WO2009091094A1

WO2009091094A1 - Air conditioner having multiple compressors

Info

Publication number: WO2009091094A1
Application number: PCT/KR2008/000338
Authority: WO
Inventors: Jae Heung Yoo; Kyung Ki Min
Original assignee: Carrier Corporation
Priority date: 2008-01-18
Filing date: 2008-01-18
Publication date: 2009-07-23
Also published as: KR20100115755A; KR101156919B1

Abstract

The present application discloses an air conditioner having multiple compressors, comprising a first compressor, a second compressor, a first heat exchanger, a second heat exchanger, an expansion device, and a direction control valve. The first compressor may be an intermittent compressor. The direction control valve comprises a high pressure portion, a low pressure portion, a line, and a moving part. The moving part moves to change the line according to the pressures of the high pressure portion and low pressure portion. The low pressure portion of the direction control valve communicates with the suction line of the second compressor by low pressure connecting means.

Description

Description AIR CONDITIONER HAVING MULTIPLE COMPRESSORS

Technical Field

[1] The present invention relates to an air conditioner having multiple compressors, in particular, an air conditioner which is capable of varying its cooling or heating capacity by turning the multiple compressors on or off. Background Art

[2] Air conditioners having variable capacity, which include multiple compressors for effectively responding to cooling or heating demands, have been known.

[3] Korean Patent No. 10-770718 discloses such an air conditioner, which is shown in

FIG. 1. Air conditioner (10) comprises intermittent compressor (12a) and continuous compressor (12b). Intermittent compressor (12a) is turned on or off according to the necessary demands, while continuous compressor (12b) is continuously operated regardless of such demands. The refrigerant discharged from compressors (12a, 12b) is condensed in condenser (20). The condensed refrigerant is expanded in expansion device (30) and then evaporated in evaporator (40). Accumulators (14a, 14b) are positioned on the suction side of compressors (12a, 12b), respectively, in order to filter the liquid-phase refrigerants which have not been evaporated in evaporator (40), thereby preventing the liquid-phase refrigerant from flowing into compressors (12a, 12b) and causing a failure.

[4] Both intermittent compressor (12a) and continuous compressor (12b) are turned on when the cooling demands are high, while intermittent compressor (12a) is turned off when the cooling demands are low. Direction control valve (60) is positioned on the discharge line of intermittent compressor (12a) so that the flow direction of the refrigerant discharged from intermittent compressor (12a) can be shifted according to whether intermittent compressor (12a) is turned on or off. Direction control valve (60) is a four- way valve comprising a high pressure portion, a low pressure portion, a line, and a plunger. The flow direction of the refrigerant is shifted when the line is changed by moving plunger (64) by utilizing the difference in pressure between the high pressure portion and the low pressure portion. The high pressure portion is connected to the discharge side of intermittent compressor (12a) or continuous compressor (12b), whereas the low pressure portion is connected to the suction side of intermittent compressor (12a).

[5] When intermittent compressor (12a) is turned off, the refrigerant discharged from intermittent compressor (12a) flows into the suction side of intermittent compressor (12a) instead of flowing through the usual discharge line. Thus, a closed loop including intermittent compressor (12a) is formed, which is separated from continuous compressor (12b). When the cooling demands become high, intermittent compressor (12a) is restarted and plunger (64) of direction control valve (60) needs to be moved so that the usual discharge line is recovered.

[6] However, according to the operation environment of air conditioner (10), a situation may occur where the pressure difference between the high pressure portion and low pressure portion is low. For example, when intermittent compressor (12a) is turned off, the discharge side of intermittent compressor (12a) is directly connected to the suction side of intermittent compressor (12a) without being connected to the usual discharge line. Thus, the pressure of the suction side of intermittent compressor (12a) becomes much higher than the pressure of the suction side during normal operation of intermittent compressor (12a), while the pressure difference between the discharge side of continuous compressor (12b) and the suction side of intermittent compressor (12a) is remarkably reduced.

