KR20080009062A - Refrigeration circuit with improved liquid/vapour receiver - Google Patents

Abstract

Refrigeration circuit comprising a compressor, a heat-rejecting heat exchanger an expansion valve, a receiver (3), and a further expansion valve/evaporator to provide cooling. A second heat exchanger (24) is arranged in an upper gas portion of the receiver and/or a third heat exchanger (34) is arranged in a lower liquid portion of the receiver. A better liquid/vapour separation of the refrigerant and/or sub-cooling of the liquid refrigerant are achieved.

Description

REFRIGERATION CIRCUIT WITH IMPROVED LIQUID / VAPOUR RECEIVER}

The present invention relates to a cooling circuit comprising a first compressor device, a heat dissipation heat exchanger, a first expansion device, a receiver having a top and a bottom, a second expansion device, and a first evaporator. The cooling circuit further includes a flow path between the top of the receiver and the compressor in which the suction side is in fluid communication with the inlet of the heat dissipating heat exchanger.

Such cooling circuits are preferably of the type designed for carbon dioxide as a refrigerant, but not limited thereto.

The cooling circuit has two stages of expansion, where the refrigerant is first expanded in one stage of expansion. One stage expansion provides cooling to complete condensation of the refrigerant in the receiver. Moreover, the section of the cooling circuit extending from the receiver to the compressor device is at a substantially lower pressure level than the remaining sections of the cooling circuit extending from the compressor device to the first expansion device.

It is an object of the present invention to provide an improved receiver in a cooling circuit.

It is further an object of the present invention to provide a receiver for outputting a flash gas from the top of the cooling circuit which has substantially no liquid droplets therein.

It is also an object of the present invention to provide a receiver for outputting a sub-cooled liquid refrigerant to a cooling circuit.

According to one embodiment of the present invention, in a cooling circuit for circulating a refrigerant in a predetermined flow direction, while in fluid communication with the first compressor device, the heat dissipation heat exchanger, the first expansion device, the first expansion device, A receiver having an upper portion and a lower portion therein, a second expansion device in fluid communication with the lower portion of the receiver, and a first evaporator in a flow direction, the upper portion of the receiver and the pressure side having the heat dissipating heat exchanger An additional flow path between the inlet of the compressor and the suction side of the compressor in fluid communication; (a) a second heat exchanger disposed within the top of the receiver, the inlet of the second heat exchanger being the heat release A second heat exchanger in fluid communication with an outlet of the heat exchanger, the outlet of the second heat exchanger in fluid communication with an inlet of the first expansion device; (b) the additional flow path comprising a third expansion device, downstream of the additional flow path, a third heat exchanger disposed within the bottom of the receiver, the element (a) and A cooling circuit is provided, characterized in that at least one element from the group consisting of (b) is provided.

The second heat exchanger disposed in the top of the receiver exchanges heat for the vapor contained in the top of the receiver. Any droplets that may be present on top of the receiver will evaporate and will be suspended and carried into the additional flow path.

The third heat exchanger disposed within the third expansion device and the bottom of the receiver provides subcooling of the liquid in the bottom of the receiver. Such subcooled liquid refrigerant causes a more efficient cooling effect by the first evaporator and reduces the formation of refrigerant vapor in the section of the circuit extending from the receiver to the second expander.

Best of all, the improved receiver provides a gaseous refrigerant that has virtually no droplets, and more complete separation with less tendency to subcool and form vapor.

The first compressor device may be a single compressor or a parallel group of several compressors. The compressor device may be of a type comprising a performance control, for example by way of controlling its rotational speed in accordance with the pressure level of the compressed gasified refrigerant achieved.

The compressor associated with the additional flow path starting from the top of the receiver may be an additional compressor. The suction side of such an additional compressor may be at a higher pressure level than the suction side of the first compressor device or may be substantially the same pressure level as the first compressor device. The compressor associated with the additional flow path is associated with the additional flow path or by using one compressor and the same compressor for compressing the gasification refrigerant coming from the top of the receiver as well as the gasification refrigerant coming from the second expansion device. By combining additional compressors into a parallel group of compressors forming the first compressor device, it can be combined with the first compressor device.

 According to an embodiment of the present invention, the cooling circuit further comprises a branch circuit branched from a position located in the section of the circuit extending from the bottom of the receiver to the inlet of the second expansion device; The branch circuit comprises a fourth expansion device, a second evaporator and a second compressor device in a flow direction, the branch circuit being in flow communication with a suction side of the first compressor device at its downstream end.

In such an embodiment, the branch circuit provides low temperature cooling, for example for deep-freezing purposes. Compared to such low temperature cooling, the second expansion device and the first evaporator provide medium temperature cooling, for example for storing food and beverages at a temperature level of 0-10 ° C.

