FR2977656A1 - THERMAL EXCHANGE SYSTEM AND METHOD FOR CONTROLLING THERMAL POWER DEVELOPED BY SUCH THERMAL EXCHANGE SYSTEM - Google Patents

Abstract

Heat exchange system (1) comprising: -two heat exchangers (5, 15) forming one an evaporator and the other a condenser, -a heat transfer fluid circuit comprising at least first (21) and second ( 22) compression stages arranged in series, the first compression stage (21) discharging the coolant in the second compression stage (22), - a control unit connected to the coolant circuit, in which the first compression stage (21) has a variable capacity in steps and the second compression stage (22) has a continuously variable capacitance, the control unit being adapted to regulate a thermal power developed by the heat exchange system (1) from variations in the capacitances of the first (21) and second (22) compression stages.

Description

2977656 Heat exchange system and method for the equation of thermal power developed by such a heat exchange system

The invention relates to a heat exchange system and to a method of regulating the thermal power developed by such a heat exchange system.

In particular, the invention relates to a heat exchange system adapted to perform heat exchange between outside air located outside a space and an internal medium flowing inside the space, said heat exchange system comprising: - first and second heat exchangers for exchanging heat respectively with the outside air and the indoor medium, said first and second heat exchangers each having an inlet and an outlet and forming the an evaporator and the other a condenser, a coolant circuit adapted to circulate a heat transfer fluid between the evaporator and the condenser, said coolant circuit comprising a compression unit placed between the outlet of the evaporator and the condenser inlet, and an expansion unit placed between the condenser outlet and the evaporator inlet, - a control unit connected to the circulator it coolant.

The invention applies, in particular, to the regulation of a thermal power developed by the heat exchange system, in particular in an operation as a heat pump associated with a space or a building, to allow to maintain an instruction of temperature inside the space or the building by bringing to this space or this building a thermal power equivalent to the thermal losses (internal and external contributions deducted).

For example, a vapor compression air / water heat pump recovers heat from outside air at an outside temperature, and then transmits this heat to the space at a temperature of a heating water circuit. If the compression unit has a constant capacity (constant suction flow), the thermal power of the cycle will decrease with the outside temperature (the density of the heat transfer fluid at the suction of the compression unit decreases, therefore, the mass flow rate of the coolant in the cycle decreases, and the thermal power carried by the heat transfer fluid of a cold source to which the evaporator draws heat to a hot well to which the condenser transfers the heat removed decreases). 2 2977656 For a constant capacity heat pump associated with a building, the calorific demand of the building and the heat production of the heat pump are therefore in opposition. If the heat pump is sized to meet the needs at a given outdoor temperature, it will be overpowered at higher outdoor temperatures with, for cons, performance losses related to cycling of the heat pump (on / off) and excess heat transported (heat exchanger losses, pressure losses).

In order to maximize the efficiency of the heat pump, it is therefore advantageous to be able to regulate the thermal power to meet the needs of the space or the building.

US 5,927,088 discloses a heat exchange system in which the compression unit comprises an additional compressor used in series with a primary compressor as a back-up when the primary compressor can not satisfy a need, in particular for heating.

The known heat exchange system does not, however, make it possible in simple fashion to precisely regulate the thermal power developed by the heat exchange system.

The invention improves the situation.

For this purpose, according to a first aspect, the invention proposes a heat exchange system adapted to perform heat exchanges between outside air located outside a space and an indoor environment circulating inside. space, said heat exchange system comprising: first and second heat exchangers for exchanging heat with the outside air and the indoor medium respectively, said first and second heat exchangers each having an inlet and a an outlet and forming one an evaporator and the other a condenser, - a coolant circuit adapted to circulate a heat transfer fluid between the evaporator and the condenser, said coolant circuit comprising a compression unit placed between the evaporator outlet and the condenser inlet, and an expansion unit placed between the condenser outlet and the evaporator inlet, said condenser unit; pressure device comprising at least first and second compression stages arranged in series, the first compression stage discharging the heat transfer fluid into the second compression stage; a control unit connected to the heat transfer fluid circuit, in which the first stage compression device has a variable capacity by 5 steps and the second compression stage has a continuously variable capacity, the control unit being adapted to regulate a thermal power developed by the heat exchange system from variations in the capabilities of the first and second compression stages.

Thus, the heat exchange system according to the invention has a simple structure whose thermal power can be regulated precisely according to the heat demand of the space.

The first compression stage may comprise a plurality of fixed capacity compressors connected in parallel, said plurality of fixed capacity compressors having a plurality of different configurations defining the capacitance steps, and the second compression stage may comprise at least one compressor with variable capacity.

Furthermore, the compression unit may comprise a bypass line connected in parallel with the first compression stage, the control unit being adapted to control: a multi-stage operation in which the first and second compression stages operate in series, the coolant circulating successively in the first and second compression stages, - a single-stage operation in which the second compression stage operates, the first compression stage being stopped, the heat transfer fluid circulating successively in the pipe of bypass and in the second compression stage. In one embodiment, the heat exchange system may further comprise a subcooling exchanger located between the first and second heat exchangers, and an injection line connecting the second heat exchanger to an inlet. suction of the second compression stage through the sub-cooling exchanger, the control unit being adapted to, in multi-stage operation, circulating a first portion of the coolant from the outlet of the second heat exchanger forming the condenser to the suction inlet 2977656 of the second compression stage through the injection pipe, and a second portion of the heat transfer fluid from the outlet of the second heat exchanger forming the condenser to the inlet of the first heat exchanger forming the evaporator. Such provisions improve the performance and capacity of the cycle.

