JP2011106688A - Condensation pressure detecting system and refrigeration cycle system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air conditioning device capable of controlling supercooling with high accuracy by calculating a condensation pressure in a condenser from an operation state quantity of the air conditioning device. <P>SOLUTION: This condensation pressure detecting system 70 of a refrigeration cycle device constituting a refrigerant circuit by connecting a compressor 1, indoor heat exchangers 11b, 11c condensing a refrigerant in a full heating operation and a heating-based operation, flow control devices 12b, 12c adjusting a pressure of the condensed refrigerant, and a heat source-side heat exchanger 3 evaporating the refrigerant, by piping, further includes a low-pressure pressure loss operating section 72 calculating pressure loss of a low-pressure refrigerant pipe in the refrigerant circuit, a high-pressure pressure loss calculating section 74 calculating pressure loss of a high-pressure refrigerant pipe based on a ratio of cross-sectional areas of the high-pressure refrigerant pipe and the low-pressure refrigerant pipe, and the pressure loss of the low-pressure refrigerant pipe, and a condensation pressure calculating section 75 calculating a condensation pressure in the indoor heat exchangers 11b, 11c by subtracting the high-pressure pressure loss from a pressure at a discharge side of the compressor 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an air conditioner that constitutes a refrigerant circuit that circulates a refrigerant by connecting an outdoor unit and an indoor unit, and condensing to operate the air conditioner with high efficiency by estimating the condensation pressure of the condenser. The present invention relates to a pressure detection system and the like.

  2. Description of the Related Art Conventionally, there is a separate type air conditioner that configures a refrigerant circuit that circulates a refrigerant between an outdoor unit and an indoor unit by connecting the outdoor unit and the indoor unit via a connection pipe. Examples of the separate type air conditioner include a room air conditioner and a packaged air conditioner. Hereinafter, the air conditioner is a separate type air conditioner.

  Here, in the air conditioner, the refrigerant flowing through the refrigerant circuit undergoes a pressure drop due to pressure loss (hereinafter referred to as pressure loss) in the connection pipe. And as the length of the connecting pipe between the outdoor unit and the indoor unit (usage unit) increases, the pressure loss increases and the pressure drops. In the heating operation, the high-temperature and high-pressure gas refrigerant discharged from the compressor flows through the heat exchanger of the indoor unit that performs heating against the pressure at the discharge of the compressor due to the pressure drop in the process of flowing through the connection pipe. Since the pressure of the refrigerant | coolant to perform becomes low, a condensation temperature falls.

  Therefore, conventionally, in order to detect a decrease in the condensing temperature due to the pressure effect, a temperature sensor is added at a substantially intermediate position of the heat exchanger of the indoor unit that is heating, and the temperature is set as the condensing temperature (saturation temperature) It was. In addition, a temperature sensor that detects the liquid temperature of the refrigerant is also arranged at the refrigerant outlet of the heat exchanger to detect the degree of supercooling that is the temperature difference between the condensation temperature and the temperature at the refrigerant outlet of the heat exchanger. The degree of opening of a throttle means such as an expansion valve is controlled so that the degree of supercooling becomes a desired temperature (see, for example, Patent Document 1).

  FIG. 8 is a graph showing the relationship between the degree of supercooling at the outlet of the condenser and the coefficient of performance COP of the refrigeration cycle. As shown in FIG. 7, in general, the greater the degree of supercooling, the greater the enthalpy difference before and after the condenser and the higher the efficiency, but the proportion of the liquid phase in the condenser increases. For this reason, the ratio of the gas-liquid two-phase part with a high heat transfer rate in the condenser is reduced, and the heat passing rate is reduced. From the above, there is an optimum degree of supercooling in the relationship between efficiency and heat transfer rate. Therefore, in order to realize an efficient operation of the air conditioner, it is necessary to accurately detect the degree of supercooling and optimally control it.

