JP4462435B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigeration apparatus applied to an air conditioner, and more specifically, a receiver tank (gas-liquid separator) and a supercooling heat exchanger are connected between a condenser and an evaporator. In addition, the present invention relates to a refrigeration apparatus in which a receiver tank is provided with a liquid level detection means.

  The air conditioner includes an outdoor unit having a compressor, a four-way valve and an outdoor heat exchanger, and an indoor unit having an indoor heat exchanger. By switching the four-way valve, a cooling operation and a heating operation are selected. In the cooling operation, the outdoor heat exchanger side is a condenser and the indoor heat exchanger side is an evaporator. On the contrary, in the heating operation, the outdoor heat exchanger side is an evaporator and the indoor heat exchanger side is a condenser.

  Among air conditioners, in a multi-room type air conditioner in which multiple indoor units are connected to one outdoor unit, the operation mode (cooling or heating), the capacity of the operating indoor unit, and the indoor and outdoor temperatures The amount of refrigerant required for operation varies depending on conditions.

  In order to absorb the difference in the refrigerant amount, a receiver tank is usually provided between the condenser and the evaporator. Various techniques for detecting the liquid level in the receiver tank have been proposed in order to monitor whether or not the refrigerant charge amount in the refrigeration cycle is appropriate.

  As an example, in the invention described in Patent Literature 1, pipes are connected to different positions above and below the receiver tank, and the liquid level in the receiver tank is calculated from the refrigerant temperature difference after decompressing the refrigerant taken out from each pipe. The level is detected.

  However, if there is no difference in the refrigerant temperature obtained from the pipes connected to different positions above and below the receiver tank, within the height range (two pipes are connected to the receiver tank, for example, the top and bottom If it is, it cannot be determined whether the refrigerant in the receiver tank as a whole is in the liquid phase or in the gas phase.

  Further, if the refrigerant taken out from the receiver tank is only decompressed, it is difficult to produce a temperature difference between the liquid refrigerant and the gas refrigerant, and it is difficult to reliably detect the liquid level. FIG. 7 is a transcription of the Mollier diagram described in FIG. 3 in Patent Document 1 above. The width between the isothermal line 22 passing through the point 20 and the isothermal line 23 passing through the point 21 is the liquid refrigerant. Although it is a temperature difference from a gas refrigerant, its width is narrow. Therefore, in the case of a non-fluorocarbon type R410A refrigerant that has been recommended especially in recent environmental problems, even if the high-pressure gas saturated refrigerant and the high-pressure liquid saturated refrigerant are decompressed, There is almost no temperature difference.

  Therefore, the applicant of the present invention reduces the temperature of the refrigerant taken out from the receiver tank and then heats it, so that a clear temperature difference between the liquid refrigerant and the gas refrigerant occurs, and the receiver tank has only the liquid refrigerant or the gas refrigerant. In the case where the phase state is only, the invention that makes it possible to detect the phase state has been filed as Japanese Patent Application No. 2005-70295 (hereinafter referred to as the prior invention).

  The prior application invention will be described with reference to FIGS. 4 is a schematic diagram showing the overall configuration of an air conditioner to which the invention of the prior application is applied, FIG. 5 is a schematic diagram showing liquid level detection means provided in the invention of the prior application, and FIG. 6 is a diagram of the invention of the prior application. It is a Mollier diagram for demonstrating an effect | action.

  First, referring to FIG. 4, the air conditioner according to the prior invention includes an outdoor unit 10 and an indoor unit 20. The outdoor unit 10 and the indoor unit 20 are a split type in which they are connected via a predetermined piping member, and include a heat pump type refrigerant circuit capable of cooling operation and heating operation.

  Therefore, the outdoor unit 10 is provided with a compressor 11, a four-way valve 12, an outdoor heat exchanger 13 having an outdoor blower fan 13a, a receiver tank (gas-liquid separator) 14, and an accumulator 15 as a basic configuration. Yes.

  As a basic configuration, the indoor unit 20 includes an indoor heat exchanger 21 having an indoor fan 21a, one end of which is connected to the outdoor heat exchanger 13 via an electronic expansion valve 23 and a receiver tank 14, and the other end. Is selectively connected to either the compressor 11 or the accumulator 15 via the four-way valve 12.