The control unit may be adapted to: - adjust a thermal power level of the heat exchange system by selecting one of a plurality of capacitance steps of the first compression stage, and - modulate the thermal power of the system heat exchange around the adjusted level using the capacity of the second compression stage.

In one embodiment, the heat exchange system may further comprise an air circuit and a water circuit to which the first and second heat exchangers are respectively associated, and wherein the control unit may be adapted to measure a water temperature in the water circuit and to determine a set water temperature in the water circuit, the control unit being adapted for successively and continuously: - choose one capacity steps of the first compression stage, - varying the capacity of the second compression stage to reduce a difference between the measured water temperature and the set water temperature, - if the capacity of the second compression stage reaches a terminal and if the difference 25 remains greater than a threshold difference, change the capacity step of the first compression stage.

The control unit can then be adapted to measure an air temperature in the air circuit, the control unit being adapted to select an initial capacity step of the first compression stage at least as a function of the temperature. air.

Furthermore, the control unit can be adapted to select an initial capacity of the second compression stage at least as a function of the capacity step of the first compression stage. In addition, the control unit is adapted to change the capacity step of the first compression stage if the capacity of the second compression stage is in a determined range.

In another embodiment, the heat exchange system may further comprise an air circuit and a water circuit to which the first and second heat exchangers are respectively associated, and wherein the control unit can be adapted to measure a water temperature in the water circuit and to determine a set water temperature in the water circuit, the control unit 10 being adapted for successively and continuously: - determine a plurality capacitance pairs each comprising one of the capacity steps of the first compression stage and one of the capabilities of the second compression stage; selecting one of the capacitance pairs to reduce a difference between the water temperature measured and the target water temperature, - if the difference remains greater than a threshold difference, change the capacity pair.

The control unit can then be adapted to measure an air temperature in the air circuit and to determine a target thermal power, the control unit being adapted to determine the plurality of capacitance pairs according to the air temperature and target thermal power.

In either embodiment, the control unit may be adapted to limit the capacity of the second compression stage between a minimum capacity and a maximum capacity, said minimum and maximum capacities being chosen to maintain the first and second compression stages in respective operating envelopes and to obtain a coefficient of performance greater than or equal to a determined minimum coefficient of performance.

In particular, the control unit can be adapted to vary the minimum and maximum capacities of the second compression stage as a function of the capacity step of the first compression stage.

The control unit can be adapted to reduce the capacity of the second compression stage when a magnitude representative of an operating state of the second compression stage reaches a critical value, in particular said magnitude is selected from a temperature measured in output of the second compression stage, 2977656 a measured pressure at the output of the second compression stage, an electric current supplying the second compression stage and a compression ratio supported by the second compression stage

According to a second aspect, the invention proposes a method of regulating a thermal power developed by a heat exchange system, said method implementing a heat exchange system adapted to perform heat exchanges between outside air. located outside a space and an interior medium flowing inside the space, said heat exchange system comprising: first and second heat exchangers for exchanging heat respectively with the air external and internal medium, said first and second heat exchangers each having an inlet and an outlet and forming one an evaporator and the other a condenser, a coolant circuit adapted to circulate a heat transfer fluid 15 between evaporator and the condenser, said coolant circuit comprising a compression unit placed between the evaporator outlet and the inlet of the cone denser, and an expansion unit placed between the outlet of the condenser and the inlet of the evaporator, said compression unit comprising at least first and second compression stages arranged in series, the first compression stage discharging the heat transfer fluid 20 in the second compression stage, the first compression stage having a stepwise variable capacitance and the second compression stage having a continuously variable capacitance; a control unit connected to the heat transfer fluid circuit, said regulating method providing for regulating the thermal power 25 developed by the heat exchange system from variations in the capacities of the first and second compression stages.

In a particular embodiment, the control method implements a heat exchange system as defined above. In particular, the control method may provide for setting a thermal power level of the heat exchange system by selecting one of a plurality of capacitance steps of the first compression stage, and modulating the thermal power of the heat exchange system. heat exchange around the set level using the capacity of the second compression stage. The compression unit may comprise a branch line connected in parallel with the first stage of compression. The control method may then provide for controlling: a multi-stage operation in which the first and second compression stages operate in series, the coolant flowing successively in the first and second compression stages, a single-stage operation wherein the second compression stage operates, the first compression stage being stopped, the heat transfer fluid flowing successively in the bypass line and in the second compression stage.

In one embodiment, the heat exchange system may further comprise a subcooling exchanger located between the first and second heat exchangers, and an injection line connecting the first heat exchanger to an inlet. suction of the second compression stage through the subcooling exchanger. The control method can then provide, in multi-stage operation, to circulate a first portion of the heat transfer fluid from the outlet of the first heat exchanger forming the condenser to the suction inlet of the second compression stage by the control pipe. injection, and a second portion of the coolant from the outlet of the first heat exchanger forming the condenser to the inlet of the second heat exchanger forming the evaporator.

In one embodiment, the heat exchange system may further comprise an air circuit and a water circuit to which the first and second heat exchangers are respectively associated, the control method being able to provide: a water temperature in the water circuit and determine a set water temperature in the water circuit, and - successively and continuously carry out the steps of: choosing one of the first stage capacity steps compression, the capacity of the second compression stage is varied to reduce a difference between the measured water temperature and the set water temperature, if the capacity of the second compression stage reaches a limit and the difference remains greater than a threshold difference, change the capacity step of the first compression stage. The control method may include: measuring an air temperature in the air circuit; and selecting an initial capacity step of the first compression stage at least as a function of the air temperature.

