WO2012056150A2 - Refrigeration system - Google Patents

Abstract

This refrigeration system (1) comprises a circuit (2) through which there circulates a refrigerant fluid notably comprising a compression device (6) comprising first and second compressors (7, 8), each compressor comprising a body (9) comprising, on the one hand, a low-pressure part (11) containing a motor (12) and an oil pan (13) and, on the other hand, a refrigerant fluid intake orifice (15) opening into the low-pressure part, first and second branch pipes (21, 22) placing a refrigerant fluid distribution pipe respectively in communication with the intake orifices (15) of the compressors (7, 8), an oil level equalizing pipe (23) placing the oil pans (13) of the compressors in communication with each other, and a pressure equalizing pipe (24) placing the low-pressure parts (11) of the compressors in communication with each other. The first branch pipe comprises means for reducing the bore section for the flow of the refrigerant gas along said branch pipe.

Description

 Refrigeration system

 The present invention relates to a refrigeration system.

 In a known manner, a refrigeration system comprises: a circulation circu lation of a refrigerant fluid successively comprising a condenser, an expander, an evaporator and a compression device connected in series, the compression device comprising at least one first compressor and a second compressor mounted in parallel, each compressor comprising a body comprising on the one hand a low pressure portion containing a motor and an oil sump disposed in the bottom of the body, and on the other hand an inlet orifice of refrigerant discharging into the low pressure part, and

 a refrigerant dispensing device comprising a dispensing line connected to the evaporator, a first bypass line putting the dispensing line into communication with the inlet orifice of the first compressor, and a second bypass pipe putting into operation communicating the distribution line with the inlet of the second compressor.

 To ensure proper operation and reliability of such a refrigeration system, it is necessary to balance the oil levels in the casings of the two compressors. This balancing of the oil levels is advantageously obtained by balancing the pressures prevailing in the low-pressure parts of the two compressors and by connecting the oil sump of the latter via an oil level equalization line.

 A first known solution for balancing the pressures of the low pressure parts of the two compressors is to have a section reduction means inside one of the bypass lines, the reduction means being arranged to generate losses of load adapted so that the total pressure drop of the dispensing device ensures a satisfactory balancing of the pressures prevailing in the low pressure parts of the two compressors.

 This first solution is satisfactory for a refrigeration system comprising two compressors with fixed capacity, but absolutely not for a refrigeration system comprising at least one variable capacity compressor for the reasons mentioned below.

The term "variable capacity compressor" means any compressor that can have a variable flow rate (or several flow rates) at the suction of the compressor. compressor for the same operating point (an operating point corresponding to a given suction pressure, suction temperature and discharge pressure). Among the known technical solutions for producing a variable capacity compressor, there will be mentioned, for example:

 a compressor driven by a variable speed motor,

a compressor driven by a 2-speed motor (type 2/4 pole motor),

 a compressor driven by a fixed speed motor plus a gearbox,

 a compressor driven by a fixed speed motor plus an epicyclic gear (planetary),

 a compressor with discharge valves opening or closing an internal bypass to the compressor,

 a compressor with multiple compression units, some of which can be deactivated,

 - a compressor with internal mechanism to create intermittent compression.

 The use of a variable capacity compressor has the consequence that the inlet conditions (speed, pressure, density) of the refrigerant in each bypass duct can be extremely variable.

 However, since the pressure losses of the bypass lines, the equalization line and the reduction means are linked to the refrigerant velocity profiles in each bypass duct, significant variations in the inlet conduction conditions are observed. refrigerant in each bypass line can significantly alter the behavior of the refrigeration system, thereby preventing a balancing of the pressures in the low pressure parts of the compressors, thus oil levels in the different compressors .

 Thus, the above-mentioned solution does not make it possible to obtain satisfactory equilibration of the oil levels that are the operating conditions of the refrigeration system, when at least one of the compressors is a compressor with variable capacity.

A second known solution for balancing the pressures of the low pressure parts of the two compressors is to put in contact the oil sump of the two compressors via a first equalization pipe promoting the transfer of oil between the two compressors, and to connect the low pressure parts of the two compressors via a second equalization duct promoting the transfer of fluid refrigerant between the two compressors.

 As with the first solution, this second solution, although satisfactory for a refrigeration system comprising two compressors with fixed capacity, is absolutely not suitable for a refrigeration system comprising at least one compressor with variable capacity, and more particularly variable speed.

 Indeed, given the large variations in speeds during operation of the variable speed compressor, the second equalizing pipe should have a large diameter to ensure a satisfactory balance of pressure in the low pressure parts of the two compressors whatever the conditions operation of the latter, which would have the effect of increasing the size and cost of the refrigeration system.