  During the cooling operation, the four-way valve 12 is switched as indicated by the solid line in FIG. 1, and the refrigerant is compressor 11 → four-way valve 12 → outdoor heat exchanger 13 → receiver tank 14 → electronic expansion valve 23 → indoor heat exchanger 21 → four-way. It flows from the valve 12 to the accumulator 15 to the compressor 11. In this case, the outdoor heat exchanger 13 acts as a condenser, and the indoor heat exchanger 21 becomes an evaporator.

  During the heating operation, the four-way valve 12 is switched as indicated by the chain line in FIG. 1, and the refrigerant is compressor 11 → four-way valve 12 → indoor heat exchanger 21 → electronic expansion valve 23 → receiver tank 14 → outdoor heat exchanger 13 → four-way. It flows from the valve 12 to the accumulator 15 to the compressor 11. In this case, the indoor heat exchanger 21 acts as a condenser, and the outdoor heat exchanger 13 becomes an evaporator. In both the cooling operation and the heating operation, the piping system including the accumulator 15 is the low-pressure side piping system of the refrigeration cycle (refrigerant circuit).

  In the above-mentioned prior application invention, the liquid level detecting means 30 for detecting the liquid level in the receiver tank 14 is provided between the low pressure side piping system and the receiver tank 14. In the prior invention, the refrigerant liquid level detecting means 30 also operates as a refrigerant state detecting means as will be described later.

  Referring to FIG. 5, the liquid level detection means 30 includes a liquid level detection pipe connected to different height positions of the receiver tank 14. The height position is at least two places, an upper limit position and a lower limit position. In this example, there are three places, an upper limit position, an intermediate position, and a lower limit position. A second liquid level detection pipe 32 and a third liquid level detection pipe 33 are connected to the lower limit position.

  Each liquid level detection pipe 31, 32, 33 is provided with capillary tubes 31a, 32a, 33a as decompression means. The specifications of each capillary tube may be arbitrarily determined on the condition that they are the same, but as an example, a capillary tube having an inner diameter of 0.8 mm and a length of 1000 mm can be used.

  A heating means 34 for heating the decompressed refrigerant is provided on the downstream side of the capillary tubes 31a, 32a, 33a. The heating means 34 may be provided on the upstream side of the capillary tubes 31a, 32a, 33a. An electric heater or the like may be used as the heating unit 34, but it is preferable to use heat generated from the refrigerant discharge pipe of the compressor 11. For this purpose, a part of the pipe may be welded along the refrigerant discharge pipe.

  Each of the liquid level detection pipes 31, 32, 33 is provided with temperature sensors 31b, 32b, 33b made of, for example, a thermistor for detecting the temperature of the heated refrigerant. The refrigerant temperatures detected by the temperature sensors 31b, 32b, and 33b are input to the control unit (CPU) 30A, and the control unit 30A determines the liquid level and phase state in the receiver tank 14 based on the detected refrigerant temperatures. Determine.

  The liquid level detection pipes 31, 32, 33 are finally combined into one after the refrigerant is heated by the heating means 34, and are accumulators included in the low-pressure side pipe system of the refrigeration cycle via the electromagnetic valve 35. 15 is connected.

  Here, the liquid level in the receiver tank 14 is between the upper limit position and the intermediate position, the gas refrigerant flows through the first liquid level detection pipe 31, and the second and third liquid level detection pipes 32. , 33, the operation of the refrigerant liquid level detection means 30 will be described on the assumption that liquid refrigerant flows. Since the second liquid level detection pipe 32 and the third liquid level detection pipe 33 are placed under the same conditions, the third liquid level detection pipe 33 will be described on the liquid refrigerant side.

  In the first liquid level detection pipe 31, the inlet point of the capillary tube 31a is A1, the outlet point is C1, and the detection point of the temperature sensor 31b is E1. In the third liquid level detection pipe 33, the inlet point of the capillary tube 33a is B1, the outlet point is D1, and the detection point of the temperature sensor 33b is F1.

  In the pressure system, the pressure in the receiver tank 14 is the discharge pressure Ph, the saturation pressure at the detection points E1 and F1 is Pm, and the pressure on the outflow side of the solenoid valve 35 is the suction pressure Pl. Each of these pressures is preferably measured by a pressure sensor (not shown), but the saturation pressure Pm is measured from the low pressure value measured by the low pressure sensor 16 of the low pressure piping system of the accumulator 15 to the liquid level detector. An estimated value obtained by calculation in consideration of the pressure loss may be adopted.

