DK159662B - LIQUID FOR A HEAT PUMP AND PROCEDURE FOR HEATING AND / OR THERMAL CLIMATIZATION OF A ROOM USING A COMPRESSION HEAT PUMP USING A MIXED WORKING LIQUID - Google Patents

Description

in

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The present invention relates to novel liquids for heat pumps and to a method of heating and / or thermal air conditioning of a room by means of a compression heat pump using a mixed working fluid.

5 The following working liquids have already been proposed in heat pumps: R12: Dichlorodifluoromethane (boiling point: -29.8 ° C), R22: Monochlorodifluoromethane (boiling point: -40.8 ° C), R23: Trifluoromethane (boiling point: -82.1 ° C), R550: Azeotrope (temperature: -23.5 ° C consisting of 73.8% by weight dichlorodifluoromethane R12 and 26.2% by weight difluoro-ethane R152a (temperature: -24.75 ° C), R501: Azeotrope (temperature: - 41.4 * 0 consisting of a mixture of 75% by weight chlorodifluoromethane R22 and 25% by weight dichlorodifluoromethane R12, R502: Azeotrope (temperature: -45.6 ° C) consisting of a mixture of 48.8% by weight chlorodifluoromethane R22 and 51.2% by weight chlorpentafluoromethane R115 (temperature: -38.7 ° C), and R503: Azeotrope of 40.1% by weight of trifluoromethane R23 and 59.9% by weight of chlorotrifluoromethane R13.

The halogenated liquids mentioned above are used continuously in heat pump systems, which are intended for heating and / or conditioning of premises or urban heating and for low temperature industrial applications, e.g. certain drying or concentration operations.

The use of monochlorodifluoromethane (R22) or of R502 is very frequent in heat pumps used for local heating, which uses groundwater, wells or rivers, external air or exhaust air, and as heat source uses heating water 30 or room air to temperatures which may be 55 "C at the heat source.

The substitution of R502 or R22 in a heat pump does not greatly increase the thermal capacity of the pump but allows a substantial reduction in the return flow temperature. The use of R12 35 or of R500 is particularly adapted to relatively high temperature levels e.g. above 50 ° C and less than 80 ° C.

There are two known options for increasing the heat output emitted by a heat pump, and the first option is to equip the heat pump with a compressor having a larger capacity,

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2 which allows a larger volume of suction to be sucked, but this solution entails an extra investment. The other option to increase the heat output of a heat pump consists of using a working fluid whose boiling point is lower than the boiling point of the usual fluid. In any case, such substitution results in a degradation of the power factor as well as a very limited range of use of the apparatus, which range is given since the critical temperature for lower boiling point fluids is generally less. The use of mixtures of non-azeotropic liquids in a heat pump to improve the efficiency of the heat pump in question is subject to the following older French patent applications: FR-A Nos. 3337885, 2474151, 2474666 and 2497931).

In particular, French Patent Application FR-A No. 2474151 does not disclose azeotropic mixtures of two components which permit an increase in the performance of a heat pump and thus allow a reduction in the operating cost of the heat pump in question. However, the two-component mixtures described in this specification do not allow to increase the thermal power of a given compressor.

It is the object of the present invention to show that 20 special mixtures of liquids make it possible to increase the heat output delivered by a heat pump relative to the case where the same heat pump is operated with a clean liquid. Thus, by using the liquid mixtures proposed according to the invention in a heat pump, it is possible to reduce the investment costs. Accordingly, the mixed working fluids of the invention will allow an increase in the heat output of a given heat pump without changing the components of the heat pump and especially without changing the compressor.

According to a first embodiment of the present invention, a liquid for a heat pump consists of a mixture of 30 (a) 95 to 80 mole% R22 or R502 with (b) 5 to 20 mole% R23 or R503 wherein R22 is monochlorodifluoromethane, R23 is trifluoromethane, R502 is a mixture of 48.8% by weight monochlorodifluoromethane with 51.2% by weight chlorpentafluoroethane, and R503 is a mixture of 40.1% by weight trifluoromethane with 59.9% by weight monochlorotrifluoromethane where the component (a) does not form an azeotrope the constituent (b) of the same mixture.

