FR2513747A1 - MULTIMOTOCOMPRESSOR REFRIGERATION SYSTEM - Google Patents

Abstract

REFRIGERATION SYSTEM WITH MULTIMOTOCOMPRESSORS WITH ONE LOW PRESSURE STAGE 12 AND AT LEAST ONE HIGH PRESSURE STAGE 13 MOUNTED IN COMPOUND INCLUDING ON THE ONE PART OF THE POINTS OF USE 14, 15, SPECIFIC TO EACH OF THESE STAGES AND AT RESPECTIVELY DIFFERENT AND VAPORATION TEMPERATURES ON THE OTHER HAND, A REFRIGERANT CIRCUIT SUPPLYING ALL OF THESE POINTS OF USE, BY REFRIGERATING LIQUID UNDER THE SAME HIGH PRESSURE, FROM A CONDENSED REFRIGERANT TANK 28, COMMON TO THESE STAGES.

Description

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  MULTIMOTOCOMPRESSOR REFRIGERATION SYSTEM

  The present invention relates to a refrigeration installation with multi-compressors.

  To obtain a low temperature below -35 C approx.

  Ron, it is known to subdivide in a refrigeration plant, the compression in two stages to avoid the disadvantages of a high compression ratio in a single-stage operation These disadvantages are both thermodynamic and constructive In effect a high superheat heat may lead to a breakdown of the lubrication medium and

  a large pressure difference may compromise the water

  the high quality of the valves of the central compressor units However in compound refrigeration plants or with known cascade stages, there are frequently points of use at a single low evaporation temperature In a refrigeration system with points of use at different temperatures from evaporation carried out according to known solutions, such a compound refrigeration plant

  is associated with other plants with independent refrigeration circuits

  pendants respectively giving required evaporation temperatures There are thus in this installation as many refrigeration circuits as associated power stations and the refrigeration installation produced according to these known solutions proves to be expensive both

  construction cost than operating cost.

  The object of the present invention is to avoid these inconveniences.

  nients, allows for a multi-refrigeration installation

  motor-compressors, economical at points of use at temperatures

  different evaporation systems with good mechanical functioning

  nique and excellent refrigeration efficiency According to the invention a refrigeration installation with multi-compressors, having a stage

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  low pressure and at least one high pressure stage, mounted as a compound comprises on the one hand points of use, suitable for

  each of these stages and at respective evaporation temperatures

  different, and on the other hand a refrigeration circuit

  as all of these points of use, in liquid refrigerant under

  same high pressure, coming from a refrigerant tank

dense, common to these floors.

  In order to better understand the invention, a certain number of exemplary embodiments are illustrated below by way of illustration, illustrated by the attached drawings, in which: FIG. I represents a diagram of a known compound refrigeration plant, Figure 2 shows a schematic view of a first

  exemplary embodiment according to the invention, of a refrigeration installation

  fique compound, at points of use at different evaporation temperatures, and FIG. 3 represents a schematic view of a second

  exemplary embodiment according to the invention of a refrigeration installation

  compound compound at points of use at different temperatures

evaporation.

  A known compound l refrigeration plant usually comprises

  on the one hand, a low pressure motor compressor 2 which sucks expanded refrigerant gas at the pressure Po from the points of use 3 at a single low evaporation temperature for example -380 C, compresses it to the pressure Pm and discharges it into an intermediate bottle 4 o the compressed refrigerant gas desuperheats, and from other hand a high pressure motor compressor 5 which sucks desuperheated refrigerant gas from the bottle 4, compresses it to the pressure Pk and discharges it into a condenser 6 The condensed refrigerant coming from the condenser 6 accumulates in the form of liquid in a tank 7 and passes partly in a coil 8 arranged in the lower zone of the intermediate bottle 4, and in

  part through a regulator 9 in the bottle 4 o, by evapo-

  ration, it desuperheats the compressed compressed refrigerant vapors

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  by the low-pressure motor compressor 2, and under cools the stream of liquid refrigerant which borrows the coil 8 to go to relax through the pressure reducer 10 in the points of use 3 to

  a single low evaporation temperature -381 C for example.

