WO2007057025A2

WO2007057025A2 - Cooling system with integrated condenser and expansion valve

Info

Publication number: WO2007057025A2
Application number: PCT/DK2006/000647
Authority: WO
Inventors: Lars Skovlund Andersen
Original assignee: Johnson Controls Denmark Aps
Priority date: 2005-11-21
Filing date: 2006-11-21
Publication date: 2007-05-24
Also published as: CN101317049A; US20080282726A1; WO2007057025A3; EP1957892A2

Abstract

Cooling system with an integrated condenser (16), the cooling system containing at least one compressor (4) which via a pressure outlet may conduct a first coolant through a line to at least one condenser (16), from where the first coolant flows through at least one expansion valve (18) to at least one evaporator (22), from where the first coolant (12) is sucked back to the compressor via the suction line of the compressor, where the condenser and the evaporator may both be constructed as closed containers (24, 26), the containers each containing at least one heat exchanger (28, 30), where a second coolant (34) flows through the heat exchanger of the evaporator, and where a cooling medium (38) flows through the heat exchanger of the condenser, the cooling medium exchanging heat with the surroundings. The container containing the heat exchanger of the condenser may also contain means for oil separation (54), and the container may interact with an expansion valve (18). Hereby may be achieved that largely all cooling functions occurring at the same pressure level are integrated in a common pressure vessel.

Description

Cooling System with Integrated Condenser and Expansion Valve

Field of the Invention

The present invention concerns a cooling system with containing at least one compressor which via a pressure outlet may conduct a first coolant through a line to at least one condenser, from where the first coolant flows through at least one expansion valve to at least one evaporator, from where the first coolant is sucked back to the compressor via the suction line of the compressor, where the condenser containing the heat exchanger of the condenser also contains means for oil separation, and where the container can interact with an expansion valve, the containers each containing at least one heat exchanger, where a second coolant flows through the heat exchanger of the evaporator, and where a cooling medium flows through the heat exchanger of the condenser, the cooling medium exchanging heat with the surroundings.

The invention also concerns an integrated condenser, where the condenser may be provided in a closed container which is formed with an inlet and an outlet for coolant, where the container contains a heat exchanger designed with an inlet and an outlet for a cooling medium, where a cooling medium may flow through the heat exchanger and cooled outside the closed container.

Background of the Invention

WO 03060411 Al describes a flooded evaporator with integrated heat exchanger. Herein is disclosed an evaporator provided in a pressure container which contains a flooded evaporator, where the evaporator is constructed as a plate heat exchanger which is entirely flooded by coolant. The plate elements forming the heat exchanger have a shape so that their outer sides over the larger part of the lowermost section of the container follow the inner wall of the container. Thereby is achieved that the amount of fluid coolant required to flood the plate stack is reduced as much most as possible. Between the plates of the heat exchanger is formed a large number of channels which run in a zigzag pattern upwards against the upper edge of the heat exchanger. A violent boiling of coolant occurs in the heat exchanger, which due to bubble formation causes an upwards flow through the heat exchanger. Above the heat exchanger there may be provided a liquid separator so that possible liquid drops are caught and run back into the container, whereby coolant can be sucked out of the container with a very limited content of fluid coolant.

GB 398 691 discloses a cooling system with an evaporator containing a heat exchanger in the shape of longitudinal pipes having brine flowing through them. A condenser is provided outside the evaporator, entirely surrounding the evaporator.

The condenser contains a heat exchanger formed of longitudinal pipes. The pipes in the condenser have cooling water flowing through them. Between evaporator and condenser an insulation material is provided. Both condenser and evaporator have means for oil separation.

Object of the Invention

It is the object of the invention to indicate an efficient and compact liquid cooling system that forms an assembled unit including all cooling functions.

It is also an object of the invention to indicate an integrated condenser where a plurality of functions in connection with the condenser is integrated in a common pressure vessel.

Description of the Invention

The first object may be fulfilled if the heat exchangers of both the evaporator and the condenser are constructed with substantially vertical channels in which coolant is flowing through.