The control method may provide for selecting an initial capacity of the second compression stage at least as a function of the capacity step of the first compression stage.

The control method may provide for changing the capacity step of the first compression stage if the capacity of the second compression stage is in a determined range.

In another embodiment, the heat exchange system may further comprise an air circuit and a water circuit to which the first and second heat exchangers are respectively associated, the control method being able to provide: measuring a water temperature in the water circuit and determining a set water temperature in the water circuit, and - successively and continuously performing the steps of: determining a plurality of capacitance pairs each comprising the one of the capacity steps of the first compression stage and one of the capacities of the second compression stage, choose one of the capacitance pairs to reduce a difference between the measured water temperature and the water temperature of setpoint, if the difference remains greater than a threshold difference, change the capacity pair. The control method may include: measuring an air temperature in the air circuit and determining a target thermal power; determining the plurality of capacitance pairs as a function of the air temperature and the target thermal power.

In either embodiment, the control method may provide for limiting the capacity of the second compression stage between a minimum capacity and a maximum capacity, said minimum and maximum capacitances being selected to maintain the first and second capacitors. second compression stages in respective operating envelopes and to obtain a determined coefficient of performance. The control method may provide for varying the minimum and maximum capacities of the second compression stage according to the capacity step of the first compression stage. The control method can provide for reducing the capacity of the second compression stage when a quantity representative of an operating state of the second compression stage reaches a critical value, in particular said quantity is chosen from a temperature measured at the output of the second compression stage. second compression stage, a pressure measured at the output of the second compression stage, an electric current supplying the second compression stage and a compression ratio supported by the second compression stage.

Other objects and advantages of the invention will appear on reading the following description of particular embodiments of the invention given by way of non-limiting example, the description being made with reference to the appended drawings in which: - Figure 1 is a schematic representation of a heat exchange system according to one embodiment of the invention, the heat exchange system 20 comprising a two-stage compression unit, the compression unit comprising a first compression stage with variable capacity per step and a second series compression stage in continuously variable capacity, the heat exchange system operating in an air conditioner mode; FIG. 2 is a schematic representation of the heat exchange system 25 of FIG. 1 operating in a heat pump mode; FIG. 3 is a diagrammatic representation of four configurations of the first compressor stage; 2, the configurations making it possible to obtain different thermal powers developed by the heat exchange system; FIG. 4 is a graph schematically illustrating the evolution of the thermal power developed by FIG. each of the configurations of FIG. 3 as a function of an outside temperature situated outside a space to be heated; FIG. 5 is a diagram illustrating the steps of a first embodiment of a control method of the thermal power developed by the heat exchange system of FIG. 2, the control method providing for regulating the thermal power by selecting a capacity step of the first compression stage and then varying the capacity of the second compression stage, FIG. 6 illustrates a step of selecting the initial configuration of the first compression stage in the method of FIG. 7 illustrates a variant of the step of selecting the initial configuration of the first compression stage in the control process of FIG. 5, the selection being made from abacuses giving the initial configuration as a function of the outside temperature, a target water temperature and a target thermal power; FIG. 8 is a diagram illustrating the steps of a second embodiment of the method for regulating the thermal power developed by the heat exchange system of FIG. 2, the regulation method providing for regulating the thermal power by choosing one of a plurality of pairs of capacitors each comprising one of the capacity steps of the first compression stage and one of the capabilities of the second compression stage; FIG. 9 illustrates a step torque selection system comprising the configuration of the first compression stage and the capacity of the second compression stage in the control method of FIG. 8, the selection being made from abacuses giving the torque as a function of the outside temperature, a set water temperature and a power indicator. In the figures, the same references designate identical or similar elements.

FIGS. 1 and 2 show a heat exchange system 1 respectively for cooling and heating an interior medium, for example water, circulating in a space 2, such as a part of a dwelling, a technical room or other. Alternatively, the internal environment could be other than water, including air. The heat exchange system 1 allows either to heat the water by drawing heat from outside air located outside the space 2 (cold source) and transferring to the water 30 (hot source hot well) the heat taken (Figure 2), either to cool the water by taking heat (cold source) and transferring to the outside air (hot source / hot well) the heat taken (Figure 1) .

The heat exchange system 1 comprises: a first heat exchanger 5, selectively forming an evaporator or a condenser, for heat exchange with the outside air, the first heat exchanger having a first end; 6 and a second end 7 which form one an inlet E and the other an outlet S, - a second heat exchanger 15, selectively forming an evaporator or a condenser, intended to perform heat exchanges with the water, the second heat exchanger 15 having a first end 16 and a second end 17 which form one an inlet E and the other an outlet S; - a heat transfer fluid circuit connected to the first and second heat exchangers 15 and adapted for circulating a coolant, such as a refrigerant, between the first heat exchanger 5 and the second heat exchanger 10 15.

The heat transfer fluid circuit comprises a multi-stage compression unit 20 and an expansion unit 10.

In Figures 1 and 2, the compression unit 20 is bi-staged and includes a first compression stage 21 and a second compression stage 22 arranged in series. Alternatively, the compression unit 20 could comprise more than two compression stages arranged in series.

The first compression stage or low pressure (LP) stage 21 has a variable pitch capacitance, i.e. it has a plurality of discrete capacitance values each defining a capacitance step. For this purpose, the low-pressure compression stage 21 comprises only a plurality of fixed-capacity compressors connected in parallel, and is devoid of a variable-capacity compressor. In the embodiment shown, the low pressure compression stage 21 comprises two first compressors or low pressure compressors (LP) 23a, 23b connected in parallel. Advantageously, the low-pressure compressors 23a, 23b respectively have different displacements. In particular, the low-pressure compressor 23b has a higher capacity than that of the low-pressure compressor 23a. Alternatively, the low pressure compression stage 21 could comprise one or more two low pressure compressors 23 in parallel.