[7] Meanwhile, because the kinetic energy of a gas is lower as the temperature of the gas decreases, the pressure of the gas phase refrigerant discharged from the compressor becomes lower as the temperature decreases. Thus, the pressure of the refrigerant discharged from continuous compressor (12b) is much lower in the winter when the outdoor temperature is low, than in other seasons. In addition, the pressure difference between the discharge side of continuous compressor (12b) and the suction side of intermittent compressor (12a) is remarkably reduced in the winter.

[8] As such, if the pressure at the discharge side of continuous compressor (12b), affecting the high pressure portion of direction control valve (60), is decreased, or if the pressure at the suction side of intermittent compressor (12a), affecting the low pressure portion of direction control valve (60), is increased, and there is little difference in pressure between the high pressure portion and low pressure portion, enough power to move plunger (64) is not generated. Thus, the flow direction of the refrigerant is not properly shifted. Accordingly, intermittent compressor (12a) cannot be restarted within a short time. Disclosure of Invention Technical Problem

[9] The present invention is to solve the above-noted problems in the art, where it provides an air conditioner in which a compressor that is off can be rapidly restarted at any time. Technical Solution

[10] In order to achieve the above objective, the present invention provides an air conditioner comprising a first compressor, a second compressor, a first heat exchanger, a second heat exchanger, an expansion device, and a direction control valve. The first compressor is an intermittent compressor which can be turned on or off during the operation of the second compressor. The second compressor may be a continuous compressor. Alternatively, the second compressor may be an intermittent compressor, with a backflow prevention check valve positioned in the discharge line of the second compressor.

[11] The discharge line of the first compressor and the discharge line of the second compressor are connected to the first heat exchanger through a common discharge line. The first heat exchanger is connected to the second heat exchanger by way of an expansion device. The second heat exchanger is connected to a common suction line. The common suction line is connected downstream to the suction line of the first compressor and the suction line of the second compressor.

[12] The discharge line of the first compressor comprises a first discharge line connecting the discharge side of the first compressor to the direction control valve and a second discharge line connecting the direction control valve to the common discharge line. The suction line of the first compressor comprises a first suction line connecting the common suction line to the direction control valve and a second suction line connecting the direction control valve to the suction side of the first compressor.

[13] The direction control valve comprises a high pressure portion, a low pressure portion, a line, and a moving part. The moving part moves to change the line according to the pressures of the high pressure portion and low pressure portion. When the first compressor is on, the direction control valve allows the first discharge line to connect with the second discharge line. When the first compressor is off, the direction control valve allows the first discharge line to connect with the second suction line.

[14] The high pressure portion of the direction control valve communicates with the above-mentioned second discharge line, while the low pressure portion of the direction control valve communicates with the suction line of the second compressor by low pressure connecting means. The low pressure connecting means is a connection pipe extending between the second suction line and the suction line of the second compressor.

[15] In another embodiment of the present invention, the air conditioner further comprises a second direction control valve. The second direction control valve is connected to the discharge line of the first compressor and the discharge line of the second compressor via the common discharge line. The second direction control valve is connected to the first heat exchanger by a first connection line and is connected to the second heat exchanger by a second connection line. The second direction control valve is connected to the suction line of the first compressor and the suction line of the second compressor via the common suction line. [16] The second direction control valve connects the second heat exchanger to the common suction line, while simultaneously connecting the common discharge line to the first heat exchanger. Alternatively, the second direction control valve connects the first heat exchanger to the common suction line, while simultaneously connecting the common discharge line to the second heat exchanger.

Advantageous Effects

[17] According to the present invention, the low pressure portion of direction control valve communicates with suction line of second compressor. Thus, the pressure of the low pressure portion of direction control valve is equalized with the low pressure of suction line of second compressor, thereby reducing the pressure of the low pressure portion. Accordingly, the pressure difference between the high pressure portion and low pressure portion can be maintained above a certain value, regardless of the operation environment of air conditioner. As a result, enough power can be generated to move plunger such that the flow direction of the refrigerant can be properly shifted. Accordingly, first compressor that is off can be rapidly restarted at any time. Brief Description of the Drawings

[18] Figure 1 is a schematic diagram illustrating a conventional air conditioner having multiple compressors.