  When the electromagnetic valve 35 is opened, the gas refrigerant flows through the first liquid level detection pipe 31 and the liquid refrigerant flows through the third liquid level detection pipe 33. Each refrigerant is decompressed equally to the capillary tubes 31a and 33a, and as shown in the Mollier diagram of FIG. 6, point A1 is in the state of point C1, and point B1 is in the state of point D1.

  Since C1 point and D1 point are both on the pressure line of Pm, they are at the same temperature. Thereafter, the first liquid level detection is performed by heating by the heating means 34 (preferably heat exchange with the refrigerant discharge pipe of the compressor 11). The temperature of the gas refrigerant on the piping 31 side rises from point C1 to point E1 in the overheated region. Even in the case of R410A, the temperature TE at the point E1 is preferably higher by 10 ° C. or more than the temperature TC at the point C1 (TE> TC + 10 ° C.).

  On the other hand, since the refrigerant on the third liquid level detection pipe 33 side is a liquid refrigerant, the enthalpy rises even after the pressure is reduced and heated, but the temperature does not change and exists in the saturation region, and the point D1 has the same temperature. It just moves to F1 point. That is, the temperature TD at the point D1 and the temperature TF at the point F1 are the same temperature (TD = TF).

  The controller 30A compares the temperature TE at the point E1 detected by the temperature sensor 31b with the temperature TF at the point F1 detected by the temperature sensor 33b, and determines the liquid level in the receiver tank 14. . In this case, since TE> TF, it is determined that the liquid level is between the upper limit position and the lower limit position. However, according to the prior invention, the temperature difference is large, so the determination result has high reliability. Is obtained.

  By the way, when the detected temperature TE of the temperature sensor 31b and the detected temperature TF of the temperature sensor 33b are equal, the receiver tank 14 is assumed to have only two types of gas refrigerant or liquid refrigerant. In order to make it possible to determine the overall phase state in the receiver tank 14, in the prior application invention, the control unit 30A performs the following processing.

  That is, the saturation temperature T (Pm) obtained from the pressure Pm at the point F1 is set as the reference temperature Ts, the reference temperature Ts is compared with the detected temperature TF obtained from the temperature sensor 33b, D is set as a predetermined value, and TF− When Ts <D is satisfied, it is determined that the receiver tank 14 is in a state of only liquid refrigerant, and when TF−Ts <D is not satisfied, the receiver tank 14 is in a state of only gas refrigerant.

As described above, the saturation temperature T (Pm) at the point F1 may be an estimated value estimated from the low pressure value measured by the low pressure sensor 16, but is estimated at the point F1. The saturation temperature Ts ′ (Pm) is
Ts ′ (Pm) = T (Pl) + dT
It is calculated by. Where T (Pl) is the low pressure saturation temperature on the suction pressure Pl side of the solenoid valve 35, dT is the temperature loss at the solenoid valve 35,
dT = C1 × (Ph−Pl) + C2
(C1 and C2 are constants).

  As described above, according to the invention of the prior application, a large temperature difference is generated between the liquid refrigerant and the gas refrigerant because the refrigerant is taken out from the receiver tank 14 and the refrigerant is decompressed and then heated. Therefore, the liquid level in the receiver tank can be reliably detected. Even when only the liquid refrigerant or the gas refrigerant is contained in the receiver tank 14, the phase state can be detected.

JP-A-6-201234

  By the way, in the prior invention, since the refrigerant taken out from the receiver tank 14 for detecting the liquid level is returned to the accumulator 15 of the low-pressure side piping system, the enthalpy at the point F1 is If [kJ / kg], point C1. Is ic [kJ / kg] and the mass of the extracted refrigerant is qm [kg / s], the evaporation capacity of Q = qm × (Ic−If) [kW] is wasted. As the liquid level in the receiver tank 14 rises and the amount of liquid refrigerant taken out increases, the amount of refrigerant that is wasted (bypass loss in the outdoor unit 10) increases.

  For this reason, the solenoid valve 35 is controlled to open only when the liquid level is detected and the solenoid valve 35 is closed otherwise. However, according to this, the state of the outdoor unit 10 is changed by opening and closing the solenoid valve 35. Other control may be adversely affected, and since the liquid level is not constantly detected, there is a problem that a delay may occur in the control system that operates according to the liquid level state.