The second compression stage or high pressure (HP) compression stage 22 has a continuously variable capacitance, i.e. it has a plurality of capacitance values in a given range. To do this, the high pressure compression stage 22 comprises one or more variable speed compressors. In the embodiment shown, the high pressure compression stage 22 is devoid of fixed capacity compressor and comprises a single second compressor or high pressure compressor (HP) 24. Alternatively, the high pressure compression stage 22 could include several high-pressure compressors 24 in parallel of which at least one is continuously variable capacity. Each of the low pressure compressors 23a, 23b and high pressure 24 has a suction inlet 25 and a discharge outlet 26. In the embodiment shown, the suction inlets 25 of the low pressure compressors 23a, 23b are connected to a same suction line 27 and the discharge outlets 26 of the low-pressure compressors 23a, 23b are connected to the same discharge line 28. The low-pressure compressors 23a, 23b and high pressure 24 are arranged in series, it is that is, the discharge line 28 of the low pressure compressors 23a, 23b is connected to the suction inlet 25 of the high pressure compressor 24. Moreover, as will be apparent from the rest of the description, the line of suction 27 of the low pressure compressors 23a, 23b is connected to the output S of that of the first 5 and second 15 heat exchangers which forms the evaporator, and the discharge outlet 26 of the high pressure compressor The ion 24 is connected to the input E of the first and second heat exchangers which forms the condenser.

To enable single-stage operation in addition to two-stage operation to be described later, the compression unit 20 comprises a bypass line 11 provided with a valve 12 connected in parallel with the low pressure compression stage. 21, with an upstream end connected upstream of the suction line 27 and a downstream end connected downstream of the discharge line 28 of the low pressure compressors 23a, 2311 The bypass line 11 bypasses the compression stage low pressure 21 to use only the high pressure compression stage 22 in the single-stage operation.

As shown, a bypass line 3 provided with a valve 4 may also be provided in parallel with the high pressure compression stage 22, with an upstream end connected upstream of the suction inlet 25 and a downstream end. connected downstream of the discharge outlet 26 of the high-pressure compressor 24. This bypass pipe 3 has a role of protection against possible high pressures in the event of failure of the high-pressure compressor 24 while the low-pressure compressors 23a, 23b are running. In the embodiment shown, the heat exchange system, used in heat pump mode described below and according to the two-stage operation, operates according to an injection cycle with a subcooling exchanger 45 or economizer. To do this, the subcooling exchanger 45 is connected to the first end 6 of the first heat exchanger 5 and to the second end 17 of the second heat exchanger 15. The heat exchange system 1 further comprises a pipe injection valve 46 connecting the second end 17 of the second heat exchanger 15 to the suction inlet 25 of the high pressure compressor 24 through the subcooling exchanger 45. An expander 47 is placed in injection 46, between the second heat exchanger 15 and the subcooling exchanger. In this embodiment, a liquid receiver 48 may be provided. It is thus possible to cool the heat transfer fluid between the low pressure compression stage 21 and the high pressure compression stage 22 to limit the temperature at the discharge outlet 26 of the high pressure compression stage 22 and thereby achieve a higher condensation pressure. Cooling is carried out here by taking condensed heat transfer fluid at the outlet of the condenser and re-injecting it between the discharge line 28 of the low pressure compression stage 21 and the suction inlet 25 of the cooling stage. high pressure compression 22.

The invention is however not limited to a heat exchange system implementing an injection cycle with a subcooling exchanger and applies to a heat exchange system implementing for example an injection cycle 25, a partial injection cycle or a cascade cycle, the heat exchange system being adapted accordingly.

The heat transfer fluid circuit also comprises a distribution circuit 40 for circulating the coolant from the compression unit 20 to the first heat exchanger 5 or from the compression unit 20 to the second heat exchanger 15 so that to ensure the reversibility, or invertibility, of the heat exchange system 1.

In particular, the distribution circuit 40 comprises a compression loop 41 35 in which the low pressure compressors 23a, 23b and high pressure 24 are placed, and a four-way valve 42 connecting the compression loop 41 to the first 5 and second 15 exchangers heat. The four-way valve 42 is adapted to circulate the coolant from one of the first 5 and second 15 heat exchangers and entering the compression loop 41 to the suction line 27 of the low pressure compressors 23a, 23b, and to distribute the heat transfer fluid from the discharge outlet 26 of the high pressure compressor 24 to the other heat exchanger 5, 15.

The expansion unit 10 comprises an expansion valve connecting, via one or more pipes, the outlet of that of the first 5 and second 15 heat exchangers which forms the condenser and the inlet of that of the first 5 and second 10 heat exchangers which forms the evaporator.

The heat exchange system 1 also comprises an air circuit 35 associated with the first heat exchanger 5 for effecting a heat exchange between the coolant and the outside air, and a water circuit 36 associated with the second heat exchanger 15. heat 15 to achieve a heat exchange between the coolant and the water flowing inside the space 2. In particular, the air circuit 35 may comprise pipes, not shown, connected to an air inlet and an air outlet, and a fan 39 adapted to circulate the air between the air inlet and the air outlet through the first heat exchanger 5. The water circuit 36, for example of a sanitary or floor heating installation, may comprise pipes connected to a pumping system ensuring the circulation of water in the pipes.