The cooling circuit may comprise one or several second expansion devices / first evaporators, arranged in parallel, and any one or several fourth expansion devices or second evaporators, arranged in parallel.

The refrigerant in the cooling circuit may be a refrigerant having one component or a refrigerant having multiple components.

In the details already mentioned, various expansion devices can be referred to. It should be emphasized that expansion devices of various structures and designs may be provided. A fairly common type of expansion device is an expansion valve. Such expansion device may be a throttling device or a throttle valve. Such an expansion device, depending on the location, may be used to expand the liquid refrigerant into the gasified refrigerant or may expand the gasified refrigerant from a higher pressure level to a lower pressure level.

This invention further relates to a cooling machine comprising the cooling circuit disclosed in the present application.

The cooling machine of this invention can be provided with a heat pump. The technical elements of the cooling machine and the heat pumps are identical. In cooling machines, the purpose of cooling is the main purpose, and the associated production of heat is usually a side effect. The associated cooling effect of the evaporator (s) is usually considered a less useful side effect, while in heat pumps, the generation of heat is the intended purpose. This invention also discloses a heat pump having a circuit disclosed in the present application. Such a circuit can be directed to a cooling circuit because it includes a refrigerant that undergoes condensation and evaporation. Sometimes people prefer to use the term working fluid rather than the term refrigerant when describing heat pumps.

The cooling circuit comprising carbon dioxide as the refrigerant is a circuit operated in a transcritical cycle or a circuit operated in a subcritical cycle, or depending on parameters such as the compressor device environmental temperature and pressure level. It may be a circuit operable in a supercritical cycle or a subcritical cycle. In typical applications such as cooling temperature sensitive products, deep freezing, cooling buildings, the cooling circuit does not reach the subcritical temperature level in the heat dissipating heat exchanger, at least in summer. This circuit operates in a supercritical cycle. In such a situation, the heat dissipating heat exchanger operates as a gas cooler. In the case of subcritical cycles, the heat dissipating heat exchanger operates as a combined gas cooler and condenser.

The primary functions of the receiver are to permanently make available a sufficient amount of liquid refrigerant and to provide separation between the liquid refrigerant and the gasified refrigerant (steam). In the case of a supercritical cycle, the condensation of the refrigerant by flash cooling provided by the first expansion device is an additional function.

The cooling machine or heat pump of this invention applies to a large number of preferred fields. Most importantly, cooling food and beverages in stores in restaurants or in other areas; Cooling of temperature sensitive products such as pharmaceuticals; Deep-freezing; Cooling some types of buildings; Cars, airplanes, ships, trains, etc. are cooling cars in many ways.

This invention further relates to a cooling method. In an embodiment of the invention, the cooling method comprises (i) operating a heat source in the top of the receiver, and (ii) operating a heat sink in the bottom of the receiver. At least one of the groups of steps that occur.

An exemplary embodiment of the present invention will be described next. The features of such embodiments are the preferred features of the cooling circuit of this invention.

1 is a diagram of a cooling circuit for showing the basic configuration of the cooling circuit,

FIG. 2 shows a receiver or separator on a larger scale, which may be included in the cooling circuit of FIG. 1.

The overall cooling circuit shown in FIG. 1 includes the first described (basic) circuit, the second described additional flow path, the third described branch circuit and some additional elements.

The basic circuit includes the following elements when starting with the compressor device 6 and proceeding in the flow direction of the carbon dioxide refrigerant.

Compressor units (6 or 6 and 6´)

-Conduit (7)

Heat dissipating heat exchanger 1 (gas cooler and / or condenser)

-Conduit (2)

-First expansion valve (a)

Receiver (3)

-Conduit (4)

Two parallel second expansion valves (b, c)

Two parallel evaporators (E2, E3)

A conduit (5) returning to the compressor device (6).

The compressor device 6 further comprises three parallel compressors and further an additional compressor 6 ', which will be described in more detail below. The suction sides of the three compressors are supplied by a conventional supply space 20. Typically, the compressor device 6 compresses the supplied gasified carbon dioxide to a pressure in the range of 50 to 120 bar, thereby increasing the temperature of the compressed gasified carbon dioxide to about 50 to 150 ° C. In subcritical operation, the pressure of the compressed gasified carbon dioxide is typically in the range of 40 to 70 bar.