Japanese Patent No. 2508347

  In the above-mentioned Patent Document 1, a flow control device such as an expansion valve is controlled based on a temperature difference between an intermediate temperature sensor that detects the intermediate temperature of the condenser and an outlet temperature sensor that detects the outlet temperature of the condenser. . However, when the refrigerant amount is insufficient or when the refrigerant is excessively charged, the temperature detected at the assumed intermediate temperature sensor portion does not become the condensation temperature. For example, when the amount of the refrigerant is insufficient, the refrigerant becomes a gas refrigerant and is detected to be higher than the condensation temperature. When the refrigerant is excessively charged, the refrigerant is a liquid refrigerant and is detected to be lower than the condensation temperature. For this reason, the calculated degree of supercooling is not accurate, and there is a problem that appropriate supercooling degree control cannot be performed.

  The present invention has been made to solve the above-described problems, and in the case of an air conditioner in which an outdoor unit and an indoor unit are connected via a refrigerant pipe, the refrigerant pipe length is unknown. Even if there is an excess or deficiency in the amount of refrigerant charged, the pressure loss on the high pressure side is estimated from the operating state quantity of the air conditioner, and the condensation pressure in the condenser, which is necessary for calculating the degree of supercooling, is estimated. The purpose is to calculate. And it aims at obtaining the condensation pressure detection system applicable to refrigeration cycle systems, such as an air conditioning apparatus which can implement | achieve accurate supercooling control.

  At the same time, the condensing pressure detection of the air conditioner can improve the stability of the operating state and the comfort of the user by suppressing the occurrence of control hunting and refrigerant noise due to erroneous detection by the expansion valve throttle means. The purpose is to obtain a system.

  In order to solve the above-described problems, the pressure loss detection system for a high-pressure connection pipe according to the present invention employs the following means: a compressor that compresses the refrigerant, and a condenser that condenses the refrigerant by heat exchange. And a flow rate control device for adjusting the pressure of the condensed refrigerant, and an evaporator for exchanging heat between the decompressed refrigerant and air to evaporate the refrigerant, and connecting the pipes to each other, A condensing pressure detecting system for detecting condensing pressure, a low pressure pressure loss calculating unit for calculating a pressure loss of a low pressure refrigerant pipe serving as a low pressure refrigerant pipe in the refrigerant circuit, and a high pressure serving as a high pressure side refrigerant pipe in the refrigerant circuit. Based on the pipe cross-sectional area ratio between the refrigerant pipe and the low-pressure refrigerant pipe and the pressure loss of the low-pressure refrigerant pipe, the high-pressure pressure loss calculation unit that calculates the pressure loss of the high-pressure refrigerant pipe and the high pressure from the pressure on the discharge side of the compressor It is intended and a condensing pressure calculating section for calculating a condensing pressure in the condenser subtracting the pressure loss.

  According to the present invention, the condensation pressure calculation unit calculates the condensation pressure from the low pressure loss calculated by the low pressure loss calculation unit and the high pressure loss calculated by the high pressure loss calculation unit. Appropriate condensing pressure can be detected without the influence of pressure loss or the like in the refrigerant piping of the refrigeration cycle apparatus. For this reason, since supercooling control can be performed based on an appropriate condensation temperature converted from the condensation pressure, it is possible to perform precise supercooling control. And the hunting and refrigerant | coolant sound in a flow control apparatus can be suppressed, and an efficient driving | running state can be implement | achieved.

It is a refrigerant circuit figure of the air harmony device of an embodiment of this invention. It is a refrigerant circuit figure at the time of the cooling only operation | movement of the air conditioning apparatus of embodiment of this invention. It is a refrigerant circuit figure at the time of the all heating operation of the air conditioning apparatus of embodiment of this invention. It is a refrigerant circuit figure at the time of heating main operation of the air harmony device of an embodiment of this invention. It is a refrigerant circuit figure at the time of the cooling main operation | movement of the air conditioning apparatus of embodiment of this invention. It is a figure showing the structure of the control arithmetic unit 70 of Embodiment 1 of this invention. It is a figure showing structures, such as control arithmetic unit 70 of Embodiment 2 of this invention. It is a figure which shows the relationship between a supercooling degree and COP of a refrigerating cycle.