[19] Figure 2 is a schematic diagram illustrating the flow of a refrigerant in an air conditioner having multiple compressors according to the present invention, where the first and second compressors are both turned on.

[20] Figure 3 is a schematic diagram illustrating the flow of a refrigerant in an air conditioner having multiple compressors according to the present invention, where the first compressor is turned off.

[21] Figure 4 is a schematic diagram illustrating the flow of a refrigerant in an air conditioner having multiple compressors according to the present invention, where the second compressor is turned off.

[22] Figure 5 is a schematic diagram illustrating the flow (in one direction) of a refrigerant in an air conditioner according to another embodiment of the present invention.

[23] Figure 6 is a schematic diagram illustrating the flow (in a direction reverse to the flow shown in Figure 5) of a refrigerant in an air conditioner according to another embodiment of the present invention. Best Mode for Carrying Out the Invention

[24] The various embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[25] FIG. 2 illustrates the refrigerant flow in an air conditioner according to the first em- bodiment of the present invention, where the first and second compressors are both turned on. FIG. 3 illustrates the refrigerant flow in the air conditioner according to the first embodiment of the present invention, where the first compressor is turned off. FIG. 4 illustrates the refrigerant flow in the air conditioner according to the first embodiment of the present invention, where the second compressor is turned off.

[26] Air conditioner (100) comprises first compressor (110a), second compressor (HOb), first heat exchanger (120), expansion device (130), second heat exchanger (140), and direction control valve (160). First compressor (HOa) is an intermittent compressor which can be turned on or off during the operation of second compressor (110b). Discharge lines (150a, 150b) of first compressor (110a) and discharge line (152) of second compressor (110b) are connected to first heat exchanger (120) via common discharge line (154). First heat exchanger (120) is connected to second heat exchanger (140), wherein the expansion device (130) is positioned in between. Second heat exchanger (140) is connected to common suction line (155). Further downstream, common suction line (155) branches into suction lines (156a, 156b) of first compressor (110a) and suction line (158) of second compressor (110b). Positioned at the branch point is common receiver (190).

[27] First discharge line (150a) of first compressor (110a) connects the discharge side of first compressor (110a) to direction control valve (160), whereas second discharge line (150b) of first compressor (110a) connects direction control valve (160) to common discharge line (154). First suction line (156a) of first compressor (110a) connects common suction line (155) to direction control valve (160), whereas second suction line (156b) of first compressor (110a) connects direction control valve (160) to the suction side of first compressor (110a).

[28] Direction control valve (160) is a four- way valve comprising a high pressure portion, low pressure portion, a line, and a plunger. The flow direction of the refrigerant is shifted when the line is changed by moving plunger (64) by utilizing the pressure difference between the high pressure portion and the low pressure portion. As shown in FIG. 2, when the first compressor (110a) is on, direction control valve (160) connects first discharge line (150a) with second discharge line (150b). As shown in FIG. 3, when first compressor (110b) is off, direction control valve (160) allows first discharge line (150a) to connect with second suction line (156b).

[29] The high pressure portion of direction control valve (160) communicates with second discharge line (150b). The low pressure portion of direction control valve (160) communicates with suction line (158) of second compressor (110b) via low pressure connecting means. The low pressure connecting means is connection pipe (195) extending between second suction line (156b) and suction line (158) of second compressor (110b). The diameter of connection pipe (195) is smaller than that of second suction line (156b) and suction line (158) of second compressor (110b). Preferably, the diameter of connection pipe (195) is equal to or smaller than 1/6 of the diameter of second suction line (156b) and suction line (158) of second compressor (HOb).

[30] According to the embodiments shown in the figures, the low pressure portion of direction control valve (160) communicates with suction line (158) of second compressor (HOb) via second suction line (156b) and connection pipe (195). However, the low pressure portion of direction control valve (160) may be directly connected to suction line (158) of second compressor (110b) via the low pressure connecting means. The significance lies in the fact that the refrigerant pressure in suction line (158) of second compressor (110b) affects the low pressure portion of direction control valve (160).