Depending on the direction of circulation of the coolant, the heat exchange system 1 can operate in an air conditioner mode (Figure 1) or in a heat pump mode (Figure 2). A control of the heat exchange system 1 between the different modes is provided by a control unit connected to the coolant circuit. The control unit comprises for example an electronic microprocessor to which a temperature sensor adapted to measure an outside temperature (Text) of the outside air is connected. Other sensors or measuring instruments of the control unit may be connected to the electronic microprocessor. In particular, the control unit may comprise a temperature probe adapted to measure an internal temperature (Tint) of the indoor air located inside the space 2, a temperature probe adapted to measure the temperature of water (Tw) in the water circuit 36. The control unit may also comprise a memory in which different data, and in particular a threshold temperature for the outside temperature and a set water temperature 2977656 (Tw c ) for the water circuit 36 or, as will appear in the following description, charts or water laws, are stored.

The control of the heat exchange system 1 according to the air conditioner mode and the heat pump mode can be achieved according to the need for cooling or heating of the indoor environment. The need for cooling or heating can be determined in any suitable manner. For example, an operator can choose the mode by acting directly on an input interface of the control unit. Alternatively, the control unit may comprise a thermostat measuring a temperature of the interior medium and determining the mode of the heat exchange system 1 from a set temperature for the indoor environment. According to another variant, the control unit can determine the mode of the heat exchange system 1 from the outside temperature, in particular by means of a water law stored in the memory of the control unit. . Thus, when there is a need for cooling of the internal environment, the heat exchange system 1 is in air conditioner mode, shown in FIG. 1. The heat transfer fluid then circulates in a closed loop: from the compression unit towards the second end 7, forming the inlet 20 E, of the first heat exchanger 5, then - since the first end 6, forming the outlet S, of the first heat exchanger 5 towards the second end 17, forming the inlet E , the second heat exchanger 15 through the expansion unit 10 and the subcooling exchanger 45, then 25 - from the first end 16, forming the output S, the second heat exchanger 15 to the compression unit 20.

The second heat exchanger 15 forms the evaporator which draws heat into the interior and the first heat exchanger 5 forms the condenser transferring the heat to the outside air so as to cool the internal environment.

When there is a need for heating the indoor environment, the heat exchange system 1 is in heat pump mode, shown in Figure 2. The heat transfer fluid then flows in a closed loop: - from the compression unit 20 to the first end 16, forming the inlet E, the second heat exchanger 15, and then 2977656 - from the second end 17, forming the outlet S, the second heat exchanger 15 to the first end 6, forming the inlet E, the first heat exchanger 5 through the expansion unit 10 and the subcooling exchanger 45, then 5 - from the second end 7, forming the output S, the first heat exchanger 5 to the compression unit 20.

The first heat exchanger 5 forms the evaporator which draws heat from the outside air and the second heat exchanger 15 forms the heat transfer condenser, thereby heating the interior medium.

The heat exchange system described above makes it possible in particular to ensure operation in heat pump mode in which a thermal power level can be adjusted by acting on the capacity step of the low pressure compression stage 21, the capacity the continuously variable high pressure compression stage 22 being modulated to regulate the thermal power of the heat pump (around a value set by the capacity step of the low pressure compression stage 21).

Indeed, as shown in FIGS. 3 and 4, as a function of the low pressure compressors 23a, 23b and high pressure 24 in operation, the compression unit 20 can deliver a more or less high condensing pressure so as to regulate the pressure. thermal power developed by the heat exchange system.

In the single-stage operation, identified as Config.1 in FIGS. 3 and 4, only the high-pressure compressor 24 functions allowing the heat exchange system to develop a thermal power in a first range, in particular as a function of the speed of the compressor. high pressure 24 and an outside temperature of the outside air. In a first two-stage operation, identified Config.2 in FIGS. 3 and 4, the low-pressure compressor 23a of smaller capacity operates in series with the high-pressure compressor 24 enabling the heat exchange system to develop a thermal power. in a second range, greater than the first range, depending in particular on the speed of the high-pressure compressor 24 and an outside temperature of the outside air. In a second two-stage operation, identified Config.3 in FIGS. 3 and 4, the higher-capacity 23b low-pressure compressor operates in series with the high-pressure compressor 24 enabling the heat exchange system to develop power. thermal in a third range, greater than the first 5 and second ranges, depending in particular on the speed of the high pressure compressor 24 and an outside temperature of the outside air.

In a third two-stage operation, identified Config.4 in FIGS. 3 and 4, the two low-pressure compressors 23a, 23b operate in series with the high-pressure compressor 24 enabling the heat exchange system to develop a thermal power in a fourth range, greater than the first, second and third ranges, depending in particular on the speed of the high-pressure compressor 24 and an outside temperature of the outside air.

By way of example, a relative dimensioning of the low-pressure compressors 23a, 23b and high-pressure 24 for the third two-stage operation offering an optimized coefficient of performance is: for the high-pressure compression stage 22, a supercharger variable speed 24 of capacity varying from X to 100%, with X less than 50 ° / 0, 20 - for the low pressure compression stage 21, two fixed speed compressors 23a, 23b of fixed capacities at 800/0 and 120 ° / O.

In each of the first, second and third two-stage operations, to improve the efficiency and capacity of the heat pump, the control unit acts on the heat transfer fluid circuit so that a first portion of the heat transfer fluid circulates from the second end 17 (outlet) of the second heat exchanger 15 (condenser) towards the suction inlet 25 of the high-pressure compressor 24 via the injection pipe 46, and a second part of the heat-transfer fluid from the second end 17 ( outlet) of the second heat exchanger 15 (condenser) to the first end 6 (inlet) of the first heat exchanger 5 (evaporator).

