inner wall 402 forms an inner compartment 410. The outer compartment has one inlet tubing 416 and one outlet tubing 415, where between cooling substance can flow. The device 400 further comprises a block 413 through which inlet tubing 407 and outlet tubing 408 is arranged. The outlet tubing 408 is extended into the inner compartment 410 with a tubing 412 ending in an inlet part 414. The reference numeral 418 represents a level of liquid cooling substance.

The operation of the second embodiment is as follows. Hot liquid/gas 403 from the condenser enters into the receiver/drier 400 through a tube 407 from the condenser and sub-cooled liquid 404 exits through a tube 408 to a thermostatic expansion valve (TXV). The tube 408 providing the TXV with sub-cooled liquid 404 may be extended 412 to the bottom of an inner compartment 410 of the receiver/drier 400. Cold liquid/gas 405 from the evaporator enters through a tube 416 into an outer compartment 417 surrounding the inner compartment 410 of the receiver/drier 400. The inner compartment 410 is surrounded by an inner wall 402 and the outer compartment 417 is provided between the inner wall 402 and an outer wall 401. The cold liquid/gas 405 entering into the outer compartment 417 is slightly heated and exits as gas phase cooling substance 406 to the compressor through a tube 415. A block 413 may be provided through which the tubing related to the hot liquid/gas from the condenser and sub-cooled liquid to the TXV is provided.

Again, the above mentioned embodiment has two advantages: it ensures that the cold cooling substance in liquid or gas phase is slightly warmer and thus the risk of transferring liquid phase cooling substance to the compressor is reduced and the warm liquid from the condenser is slightly cooled (sub-cooled) before reaching the thermostatic expansion valve 26, which increases the efficiency of the cooling process in the end.

In both embodiments both or either surfaces of the outer compartment 303, 417 may be provided with a flow controlling structure, such as a spiraling structure or a micro or nano structure imprinted on the surface providing an optimal flow around the inner surface 302, 402 for optimal heat exchange. This ensures a good temperature distribution and good flow of cooling substance around the inner compartment. It may also be located on the surface of the inner compartment for the same purpose.

Care should also be taken in choosing the appropriate material in order to enable a high heat transfer between the inner 309, 410 and outer 303, 417 compartments, for example, but not limited to, aluminum, whereas the outer wall 301, 401 may for example be made of steel or aluminum. Other considerations to take in the choosing of material are for instance production/assembly properties, such as welding, soldering, or brazing properties, and corrosion properties.

Other variations of flow/temperature/pressure regulating components may be used without departing from the scope of the present invention.

Advantages of the present invention as compared to conventional systems are, for example:

1. Reduced number of parts.

2. Reduced cost. 3. Reduced weight

4. Reduced packaging space.

5. Reduced number of tube connections.

6. Reduced risk of liquid slugs reaching the compressor. 7. Reduced need for noise silencer or mini-accumulator in car installations.

The wording "tube" and "tubing" refer to transfer means in general and may be for instance tube, pipe, hose, and so on as understood by the person skilled in the art. The cooling substance may be any suitable substance for air conditioning systems e.g. hydro fluorocarbons (HFC), hydro chlorofluorocarbons (HCFC), CO₂, and hydrocarbons (HC).

It should be noted that the word "comprising" does not exclude the presence of other elements or steps than those listed and the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements. It should further be noted that any reference signs do not limit the scope of the claims, that the invention may be implemented by means of both hardware and software, and that several "means" may be represented by the same item of hardware.

The above mentioned and described embodiments are only given as examples and should not be limiting to the present invention. Other solutions, uses, objectives, and functions within the scope of the invention as claimed in the below described patent claims should be apparent for the person skilled in the art.