The invention further relates to a method for heating and / or for thermal air conditioning of a room by means of a 3

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compression heat pump using a mixed working fluid, in which this liquid extracts heat from a heat source with a temperature of -15e to + 40 ° C and delivers the heat to a liquid with a temperature of 20 ° to 75 ° C and where the pump works with a condensate 5 steps, an expansion step, an evaporation step and a compression step using this working fluid. According to the present invention, this process is characterized in that the working fluid has the following composition: (a) 95 to 90 mole% R12, R22, R500, R501 or R502 with 10 (b) 5-20 mole% R23 or R503 where R12 is dichlorodifluoromethane, R500 is a mixture of 73.8% dichlorodifluoromethane with 26.2% difluoroethane, R501 is a mixture of 75% chlorodifluoromethane with 25% dichlorodifluoromethane and wherein R22, R23, R502 and R503 are defined as follows, The component (a) of the mixture does not form azeotrope with the same component (b) of the same mixture.

In the cycle of a heat pump, the evaporation pressure in a mixture of the above type under identical operating conditions, all else equal, will be greater than the evaporation pressure of the largest 20 element if it was used in the pure state.

Accordingly, the mole volume of the vapors aspirated by the compressor is smaller, which for a compressor with a given cylinder volume increases the molar fluid volume and thus the heat output of the heat pump. In addition, the use of a mixed working fluid containing a 25 basic element (R22 or R12 or R500 or R501 or R502) and a minor element (R23 or R503), where the boiling point is lower, will generally result in a reduction in the compression ratio. This increases the volumetric performance in the case of compressors with alternating pistons, and is thus advantageous in the same way as an increase in heat output. This is also greater, since the molar concentration of the smallest element is important. The molar portion of the least basic element (R23 or R503) should be between 5 and 20%; in fact, too much of this basic element will cause a degradation of the power factor and an excessive condensation pressure. In fact, the compressors have a range limited by certain operating parameters (compression temperature and the difference between maximum pressures) and in particular by the maximum pump pressure. The compressive pressure of a mixture according to the invention is preferably less than 30 bar.

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The fluid mixtures proposed by the invention are particularly useful when the temperature of the hot source is preferably (preferably between 20 ° C and 75 ° C, and when the temperature of the cold source is preferably between -15 ° C and +40 ° C.

Heat pumps in which the above-defined mixtures are useful can be of any type. The compressor can e.g. be a compressor with lubricated pistons or with dry pistons, screw compressor or a centrifugal compressor. The heat exchangers can e.g. be double-tube heat exchangers, heat exchangers 10 with pipes and calender, plate heat exchangers, heat exchangers with slats or classic heat exchangers with tabs for heat transfer with air. A counter heat exchange is preferred; this is provided in the case of coaxial heat exchangers used for the exchange of water / coolant in low power heat pumps. This can be done in a manner similar to the air / coolant heat exchanger according to a device as described in French Patent 2,474,666. The heat output delivered may vary, e.g. between several kilowatts in heat pumps used for local heating and several megawatts in heat pumps intended for collective heating.

A preferred method is that described in French Patent No. 2,497,931.

This method comprises the following steps: (a) the mixed working fluid is compressed in the vapor phase; (b) the mixed compressed fluid from the step (a) is brought into a heat exchange contact with an outer relatively cold fluid and this contact is maintained until approximately a complete condensation of the mixed fluid, (c) the mixed fluid, which is approximately completely condensed, coming from step (b), is brought into heat exchange contact with a cooling fluid provided at step (f) in a manner so that the mixed fluid is further cooled, (d) the mixed cooled fluid coming from step (c) is expanded, (e) the mixed and expanded fluid coming from step (d) is brought into a thermal heat exchange contact with an exterior fluid which constitutes a heat source and the contact states allow a partial evaporation of the mixed and expanded fluid, (f) the mixed and partially evaporated fluid coming from the step (s) being brought in heat exchange contact with the mixed fluid, which is approximately completely densified and emitted from step (c), which mixed and partially evaporated fluid constitutes the cooling fluid of step (c), and

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the contact states allow the evaporation started at step (e) to continue and (g) the mixed and evaporated fluid coming from step (f) is sent back to step (a).

The following examples illustrate the realization of the particular fluid mixtures of the invention.

Attached to the examples are the figures, of which fig. 1 shows an embodiment of a heat pump system in which the liquid according to the present invention can be used, and FIG. 2 shows another embodiment of a heat pump system by which the method according to the present invention can be practiced.

Example 1 15

A water / water heat pump is shown schematically in FIG. This heat pump comprises an evaporator E1, wherein the mixture is introduced through a line 1 and is evaporated out through a line 2, a compressor K1 where the vapor mixture is compressed, and 20 where it is taken out through a line 3 to be sent into a capacitor E2, from which it is taken out condensed through a conduit 4, which is then expanded in an expansion valve D1 and recycled to the evaporator. The evaporator and condenser are constituted by double-tube heat exchangers in which the introduced fluids conduct heat exchange at a countercurrent circulation.