 Thus, the second solution involves the realization of an expensive and bulky refrigeration system to obtain a satisfactory balance of oil levels whatever the operating conditions of the refrigeration system, when at least one of the compressors is a compressor with variable capacity.

 The present invention therefore aims to remedy these drawbacks. The technical problem underlying the invention therefore consists in providing a refrigeration system with a simple and economical structure, making it possible to limit the pressure difference between the low-pressure parts of the compressors, whatever the operating conditions of the compressor system. refrigeration.

 For this purpose, the present invention relates to a refrigeration system, comprising:

- a circu lation of a fl uid refrigerant successively comprising a condenser, an expander, a evaporator and a compression device connected in series, the compression device comprising at least a first compressor and a second compressor connected in parallel , each compressor comprising a body comprising on the one hand a low pressure part containing a motor and an oil sump disposed in the bottom of the body, and on the other hand a refrigerant inlet opening opening in the low pressure part,

 a refrigerant dispensing device comprising a dispensing line connected to the evaporator, a first bypass line putting the dispensing line into communication with the inlet orifice of the first compressor, and a second bypass pipe putting into operation communicating the distribution line with the inlet of the second compressor,

 an oil level equalization circuit bringing the oil pans of the first and second compressors into communication,

 a pressure equalization line putting in communication the low pressure parts of the first and second compressors,

 characterized in that the first compressor is a variable capacity compressor, and the second compressor is a fixed capacity compressor, and in that the first branch line comprises means for reducing the flow section of the refrigerant gas in said first bypass line, the reduction means being arranged such that the flow section of the refrigerant gas at the reduction means is smaller than the flow section of the refrigerant gas at the corresponding inlet orifice .

 The combination of a pressure equalization pipe with reduction means arranged in the first bypass pipe makes it possible to limit the pressure difference between the low-pressure parts of the two compressors whatever the operating conditions of the compressor to be. variable capacity, and in the case of a variable speed compressor, regardless of the speed of operation of the engine of the latter.

 Thus, the combination of a pressure equalization line with reduction means disposed in the first branch line allows the use of a reduced diameter pressure equalization line. The result is a reliable, compact and economical refrigeration system.

Advantageously, each branch line comprises a connection portion connected to the corresponding inlet port. Preferably, each bypass line comprises a bypass tube connected to the distribution line and a connecting sleeve arranged to connect said bypass tube to the corresponding inlet port. According to a first alternative of the invention, the reduction means are disposed in the bypass tube of the first branch line. According to a second alternative of the invention, the reduction means are arranged in the connection sleeve of the first branch line.

 Preferably, the reduction means is arranged to reduce the flow section of the refrigerant gas centrally with respect to the wall of the first bypass line.

 The reduction means preferably comprise a ring fixed in the first bypass line, for example by brazing or crimping, the ring having a longitudinal through orifice.

 Preferably, the orifice of the ring is centered with respect to the wall of the first bypass pipe.

 The oil level equalization line preferably has a diameter of between 0.5 and 1 times the diameter of the first or second bypass duct of the dispensing device. The pressure equalizing line preferably has a diameter of between 0.7 and 1.4 times the diameter of the first or second bypass line of the dispensing device.

 According to one embodiment, the oil level equalization line is arranged such that, under optimum operating conditions, the lower part of said equalization line opens into the first and second oil sump. compressors and the upper part of said equalization line opens into the low pressure parts of the first and second compressors.

 Preferably, the refrigeration system comprises control means arranged to mod uler the capacity of the first variable capacity compressor between a minimum capacity value and a maximum capacity value.

The reduction means are more particularly arranged such that the low pressure portion of the first variable capacity compressor has a higher pressure than the low pressure portion of the second fixed capacity compressor when the first variable capacity compressor function has capacity. In addition, the second fixed capacity compressor operates, and such that the low pressure portion of the first variable capacity compressor has a lower pressure than the low pressure portion of the second compressor. fixed capacity when the first variable capacity compressor is operating at maximum capacity and the second fixed capacity compressor is operating.

 Preferably, the reduction means are also arranged such that the pressure difference in the low pressure portions of the first and second compressors, when the first variable capacity compressor operates at minimum capacity and the second fixed capacity compressor operates, is substantially equal in absolute value to the pressure difference in the low pressure parts of the first and second compressors, when the first variable capacity compressor operates at maximum capacity and the second fixed capacity compressor operates.

