FR2864609A1 - Refrigerating plant for heat pump, has auxiliary compressor selectively placed in active/inactive state when main compressor is in active state and bistable circuit unit placed in passing state when auxiliary compressor is in inactive state - Google Patents

Abstract

The plant has a bistable circuit unit (81) placed between an inlet (30) and an outlet (31) of an auxiliary compressor (3), and selectively adopting passing and blocking states to respectively connect and separate the inlet and outlet. The compressor (3) is selectively placed in active or inactive state when a main compressor (2) is in active state and the unit is placed in the passing state when the compressor (3) is in inactive state.

Description

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  The invention relates generally to the field of applied thermodynamics.

  More specifically, the invention relates, according to a first aspect, to a thermal installation, such as a refrigeration plant, comprising a phase change heat transfer fluid circuit, a bypass, a main compressor, and an auxiliary compressor, the circuit having first and second ends of which one forms, in operation, a high pressure end and the other a low pressure end and between which are connected in series at least one element of a first main exchanger, a first element an internal exchanger, a first expander, and an element of a second main heat exchanger, the main compressor having an input connected to the low-pressure end of the circuit and an output connected to the high-pressure end of the circuit, the bypass connecting a branch point of the circuit, intermediate between the element of the first main exchanger and the first element of the exchanger in at the input of the main compressor, and including, in series and in this order, a second expander and a second element of the internal exchanger in thermal communication with the first element of the internal exchanger, and the auxiliary compressor having an input connected to the low-pressure end of the circuit and an output connected to the input of the main compressor downstream of the second element of the internal exchanger.

  Thermal installations of this type are known to those skilled in the art for the production of cold.

  These known double-stage installations, in which the main compressor and the auxiliary compressor operate systematically at the same time, have a useful operating characteristic limited to a very narrow temperature range, which itself limits the scope of these installations. .

  Moreover, the simultaneous operation of the compressors being made necessary by the design of these installations, the compressors are doomed to a virtually certain degradation in case of accidental shutdown of one of them.

  In this context, a first object of the present invention is to provide a thermal installation free from the aforementioned defects.

  To this end, the thermal installation of the invention, moreover in accordance with the generic definition given in the preamble above, is essentially characterized in that it further comprises a first bistable circuit element arranged between the input and output of the auxiliary compressor, this first bistable element selectively adopting an on state or a blocking state in which it connects or isolates from each other, respectively, the input and the output of the auxiliary compressor, the compressor auxiliary being selectively placed in an active or inactive state when the main compressor is in an active state and the first bistable circuit element is placed in its on state when the auxiliary compressor is in its inactive state, this facility can thus operate at will , on one or two floors.

  Insofar as a thermal installation thus defined offers an operating characteristic adapted to a much wider temperature range, a second object of the present invention is to propose a thermal installation capable of operating as a reversible heat pump.

  To do this, it is advantageous to provide on the one hand that the heat transfer fluid circuit further comprises a second bistable circuit element, a third expander, and two nonreturn valves, the second bistable circuit element being installed between the first and second ends of the circuit and between the output of the main compressor and the input of the auxiliary compressor, and selectively adopting first or second states in which the first end of the circuit is respectively connected to the output of the main compressor and to the input of the auxiliary compressor, the second end of this circuit being respectively connected to the input of the auxiliary compressor and the output of the main compressor, to further provide that the third expander is installed between the element of the first main exchanger and the point of diversion, and to finally provide that the check valves are respectively mounted in allele on the first and third regulators and are passers for the heat transfer fluid flowing to the branch point.

  In many cases, the first main exchanger may for example be constituted by a water exchanger, and the second main exchanger by an air exchanger.

  In addition, the auxiliary compressor preferably has a variable displacement.

  To do this, it is possible to provide that this auxiliary compressor has a variable speed of rotation, and / or that it comprises at least two compression modules connected in parallel and placed in respective states active or inactive independently one of the other.