  According to a known technique, in order to produce a refrigeration installation with points of use at two different evaporation temperatures, for example -38 C and -100 C, a combined refrigeration plant l above is combined with another plant with independent refrigeration circuit , of known type, not shown giving cold at a single evaporation temperature -10 C. One of the great drawbacks of this known solution is already mentioned in a

previous paragraph.

  A refrigeration installation produced according to the invention, at points of use at different evaporation temperatures, for example at two low evaporation temperatures tl and t 2 with t I less than t 2, is a refrigeration installation with multi-compressors having in its refrigeration circuit, at least on the one hand a low pressure stage and a high pressure stage which have their own points

  of use and including the common suction collectors of moto-

  compressors are maintained at pressures, equal respectively to the evaporation pressures tl and t 2 of the points of use of these two stages, the capacity and the number of the compressors of the low pressure stage are provided to supply the points correctly with refrigerant of use specific to this stage, and the capacity and the number of motor-compressors of the high-pressure stage are determined to supply - correctly by refrigerating the points of use of these two stages, the refrigerant gas discharged from the low stage pressure being admitted into the common suction manifold of the high pressure stage at the same time as the expanded refrigerant gas coming from the clean points of use of this high stage

  pressure, and on the other hand devices to ensure sub-cooling

  liquid refrigerant supplying the points of use of the low pressure stage and desuperheating of the refrigerant gas discharged from the low pressure stage so that the entry of the latter into

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  the common suction manifold of the high pressure stage maintains the temperature of the gas mixture therein at a

desired level of desuperheating.

  In a first embodiment of the invention, illustrated in FIG. 2, the compound refrigeration installation 11 comprises a low pressure stage 12 and a high pressure stage 13 having

  respectively of the points of use 14 at a temperature of eva-

  poration tl, equal to -38 g C, and points of use 15 at an evaporation temperature t 2, equal to -100 C. The low pressure stage 12 comprises two motor compressors 16, 17 whose total capacity is sufficient to supply refrigerant to the points of use'14 while the upper stage

  pressure comprises three motor compressors 18, 19, 20 whose capacity

  total city is determined to properly supply refri-

  managing the points of use 14 and 15 of the two stages 12 and 13 The common suction manifold 21 of the compressors 16, 17 of the low pressure stage is maintained at a pressure equal to the pressure

  -381 C of the points of use 14 The motocompres-

  sors 16 and 17 draw in expanded refrigerant gas from the points of use 14 and discharge it through their common discharge line 22 and an oil separator 23, into a common manifold

  suction 24 of the high pressure stage 13 compressors.

  The suction manifold 24, maintained at a pressure equal to the evaporation pressure -10 C from the points of use 15, receives both expanded refrigerant gas coming from these points of use 15 and refrigerant gas discharged from the low pressure stage 12 The high pressure stage compressors 18, 19, 20 13 suck refrigerant gas from their suction manifold 24 and discharge it through their common discharge pipe 25 and an oil separator 26, into a condenser 27 The refrigerant gas condensed in the form of liquid passes from the condenser 27 into a reservoir 28 common to the two stages 12 and 13 which supplies under the same high pressure both the points of use 14 and 15 of these two stages An exchanger 29 to against current went up between these two

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  stages 12 and 13 for, on the one hand, cooling the stream of liquid refrigerant supplying the points of use 14 of the low pressure stage 12 and, on the other hand, desuperheating the refrigerant gas discharged by the low pressure stage 12 into the manifold suction 24 of the high pressure stage 13 In this exchanger 29, part

  coolant coming from the reservoir 28 passing through a detente

  Deur 30 is injected against the current into the body of the exchanger 29 to sub-cool the flow of liquid refrigerant going from this reservoir 28 to the points of use 14 at evaporation temperature -381 C while the refrigerant expanded in the body of the exchanger 29 is injected through a valve 31 into the stream of refrigerant gas discharged by the low pressure stage 12 and desuperheats it to a selected level before it enters the common manifold

  suction 24 of the high pressure stage 13.

  As a result, the expanded gas from the points of use

  the high pressure stage is also desuperheated.