  EMBODIMENT OF THE INVENTION Below, embodiment which concerns on the condensing pressure detection system of the frozen air conditioning apparatus concerning this invention is described with reference to drawings. First, after describing an air conditioner to which the present invention can be applied, a condensing pressure detection system according to the present invention will be described.

Embodiment 1 FIG.
1 is a refrigerant circuit diagram illustrating a configuration of a refrigeration air conditioning apparatus according to Embodiment 1. FIG. FIG. 1 shows an example of a multi-room heat pump air conditioner in which a plurality of indoor units are connected to one outdoor unit. The air conditioner of the present embodiment shows an example in which air conditioning can be selectively performed for each indoor unit, and an indoor unit that performs cooling and an indoor unit that performs heating can be operated simultaneously. Here, in this embodiment, as shown in FIG. 1, a case where two indoor units and one shunt controller are connected to one outdoor unit will be described, but three or more indoor units and two or more units are connected. Even when the shunt controller is connected, the same operation can be performed. Moreover, the refrigerant | coolant used for an air conditioning apparatus is not specifically limited. For example, HFC refrigerants such as R410A, R407C, and R404A, HCFC refrigerants such as R22 and R134a, or natural refrigerants such as hydrocarbon and helium can be used. Here, the level of pressure in the refrigerant circuit represents the level of relative pressure in the refrigerant circuit caused by compression of a compressor or the like, pressure reduction by refrigerant flow rate control, or the like. The same applies to the temperature level. In addition, the suffixed means may be described with the suffix omitted if it is not particularly necessary to distinguish or specify the suffix.

  In FIG. 1, A is an outdoor unit. B and C are indoor units connected in parallel to each other as will be described later, and have the same configuration in this embodiment. D is a shunt controller that connects the outdoor unit A and the indoor units B and C.

  The outdoor unit A is configured by each component described below. For example, a compressor 1 that compresses refrigerant, a four-way switching valve 2 that is connected to the compressor 1 and switches the flow direction of the refrigerant, an outdoor heat exchanger 3 that exchanges heat between the outside air and the refrigerant, and a four-way switching valve 2 and the accumulator 4 connected between the compressor 1 and the outdoor heat exchanger 3 and a first connection pipe 6 to be described later, from the outdoor heat exchanger 3 to the first connection pipe 6. The refrigerant is provided only between the first check valve 5a that allows refrigerant flow only, the four-way switching valve 2 and the second connection pipe 7 described later, and only in the direction from the second connection pipe 7 to the four-way switching valve 2. Provided between the second check valve 5b that allows the flow, the four-way switching valve 2 and the first connection pipe 6, and allows the refrigerant to flow only from the four-way switching valve 2 to the first connection pipe 6. Provided between the third check valve 5c, the outdoor heat exchanger 3 and the second connection pipe 7, The is composed of a fourth check valve 5d that allows only refrigerant flow from the connecting pipe 7 in the direction of the outdoor heat exchanger 3.

  Each of the indoor units B and C includes load-side heat exchangers 11b and 11c, and flow control devices 12b and 12c such as expansion devices connected in series to the load-side heat exchangers 11b and 11c. . The flow rate control devices 12b and 12c are controlled to be opened and closed by the degree of superheat on the outlet side of the load side heat exchangers 11b and 11c during cooling, and also by the degree of supercooling on the outlet side during heating. ing.

  The shunt controller D is connected to the thick second connection pipe 7 and the outdoor heat exchanger 3 connected to the four-way switching valve 2, and is connected to the outdoor unit A by the first connection pipe 6 narrower than the second connection pipe 7. The load-side second connection pipes 7b and 7c connected to the load-side heat exchangers 11b and 11c of the indoor units B and C and the load-side connected to the flow control devices 12b and 12c of the indoor units B and C It connects with each indoor unit B and C by the 1st connection piping 6b and 6c.