  The invention also relates, according to a second aspect, to an air exchanger particularly designed to constitute the second main exchanger of an installation as defined above, this exchanger being of the type comprising first and second branching orifices, a distributor on which there is provided the first branch port, at least a first at least partially vertical collection line and connected to the second branch port, and an array of coils each having first and second ends, the second branch port being disposed below coils and coils being connected to the manifold at their respective first ends by means of respective delivery strands, and being connected in parallel with the first collection line by their respective second ends.

  Known exchangers of this type have indeed the serious drawback, when used in a reverse cycle installation and in low ambient temperature conditions, to be difficult or even impossible to defrost during heat exchanges to low temperature.

  Thus, the hot heat transfer fluid has a tendency to migrate towards the top of the exchanger and to condense until the liquid filling of the bottom of the exchanger element, which prevents the arrival of hot gases.

  When restarting after such a bad defrosting, a new glaciation may occur in the badly defrosted part, resulting in its crushing and irreversible damage to the exchanger.

  The heat from the top of the heat exchanger is unnecessarily lost, while the bottom of the heat exchanger may not defrost.

  To solve these problems, the specific exchanger of the invention is essentially characterized in that the respective first ends of the coils are all located above the distributor, and in that the distribution strands are, over their entire length, in downward slope towards the distributor.

  With this arrangement, the coolant naturally migrates upwardly from the exchanger element, which it defrosts.

  The water that falls from the upper part of the exchanger meets the hottest parts of the latter, thus avoiding cooling down and taking in ice.

  The migrations of heat are no longer lost, and the exchanger is defrosted.

  For example, it is possible to provide that such an exchanger comprises a second collection pipe disposed horizontally, that the first collection pipe has a horizontal portion, and that the horizontal portion of the first collection pipe is connected to the second pipe collecting at least one sheet of substantially horizontal tubes, and is connected to the second branch port through this sheet of tubing and through this second collection line.

  In addition, it may be advantageous to make this heat exchanger much less sensitive to weather conditions by equipping it with a hood that caps it while leaving at least two air circulation passages at the base of this exchanger.

  Indeed, a problem repeatedly encountered during the defrosting of a heat pump on the air is that the air exchanger provides the wind a high capacity surface that dissipates the heat for defrosting, the point that it can become impossible in case of a kiss.

  Thanks to the presence of the previously defined hood, which forms from the bottom of the exchanger a containment bell of the latter and which leaves only one inlet and one air outlet sufficient for the mechanical mixing of the air and its renewal, the area offered to the wind is then zero.

  The heat released by the exchanger is trapped under the bell that forms the hood, which improves the defrosting of this exchanger.

  In addition, the aesthetics of the exchanger is greatly improved by the masking of the fan.

  Finally, the noise produced by the latter is stifled by the hood and all the less noticeable that the source of noise that constitutes this fan is no longer visible, the impossibility of bringing the connection between a low noise and its source making by experience this noise even less audible.

  Other characteristics and advantages of the invention will emerge clearly from the description which is given hereinafter, by way of indication and in no way limiting, with reference to the appended drawings, in which: FIG. 1 is a schematic diagram of a two-stage thermal installation of known type; FIG. 2 is a schematic diagram of the most advanced embodiment of a two-stage thermal installation according to the invention; - Figure 3 is a partial structural diagram of a thermal installation made according to the principle shown in Figure 2, used in its air conditioning function, and both floors are active; FIG. 4 is a partial structural diagram of a thermal installation carried out according to the principle illustrated in FIG. 2, used in its air conditioning function, and of which only the main stage is active; FIG. 5 is a partial structural diagram of a thermal installation realized according to the principle illustrated in FIG. 2, used in its heating function, and whose two stages are active; - Figure 6 is a partial structural diagram of a thermal installation made according to the principle shown in Figure 2, used in its heating function, and only the main stage is active.

  - Figure 7 shows in perspective, schematically and schematically, the internal arrangement of an air exchanger forming an integral part of the invention; FIG. 8 is a schematic perspective view of such an exchanger; and FIG. 9 is a schematic view showing a variant of the installation illustrated in FIG. 2.