Hereby may be achieved that largely all cooling functions occurring at the same pressure level are integrated in a common pressure vessel. This may be enabled by two different pressure vessels, so that a vessel having about the pressure level existing at the pressure outlet of the compressor includes condensing, oil separation as well as expansion valve. On the evaporator side where the pressure in the container is about equal to the suction pressure of the compressor, there may thus be provided integration of an efficiently flooded evaporator and a liquid separator. By disposing both pressure vessels relatively close to each other and immediate vicinity of a compressor, the required pipe connections between the cooling units may be reduced to a minimum. Loss of power to the surroundings may thereby be reduced, and at the same time the cooling system itself is made cheaper. Besides compressor and possibly a motor for driving the compressor, the frame may include an electronic control and regulating system that performs the electric regulation of the compressor motor. Thus it becomes possible to let the compressor work with variable rotational speed which may be adjusted to the actual cooling demand.

Fluid coolant may flow through the heat exchanger in the evaporator, the coolant being heated to title boiling point by contact with the heat exchanger, whereby coolant in gaseous state flows upwards through the channels. Coolant gas flows through the corresponding channels in the heat exchanger of the condenser from above, the coolant gas forming droplets by condensing, where the droplets are collected in an underlying collecting tray. Hereby is achieved that the force of gravity, in evaporation as well as in condensing, ensures optimal flow in the channels in the heat exchanger. On the evaporator side gas bubbles will appear because the liquid is boiling. These gas bubbles will ensure an upward going flow of coolant through the channels. By condensing, formation of droplets will occur which due to the force of gravity will rapidly run down through the channels for collection in the underlying collecting tray. Use of a collecting tray has the advantage that the total volume of fluid coolant can be reduced because the collecting tray may conduct the fluid coolant towards a collecting unit and away from the heat exchanger, which to the largest possible extent is surrounded by coolant in the gaseous state. By aiming at the least possible coolant in the condenser, the total filling of coolant in the system can be reduced to a minimum.

The integrated condenser may advantageously contain a collecting tray that substantially surrounds the lowermost part of the heat exchanger, where the collecting tray may contain a volume for collecting fluid coolant. The integrated condenser may also contain an oil separator, and the integrated condenser may interact with an expansion valve. Hereby may be achieved that the integrated condenser simultaneously may accommodate a number of further components that are to function at the same pressure level as the one prevailing in the condenser.

The heat exchanger of the condenser may interact with an underlying collecting tray, where the collecting tray forms a collecting volume for fluid coolant. Hereby may be achieved that the condensed coolant may be rapidly and efficiently collected in the collecting volume suited therefor, so that the total amount of fluid coolant contained in the integrated condenser is minimised.

The collecting volume of the collecting tray may contain at least one float interacting with an expansion valve, the degree of opening of which may be regulated by the position of the float. Hereby may be achieved that the collecting volume of the collecting tray may be kept below an upper limit all the time. As soon as the liquid level in the collecting volume rises, the float will act to open the expansion valve. In practice, a balance will be produced so that the expansion valve is standing slightly open, and the liquid level remains at the same level all the time. Any change in the cooling load on the system will change the liquid level, thus automatically changing the degree of opening of the expansion valve. Therefore, an increase the capacity of the compressor caused by a want of larger cooling performance will automatically cause the degree of opening of the expansion valve to change so that a larger amount of fluid coolant is injected into the evaporator. In that way a self-regulating expansion valve may thus be formed which does not have any other movable component except the float, where the expansion valve can be integrated in the container and be disposed in association with the collecting volume.

In an alternative embodiment of the invention, the collecting volume of the collecting tray may interact with at least one level sensing device for determining the actual coolant level in the collecting volume, where the output signal of the level sensing device is used for regulating the degree of opening of at least one expansion valve. Hereby may be achieved that known electronically controlled expansion valves may be applied.

At its upper edge, the collecting tray may interact with an oil separator having coolant in gaseous state flowing through it, and separated oil is conducted along the inner side of the container, where the bottom of the container is used for collecting oil from where the collected oil is returned to the compressor. Hereby may be achieved that the oil which a compressor has admixed to the coolant gas flowing from the compressor is separated directly in connection with condensing of coolants. Thereby it is entirely avoided using a separate oil separator which is a standard component in most cooling facilities. Hot coolant in the gaseous state may be conducted into the container under the collecting tray, the hot coolant gas flowing around the collecting tray and passing up along the inclining sides of the collecting tray and further up through the oil separator to the top side of the heat exchanger, from where the coolant gas flows through substantially vertical conducting channels formed in the heat exchanger, down through the heat exchanger, whereby the coolant gas is condensed into fluid coolant which is collected in the collecting tray. Hereby may be attained a very efficient heat exchange between coolant and the cooling medium flowing through the heat exchanger. In order to ensure that the pressurised gas is driven the right way through the condenser, a longitudinal sealing strip is provided between the collecting tray and the heat exchanger, preventing pressurised gas from flowing up into the heat exchanger from the bottom side in counter-flow to the condensing coolant. The unidirectional gas flow direction ensures that the heat exchanger is effectively emptied of liquid so that the largest possible area is available for condensing.