  In a comparison between two refrigeration installations of equivalent capacity, one of which is an installation produced according to a known technique consisting of a side-by-side grouping of a compound power station with points of use at a temperature

  evaporator -380 C and a central refrigeration circuit

  pendant at points of use at evaporation temperature -10 OC, and the other is an installation 11 produced according to the invention described in a previous paragraph, it is noted that thanks to a voluntary desuperheating of the expanded gas coming from the points of use 15 of the high pressure stage 13 and of the gas discharged from the low pressure stage 12 of the installation 11 an appreciable saving of energy expended is achieved in the production of cold at these points of use at evaporation temperatures -381 C and -10 'C Indeed because of the independence of the refrigeration circuits in the installation carried out, according to the known technique, the expanded superheated refrigerant gas coming from the points of use at evaporation temperature -100 C is not not cooled or desuperheated before being vacuumed and compressed

by motor compressors.

  To obtain a good mechanical functioning by a grease-

  correct correct of the compressors, in the installation 11 illustrated in FIG. 2, the casings of the compressors of the compressors 16 and 17 of the low pressure stage 12 are connected together by a large section pipe 32 whose double function is to allow the oil to balance in the compressor crankcases and to have the same pressure in these crankcases In the high-pressure stage 13 of the installation 11, the oil recovered by the oil separator 26 as well as the gaseous refrigerant entrained by the oil are brought into an oil tank 33 the lower part of which is connected to the casings of the motor compressors 18, 19, 20 by a line 34 and float devices 35, 36, 37 and the upper part is connected to the manifold common suction 24 of the compressors by a line 38 and a calibrated valve 39 which creates a pressure drop of approximately one bar to bring the oil tank 33 to a pressure of one bar higher than the pressure in motor crankcases mpresseurs 18, 19, 20 The oil from the reservoir 33 is thus brought under a pressure difference of one bar, into each of these casings through devices 35, 36, 37 whose float maintains

  oil at a preset level.

  In a second embodiment of the invention, diagram

  shown in Figure 3, the refrigeration system includes

  pound 40 includes in its refrigeration circuit, on the one hand like that of the first example (FIG. 2), a low pressure stage 41 and a high pressure stage 42 mounted in compound with their own points of use 43, 44, the temperatures of which evaporation are respectively - 381 C and -100 C, and on the other hand by a second high pressure stage 45 having its own points of use whose evaporation temperature t 3 of the order of -30 C to -8 o C, t 3 chosen in this example is equal to -61 C The low pressure stage 41 comprises two motor compressors 47, 48, a common suction manifold 49, an oil separator 50 and a common discharge line 51 The first high pressure stage 42 comprises three motor compressors 52, 53, 54 and a common suction manifold which receives both refrigerant gas coming from its own points of use 44 and refrigerant gas discharged from the low pressure stage 41 An exchanger 56 mounted between these two floors 41 for

  under cool the liquid refrigerant supplying the points of use

  sation 43 of the low pressure stage 41 and desuperheating the refrigerant gas discharged from this low pressure stage and the expanded gas coming from the points of use 44 of this first high pressure stage 42 in the common suction manifold 55 The second high stage pressure 45 includes three motor compressors 57, 58, 59, one

  common suction collector 60, independent of the vacuum collector

  ration 55 of the high pressure first stage 42 and a pipe

  delivery community 61 for all six motorcycles

  compressors of these two high pressure stages 42 and 45.

  The suction manifold 55 of the first high pressure stage 42 is maintained at a pressure equal to the evaporation pressure

  -10 C from its points of use 44 while the vacuum collector

  ration 60 of the second high pressure stage 45 is maintained at a pressure equal to an evaporation pressure -61 C of its own

  points of use 46 The refrigerant gas compressed by motorcycles

  compressors of the two high-pressure stages 42, 45 are discharged through the common discharge line 61 and an oil separator 62

  in a condenser 63 common to the three stages 41, 42, 45.

  The refrigerant in the form of liquid from the condenser 63 accumulates in a reservoir 64 common to these three stages 41, 42,

  45 before going to feed under the same high pressure respectively

  Points of use 43, 44, 46.