  As previously announced, the invention relates to a thermal installation, in particular usable as a cold production installation, of the type comprising a circuit 11 in which circulates a heat transfer fluid with a phase change, a bypass 12, a main compressor 2, and an auxiliary compressor 3.

  The heat transfer fluid circuit 11 has two ends, 111 and 112, one of which is, in operation, connected to the outlet 21 of the main compressor 2 and forms a high pressure end, and the other of which is connected to the inlet 20 of this main compressor 2 and forms a low pressure end.

  Between the ends 111 and 112 of the heat transfer fluid circuit 11 are connected in series an element 41 belonging to a first main exchanger 4, for example water, a first element 51 belonging to an internal exchanger 5, a first expander 61, and a element 71 belonging to a second main exchanger 7, for example air.

  The branch 12, which connects a branch point 113 of the circuit 11 to the inlet 20 of the main compressor 2, includes, in series and in this order, a second expander 62 and a second element 52 of the internal exchanger 5.

  As shown in the figures, the branch point 113 of the circuit 11 is disposed between the element 41 of the water exchanger 4 and the first element 51 of the internal exchanger 5, and the second element 52 of the internal exchanger 5 is in thermal communication with the first element 51 of this same exchanger.

  The auxiliary compressor 3, which typically has a compression ratio lower than that of the main compressor 2, has an input 30 connected to the low-pressure end of the circuit 11 and an output 31 connected to the input 20 of the main compressor. 2 downstream of the second element 52 of the internal exchanger 5.

  Whereas the known installation, as illustrated in FIG. 1 and including all the characteristics stated up to now, can only work with the two stages constituted by the compressors 2 and 3, the installation of the invention, an advanced embodiment of which is shown in FIGS. 2 to 6, is designed to be able to operate as a single stage or a double stage.

  To do this, this installation comprises a first bistable circuit element 81, disposed between the inlet 30 and the outlet 31 of the auxiliary compressor 3, and the auxiliary compressor is designed to be placed in an active or inactive state independently of the active or inactive state in which is placed the main compressor 2, however, it being specified that the inactive state of the main compressor 2 imposes the inactive state of the auxiliary compressor 3.

  More precisely, the first bistable element 81 adopts at will an on-state in which it connects the inlet 30 and the outlet 31 of the auxiliary compressor 3 (FIGS. 4 and 6), or a blocking state (FIGS. 2, 3 and 5). wherein it isolates from each other this input 30 and this output 31, and the auxiliary compressor 3 is placed in its inactive state when the first bistable circuit element 81 is in its on state.

  The installation therefore operates on one stage when the first bistable circuit element 81 is in its on state, and on two stages when the first bistable circuit element 81 is in its blocking state.

  The thermal installation of the invention may further be designed so as to ensure, at will, a cooling function or a reheating function.

  To do this, the heat transfer fluid circuit 11 comprises a second bistable circuit element 82, a third expander 63, and two nonreturn valves, 91 and 92.

  The second bistable circuit element 82 is installed both between the ends 111 and 112 of the circuit 11 and between the output 21 of the main compressor 2 and the inlet 30 of the auxiliary compressor 3.

  This second bistable element 82 is also designed to adopt at will a first state in which the ends 111 and 112 of the circuit 11 are respectively connected to the output 21 of the main compressor 2 and the input 30 of the auxiliary compressor 3 (FIGS. 2 to 4) or a second state in which the ends 111 and 112 of the circuit 11 are respectively connected to the inlet 30 of the auxiliary compressor 3 and to the outlet 21 of the main compressor 2 (FIGS. 5 and 6), the circulating heat transfer fluid in the circuit 11 from the high pressure end 111 to the low pressure end 112 in the first case, and from the high pressure end 112 to the low pressure end 111 in the second case.