Heat release heat exchangers remove heat from carbon dioxide. In subcritical operation, carbon dioxide is typically cooled to 10-30 ° C. and condensed in the heat dissipating heat exchanger 1. In this case the heat exchanger 1 acts as a combined gas cooler and condenser. In supercritical operation, carbon dioxide is typically cooled to a temperature of 25 to 45 ° C., without condensation of the subcritical portion of carbon dioxide in the heat dissipating heat exchanger. In this case the heat exchanger 1 operates as a gas cooler. In order to remove heat from the carbon dioxide, the heat exchanger 1 is gas cooled or liquid (water) cooled.

In subcritical operation the vapor or liquid / vapor mixture or liquid carbon dioxide is expanded by an expansion valve (a) provided next to the receiver 3, thereby providing flash gas in the top of the receiver 3. Typically, the internal pressure level of the receiver 3 is 30 to 40 bar. The lower part of the receiver 3 contains liquid carbon dioxide. The receiver 3 also acts as a separator of liquid carbon dioxide and carbon dioxide vapor.

By expansion valves (b, c), liquid carbon dioxide is typically inflated to a temperature of minus 15 to 0 [deg.] C., and the pressure level is typically 20 to 35 bar. Evaporators E2 and E3 next to expansion valves b and c are used to allow complete evaporation of carbon dioxide, typically moving on the principle of "cold air is heavier than warm air" or forced air. With the air moving it is used to provide wide cooling surfaces from where cooling takes place properly.

The compressor device 6 and the receiver 3 are typically mounted in a conventional metal frame, which also supports the control equipment of the cooling machine. (First) The heat exchanger 1, that is, the heat dissipation heat exchanger, is usually located at some distance from the compressor device 6, the receiver 3, and the expansion valve 8, for example, to provide the best cooling. It is located outside the building. It is important to note that only the sections of the basic circuit extending from the pressure side of the compressor device 6 to the outlet side of the expansion valve 8 are typically at high pressure levels of 50 to 120 bar. The remaining section of the basic circuit extending from the outlet side of the expansion valve (a) to the suction side of the compressor device (6), typically 30 to 40 bar in front of the expansion valves (b, c) and the compressor device (6) Typically at 25 to 30 bar in front, at two substantially lower pressure levels. As a result, the second mentioned section of the basic circuit may be by using such lower pressure levels, ie tubes with thinner walls, or by using less sophisticated connections through which carbon dioxide is flowing. For example, it can be designed for such lower pressure levels by using evaporators adapted to relatively low pressure levels.

It starts with the conduit 12 and at the outlet side of the upper part (steam part) of the receiver 3 and includes an expansion valve e or a throttle valve and finally via the conduit 11 the inlet side of the compressor device 6. There is an additional flow path leading to. Expansion valve (e) is used to reduce the pressure of gasified carbon dioxide to a level present on the suction side of compressor device (6).

Alternatively, there is a conduit 12, 15 from the top of the receiver 3 to the added compressor 6 ′ without the expansion valve e being used. The suction side of such an added compressor 6 ′ is at a higher pressure level than the suction side 20 of the compressor device 6. The pressure sides of all the compressors 6, 6 ′ have the same pressure level. In addition to providing an additional compressor 6 ′, it is also possible to feed from line 15 to one or several of the compressors of the compressor device 6, but in a step after the first compression step, the flash Gas is supplied to the compressor device 6 at the correct pressure level of the compressors.

Moreover, Figure 1 shows a branch circuit comprising: A conduit 8 branched from an upstream conduit 4 of the expansion valves b and c; (4) expansion valve (d); Second evaporator E4; Conduit 9; A second compressor device 10 and a conduit 11 providing a fluid flowable connection with the suction side of the first compressor device 6. The expansion valve d and the second evaporator E4 are designed to provide expansion of the liquid carbon dioxide at a lower pressure level than that present on the suction side 20 of the compressor device 6. The temperature level reached in evaporator E4 is lower than the temperature level reached in evaporators E2 and E3, thereby providing means for storage at deep freezing or deep freezing temperatures. Typical values in evaporator E4 are 7 to 15 bar and minus 50 to minus 25 ° C.

Finally, FIG. 1 shows that the conduit 13 is branched from the conduit 2, leading from the first heat exchanger 1 to the expansion valve a to the heat exchanger E1, and the expansion valve f is connected to such a conduit ( 13) is provided. The conduit 14 is connected to the suction side of the compressor 6 'added from the heat exchanger E1. Heat exchanger E1 exchanges heat for carbon dioxide flowing through conduit 2. Since the expansion valve f provides cooling gasified carbon dioxide, the carbon dioxide flowing through the conduit 2 is cooled, thereby helping to condense the carbon dioxide or to sub-cool the liquid carbon dioxide.

FIG. 2 shows a schematic cross section of the receiver 3 at a scale larger than FIG. 1. The receiver 3 has an upper portion 3a and a lower portion 3b therein. The amount of liquid carbon dioxide is contained in the receiver 3, filling the interior of the receiver 3 to level 22. Depending on the operating conditions of the cooling circuit, the level 22 can be higher or lower than shown in FIG.