[31] Accumulator (112a) is positioned on second suction line (156b), while the connection portion of connection pipe (195) and second suction line (156b) is located upstream of accumulator (112a). Accumulator (112b) is positioned on suction line (158) of second compressor (110b), while the connection portion of connection pipe (195) and suction line (158) is located upstream of accumulator (112b).

[32] Backflow prevention check valve (170) is positioned on first suction line (156a). As shown in FIG. 3, check valve (170) prevents the refrigerant discharged from second compressor (110b) from flowing into the suction side of second compressor (110b) when first compressor (110a) is off.

[33] Second compressor (110b) may be an intermittent compressor, where backflow prevention check valve (180) is positioned on discharge line (152) of second compressor (110b). As shown in FIG. 4, check valve (180) prevents the refrigerant discharged from first compressor (110a) from flowing into the discharge side of second compressor (110b) when second compressor (110b) is off. Instead of check valve (180), a direction control valve may be positioned on the discharge line of second compressor (110b), as on the discharge line of first compressor (110a). Alternatively, second compressor (110b) may be a continuous compressor with no components positioned on the discharge line of second compressor (110b).

[34] The operation of the air conditioner according to one embodiment of the present invention will be further described.

[35] When the required cooling demands are high, both first compressor (110a) and second compressor (110b) are turned on, as shown in FIG. 2. Direction control valve (160) allows first discharge line (150a) to connect with second discharge line (150b), while the refrigerants having high temperature and high pressure, which are discharged from first compressor (110a) and second compressor (110b), merge together to flow into common discharge line (154). The refrigerant, initially a gaseous refrigerant of high temperature and high pressure, is condensed into a liquid refrigerant of medium temperature and high pressure when flowing through first heat exchanger (120) and loses heat into the surroundings. Next, the refrigerant is expanded to a refrigerant of low temperature and low pressure while flowing through expansion device (130). Then, the refrigerant is evaporated into a gaseous state while passing through second heat exchanger (140), and absorbs heat from the surroundings. That is, first heat exchanger (120) and second heat exchanger (140) function as a condenser and an evaporator, respectively. Subsequently, via common receiver (190), the evaporated refrigerant diverges to flow into first compressor (HOa) and second compressor (110b) via accumulators (112a, 112b), respectively.

[36] Meanwhile, when the required cooling demands are low, first compressor (110a) is turned off, as shown in FIG. 3, or second compressor (HOb) is turned off, as shown in FIG. 4. The compression capacities of first compressor (110a) and second compressor (110b) do not have to be identical. By having different compression capacities for the compressors, however, it is possible to respond more comprehensively to variations in the required cooling demands. When first compressor (110a) is off, direction control valve (160) allows first discharge line (150a) to connect with second suction line (156b). The refrigerant discharged through first discharge line (150a) of first compressor (110a) does not flow into common discharge line (154) via second discharge line (150b), but flows into the suction side of first compressor (110a) via second suction line (156b).

[37] If the cooling demands become high again, first compressor (110a) is restarted and plunger (164) of direction control valve (160) should be moved such that first discharge line (150a) of first compressor (110a) is connected to second discharge line (150b). The low pressure portion of direction control valve (160) communicates with suction line (158) of second compressor (110b). In the embodiments shown in the figures, the low pressure portion of direction control valve (160) communicates with suction line (158) of second compressor (110b) via second suction line (156b) and connection pipe (195). Thus, the pressure of the low pressure portion of direction control valve (160) is equalized with the low pressure of suction line (158) of second compressor (110b), thereby reducing the pressure of the low pressure portion. Accordingly, the pressure difference between the high pressure portion and low pressure portion can be maintained above a certain value, even when first compressor (110a) is off and the pressure of second suction line (156b) of first compressor (110a), which affects the low pressure portion of direction control valve (160), is higher than the pressure in second suction line (156b) during normal operation of first compressor (110a). The pressure difference between the high pressure portion and low pressure portion can also be maintained above a certain value in winter when the outdoor tern- perature is low and the pressure of the refrigerant discharged from second compressor (HOb), which affects the high pressure portion of direction control valve (160), is lower than that in other seasons. As a result, enough power can be generated to move plunger (164) such that the flow direction of the refrigerant can be properly shifted. Accordingly, first compressor (110a) that is off can be rapidly restarted at any time.