  Accordingly, an object of the present invention is to reduce the capacity loss due to the liquid level detection and constantly detect the liquid level in the refrigeration apparatus having the liquid level detecting means for taking out the refrigerant from the receiver tank and detecting the liquid level. Is to make it possible.

In order to solve the above problems, the present invention includes a refrigeration cycle including a compressor, a condenser, and an evaporator, and a receiver tank and a supercooling heat exchanger are connected between the condenser and the evaporator. In the refrigeration apparatus in which the receiver tank is provided with a liquid level detection means, the liquid level detection means has at least one liquid level detection pipe having one end connected to a predetermined height portion of the receiver tank. Pressure reducing means for reducing the pressure of the refrigerant flowing in the liquid level detection pipe, heating means for heating the refrigerant in the liquid level detection pipe, and temperature for detecting the temperature of the refrigerant heated by the heating means And the other end of the liquid level detection pipe is connected to the cooling side pipe on the downstream side of the electronic expansion valve for the supercooling heat exchanger provided in the cooling side pipe of the supercooling heat exchanger. Connected and used for liquid level detection Refrigerant is characterized by flowing to the subcooling heat exchanger.

According to a preferred embodiment of the present invention, if only the use of vaporization latent heat of the refrigerant used for detection on SL liquid surface is not supercooled to obtain a target, additionally the supercooling heat exchanger electronic expansion valve is opened Controlled in direction.

  The liquid level detection means detects the phase state of the refrigerant in the receiver tank at a position where one end of the liquid level detection pipe is connected based on the refrigerant temperature obtained from the temperature detection means. Moreover, it is preferable to use the heat generated from the refrigerant discharge pipe of the compressor as the heating means.

  According to the present invention, the refrigerant taken out from the receiver tank is depressurized and heated in the liquid level detection pipe and then supplied to the cooling side pipe of the supercooling heat exchanger. It can be effectively used for supercooling. Therefore, even if the refrigerant is always taken out from the receiver tank and the liquid level is constantly monitored, the capacity loss can be reduced, and the controllability (control responsiveness) is also improved.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3, but the present invention is not limited to this. FIG. 1 is a schematic diagram showing an overall configuration of an example in which the refrigeration apparatus of the present invention is applied to an air conditioner. FIG. 2 is a schematic diagram of a liquid level detection means of a receiver tank, a supercooling heat exchanger, FIG. 3 is a Mollier diagram for explaining the operation of the present invention. 1 and 2, the same reference numerals are used for components that may be regarded as the same as or the same as those of the prior application invention described with reference to FIGS. 4 and 5.

  First, the overall configuration of the air conditioner according to this embodiment will be described with reference to FIG. This air conditioner includes an outdoor unit 10 and an indoor unit 20. The outdoor unit 10 and the indoor unit 20 are of a split type in which they are connected via a predetermined piping member. However, the indoor unit 20 may be of a wall-mounted type, a ceiling embedded type, or a floor type. In this example, the indoor unit 20 includes two indoor units 20a and 20b connected in parallel with the same configuration.

  The air conditioner in this example includes a heat pump type refrigerant circuit capable of cooling operation and heating operation. Therefore, the outdoor unit 10 includes a compressor 11, a four-way valve 12, an outdoor heat exchanger 13 having an outdoor blower fan 13a, a receiver tank (gas-liquid separator) 14, and an accumulator 15 as a basic configuration. In this case, the receiver tank 14 is provided with the liquid level detecting means 30, and the receiver tank 14 is connected with the supercooling heat exchanger 40. In this example, the compressor 11 includes a variable speed compressor 11a controlled by an inverter and a constant speed compressor 11b.

  Referring to FIG. 2, the liquid level detection means 30 is the same as the first liquid level detection pipe 31 connected to the upper limit position of the receiver tank 14, for example, as described in FIG. Three liquid level detection pipes 32 and a third liquid level detection pipe 33 connected to the lower limit position.

  Each of the liquid level detection pipes 31, 32, 33 is provided with capillary tubes 31a, 32a, 33a as pressure reducing means, and on the downstream side thereof, heating means 34 for heating the decompressed refrigerant is provided. ing. The heating means 34 may be provided on the upstream side of the capillary tubes 31a, 32a, 33a. In this example, strainers 31c, 32c, and 33c for preventing clogging of the capillary tube are further provided upstream of the capillary tubes 31a, 32a, and 33a.