 Advantageously, the engine of the first variable capacity compressor is a variable speed motor. In this case, the control means are arranged to modulate the motor speed of the variable capacity compressor between a minimum speed and a maximum speed. As a result, the reduction means are more particularly arranged such that the low pressure part of the first variable capacity compressor has a higher pressure than the low pressure part of the second fixed capacity compressor when the first variable capacity compressor at least a minimum speed function andthat the second fixed capacity compressor operates, and such that the low pressure portion of the first variable capacity compressor has a lower pressure than the low pressure portion of the second fixed capacity compressor when the first compressor variable capacity operates at maximum speed and that the second fixed capacity compressor operates.

 Advantageously, the control means are arranged to selectively control the tilting of the first fixed capacity compressor between a running mode and a stopping mode.

 According to one embodiment, the first branch line has, outside the zone where the reduction means are arranged, a substantially identical section to that of the second branch line.

 According to another embodiment, the second bypass line has a substantially identical section to that of the pressure equalization line.

Preferably, the first and second compressors are scroll refrigeration compressors. According to an alternative of the invention, the reduction means consist of a deformation towards the inside of the wall of the first bypass pipe. Advantageously, the deformation of the wall of the first bypass pipe comprises a first convergent frustoconical portion and a second divergent frustoconical portion. Preferably, the deformation of the wall of the first branch pipe comprises a third cylindrical portion interposed between the first and second frustoconical portions.

 According to another alternative of the invention, the deformation of the wall of the first bypass pipe has a domed profile inwards.

 In any case, the invention will be better understood with the aid of the description which follows with reference to the appended schematic drawing showing, by way of a non-limiting example, one embodiment of this refrigeration system.

 Figure 1 is a schematic view of a refrigeration system according to the invention.

 Figure 2 is a partial perspective view of the refrigeration system of Figure 1.

 Figure 3 is a partial schematic sectional view of the refrigeration system of Figure 1.

 Figure 1 shows schematically the main components of a refrigeration system 1.

 The refrigeration system 1 comprises a circulation circuit 2 of a refrigerant fluid successively comprising a condenser 3, an expander 4, an evaporator 5 and a compression device 6 connected in series.

 The compression device 6 comprises a first variable capacity compressor 7 and a second fixed capacity compressor 8 connected in parallel. Each compressor 7, 8 comprises a body 9 comprising a low-pressure part 1 1 containing a motor 12 and an oil pan 13 disposed in the bottom of the body, and a high-pressure part 14 disposed above the low-pressure part. , containing a compression stage.

The body 9 of each compressor further comprises a refrigerant inlet opening 15 opening into an upper portion of the low pressure portion 1 1, a first equalizing orifice 16 opening into the oil sump, a second orifice d equalization 17 opening in an intermediate portion of the low pressure portion 1 1, and a discharge orifice 18 opening into the high pressure portion 14.

 The refrigeration system 1 also comprises a refrigerant dispensing device 19. The dispensing device 19 comprises a distribution pipe 20 connected to the evaporator 5, a first bypass line 21 putting the distribution pipe 20 into communication with the inlet orifice 15 of the first compressor 7, and a second pipe of bypass 22 placing the distribution pipe 20 in communication with the inlet orifice 15 of the second compressor 8.

 Each bypass line 21, 22 respectively comprises a bypass tube 21a, 22a connected to the distribution line 20 and a connecting sleeve 21b, 22b connected to the corresponding admission port 15.

 The refrigeration system 1 further comprises an oil level equalizing line 23 connecting the first equalization orifices 16 of the two compressors and thereby putting into communication the oil sumpers 13 of the first and second compressors, and a pressure equalization line 24 connecting the second equalization orifices 17 of the two compressors and thereby putting into communication the low-pressure parts 1 1 of the first and second compressors.

 The refrigeration system 1 also includes a refrigerant delivery device. The dispensing device 25 comprises a delivery line 26 connected to the condenser 3, a first bypass line 27 putting the discharge line 26 into communication with the delivery port 18 of the first compressor 7, and a second bypass line 28 placing the discharge line 27 in communication with the delivery port 18 of the second compressor 8.

 The refrigeration system 1 further comprises control means 29 arranged from one hand to selectively control the respective switching of the first and second compressors between a running mode and a stop mode, and secondly to modulate the speed of the motor 12 of the first compressor 7 between a minimum speed and a maximum speed.

As shown in FIG. 3, the first bypass pipe 21 comprises means for reducing the flow section of the refrigerant gas in said bypass pipe, the reduction means being arranged such that the flow section of the refrigerant gas at the reduction means is smaller than the flow section of the refrigerant gas at the inlet 15 of the first compressor 7.