[38] Second suction line (156b) of first compressor (110a) is connected to suction line

(158) of second compressor (HOb) via connection pipe (195). Connection pipe (195) has a smaller diameter than that of second suction line (156b) and suction line (158) of second compressor (110b). Thus, it is possible to avoid sudden changes in pressure between second suction line (156b) and suction line (158) of second compressor (110b) and reduce the occurrence of vibration. In order to obtain such effects, the diameter of connection pipe (195) is preferably equal to or smaller than 1/6 of the diameter of second suction line (156b) and suction line (158) of second compressor (110b).

[39] FIGS. 5 and 6 illustrate an air conditioner according to another embodiment of the present invention. Like reference numerals refer to like components shown for the first embodiment of the present invention in FIGS. 2-4. Air conditioner (200) further includes second direction control valve (210), compared to air conditioner (100).

[40] Second direction control valve (210) is connected to second discharge line (150b) of first compressor (110a) and discharge line (152) of second compressor (110b) via common discharge line (154). Second direction control valve (210) is connected to first suction line (156a) of first compressor (110a) and suction line (158) of second compressor (110b) via common suction line (155). First connection line (157) connects second direction control valve (210) to first heat exchanger (120). Second connection line (159) connects second direction control valve (210) to second heat exchanger (140).

[41] As shown in FIG. 5, second direction control valve (210) connects second heat exchanger (140) to common suction line (155), while simultaneously connecting common discharge line (154) to first heat exchanger (120). In this case, first heat exchanger (120) and second heat exchanger (140) function as a condenser and an evaporator, respectively. Alternatively, as shown in FIG. 6, second direction control valve (210) connects first heat exchanger (120) to common suction line (155), while simultaneously connecting common discharge line (154) to second heat exchanger (140). In this case, second heat exchanger (140) and first heat exchanger (120) function as a condenser and an evaporator, respectively. As such, by including second direction control valve (210) to shift the flow direction of the refrigerant cycle, air conditioner (200) is capable of performing both cooling and heating operations.

[42] Although the invention has been described in detail for the purpose of illustration, it is understood that such detail is solely for that purpose, and variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention which is defined by the claims that follow. While the air conditioner according to one embodiment of the present invention comprises two compressors, it can further comprise a third compressor. For example, another embodiment of the present invention can be considered where the air conditioner further comprises a third compressor with a direction control valve positioned on the common discharge line of the first and second compressors. Such a modification would be considered obvious to one of ordinary skill in the art.

Claims

[1] An air conditioner having multiple compressors, comprising: a first compressor; a second compressor; a first heat exchanger; a second heat exchanger; an expansion device; and a direction control valve comprising a high pressure portion, a low pressure portion, a line, and a moving part, wherein the moving part moves to change the line according to the pressures of the high pressure portion and low pressure portion, wherein the first compressor comprises a discharge line and a suction line and is an intermittent compressor which is turned on or off during the operation of the second compressor; wherein the second compressor comprises a discharge line and a suction line; wherein the discharge line of the first compressor and the discharge line of the second compressor are connected to the first heat exchanger through a common discharge line, the first heat exchanger is connected to the second heat exchanger by way of the expansion device, the second heat exchanger is connected to a common suction line, the common suction line is connected downstream to the suction line of the first compressor and the suction line of the second compressor; wherein the discharge line of the first compressor comprises a first discharge line and a second discharge line, the first discharge line connecting a discharge side of the first compressor to the direction control valve, the second discharge line connecting the direction control valve to the common discharge line; wherein the suction line of the first compressor comprises a first suction line and a second suction line, the first suction line connecting the common suction line to the direction control valve, the second suction line connecting the direction control valve to the suction side of the first compressor; wherein the direction control valve allows the first discharge line to connect with the second discharge line when the first compressor is on, while allowing the first discharge line to connect with the second suction line when the first compressor is off; and wherein the low pressure portion of the direction control valve communicates with the suction line of the second compressor by low pressure connecting means.