  Furthermore, the third expander 63 is installed between the element 41 of the water exchanger 4 and the bypass point 113, and the non-return valves 91 and 92 are respectively connected in parallel to the expander 61 and 63, these valves passing that the heat transfer fluid flowing to the branch point 113.

  Under these conditions, the coolant produces cold in the air exchanger 7, as a result of its expansion in the expander 61, when the bistable element 82 is in its first state, and produces heat in the air exchanger 7, as a result of its compression by the main compressor 2, when the bistable element 82 is in its second state, this installation can therefore operate in reversible heat pump.

  To give the plant thus designed an optimum operating flexibility, the auxiliary compressor 3 preferably has a variable displacement.

  For example, this compressor 3 has a variable speed of rotation and / or comprises two or more compression modules, connected in parallel and placed in respective states active or inactive independently of one another.

  As shown in FIG. 9, the characteristics of the compressor 3 can also be improved by providing an injection in a compression medium (screw or scroll compressor) allowing additional cooling of the liquid before expansion and leading to a better cooling or heating efficiency. .

  The installation then typically comprises an additional internal exchanger 50 and an additional expander 60, mounted as illustrated in FIG. 9.

  Figures 7 and 8 show an air exchanger particularly designed to form the second main heat exchanger 71 of an installation as previously described.

  Such an exchanger comprises, in a manner known per se, a first connection orifice 711a, a second connection orifice 717a, a distributor 711, a collection conduit 712, and an array of coils such as 713a to 713d.

  As shown in FIG. 7, the first connection port 71a1 is formed on the distributor 711.

  The collection pipe 712, which is disposed vertically over at least part of its length, is connected to the second branching orifice 717a, which is arranged below the coils 713a to 713d, ie at a level below the lower level of these coils.

  Furthermore, each coil comprises a first end such as 714a to 714d, and a second end such as 715a to 715d.

  These coils are connected to the distributor 711 by their respective ends 714a to 714d by means of respective dispensing strands 716a to 716d.

  Furthermore, these coils are connected in parallel with the collection conduit 712 by their respective second ends, 715a to 715d.

  In the exchanger of the invention, the first respective ends 714a to 714d of the coils 713a to 713d are all located above the distributor 711, and the distribution strands 716a to 716d are, along their entire length, downwardly sloping towards the 711 distributor.

  To further increase the efficiency of its defrosting, the air exchanger of the invention may advantageously comprise a second collection pipe 717 arranged horizontally.

  In this case, the first collection conduit 712 for example has a horizontal portion 712a connected to the second collection conduit 717.

  More specifically, the horizontal portion 712a of the first collection pipe 712 is connected to the second collection pipe 717 by one or more substantially horizontal plies 718, and is connected through this ply of tubings 718 and through this second collection line 717, at the second branch port 717a.

  As shown in Figure 7, each of the tubing 718 may be shaped hairpin, so that all of these tubing forms two parallel horizontal sheets and superimposed.

  Finally, as shown in FIG. 8, the exchanger of the invention is preferably equipped with a cap 719 which caps it leaving, at its base 719, at least two main air passages PA1 and PA2, allowing the air circulation under this hood.

Claims (10)