  An electric heater or the like may be used as the heating unit 34, but it is preferable to use heat generated from the refrigerant discharge pipe of the compressor 11. For this purpose, a part of the pipe may be welded along the refrigerant discharge pipe.

  Each of the liquid level detection pipes 31, 32, 33 is provided with temperature sensors 31b, 32b, 33b made of, for example, a thermistor for detecting the temperature of the heated refrigerant. The refrigerant temperature detected by each temperature sensor 31b, 32b, 33b is input to the control unit (control unit 30A in FIG. 5), and the control unit has been described in the above-mentioned prior invention based on the detected refrigerant temperature. Accordingly, the liquid level in the receiver tank 14 and the phase state are determined.

  The supercooling heat exchanger 40 is a double heat exchanger in which an inner cooling side pipe (inner pipe) 41 and an outer cooled side pipe (outer pipe) 42 are coaxial pipes, and the outer cooled side pipe 42. The liquid refrigerant taken out from the receiver tank 14 is flowed, and the liquid refrigerant taken out from the bottom of the receiver tank 14 is decompressed by the electronic expansion valve 43 for the supercooling heat exchanger in the inner cooling side pipe 41, and the low-pressure gas The refrigerant in the state is flowed.

  In the present invention, the liquid level detection pipes 31, 32, 33 of the liquid level detection means 30 are finally combined into one after the refrigerant is heated by the heating means 34, and are supercooled via the electromagnetic valve 35. It is supplied to the cooling side pipe 41 inside the supercooling heat exchanger 40 on the downstream side of the electronic expansion valve 43 for heat exchanger.

  Contrary to the above example, the liquid refrigerant taken out from the receiver tank 14 is flowed with the inner pipe 41 as the cooled pipe, and the electronic expansion valve 43 for the supercooling heat exchanger is used with the outer pipe 42 as the cooling pipe. It is good also as a structure which flows the refrigerant | coolant from the pressure reduction and the low pressure gas state, and the liquid level detection means 30.

  Each indoor unit 20a, 20b includes an indoor heat exchanger 21 having an indoor blower fan 21a. Each indoor unit 20a, 20b is provided with an electronic expansion valve 23 as a decompression means, and the flow rate is adjusted by the electronic expansion valve 23. Done.

  One end of the indoor heat exchanger 21 is connected to the outdoor heat exchanger 13 via the electronic expansion valve 23, the supercooling heat exchanger 40 and the receiver tank 14, and the other end is connected to the compressor 11 or accumulator via the four-way valve 12. 15 is selectively connected to any one of 15.

  At the time of cooling operation, the four-way valve 12 is switched as shown by the solid line in FIG. 1, and the refrigerant is compressor 11 → four-way valve 12 → outdoor heat exchanger 13 → receiver tank 14 → supercooling heat exchanger 40 → electronic expansion valve 23 → It flows from the indoor heat exchanger 21 → the four-way valve 12 → the accumulator 15 → the compressor 11. In this case, the outdoor heat exchanger 13 acts as a condenser, and the indoor heat exchanger 21 becomes an evaporator.

During this cooling operation, the temperature detected by the evaporation temperature detection thermistor 22a provided at a refrigerant inlet side of the indoor heat exchanger 21 TH _in, the detection of superheat (SH) detecting thermistor 22b provided on the refrigerant outlet side When the temperature is TH _out , a control unit (not shown) on the indoor unit 20 side controls the electronic expansion valve 23 on the indoor unit 20 side as follows to perform target SH control (maximum capability control).

That is, the actual SH is SH _R (= TH _out −TH _in ), the target SH is SH _T , and when SH _T <SH _R , the electronic expansion valve 23 is controlled so that SH _T > SH _In the case of _R , the electronic expansion valve 23 is controlled to open. In general, SH _T = 1 to 3 ° C. is set in order to maximize the ability.

Regarding the relationship with the room temperature control, the target SH is set according to the difference between the set temperature T _SET (usually 18 to 30 ° C.) of the indoor unit 20 and the indoor temperature T _ROOM detected by a temperature sensor (not shown). Change (SH _T ). That is, when T _ROOM -T _SET is small, the electronic expansion valve 23 is throttled to increase the target SH _T , and when T _ROOM -T _SET is large, the electronic expansion valve 23 is opened and the target SH _T is decreased. To do.