 The reduction means are advantageously arranged near the inlet 15 of the first compressor 7. The reduction means comprise an annular ring 30 fixed in the first bypass duct 21, for example by brazing or crimping. The annular ring 30 has a longitudinal through hole centered with respect to the wall of the first branch pipe 21. It should be noted that the outer diameter of the annular ring 30 corresponds substantially to the inside diameter of the bypass tube 21a of the first bypass line 21.

 The annular ring 30 is arranged such that the low pressure portion of the first compressor 7 has a higher pressure than the low pressure portion of the second compressor 8 when the first compressor is operating at minimum speed and the second compressor is in operation. in operation, and in such a way that the low pressure part of the first compressor has a lower pressure than the low pressure part of the second compressor when the first compressor is operating at maximum speed and the second compressor is in operating mode.

 The annular ring 30 is furthermore arranged so that the pressure difference in the low pressure portions of the first and second compressors when the first compressor is operating at minimum speed and the second compressor is in the operating mode is substantially equal in value. absolute at the pressure difference in the low pressure portions of the first and second compressors when the first compressor is operating at maximum speed and the second compressor is in the operating mode.

 According to an alternative embodiment not shown in the figures, the annular ring 30 could be fixed in the connection sleeve of the first branch pipe 21.

 As goes without saying, the invention is not limited to the sole embodiment of this refrigeration system, described above as an example, it encompasses all the variants.

Claims

1. Refrigeration system (1), comprising:  - a circulation circuit (2) of a refrigerant successively comprising a condenser (3), an expander (4), an evaporator (5) and a compression device (6) connected in series, the compression device comprising at least one at least one first compressor (7) and a second compressor (8) connected in parallel, each compressor comprising a body (9) having on the one hand a low pressure part (1 1) containing a motor (12) and a housing oil (13) disposed in the bottom of the body, and secondly a refrigerant inlet (15) opening into the low pressure part,  a refrigerant distribution device (19) comprising a distribution line (20) connected to the evaporator (5), a first bypass line (21) putting the distribution line (20) in communication with the an intake port (15) of the first compressor (7), and a second bypass line (22) communicating the detuning conduit with the inlet (15) of the second compressor (8),  an oil level equalization line (23) putting into communication the oil sump (13) of the first and second compressors,  a pressure equalization line (24) putting into communication the low pressure parts (1 1) of the first and second compressors, characterized in that the first compressor (7) is a variable capacity compressor, and the second compressor (8) is a fixed capacity compressor, and in that the first branch pipe (21) comprises reduction means (30). ) of the flow section of the refrigerant gas in said first bypass line, the reduction means (30) being arranged such that the flow section of the refrigerant gas at the reduction means is less than the section of the flow of the refrigerant gas at the corresponding inlet port (15). 2. Refrigeration system according to claim 1, characterized in that each branch line (21, 22) comprises a connecting portion (21b, 22b) connected to the corresponding inlet port (15). Refrigeration system according to Claim 1 or 2, characterized in that the reduction means are arranged to reduce the flow section of the refrigerant gas centrally with respect to the wall of the first branch line. 4. Refrigeration system according to one of claims 1 to 3, characterized in that the reduction means comprise a ring (30) fixed in the first branch line, for example by brazing or crimping, the ring having a longitudinal orifice. crossing. 5. Refrigeration system according to one of claims 1 to 4, characterized in that the refrigeration system comprises control means (29) arranged to modulate the capacity of the first compressor (7) between a minimum capacity value and a maximum capacity value. 6. Refrigeration system according to claim 5, characterized in that the reduction means are arranged such that the low pressure part of the first compressor has a higher pressure than the low pressure part of the second compressor when the first compressor operates. with a minimum capacity and the second compressor function does not, and so that the pa pa low pressure of the first compressor has a lower pressure than the low pressure part of the second compressor when the first compressor operates at maximum capacity and the second compressor works. Refrigeration system according to Claim 6, characterized in that the reduction means are arranged in such a way that the pressure difference in the low pressure parts (1 1) of the first and second compressors when the first compressor (7) operates with minimum capacity and that the second compressor operates is substantially equal in absolute value to the pressure difference in the low pressure parts (1 1) of the first and second compressors when the first compressor (7) operates at maximum capacity and the second compressor operates. 8. Refrigeration system according to one of claims 5 to 7, characterized in that the control means (29) are arranged to modulate the speed of the motor (12) of the first compressor between a minimum speed and a maximum speed.