The cold spring is groundwater. This water enters the evaporator E1 through the conduit 5 at a temperature of 12 ° C and is withdrawn from the evaporator E1 through the conduit 6 at a temperature of 5 ° C.

The water heated by the capacitor E2 is introduced through conduit 7 and evacuated through conduit 8.

Two operating modes are considered according to the nature of the heating system and the temperature of the return water.

A - Heating by radiators: The return water temperature at the capacitor is 42 ° C (line 7) and the temperature of the flow water is 50 ° C (line 8).

B - heating by means of underfloor heating: The return water temperature at the capacitor is 20.5 ° C and the temperature of the flow water is 34 ° C.

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The quantities of water in the evaporator and in the condenser are a function of the heat pump's capacity corresponding to the working fluid used. In Table I below, comparative results are shown in each of cases A and B between: 5 - the operation of the heat pump using pure chlorodifluoromethane (R22) - the operation of the heat pump using a non-azeotropic mixture comprising 85 mole% of chlorodifluoromethane (R22) and 15 mol% trifluoromethane (R23).

The COP value indicates the ratio of the heat output delivered to the compression power transmitted to the fluid.

Table I

15 Case A B

Fluid R22 mixture R22 mixture R22 / R23 R22 / R23 Heat effect (W) 14260 17101 14820 18376 COP 3.52 3.48 4.56 4.63

Suction pressure (bar) 4.65 5.72 4.50 5.62 25

Pump pressure (bar) 20.64 25.13 15.15 18.42

Compression Ratio 4.44 4.39 3.37 3.28 30 Compared to pure R22 under identical temperature conditions at the cold and hot spring, the proposed mixture will allow an improved heat output of 20% in Case A and 24% in case B, the COP value is practically unchanged in both cases. The heat effect and COP value obtained with the mixture R22 / R23 are also clearly greater than those obtainable with the azeotropic mixture R502 if used alone.

R502 will e.g. in case A allow a heat output of 14545W (thus only a 2% increase over pure R22) and a COP value of 3.26. In general, the proposed mixtures can be optimized 7

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in composition to provide an improved heat output greater than 20% over a pure fluid and a COP value identical to that of the pure reference fluid. Such performance can under no circumstances be achieved by the use of e.g. R502 instead of R22 or R500 instead of R12.

French Patent No. 2,474,151 emphasizes a mixture composed of R22 and chlorotrifluoromethane R13 (t ^ = -81.4 ° C). The results obtained with this mixture, comprising 85 mole% R22 and 15 mole% R13, are compared in Table II with 10 the results obtained using the aforementioned mixture R22 / R23 (85% / 15%) .

Table II

15 Operation A B

Mixture R22 / R23 R22 / R23 R22 / R23 R22 / R23

Heat effect (W) 17,101 16,214 18,376 17,488 20 COP 3.48 3.43 4.63 4.55

Suction pressure (bar) 5.72 5.65 5.62 5.54 25 Pump pressure (bar) 25.13 24.37 18.42 18.01

Compression pressure (bar) 4.39 4.32 3.28 3.25 Thus, the mixture R22 / R23, for substantially identical operating pressures, will provide a heat effect that is clearly greater than that of the mixture R22 / R13.

The heating temperature obtained with a water / water or air / water type heat pump using the mixture R22 / R23 is less at 55 ° C and preferably less or equal to 52 ° C if it is desired that the pump pressure is less than 30 bar and preferably less than 28 bar. The molar proportion of R23 in a mixture R22 / R23 or R502 / R23 is preferably between 12% and 18%. The temperature variation of the water to the capacitor is preferably between 8

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5 ° C and 15 ° C to be in the vicinity of the condensation range of the mixtures proposed according to the invention. In the case of a clean fluid, the condensation temperature is insensitive to the return water temperature, but it is in principle greater than the heating temperature. In contrast, for the proposed non-azeotropic mixtures, in the case of a countercurrent water condenser, a temperature will be obtained at the end of the condensation and a corresponding pressure, which is a direct function of the water temperature at the input of the condenser. Thus, in the above described operating case 10 A, a condensation interval for the mixture of 8 ° C will be observed as the variation of the water temperature (42-50 ° C).