  During the heating operation, the four-way valve 12 is switched as indicated by a chain line in FIG. 1, and the refrigerant is compressor 11 → four-way valve 12 → indoor heat exchanger 21 → electronic expansion valve 23 → supercooling heat exchanger 40 → receiver tank. 14 → outdoor heat exchanger 13 → four-way valve 12 → accumulator 15 → compressor 11. In this case, the indoor heat exchanger 21 acts as a condenser, and the outdoor heat exchanger 13 becomes an evaporator.

  Here, the operation and effect of the supercooling heat exchanger 40 will be described. The reason for using the supercooling heat exchanger 40 is to increase the refrigeration effect by supercooling the refrigerant (liquid saturated state at this time) taken out from the receiver tank 14 during cooling operation to bring it into a liquid state. is there.

  With reference to the Mollier diagram of FIG. 3, the Mollier diagram of the refrigeration cycle when the supercooling heat exchanger 40 is not used is A → B → C → D. Point A is on the liquid saturation line at the outlet of the receiver tank 14. Point B is the inlet side of the indoor heat exchanger 21, point C is the suction side of the compressor 11, and point D is the discharge side of the compressor 11. The refrigeration effect of this refrigeration cycle is ΔIb, and the cooling capacity Qb in the indoor unit 20 is represented by Qb = qmb × ΔIb [kW], where the refrigerant circulation amount is qmb.

  On the other hand, the Mollier diagram of the refrigeration cycle when the supercooling heat exchanger 40 is used is E → F → C → D. That is, when the refrigerant at point A is supercooled by the supercooling heat exchanger 40, the refrigerant changes to point E. The refrigeration effect of this refrigeration cycle is ΔIf, and the cooling capacity Qf in the indoor unit 20 is represented by Qf = qmf × ΔIf [kW] where the refrigerant circulation amount is qmf.

  In this case, since a part of the refrigerant is bypassed to the accumulator 15 side by the supercooling heat exchanger 40, qmb> qmf is satisfied. However, since ΔIb <ΔIf, the refrigeration cycle using the supercooling heat exchanger 40 Has higher ability and efficiency. In other words, normally, the supercooling heat exchanger 40 is designed so that Qb <Qf.

  The point C is common to the above two refrigeration cycles, but this is due to the control of the electronic expansion valve 23 on the indoor unit 20 side. On the indoor unit 20 side, SH (superheat, degree of superheat) shown in FIG. Is controlled to follow a target value (for example, 3 ° C.) as described above. Therefore, on the Mollier diagram, the refrigeration effect is enhanced by the amount of increased supercooling.

  Another reason for using the supercooling heat exchanger 40 is that when the piping between the outdoor unit 10 and the indoor unit 20 is long, the pressure loss in the liquid piping increases, so that the Mollier diagram of FIG. In addition, when the refrigerant state at the outlet of the outdoor unit 10 is point A, the refrigerant state is point G on the front side of the electronic expansion valve 23 on the indoor unit 20 side.

  In a refrigeration cycle that does not use the supercooling heat exchanger 40, the liquid refrigerant easily becomes a two-phase refrigerant if there is a pressure loss. When the refrigerant enters a two-phase state on the front side of the electronic expansion valve 23 of the indoor unit 20, refrigerant sound is generated from the electronic expansion valve 23. This is a big problem as an air conditioner.

  On the other hand, in the refrigeration cycle using the supercooling heat exchanger 40, since the refrigerant at the outlet of the outdoor unit 10 is sufficiently subcooled, even if there is a pressure loss in the piping system, the indoor unit 20 The refrigerant can be kept in a liquid state before the electronic expansion valve 23. Referring to the Mollier diagram of FIG. 3, even if the refrigerant at point E changes to point H due to pressure loss in the piping, the refrigerant is still in the liquid region, so that the refrigerant noise is generated from the electronic expansion valve 23. Absent.

  In the present invention, as described above, the refrigerant used in the liquid level detection means 30 is supplied to the cooling side pipe 41 of the supercooling heat exchanger 40. As described above, since the refrigerant used for the liquid level detection has latent heat of vaporization of Q = qm × (Ic−If) [kW], the supercooling of the liquid refrigerant flowing in the cooled pipe 42 is performed. Can be used effectively.