Description of the Drawing

Fig. 1 shows a section through a cooling system, and Fig. 2 shows a section through an integrated condenser; Fig. 3 shows a section through a second embodiment.

Detailed description of the invention

On Fig. 1 appears a sectional view through a cooling system 2, consisting of a motor 3 driving a compressor 4. The compressor 4 has a pressure outlet 8 which via a pressure gas line 14 communicates with an integrated condenser 16. On Fig. 1, the condenser 16 contains an expansion valve 18 which via a coolant line 19 communicates with an integrated evaporator 22 which via a suction gas line 10 communicates with the compressor 4. The condenser 16 is provided in a container 24 containing a heat exchanger 30, where the heat exchanger 30 is surrounded by a collecting tray 46 at is bottom side, the tray 46 communicating with a collecting volume 48. The collecting volume 48 contains a float 50 interacting with the expansion valve 18. The evaporator 22 is also constructed so that it is integrated with a further cooling component in a container 26. The container 26 contains a heat exchanger 28. The space above the heat exchanger 28 constitutes a liquid separator and may, according to need, be equipped with demister mats or similar. The cooling system 2, which is shown by a section through the system on Fig. 1, operates in the way that a motor 3 drives a compressor 4 so that hot gaseous coolant 12 (Fig. 2) under high pressure flows from the pressure outlet 8 through the pressure gas line 14 to the condenser 16, where the pressure gas line 14 is partly invisible on the sectional Figure. Thus coolant 12 (Fig. 2) flows into the container 24 under high pressure and high temperature, the container 24 containing the heat exchanger 30, where the inflow of coolant occurs in the lower half of the container 24, where the coolant flows on the external side of the heat exchanger 30 up to the top of the heat exchanger 30, which contains a number of channels running in zigzag through the heat exchanger 30, however primarily in downward direction. A cooling medium exchanging heat with the surroundings also flows through the heat exchanger 30, so that cooling of the coolant 12 (Fig. 2) occurs during passage of the heat exchanger 30, whereby a condensation occurs so that droplets running downwards through the channels are formed, where the droplets are collected by the underlying collecting tray 46 communicating with the collecting volume 48. The collecting volume 48 contains the float 50 that interacts with the expansion valve 18, meaning that a rise of the liquid level automatically entails opening the expansion valve 18 if the liquid level exceeds a minimum value. After passing through the expansion valve 18, the coolant runs through the coolant line 19 to the evaporator 22. The evaporator is also provided in a container 26 where the container 26 contains a heat exchanger 28. The heat exchanger 28 also contains zigzag channels primarily running in upwards direction. The amount of coolant 12 in the evaporator 22 will be so that the heat exchanger 28 will be entirely flooded by liquid. The heat exchanger 28 has a second coolant flowing through it which is cooled by giving off heat to the coolant 12 which thereby begins to boil. This boiling entails a violent bubble formation in the 28 channels of the heat exchanger, which by entraining liquid increases liquid flow through and efficiency of the evaporator 22. The suction gas line 10 connects the top of the evaporator with the suction side of the compressor.

Fig. 2 shows a section through an integrated condenser 16 provided in a container 24. The container 24 contains a heat exchanger 30 which at the lowermost side is surrounded by a collecting tray 46 communicating with a liquid collecting volume 48. The container 24 contains oil separators 54 from where oil in the form of droplets 60 run to an oil collecting volume at the bottom of the container 24, from where the oil collecting volume 60 may be drained off and returned to the compressor.

Fig. 2 operates in the way that coolant 12 flows into the container 24 where the coolant 12 flows through oil separators 54 to a superposed space, from where the coolant 12 flows through the heat exchanger 30 where the coolant is cooled, because the heat exchanger communicates with a cooling medium through the two shown branches, where the cooling medium e.g. flows to a cooling tower for cooling and back to the heat exchanger 30. On the way down through zigzag channels in the heat exchanger 30, condensing and thereby drop formation occurs, so that droplets flow down into the underlying collecting tray 46. From here, fluid coolant runs down into the collecting container 48 from where coolant is conducted through a coolant connection containing an expansion valve and onwards in the cooling circuit. The coolant 12 flows through the oil separators 54, whereby possible oil content is separated off so that oil 60 drips down from the oil separators 54 onto the inner side of the container 24. The oil 60 is collected at the bottom of the container 24 from where the oil can be drained off, and the oil can be returned to the compressor via an oil return duct system, and from where the oil can be recycled.