  Regarding the configuration of the shunt controller D, first, the valve devices 13a1, 13a2, 13b1, and 13b2 connect the load-side second connection pipes 7b and 7c to the first connection pipe 6 or the second connection pipe 7 in a switchable manner. To do. One end of each of the two first valve devices 13a1 and 13a2 is connected to the load-side second connection pipes 7b and 7c, and the other end is connected to the first connection pipe 6 in a lump. In addition, one end of each of the two second valve devices 13b1 and 13b2 is connected to the second connection pipes 7b and 7c on the load side, and the other end is connected to the second connection pipe 7 in a lump. Yes. The second connection pipes 7b and 7c on the load side are connected to the first connection pipe 6 by opening the first valve device 13a1, closing the 13a2, closing the second valve device 13b1, and closing the 13b2. In addition, the first valve device 13a1 is closed, 13a2 is opened, the second valve device 13b1 is closed, and 13b2 is opened, so that the second connection pipes 7b and 7c on the load side are second connected. This is connected to the pipe 7.

  In addition, a gas-liquid separator 14 is provided in the middle of the first connection pipe 6, and its gas phase part is connected to the first valve device 13 a via the second half part of the first connection pipe 6, and the liquid phase thereof The parts are connected to the first connection pipes 6b, 6c on the load side via the first heat exchange part 15, the second flow control device 16 that can be opened and closed, and the second heat exchange part 17. In addition, a part of the liquid refrigerant from the gas-liquid separator 14 exchanges heat with the second heat exchange unit 17 and the first heat exchange unit 15 via the third flow rate control device 19 provided in the bypass pipe 18. The liquid refrigerant from the gas-liquid separator 14 is supercooled and returned to the second connection pipe 7.

  The pressure sensors 20 and 21 are installed on the discharge side and the suction side of the compressor 1 to detect pressure. Further, the temperature sensors 22, 23, 24, and 25 (25b, 25c) are respectively connected between the second heat exchange unit 17 and the third flow control device 19, on the discharge side of the compressor 1, and on the second heat. It is installed between the exchange unit 17 and the bypass pipe 18 and between the indoor heat exchanger 11 and the flow control device 12.

  In the refrigeration air conditioning apparatus of the present embodiment configured as described above, it is assumed that the operation of three forms can be performed roughly. With regard to the form, for example, a full cooling operation that is an operation when all of the operating indoor units perform cooling, a full heating operation that is an operation when all of the operating indoor units perform heating, and Some of the indoor units perform cooling, and the other part performs simultaneous cooling and heating operation, which is an operation when heating. In addition, for the simultaneous cooling and heating operation, a heating main operation in which most of the indoor units among the plurality of indoor units perform the heating operation, and a cooling main operation in which most of the indoor units among the plurality of indoor units perform the cooling operation are further performed. Divided.

<Cooling only operation>
FIG. 2 is a diagram illustrating the flow of the refrigerant in the cooling only operation. In FIG. 2, the flow of the refrigerant during the cooling only operation is indicated by solid arrows. First, the cooling only operation will be described with reference to FIG. The high-temperature and high-pressure refrigerant gas discharged from the compressor 1 passes through the four-way switching valve 2 and is condensed by exchanging heat in the outdoor heat exchanger 3, and then passes through the first check valve 5a and the first connection pipe 6. And flows into the diversion controller D. The refrigerant flowing into the diversion controller D passes through the gas-liquid separator 14 and the second flow rate control device 16 in this order, passes through the second heat exchange unit 17, passes through the check valves 30a1 and 30b1, and passes through the first on the load side. Passes through the connecting pipes 6b and 6c, flows into the indoor units B and C, and is reduced to a low pressure by the flow rate control devices 12b and 12c controlled by the degree of superheat at the outlets of the load side heat exchangers 11b and 11c. The heat exchangers 11b and 11c exchange heat with room air, evaporate and gasify, and cool the room.