  A known independent refrigeration plant having points of use at an evaporation temperature of -10 ° C. or a refrigeration installation II of the first example illustrated in FIG. 2 can also supply points of use at its points of use. at a higher evaporation temperature t 3 for example -51 C or -61 C Indeed, according to the normal efficiency curves of a refrigeration compressor, an evaporation at -50 C for example compared to that at - 100 C brings, e

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  for the same condensation temperature, an appreciable increase in heat production of the order of about twenty percent and only a relatively small increase in the energy consumed of the order of about ten percent Evaporation at -51 C. brings a gain of around twenty percent in refrigeration efficiency at points of use at -51 C compared to evaporation at -100 C at points of use comprising constant pressure valves to maintain a evaporation -51 C. To obtain correct lubrication of the compressors in the refrigeration installation 40, the casings of the compressors of the low pressure stage 41 are also connected to each other, as in those of the first example, by a large section pipe 65 so as to have in these crankcases the same pressure and a preset oil level while in the high pressure stages 42, 45, the crankcases of the motor compressors are connected by disposi floats and a common line 66 at the lower part of an oil tank 67, the upper part of which is connected to the common suction manifold 55 of the high-pressure first stage motor compressors 42, through a line 68 and a valve calibrated 69 which creates, like that in the first example, a pressure drop of approximately one bar to bring the oil tank 67 to a pressure one bar higher than the pressure in the compressor housings.

Claims (5)

  1 Refrigeration installation with multi-compressors having a low pressure stage (12, 41) and at least one high pressure stage (13, 42) mounted as a compound, characterized in that it comprises, on the one hand, points of use (14, 15, 43, 44, 46), specific to   each of these stages and at respective evaporation temperatures   different (tl, t 2, t 3), and on the other hand a refrigeration circuit supplying all of these points of use with refrigerant   liquid under the same high pressure, from a refrigerated tank   rant condensed (28, 64), common to these floors.   2 Installation according to claim 1, characterized in that it comprises a refrigeration circuit having in the low pressure stage (12, 41) a common suction manifold (21, 49) of the compressors (16, 17, 47, 48 ) receiving expanded refrigerant gas from the points of use (14, 43) on this stage, and maintained at a pressure equal to the evaporation pressure -38 C from these points of use (14, 43) and in the '' high pressure stage (13,   42), a common suction manifold (24, 55) for motorcycles   compressors (18, 19, 20, 52, 53, 54), receiving both expanded refrigerant gas from the points of use (15, 44) of this stage (13, 42) and refrigerant gas discharged from the low pressure stage (12, 41), and maintained at a pressure equal to the evaporation pressure   -10 C of these points of use (15, 44).   3 Installation according to one of claims 1 and 2, character-   risée in that it comprises in its refrigeration circuit a second high pressure stage (45) having with the first high pressure stage (42) a common discharge line (61) for the motor compressors (52, 53, 54, 57, 58 , 59) a common condenser   (63), a common reservoir for condensed refrigerant (64) which supplies   -lies under the same high pressure in liquid refrigerant all the points of use (43, 44, 46) of the low pressure stage (41) and of the two high pressure stages (42, 45), and a common collector suction (60) for motor compressors from 13747,   second high pressure stage (45) receiving expanded refrigerant gas from the points of use (46) of this stage (45) and maintained at a pressure equal to the evaporation pressure t 3 thereof points of use (46).   4 Installation according to claim 3, characterized in that it comprises a refrigeration circuit having in the second high pressure stage (45) points of use (46) having an evaporation temperature of the order of -30 C to -80 C.   Installation according to one of claims 1 to 4, charac-   terrified in that it includes in its refrigeration circuit a   oil tank (33, 67) supplying oil to the motor casings   compressors through float devices (35, 36, 37) and a calibrated valve (39, 69) creating a pressure difference between this   oil tank (33, 67) and the casings of these motor-compressors.   6 Installation according to one of claims 1 to 5, charac-   terized in that it includes in its refrigeration circuit a counter-current exchanger (29, 56) for sub-cooling the flow of liquid refrigerant supplying the points of use (14, 43) and desuperheating the refrigerant gas discharged from the stage low pressure (12, 41) in the suction manifold (24, 55) of the high pressure stage (13, 42) and of the expanded gas coming from the points of use (15, 44) of this high pressure stage (13, 42) in this collector suction (24, 55).