The heat exchange system according to the invention then makes it possible to implement a regulation method which allows, for each capacity step of the first compression stage 21 defining a main power level (determined by the configuration of low pressure compressors 23a, 23b in operation), to benefit from a range of regulation of the thermal power of the heat pump, by acting on the speed of the high-pressure compressor 24. It is thus possible to regulate more finely the thermal power of the pump. heat and reduce losses due to configuration changes and overpowering operation. On the other hand, the regulation method does not aim at maximizing the instantaneous coefficient of performance (COP) of the heat exchange system 1. In relation to FIGS. 5 to 7, a first embodiment of the regulation method is described.

In this regulation method, there are two control loops: a main control loop which manages the choice of the low-pressure compressors 23a, 23b in operation, that is to say the choice of the configuration of the low pressure compression stage 21, or the choice of the capacity step of the low pressure compression stage 21, and a secondary regulation loop which regulates the speed of the high pressure compressor 24 in order to modulate the heat output level. of the heat pump around the main level.

The initial configuration of the low pressure compression stage 21 is selected (step S1). In a first variant, the selection of the initial configuration is made according to the outside temperature only Text. As shown in FIG. 6, each configuration Config.1, Config.2, Config.3 and Config. 4 can then correspond to a defined external temperature range Text, for example respectively between 5 ° C and 25 15 ° C, between 0 ° C and 5 ° C, between -5 ° C and 0 ° C and -10 ° C and -5 ° C.

In a second variant, the selection of the starting configuration is based on charts, shown in FIG. 7, or interpolation functions stored in the control unit and giving the starting configuration as a function of the external temperature Text, and optionally, the set water temperature Tw_c (set by a water law stored in the control unit, as a function of the outside temperature Text, Tw_c = f (Text)) and the target thermal power to be delivered (obtained in particular by a power law, as a function of the external temperature Text). In the case where no configuration corresponds to the start point, the first available higher capacity configuration may be selected. In the case where multiple configurations are available, the configuration which has the best instantaneous energy efficiency at the point under consideration (again by means of the charts or the interpolation functions) can be selected.

The startup configuration can optionally be modulated by the error 5 measurement / setpoint on the water temperature Tw at startup.

The initial speed of the high pressure compressor 24 is then selected (step S2).

In a first variant, the selection of the initial speed is based on the configuration of the low pressure compression stage 21 only (typically median value of the range of variation).

In a second variant, the selection of the initial speed is made from abacuses or interpolation functions stored in the control unit and giving the initial speed of the high-pressure compressor 24 as a function of the configuration of the low compressors. pressure 23a, 23b, the estimated thermal power and the external temperature Text (and possibly the set water temperature Tw_c). In a third variant, the selection of the initial speed is done in a mixed manner, as a function of the configuration of the low-pressure compressors 23a, 23b for the two-stage operations, and as a function of the estimated thermal power and the outside temperature. Text (and possibly the set water temperature Tw_c) for single-stage operation.

The compressors of the low pressure compression stage 21 are then actuated according to the initial configuration selected (step S3).

The secondary control loop is then entered in which the speed of the high pressure compressor 24 is controlled by a regulator of the control unit to reduce the difference between the measured water temperature Twmeasured and the water temperature. This deviation is determined by the absolute value of the difference between the measured water temperature Tw_measured and the set water temperature Tw_c (abs (Tw_measured-Tw_c)). The measured water temperature Tw can be the water flow temperature (at the heat pump output), the water return temperature (at the heat pump inlet) or a combination of both. The controller used can be a PID, PI, fuzzy logic, state space, etc. controller.

The regulator has as its input the measurement / reference error, with generally the evolution of this error, possibly taking into account the external temperature Text and its evolution.

The speed of the high pressure compressor 24 is preferably limited between a maximum speed or capacity and a minimum speed or capacity to guarantee the operation of the compressors in their respective operating envelopes and an instantaneous higher or equal instantaneous coefficient of performance (COP). a minimum coefficient of performance determined and deemed acceptable. The terminals may be: either fixed and dependent on the configuration of the low pressure compression stage only, or dynamic, to adapt the operating limits to measured operating conditions, such as the suction and discharge of the low-pressure compressors 23a, 23b and / or high-pressure 24, the discharge temperatures of the low-pressure compressors 23a, 23b and / or high-pressure 24, the intensity of the current in the compressors and the compression ratios supported by the compressors low pressure and / or high pressure.

An additional level of regulation may be provided to reduce the speed of the high pressure compressor 24 when one of the above operating conditions reaches a critical value, and particularly when: the discharge temperature of the high pressure compressor approaches by a maximum value (by acting on the setpoint of the secondary regulation loop), the current in the high-pressure compressor 24 approaches a maximum value (by acting on the setpoint of the secondary loop). - The condensing pressure at the output of the high pressure compressor 24 approaches a maximum value (by acting on the setpoint of the main loop).

The main control loop then acts on the main heat pump level of the heat pump which is regulated so that the water temperature Tw in the water circuit 36 approaches the set water temperature Tw_c. The choice of the configuration of the low pressure compression stage 21 is managed by a simple loop which increments or decrements the configuration when the water temperature Tw exits a range Tw _c +/- 4Tw (steps S5 and S6, S7 and S8).