Line 2 (providing a fluid flowable connection between the outlet of the heat exchanger 1 and the expansion valve a; see FIG. 1) extends to the receiver 3 and is arranged in the top 3a of the receiver 3. Is connected to a second heat exchanger (24). There is an additional conduit 26 extending out of the receiver 3 and connecting the downstream end of the second heat exchanger 24 with the inside of the upper portion 3a of the receiver 3, the expansion valve 28 being such a conduit. And provided within 26. Expansion valve 28 produces flash gas in upper portion 3a, which is at a lower temperature level than carbon dioxide flowing through second heat exchanger 24. Any liquid carbon dioxide droplets that may be present at the top 3a are evaporated. This minimizes the potential for corrosion of the expansion valve 34 described in the paragraphs below.

Expansion valve 28 has the same function as expansion valve (a) shown in FIG. The difference is that the conduit 2 does not lead directly to the expansion valve 28, but there is a second heat exchanger 24 upstream of the expansion valve 28. By the second heat exchanger 24, the gasified carbon dioxide exiting the upper portion 3a contains less carbon dioxide condensed than without the provision of the second heat exchanger 24.

Outside the receiver 3, there is an additional conduit 30 leading from the top 3a to the third heat exchanger 32 disposed in the bottom 3b of the receiver 3, in which an expansion valve is located. 34 is provided. The downstream end of the third heat exchanger 32 is connected by a conduit 36 to the suction side 20 of the compressor device 6. In other words, the expansion valve 34 replaces the expansion valve e shown in FIG. 1 and a third heat exchanger 32 is additionally provided.

By passing through the expansion valve 34 the carbon dioxide is colder, and the third heat exchanger 32 provides subcooling of the liquid carbon dioxide accumulated in the lower part 3b of the receiver 3. This liquid, subcooled carbon dioxide exits the bottom 3b via the conduit 4 as shown in FIG.

The gasified carbon dioxide flowing through the third heat exchanger 32 obtains a definite overheat which reduces the risk of floating and transporting liquid carbon dioxide to the compressor device 6.

Claims (9)

In a cooling circuit for circulating a refrigerant in a predetermined flow direction, A first expansion device in fluid communication with a first compressor device, a heat dissipation heat exchanger, a first expansion device, and a first expansion device, a second expansion in fluid communication with the bottom of the receiver A device, and a first evaporator in a flow direction, An additional flow path between the top of the receiver and the suction side of the compressor in fluid communication with the pressure side of the inlet of the heat dissipating heat exchanger, (a) a second heat exchanger disposed in the upper portion of the receiver, the inlet of the second heat exchanger being in fluid communication with an outlet of the heat dissipating heat exchanger, the outlet of the second heat exchanger being the first A second heat exchanger in fluid communication with the inlet of the expansion device; (b) the additional flow path includes a third expansion device and downstream of the additional flow path includes a third heat exchanger disposed within the bottom of the receiver, Cooling circuit, characterized in that at least one element from the group consisting of the elements (a) and (b) is provided. The method of claim 1, The compressor connected to the additional flow path is part of the first compressor device. The method according to claim 1 or 2, Cooling circuit, characterized in that the refrigerant is carbon dioxide. The method according to any one of claims 1 to 3, And said first compressor device comprises a parallel group of several compressors. The method according to any one of claims 1 to 4, Further includes branch circuits, The branch circuit, Branched from a position located in a section of the circuit that extends from the bottom of the receiver to the inlet of the second expansion device, A fourth expansion device, a second evaporator and a second compressor device in the flow direction, At a downstream end thereof, in fluid communication with the suction side of the first compressor device. The method according to any one of claims 1 to 5, A cooling circuit, characterized in that several parallel first evaporators are provided. A cooling machine comprising the cooling circuit specified in any one of claims 1 to 6. In the cooling method, (a) in a flow direction, a receiver having an upper portion and a lower portion therein and in fluid communication with a first compressor device, a heat dissipation heat exchanger, a first expansion device, and the first expansion device, and a flowable portion with a lower portion of the receiver; Circulating a refrigerant in a cooling circuit including a second expansion device in communication with the first evaporator; (b) the cooling circuit further comprises an additional flow path between the top of the receiver and the suction side of the compressor in which the pressure side is in fluid communication with the inlet of the heat dissipating heat exchanger; (c) (iii) operating a heat source within said top of said receiver;     (Ii) operating a heatsink within said bottom of said receiver. The method of claim 8, Cooling method characterized in that the refrigerant is carbon dioxide.

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