If the water heated by the heat pump can reach a higher temperature, e.g. greater than 60 ° C, dichlorodifluoromethane (R12) or the azeotropic mixture R500 can be replaced by chlorodifluoromethane (R22) to limit the high pressure in the circuit. Thus, a blend of the invention comprising dichlorodifluoromethane (R12) associated with trifluoromethane (R23) under given operating conditions can enable a heat output greater than that obtained with pure RI2. Thus, a mixture comprising 20 87.5 mole% of R12 and 12.5 mole% molar fraction of R23 gives an increase in heat output of 26% in case A and the pressure obtained at the compressor pressure side is less than 17 bar .

The molar fraction of R23 in a mixture of the type R12 / R23 or R500 / R23 is preferably between 8% and 18%. In the case of a water condenser, the heating temperature is preferably less than 75 ° C.

The operating diagram described in French Patent 2,497,931 provides an additional advantage in the area of heat performance of a given mixture of non-azeotropic fluids. This is the topic of Example 2.

Example 2

The operating diagram of the heat pump is shown in FIG. 2nd

The mixed working fluid exiting an expansion valve through conduit 9 is partially evaporated in evaporator E3 through the cooling of the water from the cold source which circulates countercurrent with the working fluid and which is fed into evaporator E3 through conduit 11 and withdrawn through conduit 11 12. Outflow from evaporator E3 9

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through conduit 10, the working mixture is completely evaporated and optionally heated in heat exchanger E4 by a countercurrent heat exchange with undercooled condensate which enters E4 through a conduit 18 and which is taken out through a conduit 19.

5 The mixed working fluid is sucked into gaseous state into compressor K1 through line 13 and is displaced at high pressure through line 14. Finally, the fluid is totally cooled and condensed in capacitor E5, where it enters through line 14, and from which it is withdrawn into a saturated liquid. state through conduit 15. In the course of the condensation in E5, the mixture delivers the useful heat effect to the heating water, which, between inlet conduit 16 and outlet conduit 17, circulates countercurrent with the working fluid. When the mixture is condensed in E5, it flows through line 15 into a receiving balloon B1 and is withdrawn through line 18; the sub-15 is finally cooled in the heat exchanger E4 and fed to the expansion valve VI through line 19.

In the capacity range, this diagram results in an improvement when the working fluid is a mixture of non-azeotropic fluids since the heat exchanger E4, provided at the end of the evaporation, allows the mixture to reach a higher temperature at the end of the boiling and thus a more powerful suction pressure. This method also allows a reduction in the molar volume of the suction and a reduction of the compression ratio.

Table III expresses the results obtained with the same mixture and the same operating conditions as in Example 1. The results obtained with pure chlorodifluoromethane (R22) in Example 1 are mentioned by reference. The operating diagram of FIG. 2 does not actually change the performance of the heat pump when operated with a clean fluid. The mixture specified in Example 1 has the following molar composition: Chlorodifluoromethane (R22): 85% and trifluoromethane (R23): 15%. The operating cases A and B are explained in Example 1.

According to FIG. 1, the selected mixture increases the heat output of an apparatus operated with R22 by 28% in case A and by 30% in case B. In addition, the use of the mixture will improve the COP value obtained with chlorodifluoromethane by 2, 8% in case A and 5.2% in case B.

The FIG. 2 shows an additional investment represented by the heat exchanger E4, but it is usually small.

In the present example, this heat exchanger can be constituted by

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10 2 two concentric smooth tubes having a contact surface of 0.25 m.

Table III

5 Case A B

Fluid R22 R22 / R23 R22 R22 / R23

Heat effect (W) 14260 18324 14820 19268 COP 3.52 3.62 4.56 4.80

Suction pressure (bar) 4.65 6.10 5.72 5.88 15 Pump pressure (bar) 20.64 25.09 15.15 18.37

Compression Ratio 4.44 4.11 3.37 3.13 Example 3

The use of the azeotropic mixture R502 instead of R22 allows a compressor temperature in the compressor which is substantially lower, and it is possible to avoid anomalous cooling of the engine in the case of hermetic compressors.

This advantage is significant in the case of air / water heat pumps, which operate at very low outdoor temperatures.

An air / water heat pump using R502 is operated; o the air passing through the evaporator, at an amount of 6000 m / h, an inlet temperature of 7 ° C and a relative humidity of 86%. The water circulating in the capacitor is heated to 45 ° C-50 ° C. With a non-azeotropic mixture containing 14 mol% R503 and 86 mol% R502, the results in Table IV are obtained.

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Table IV

Fluid R502 Mixture R502 / R503 5

Heat effect (VI) 11,932 13,531 COP 2.96 2.92 Compression temperature (° C) 85.2 88.7

Suction pressure (bar) 5.53 6.47

Pump pressure (bar) 21.85 25.20 15

The proposed blend results in an improvement in heat performance of 13.4% over R502, while the COP value and compression temperature are practically unchanged.