Fig. 3 shows a section through an integrated condenser 116 provided in a container 124. The container 124 contains a heat exchanger 130 which at the lowermost side is surrounded by a collecting tray 146 communicating with a liquid collecting volume

148. At the top of the container 124 is shown an oil separator 154 provided directly under an inlet for pressurised gas 114, where the coolant 112 passes through the oil separator 154 in connection with flowing into the container 124. From the oil separator 154 the oil is returned to a compressor through a not shown duct.

Claims

1. A cooling system (2) containing at least one compressor (4) which via a pressure outlet (8) conducts a first coolant (12) through a line (14) to at least one condenser (16) from where the first coolant (12) flows through at least one expansion valve (18) to at least one evaporator (22), from where the first coolant (12) is sucked back to the compressor (4) via the suction line (10) of the compressor, where the condenser (16) and the evaporator (22) are both constructed as separate closed containers (24, 26), where the container containing the condenser (16) also contains means (54) for oil separation, and where the container interacts with at least one expansion valve (18), the containers (24, 26) each containing at least one heat exchanger (28, 30), where a second coolant (34) flows through the heat exchanger (28) of the evaporator (22), and where a cooling medium (38) flows through the heat exchanger (30) of the condenser (16), the cooling medium (38) exchanging heat with the surroundings, characterised in that the heat exchangers (28, 30) of the evaporator (22) as well as the condenser (16) have substantially vertical channels in which coolant (12) flows through.

2. A cooling system according to claim 1, characterised in that fluid coolant (12) flows through the heat exchanger (28) in the evaporator (22), the coolant (12) being heated to the boiling point by contact with the heat exchanger (28), whereby coolant (12) in gaseous state flows upwards through the channels where coolant gas flows through the corresponding channels in the heat exchanger (30) of the condenser (16) from above, the coolant gas forming droplets by condensing, where the droplets are collected by an underlying collecting tray (46).

3. Integrated condenser (16), where the condenser (16) is provided in a closed container which is formed with an inlet and an outlet for coolant, where the container contains a heat exchanger (30) designed with an inlet and an outlet for a cooling medium, where a cooling medium flows through the heat exchanger (30) and is cooled outside the closed container, characterised in that the integrated condenser (16) contains a collecting tray (46) which substantially surrounds the lowermost part of the heat exchanger (30), where the collecting tray (46) contains a volume (48) for collecting fluid coolant (12), where the integrated condenser (16) contains an oil separator (54), and where the integrated condenser (16) interacts with an expansion valve (18).

4. Integrated condenser according to claim 3, characterised in that the heat exchanger (30) of the condenser (16) interacts with an underlying collecting tray (46), where the collecting tray (46) forms a collecting volume (48) for fluid coolant.

5. Integrated condenser according to claim 3 or 4, characterised in that the collecting volume (48) of the collecting tray (46) contains at least one float (50), where the float (50) interacts with at least one expansion valve (18), where the degree of opening of the expansion valve (18) is regulated by the position of the float (50).

6. Integrated condenser according to claim 3 or 4, characterised in that the collecting volume (48) of the collecting tray (46) includes at least one level sensing device for determining the actual coolant level in the collecting volume (48), where the output signal of the level sensing device is used for regulating the degree of opening of at least one expansion valve.

7. Integrated condenser according to one of claims 3 - 6, characterised in that the collecting tray (46) at its upper edge interacts with an oil separator (54) having coolant in gaseous state flowing through it, where separated oil (60) is conducted to along the inner side of the container, where the bottom of the container is used for collecting oil from where the collected oil is returned to the compressor (4).

8. Integrated condenser according to one of claims 3 -7, characterised in that hot coolant in the gaseous state is conducted into the container at the outer side of the collecting tray (46), the hot coolant gas flowing around the collecting tray (46) and passing up along the inclining sides of the collecting tray (46) and further up through the oil separator (54) to the top side of the heat exchanger (30), from where the coolant gas flows through substantially vertical conducting channels formed in the heat exchanger (30), down through the heat exchanger (30), whereby the coolant gas is condensed into fluid coolant which is collected in the collecting volume of the collecting tray.