  The refrigerant in the gas state passes through the second connection pipes 7b and 7c and the second valve device 13b on the load side, passes through the second connection pipe 7, the second check valve 5b, and the four-way switching valve 2. Then, a circulation cycle that is sucked into the compressor 1 through the accumulator 4 is formed, and the cooling operation is performed. At this time, the first valve device 13a1 is closed, 13a2 is open, the second valve device 13b1 is closed, and 13b2 is open.

  In addition, since the second connection pipe 7 is low pressure and the first connection pipe 6 is high pressure, the refrigerant inevitably flows to the first check valve 5a and the second check valve 5b. Further, during this cycle, a part of the refrigerant that has passed through the second flow rate control device 16 enters the bypass pipe 18 via the second heat exchange unit 17 and the third flow rate control device 19, and the third flow rate control. The apparatus 19 is depressurized to a low pressure, and the second heat exchange unit 17 exchanges heat with the refrigerant flowing into the first connection pipes 6b and 6c on the load side, and the first heat exchange unit 15 The refrigerant that has exchanged heat with the refrigerant flowing into the second flow control device 16 and enters the second connecting pipe 7 enters the second check valve 5b, the four-way switching valve 2, and the accumulator 4. Then, it is sucked into the compressor 1. On the other hand, the refrigerant that has exchanged heat in the first heat exchange unit 15 and the second heat exchange unit 17 and has an increased degree of supercooling is going to be cooled through the first connection pipes 6b and 6c on the load side. Flows into the existing indoor units B and C.

<Heating operation>
FIG. 3 is a diagram showing a refrigerant flow in the all-heating operation. In FIG. 3, the flow of the refrigerant at the time of heating only operation is indicated by solid line arrows. Next, the heating only operation will be described with reference to FIG. The four-way switching valve 2 is switched so as to have a flow different from that in the heating only operation. The high-temperature and high-pressure refrigerant gas discharged from the compressor 1 passes through the four-way switching valve 2, passes through the third check valve 5 c and the first connection pipe 6, and flows into the branch controller D. The refrigerant flowing into the diversion controller D passes through the first valve device 13a1 and the second 13b1 through the gas-liquid separator 14, the second half of the first connection pipe 6, and the second connection pipes 7b and 7c on the load side. , Flows into each of the indoor units B and C, exchanges heat with room air, condenses, and heats the room.

  And the refrigerant | coolant which became the liquid state passes through the flow control apparatuses 12b and 12c controlled by the subcooling degree of the exit of each load side heat exchanger 11b and 11c, and is from the load side 1st connection piping 6b and 6c. Then, after passing through the check valves 30a2 and 30b2, it flows into the third flow control device 19 of the bypass pipe 18 and is depressurized to a low-pressure gas-liquid two-phase state. The refrigerant depressurized to a low pressure passes through the second connection pipe 7 after passing through the second heat exchange unit 17 and the first heat exchange unit 15, and then enters the fourth check valve 5 d and the outdoor heat exchanger 3. The refrigerant that has flowed in, exchanged heat, and has evaporated to form a gas state constitutes a circulation cycle that is sucked into the compressor 1 through the four-way switching valve 2 and the accumulator 4, and performs the heating operation. At this time, the first valve device 13a1 is open, 13a2 is closed, the second valve device 13b1 is open, and 13b2 is closed. In addition, since the second connection pipe 7 is low pressure and the first connection pipe 6 is high pressure, the refrigerant inevitably flows to the third check valve 5c and the fourth check valve 5d.

<Heating-based operation>
FIG. 4 is a diagram showing the refrigerant flow in the heating-main operation. In FIG. 4, the flow of the refrigerant at the time of heating main operation in the simultaneous cooling and heating operation is indicated by solid arrows. Next, the heating main operation will be described with reference to FIG. Here, the case where the indoor unit B is heating and the indoor unit C is going to be cooled will be described. The high-temperature and high-pressure refrigerant gas discharged from the compressor 1 passes through the four-way switching valve 2, the third check valve 5 c, and the first connection pipe 6 and flows into the branch controller D. The refrigerant flowing into the shunt controller D passes through the gas-liquid separator 14, the second half of the first connection pipe 6, the second valve device 13 b 1, and the load-side second connection pipe 7 b in this order. It flows into the machine B, heat-exchanges with room air by the load side heat exchanger 11b, is condensed and liquefied, and the room is heated.