The main control loop is preferably provided by a discrete output PID type controller 5, possibly with hysteresis and / or a minimum duration between two configuration changes. This controller may optionally include an operating point, that is to say a calculated estimated configuration (charts) as a function of the outside temperature, and, possibly, depending on the water loop setpoint temperature (law of water) and the thermal power to be delivered (power law). In this case, the PID controller modulates the estimated configuration according to the measurement / setpoint error on the water temperature Tw.

In a simpler alternative, the controller of the main control loop can manage the succession of configurations of the low pressure compression stage 21 to maintain the water temperature Tw in a defined range around the setpoint Tw c, with hysteresis and / or a minimum time between two configuration changes.

In particular, when the speed of the high pressure compressor 24 reaches a maximum speed Vmax and the measured measured water temperature Tw remains lower than the set water temperature Tw c, to a certain extent OT w preset, the next configuration higher available capacity is selected (steps S5 and S6).

At the same time, when the speed of the high-pressure compressor 24 reaches a minimum speed Vmin and if the measured measured water temperature Tw remains above the set water temperature Tw c, to a certain extent OT w, the next configuration of lowest available capacity is selected (steps S7 and S8). Depending on the operating conditions, some configurations may not be available. For example, single-stage operation is not available when the overall compression ratio is too great to be supported by the single high-pressure compressor 24.

In addition, there may be a condition on the speed of the high pressure compressor 24 for the configuration change of the low pressure compression stage 21, the high pressure compressor speed 24 to be in a range 22 to determine the no capacity of the low pressure compression stage 21.

The control method can be carried out continuously, continuously measuring the control variables such as the external and water temperatures and successively carrying out the steps described above.

In connection with FIGS. 8 and 9, a second embodiment of the control method is described. In this control method, there is only one control loop, the choice of the configuration of the low pressure compression stage 21 and the speed of the high pressure compressor 24 being regulated in the same loop by the same one. controller of the control unit. The operating constraints related to the compressor casings and the maintenance of an acceptable instantaneous coefficient of performance are integrated in the control loop.

This method is based on the knowledge of the complete functioning mapping of the heat pump, in the form of charts, shown in FIG. 9, or of interpolation functions stored in the control unit.

The power demanded by the regulator from the heat pump is given by a capacity indicator 1 which varies continuously in the same direction as the thermal power supplied by the heat pump. This indicator 1 is translated, thanks to the complete mapping, into a pair comprising a capacity step corresponding to a configuration of the low-pressure compression stage 21, and a speed of the high-pressure compressor 24, the torque thus determined being applied. at the heat pump. The controller controls this indicator 1 to affect the heat output of the heat pump. The controller used may be PID, P1, fuzzy logic, state space, etc.

The controller controls the capacity indicator 1 to reduce the difference between the measured water temperature Tw_measured and the set water temperature Tw_c 35 (abs (tw_measured-Tw_c)) (step S1 '). 23 2977656 The input of the controller is the difference between the measured measured water temperature Tw and the set water temperature Tw c, with generally the evolution of this difference, possibly taking into account the outside temperature Text and its evolution. The capacity indicator 1 is then translated into a configuration choice of the low pressure compression stage 21 and a speed of the high pressure compressor 24, taking into account the external temperature Text and the water temperature Tw (step S2 ').

It is this step which is based on the detailed knowledge of the heat pump, whose operation map is represented by interpolation functions or charts (FIG. 9). In particular, for each point (1, Text, Tw), the control unit determines the torques comprising the capacity step of the low-pressure compression stage 21 and the speed of the high-pressure compressor 24 available. that is compatible with the operating envelopes of the compressors and with a sufficient instantaneous coefficient of performance. Of the couples available, a couple is selected. If the configuration of the low pressure compression stage 21 in progress is available, it is selected. If the current configuration is no longer available, the next available configuration is selected. Optionally, an additional condition may impose a minimum time between two configuration changes.

If the selected configuration is different from the current configuration, the low pressure compressors 23a, 23b are turned on or off according to the selected configuration (steps S3 'and S4'). On the other hand, if the selected configuration is not different from the current configuration, only the speed of the high pressure compressor 24 is changed to reach the selected speed.

The step of selecting the torque comprising the capacity step of the low pressure compression stage 21 and the speed of the high pressure compressor 24 can be processed in several ways, in particular with or without hysteresis, with or without additional conditions on the minimum time between two configuration changes, etc.

In addition, as in the control method described above, there may or may not be a complementary dynamic regulation of the speed terminals of the high pressure compressor 24 to maintain the compressors in their respective operating envelopes.

The control method can be carried out continuously, continuously measuring the control variables such as the outdoor and water temperatures and successively performing the steps described above. 5 25

Claims (16)