The electronic expansion valve 43 for the supercooling heat exchanger is detected by the outdoor unit control unit (not shown) by the detected temperature TL _in at the refrigerant inflow side temperature sensor 44 of the cooled side pipe 42 and the detected temperature TL at the refrigerant outflow side temperature sensor 45. Control is performed so that the temperature difference from _out (TL _in −TL _out : this is supercooling) follows the target value.

In parallel with this, the electronic expansion valve 43 for the supercooling heat exchanger has a detection temperature TG _in at the refrigerant inflow side temperature sensor 46 of the cooling side pipe 41 and a detection temperature TG _out at the refrigerant outflow side temperature sensor 47. The temperature difference (TG _in −TG _out : superheat in the supercooling heat exchanger 40) is controlled to be a certain level or more. This super heat control is performed in order not to return the wet refrigerant (refrigerant having latent heat of evaporation) to the suction side of the refrigeration cycle, that is, to prevent a loss of capacity.

  As described above, in the present invention, the refrigerant having the latent heat of vaporization used for liquid level detection is caused to flow to the supercooling heat exchanger 40. If the target supercooling is still not reached, the electronic expansion valve for the supercooling heat exchanger is used. 43 may be controlled as described above. In addition, since the outdoor unit 10 functions as an evaporator during heating operation, the supercooling heat exchanger 40 is also used as one of the evaporators.

  The electromagnetic valve 35 of the liquid level detection means 30 may be opened only at the time of liquid level detection. However, according to the present invention, the refrigerant having latent heat of vaporization used for liquid level detection is used for the supercooling heat exchanger 40. Since it can be used effectively as a refrigerant, it is preferable to always open the electromagnetic valve 35 in terms of performance and in order to improve control responsiveness.

The schematic diagram which shows the whole structure of the example which applied the freezing apparatus of this invention to the air conditioner. The schematic diagram which expands and shows the liquid level detection means and supercooling heat exchanger of the receiver tank which are the principal parts of this invention. The Mollier diagram for demonstrating the effect | action of this invention. The schematic diagram which shows the structure of prior invention. The schematic diagram which shows the liquid level detection means with which the said prior application invention is equipped. The Mollier diagram for demonstrating the effect | action of the liquid level detection means of the said prior application invention. The Mollier diagram of the refrigerating cycle in a prior art example (patent document 1).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Outdoor unit 11 Compressor 12 Four-way valve 13 Outdoor heat exchanger 14 Receiver tank 15 Accumulator 20 Indoor unit 21 Indoor heat exchanger 23 Electronic expansion valve 30 Refrigerant liquid level detection means 31-33 Liquid level detection piping 31a-33a Capillary tube (Pressure reduction means)
31b to 33b Temperature sensor 34 Heating means 35 Electromagnetic valve 40 Supercooling heat exchanger 41 Cooling side piping 42 Cooled side piping 43 Electronic expansion valve for supercooling heat exchanger

Claims (4)

A refrigeration cycle including a compressor, a condenser and an evaporator is provided, a receiver tank and a supercooling heat exchanger are connected between the condenser and the evaporator, and a liquid level detecting means is provided in the receiver tank. In the refrigeration apparatus provided with
The liquid level detection means includes at least one liquid level detection pipe, one end of which is connected to a predetermined height portion of the receiver tank, a pressure reduction means for depressurizing the refrigerant flowing in the liquid level detection pipe, Heating means for heating the refrigerant in the liquid level detection pipe, and temperature detection means for detecting the temperature of the refrigerant heated by the heating means,
The other end of the liquid level detection pipe is connected to the cooling side pipe on the downstream side of the electronic expansion valve for the supercooling heat exchanger provided in the cooling side pipe of the supercooling heat exchanger , and the liquid level detection A refrigeration apparatus wherein the refrigerant used in the above is passed through the supercooling heat exchanger. When the target supercooling cannot be obtained only by using the latent heat of vaporization of the refrigerant used for the liquid level detection, the electronic expansion valve for the supercooling heat exchanger is additionally controlled to open. Item 2. The refrigeration apparatus according to item 1 . The liquid level detection means detects the phase state of the refrigerant in the receiver tank at a position where one end of the liquid level detection pipe is connected based on the refrigerant temperature obtained from the temperature detection means. The refrigeration apparatus according to claim 1 or 2, characterized in that The refrigeration apparatus according to any one of claims 1 to 3 , wherein heat generated from a refrigerant discharge pipe of the compressor is used as the heating means.

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