  1. A thermal installation, such as a refrigeration plant, comprising a phase change heat transfer fluid circuit (11), a bypass (12), a main compressor (2), and an auxiliary compressor (3), the circuit ( 11) having first and second ends (111, 112), one of which in operation forms a high-pressure end and the other a low-pressure end, and between which at least one element (41) is connected in series; a first main exchanger (4), a first element (51) of an internal exchanger (5), a first expander (61), and a member (71) of a second main exchanger (7), the main compressor ( 2) having an inlet (20) connected to the low pressure end of the circuit (11) and an outlet (21) connected to the high pressure end of the circuit (11), the branch (12) connecting a branch point ( 113) of the circuit, intermediate between the element (41) of the first main heat exchanger (4) and the first element (51) of the internal heat exchanger (5), at the inlet (20) of the main compressor (2), and including, in series and in this order, a second expander (62) and a second element (52). ) of the internal heat exchanger (5) in thermal communication with the first element (51) of this internal heat exchanger (5), and the auxiliary compressor (3) having an inlet (30) connected to the low pressure end of the circuit ( 11) and an outlet (31) connected to the inlet (20) of the main compressor (2) downstream of the second element (52) of the internal heat exchanger (5), characterized in that it furthermore comprises a first bistable circuit element (81) disposed between the inlet (30) and the outlet (31) of the auxiliary compressor (3), this first bistable element (81) selectively adopting an on state or a blocking state in which it connects or isolates the inlet (30) and the outlet (31) of the auxiliary compressor (3) respectively, the auxiliary compressor (3) being ctively placed in an active or inactive state when the main compressor (2) is in an active state and the first bistable circuit element (81) is placed in its on state when the auxiliary compressor (3) is in its inactive state, this installation can thus operate, at will, on one or two floors.   2. Thermal plant according to claim 1, characterized in that the heat transfer fluid circuit (11) further comprises a second bistable circuit element (82), a third expander (63), and two non-return valves (91, 92), the second bistable circuit element (82) being installed between the first and second ends (111, 112) of the circuit (11) and between the output (21) of the main compressor (2) and the inlet (30). of the auxiliary compressor (3), and selectively adopting first or second states in which the first end (111) of the circuit (11) is respectively connected to the output (21) of the main compressor (2) and to the input ( 30) of the auxiliary compressor (3), the second end (112) of this circuit (11) being respectively connected to the inlet (30) of the auxiliary compressor (3) and to the outlet (21) of the main compressor (2) , in that the third expander (63) is installed between the element (41) of the first exp main valve (4) and the bypass point (113), and in that the non-return valves (91, 92) are respectively connected in parallel with the first and third expansion valves (61, 63) and are passable for the fluid coolant flowing to the bypass point {113), this installation can thus operate as a reversible heat pump.   3. Thermal plant according to claim 1 or 2, characterized in that the first main exchanger 10 (4) is a water exchanger.   4. Thermal plant according to any one of the preceding claims, characterized in that the second main heat exchanger (7) is an air exchanger.   5. Thermal plant according to any one of the preceding claims, characterized in that the auxiliary compressor (3) has a variable displacement.   6. Thermal plant according to any one of the preceding claims, characterized in that the auxiliary compressor (3) has a variable speed of rotation.   7. Thermal plant according to claim 5, characterized in that the auxiliary compressor (3) comprises at least two compression modules connected in parallel and placed in respective states active or inactive independently of one another.   8. Thermal plant according to any one of the preceding claims, characterized in that the second main heat exchanger (7) is of the type comprising first and second branch ports (711a, 717a), a distributor (711) on which is provided the first branch port (711a), at least a first, at least partially vertical, collection line (712) connected to the second branch port (717a), and an array of coils (713a-713d) each comprising first (714a) - 714d) and second ends (715a - 715d), in that the second connection port (717a) is arranged below the coils (713a - 713d), in that these coils are connected to the distributor (711) by their respective first ends (714a 714d) by means of respective delivery strands (716a-716d), and are connected in parallel with the first collection line (712) by their respective second ends (715a-715d), in that the first respective ends (714a-714d) of the coils (713a-713d) are all located above the distributor (711), and in that the distribution strands (716a-716d) are, throughout their entire length, in downward slope to the dispenser (711).   9. Thermal plant according to claim 8, characterized in that the second main heat exchanger (7) comprises a second collection pipe (717) arranged horizontally, in that the first collection pipe (712) has a horizontal portion (712a). and in that the horizontal portion (712a) of the first collection line (712) is connected to the second collection line (717) by at least one substantially horizontal sheet of tubings (718) and is connected to the second orifice branch (717a) through this tubing web (718) and through this second collection conduit (717).   10. Thermal plant according to any one of claims 8 and 9, characterized in that the second main heat exchanger (7) further comprises a cover (719) which caps it leaving at least two passages (PAl, PA2) circulation of air at the base of this exchanger.