REVENDICATIONS1. Heat exchange system (1) adapted to perform heat exchange between outside air outside a space (2) and an interior medium flowing inside the space (2), said heat exchange system (1) comprising: - first (5) and second (15) heat exchangers for exchanging heat with the outside air and the indoor environment respectively, said first (5) and second (15) heat exchangers each having an inlet (E) and an outlet (S) and forming one an evaporator and the other a condenser, a heat transfer fluid circuit adapted to circulate a heat transfer fluid between the evaporator and the condenser , said heat transfer fluid circuit comprising a compression unit (20) placed between the evaporator outlet (S) and the condenser inlet (E), and an expansion unit (10) placed between the outlet (S) of the condenser and the inlet (E) of the evaporator, said compressor unit ession (20) comprising at least first (21) and second (22) compression stages arranged in series, the first compression stage (21) discharging the coolant in the second compression stage (22), - a unit of control connected to the coolant circuit, said heat exchange system being characterized in that the first compression stage (21) has a variable capacity in steps and the second compression stage (22) has a continuously variable capacitance, control unit being adapted to regulate a thermal power developed by the heat exchange system (1) from variations of the capacitances of the first (21) and second (22) compression stages. The heat exchange system (1) according to claim 1, wherein the first compression stage (21) comprises a plurality of fixed capacity compressors (23a, 23b) connected in parallel, said plurality of fixed capacity compressors ( 23a, 23b) having a plurality of different configurations defining the capacitance steps, and the second compression stage (22) comprises at least one variable capacity compressor (24). The heat exchange system (1) according to claim 1 or 2, wherein the compression unit (20) comprises a bypass line (11) connected in parallel with the first compression stage (21), the unit control unit being adapted to control: 26 2977656 - multi-stage operation in which the first (21) and second (22) compression stages operate in series, the coolant circulating successively in the first (21) and second (22) compression stages, - a single-stage operation in which the second compression stage (22) operates, the first compression stage (21) being stopped, the coolant circulating successively in the branch pipe (11) and in the second compression stage (22). The heat exchange system (1) according to claim 3, further comprising a sub-cooling exchanger (45) located between the first (5) and second (15) heat exchangers, and an injection line. (46) connecting the second heat exchanger (15) to a suction inlet (25) of the second compression stage (22) through the subcooling exchanger (45), the control unit being adapted for, in multi-stage operation, circulating a first portion of the coolant from the outlet (S) of the second heat exchanger (15) forming the condenser to the suction inlet (25) of the second compression stage ( 22) through the injection line (46), and a second part of the coolant from the outlet (S) of the second heat exchanger (15) forming the condenser to the inlet (E) of the first heat exchanger (15). ) forming the evaporator. 20 5. heat exchange system (1) according to any one of claims 1 to 4, wherein the control unit is adapted to: - set a thermal power level of the heat exchange system (1) by choosing one of a plurality of capacitance steps of the first compression stage (21), and - modulating the thermal power of the heat exchange system (1) about the adjusted level using the capacity of the second compression stage (22). ). The heat exchange system (1) according to claim 5, further comprising an air circuit (35) and a water circuit (36) to which the first (5) and second (15) heat exchangers are respectively associated, and wherein the control unit is adapted to measure a water temperature in the water circuit (36) and to determine a set water temperature in the water circuit (36), the control unit being adapted for successively and continuously: selecting one of the capacity steps of the first compression stage (21); varying the capacity of the second compression stage (22) to reduce a difference between the measured water temperature and the set water temperature, 2977656 - if the capacity of the second compression stage (22) reaches a limit and if the difference remains greater than a threshold difference, change the capacity step of the first compression stage (21). 5 7. Heat exchange system (1) according to claim 6, wherein the control unit is adapted to measure an air temperature in the air circuit (35), the control unit being adapted to choose an initial capacity step of the first compression stage (21) at least as a function of the air temperature. 10 8. heat exchange system (1) according to claim 6 or 7, wherein the control unit is adapted to select an initial capacity of the second compression stage (22) at least according to the capacity step of the first stage compression (21). 15 9. heat exchange system (1) according to any one of claims 6 to 8, wherein the control unit is adapted to change the capacity step of the first compression stage (21) if the capacity of the second stage compression (22) is in a determined range. 20 The heat exchange system (1) according to claim 5, further comprising an air circuit (35) and a water circuit (36) to which the first (5) and second (15) heat exchangers are respectively associated, and wherein the control unit is adapted to measure a water temperature in the water circuit (36) and to determine a set water temperature in the water circuit (36), control unit being adapted for successively and continuously: - determining a plurality of capacitance pairs each comprising one of the capacitance steps of the first compression stage (21) and one of the capacitances of the second compression stage ( 22), - choose one of the capacitance pairs to reduce a difference between the measured water temperature and the set water temperature, - if the difference remains greater than a threshold difference, change the capacity pair . The heat exchange system (1) according to claim 10, wherein the control unit is adapted to measure an air temperature in the air circuit (35) and to determine a target thermal power, control unit being adapted to determine the plurality of capacitance pairs as a function of the air temperature and the target thermal power. 297656 2s 12. Heat exchange system (1) according to any one of claims 5 to 11, wherein the control unit is adapted to limit the capacity of the second compression stage (22) between a minimum capacity and a maximum capacity , said minimum and maximum capacities being chosen to maintain the first and second compression stages in respective operating envelopes and to obtain a determined coefficient of performance. The heat exchange system (1) according to claim 12, wherein the control unit is adapted to vary the minimum and maximum capacities of the second compression stage (22) according to the capacity step of the first stage of compression (21). 14. Heat exchange system (1) according to any one of claims 5 to 13, wherein the control unit is adapted to reduce the capacity of the second compression stage (22) when a magnitude representative of a operating state of the second compression stage (22) reaches a critical value, in particular said magnitude is selected from a temperature measured at the output of the second compression stage (22), a pressure measured at the output of the second compression stage (22) and an electric current supplying the second compression stage (22). 15. A method of regulating a thermal power developed by a heat exchange system (1), said method implementing a heat exchange system (1) according to any one of claims 1 to 14 and providing for regulating the thermal power developed by the heat exchange system (1) from variations in the capacities of the first (21) and second (22) compression stages. 16. The regulation method according to claim 15, providing for adjusting a thermal power level of the heat exchange system (1) by choosing one of a plurality of capacity steps of the first compression stage (21), and of modulating the thermal power of the heat exchange system (1) around the set level using the capacity of the second compression stage (22).