In general, it can be stated that the molar fraction of R503 in a mixture R502 / R503 or R22 / R503 should preferably be between 8% and 15%; in a mixture R500 / R503 or R12 / R503, the molar fraction should preferably be between 5% and 15%.

Example 4 25

Other mixtures have been used in a water / water heat pump and have provided a heat-to-growth effect: a) 87 mol% R22 and 13 mol% R503 30 b) 88 mol% R12 and 12 mol% R503 c) 90 mol D) 92 mol% R500 and 8 mol% R503 e) 85 mol% R502 and 15 mol% R23 f) 85 mol% R501 and 15 mol% R23 35 g) 87 mol% R501 and 13 mol % R503

The following claims relate to mixtures of the two main elements which have been described in the present patent application. It is to be understood that the invention also covers those mixtures which contain, in addition to the aforementioned elements, less amounts (less than 5 mol% and

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12 preferably less than 1 mol%) of contaminants which do not appreciably alter the good properties of these mixtures when used in heat pumps for heating or for thermal conditioning of premises. are halogen compounds of carbon-5 hydrides beyond the two required and which constitute sub-products in the preparation of the required halogen compounds.

10 15 20 25 30 35

Claims (6)

Liquid for a heat pump consisting of a mixture of (a) 95 to 80 moles «R22 or R502 with 5 (b) 5 to 20 moles« R23 or R503, wherein R22 is monochlorodifluoromethane, R23 is trifluoromethane, R502 is a mixture of 48.8% by weight monochlorodifluoromethane with 51.2% by weight chlorpentafluoroethane, and R503 is a mixture of 40.1% by weight trifluoromethane with 59.9% by weight monochlorotrifluoromethane where the component (a) does not form azeotrope with the same component (b) ). Liquid according to claim 1 consisting of (a) 88 to 82 mole% R22 or R502 with (b) 12 to 18 mole «R23. 3. A method of heating and / or thermal climatization of a room by means of a compression heat pump using a mixed working fluid, said liquid extracting the heat from a heat source with a temperature from -15 to + 40 ° C and delivering the heat to a liquid having a temperature of from 20 to 75 ° C, wherein the pump 20 operates with a condensation step, an expansion step, an evaporation step and a compression step using this working fluid, characterized in that the working fluid has the following composition: (a) 95 to (B) 5-20 moles «R23 or R503, where R12 is dichlorodifluoromethane, R500 is a mixture of 73.8% dichlorodifluoromethane with 26.2% difluoroethane, R501 is 80mol 'R12, R22, R500, R501 or R502. a mixture of 75% chlorodifluoromethane with 25% dichlorodifluoromethane and wherein R22, R23, R502 and R503 are as defined in claim 1, wherein the component (a) of the mixture does not form azeotrope with the same component (b). Process according to claim 3, characterized in that the working fluid according to claim 2 is used as the working fluid and the heat pump transfers the heat to a liquid whose inlet temperature 35 is above 20 ° C and whose outlet temperature is less than 55 ° C and takes out the heat. from a heat source whose temperature is above -15 ° C. Process according to claim 3, characterized in that the working fluid contains 92 to 82 moles «R12 or R500 and 8-18 moles% R23 and the heat pump transfers the heat to a liquid whose inlet temperature is greater than 40eC and if outlet temperature is less than 75 ° C and takes the heat from a heat source whose temperature is above 5 ° C. Process according to claims 3-5, characterized in that the heat pump operates under conditions such that (a) the mixed working fluid is compressed in the vapor phase, (b) the compressed mixed liquid from the step (a) is brought into heat exchanger contact with an external coolant. and that this contact is maintained until approximately complete condensation of the mixed liquid has occurred, (c) bringing the practically fully condensed liquid mixture of step (b) into heat exchange contact with a coolant defined in step (f) ), so that the liquid mixture is cooled even more, (d) the cooled liquid mixture from step (c) is expanded, (e) the expanded liquid mixture 15 from step (d) is brought into heat exchanger contact with an outer liquid constituting a heat source wherein the contact conditions allow a partial evaporation of the expanded liquid mixture, (f) bringing the partially evaporated liquid mixture from step (e) in heat exchanger contact with the practically fully condensed mixed liquid of step (c), and that this partially evaporated mixed liquid constitutes the coolant of step (c) and that the contact conditions are such that it began in step (e) evaporation may proceed and (g) return the evaporated mixture from step (f) to step (a). 25 30 35