[2] The air conditioner according to claim 1, wherein the high pressure portion of the direction control valve communicates with the second discharge line and the low pressure connecting means is a connection pipe extending between the second suction line and the suction line of the second compressor.

[3] The air conditioner according to claim 2, further comprising a backflow prevention check valve positioned on the first suction line.

[4] The air conditioner according to claim 2, wherein an accumulator is positioned on the second suction line, and the connection portion of the connection pipe and the second suction line is located upstream of the accumulator.

[5] The air conditioner according to claim 2, wherein the second compressor is a continuous compressor.

[6] The air conditioner according to claim 2, further comprising a backflow prevention check valve positioned on the discharge line of the second compressor, wherein the second compressor is an intermittent compressor.

[7] The air conditioner according to claim 2, wherein the diameter of the connection pipe is equal to or smaller than 1/6 of the diameter of the second suction line and the suction line of the second compressor.

[8] An air conditioner having multiple compressors, comprising: a first compressor; a second compressor; a first heat exchanger; a second heat exchanger; an expansion device; a first direction control valve comprising a high pressure portion, a low pressure portion, a line, and a moving part, wherein the moving part moves to change the line according to the pressures of the high pressure portion and low pressure portion; and a second direction control valve; wherein the first compressor comprises a discharge line and a suction line and is an intermittent compressor which is turned on or off during the operation of the second compressor; wherein the second compressor comprises a discharge line and a suction line; wherein the second direction control valve is connected to the discharge line of the first compressor and the discharge line of the second compressor via a common discharge line, to the first heat exchanger via a first connection line, to the second heat exchanger via a second connection line, and to the suction line of the first compressor and the suction line of the second compressor via a common suction line; wherein the first heat exchanger is connected to the second heat exchanger by way of the expansion device; wherein the discharge line of the first compressor comprises a first discharge line and a second discharge line, the first discharge line connecting a discharge side of the first compressor to the first direction control valve, the second discharge line connecting the first direction control valve to the common discharge line; wherein the suction line of the first compressor comprises a first suction line and a second suction line, the first suction line connecting the common suction line to the first direction control valve, the second suction line connecting the first direction control valve to the suction side of the first compressor; wherein the first direction control valve allows the first discharge line to connect with the second discharge line when the first compressor is on, while allowing the first discharge line to connect with the second suction line when the first compressor is off; wherein the low pressure portion of the first direction control valve communicates with the suction line of the second compressor by low pressure connecting means; wherein the second direction control valve connects the second heat exchanger to the common suction line while simultaneously connecting the common discharge line to the first heat exchanger, or the second direction control valve connects the first heat exchanger to the common suction line while simultaneously connecting the common discharge line to the second heat exchanger.

[9] The air conditioner according to claim 8, wherein the high pressure portion of the direction control valve communicates with the second discharge line and the low pressure connecting means is a connection pipe extending between the second suction line and the suction line of the second compressor.

[10] The air conditioner according to claim 9, further comprising a backflow prevention check valve positioned on the first suction line.

[11] The air conditioner according to claim 9, wherein an accumulator is positioned on the second suction line, and the connection portion of the connection pipe and the second suction line is located upstream of the accumulator.

[12] The air conditioner according to claim 9, wherein the second compressor is a continuous compressor.

[13] The air conditioner according to claim 9, further comprising a backflow prevention check valve positioned on the discharge line of the second compressor, wherein the second compressor is an intermittent compressor.

[14] The air conditioner according to claim 9, wherein the diameter of the connection pipe is equal to or smaller than 1/6 of the diameter of the second suction line and the suction line of the second compressor.