Reference signs

1 Accumulator

2 Compressor

3 Condenser 4 Orifice tube

5 Evaporator

10 Cooling system

20 Cooling system

22 Compressor 23 Evaporator

25 Condenser

26 Thermo expansionvalve 27 Receiver/drier

300 Accumulator

301 Outer wall

302 Inner wall 303 Outer compartment

304 Cooling substance to orifice tube

305 Cooling substance from evaporator

306 Cooling substance to compressor

307 Tubing from evaporator 308 Tubing to compressor

309 Inner compartment

310 Oil return hole

311 Splash guard

312 Liquid level 313 Lid

314 U-shaped tubing to compressor inside inner compartment

315 Cooling substance from condenser

316 Tubing from condenser

317 Tubing to orifice tube 318 Inlet to tube 314

400 Receiver/drier

401 Outer wall

402 Inner wall

403 Cooling substance from condenser 404 Cooling substance to thermo expansion valve (TXV)

405 Cooling substance from evaporator

406 Cooling substance to compressor

407 Tubing from condenser

408 Tubing to thermo expansion valve 410 Inner compartment

412 Extension of tubing 408 from inner compartment to TXV

413 Lid

414 Inlet to suction tubing 412

415 Tubing to condenser 416 Tubing from evaporator

417 Outer compartment

418 Liquid level

Claims

1. A heat exchange device for use in an air conditioning system (10, 20) in a vehicle, for receiving and heat-exchanging between a cooling substance at a first temperature (Tl) from a condenser (3, 25) and cooling substance having a second temperature (T2) from an evaporator (5, 23), characterized by that said device is formed as a first and second vessels, said second vessel being arranged inside said first vessel and forming a twin walled heat exchanging unit comprising: - an outer compartment (303, 417) between said first and second vessel,

- an inner compartment (309, 410) inside said second vessel, an outer wall of said second vessel separating said first and second vessel and providing a heat conducting wall (302, 402),

- a first inlet (316, 416) and a first outlet (315, 415) through which one of said first or second cooling substances can flow through said outer compartment,

- a second inlet (307, 407) and a second outlet (308, 408) through which one of said first or second cooling substances can flow through said inner compartment.

2. The heat exchange device according to claim 1, wherein said outer compartment (303, 417) surrounds said inner compartment (309, 410) concentrically.

3. The heat exchange device according to claim 1, wherein said inner compartment is an accumulator.

4. The heat exchange device according to claim 1, wherein said inner compartment is a receiver/drier.

5. The heat exchange device according to claim 1, wherein said outer compartment (303, 417) further comprise a flow steering structure.

6. The heat exchange device according to claim 5, wherein sad flow steering structure comprise a spiraling structure.

7. The heat exchange device according to claim 1, wherein said cooling substance of a first temperature comprises high pressure cooling substance in liquid phase from said condenser (3) and said cooling substance of a second temperature comprise low pressure cooling substance in liquid or gas phase from said evaporator (5).

8. The heat exchange device according to claim 1, wherein said cooling substance of a first temperature comprises low pressure cooling substance in gas or liquid phase from said evaporator (23) and said cooling substance of a second temperature comprise high pressure cooling substance in liquid or gas phase from said condenser (25).

9. An air conditioning system (10, 20) for use in a vehicle, comprising:

- an evaporator (5, 23); - a condenser (3, 25);

- an orifice tube (4) or thermostatic expansion valve (26); and

- a heat exchange device (300, 400) for receiving and heat-exchanging between a cooling substance at a first temperature (Tl) from a condenser (3, 25) and cooling substance having a second temperature (T2) from an evaporator (5, 23), characterized by that said device is formed as a first and second vessels, said second vessel being arranged inside said first vessel and forming a twin walled heat exchanging unit comprising: o an outer compartment (303, 417) between said first and second vessel, o an inner compartment (309, 410) inside said second vessel, o an outer wall of said second vessel separating said first and second vessel and providing a heat conducting wall (302, 402), o a first inlet (316, 416) and a first outlet (315, 415) through which one of said first or second cooling substances can flow through said outer compartment, o a second inlet (307, 407) and a second outlet (308, 408) through which one of said first or second cooling substances can flow through said inner compartment.

10. A method of heat exchange in an air condition system (10, 20) for use in a vehicle, comprising the steps of: - providing cooling substance at a first temperature in a first compartment (309, 410);

- providing cooling substance of a second temperature in a second compartment (303, 417) surrounding said first compartment (309, 410); wherein heat is exchanged through a wall (302, 402) separating said two compartments, together forming a twin walled heat exchanging unit (300, 400).

11. The method according to claim 8, wherein said cooling substance of a first temperature comprises high pressure cooling substance in liquid phase from said condenser (3) and said cooling substance of a second temperature comprise low pressure cooling substance in liquid or gas phase from said evaporator (5).

12. The method according to claim 8, wherein said cooling substance of a first temperature comprises low pressure cooling substance in gas or liquid phase from said evaporator (23) and said cooling substance of a second temperature comprise high pressure cooling substance in liquid or gas phase from said condenser (25).