  Then, the refrigerant in the liquid state is controlled by the degree of supercooling at the outlet of the load side heat exchanger 11b, and is slightly depressurized through the flow control device 12b in the almost fully open state, so that the intermediate pressure between the high pressure and the low pressure (intermediate pressure) ), And a part of the refrigerant that has flowed into the first connection pipe 6b on the load side passes through the second heat exchange part 17 as indicated by the arrow, and the first on the load side connected to the indoor unit C that is going to be cooled. After being depressurized by the flow rate control device 12c controlled by the degree of superheat at the outlet of the load side heat exchanger 11c, the gas enters the load side heat exchanger 11c of the indoor unit C, evaporates by heat exchange It becomes a state, cools the room, and flows into the second connection pipe 7 via the first valve device 13a2 connected to the indoor unit C.

  On the other hand, the other part of the refrigerant for heating the indoor unit B that has flowed from the indoor unit B into the second heat exchange unit 17 of the shunt controller D passes through the bypass pipe 18 and the high pressure and flow rate of the first connection pipe 6. Since the second connecting pipe 7 is reached through the third flow control device 19 that can be opened and closed that is controlled so as to make the difference from the intermediate pressure at the outlet of the control device 12b constant, The refrigerant that has cooled the machine C and flows into the thick second connection pipe 7 flows into the fourth check valve 5d and the outdoor heat exchanger 3, exchanges heat, evaporates, and enters the gas state. A circulation cycle that is sucked into the compressor 1 through the four-way switching valve 2 and the accumulator 4 is configured, and the heating main operation is performed.

  At this time, the first valve device 13a1 connected to the indoor unit B to be heated is open, 13a2 is closed, and the second valve device 13b1 connected to the indoor unit C to be cooled is closed. , 13b2 is open. In addition, since the second connection pipe 7 is low pressure and the first connection pipe 6 is high pressure, the refrigerant inevitably flows to the third check valve 5c and the fourth check valve 5d.

  In this cycle, the refrigerant that has entered the bypass pipe 18 is decompressed to a low pressure by the third flow control device 19 and flows into the first connection pipe 6c on the load side by the second heat exchange unit 17. The refrigerant that exchanges heat with the refrigerant and further exchanges heat with the refrigerant flowing into the second flow rate control device 16 in the first heat exchanging unit 15, and the evaporated refrigerant passes to the second connection pipe 7. Enters, passes through the fourth check valve 5d, flows into the outdoor heat exchanger 3, exchanges heat, evaporates, and enters a gas state. The refrigerant is sucked into the compressor 1 through the four-way switching valve 2 and the accumulator 4. On the other hand, the refrigerant whose degree of supercooling has been increased by exchanging heat in the second heat exchanging unit 17 flows into the indoor unit C that is going to be cooled, as described above.

<Cooling operation>
FIG. 5 is a diagram showing the flow of the refrigerant in the cooling main operation. In FIG. 5, the flow of the refrigerant | coolant at the time of the air_conditioning | cooling main operation | movement in the cooling / heating simultaneous operation is shown by the solid line arrow. Next, the cooling main operation will be described with reference to FIG. Here, the case where the indoor unit B is heating and the indoor unit C is going to be cooled will be described. The high-temperature and high-pressure refrigerant gas discharged from the compressor 1 passes through the four-way switching valve 2 and exchanges an arbitrary amount of heat in the outdoor heat exchanger 3 to become a gas-liquid two-phase high-temperature and high-pressure refrigerant, and the first check valve 5a, It passes through the first connection pipe 6 and flows into the diversion controller D. The refrigerant flowing into the diversion controller D is sent to the gas-liquid separator 14 where it is separated into a gas refrigerant and a liquid refrigerant. The separated gas refrigerant passes through the second half of the first connection pipe 6 in the order of the second valve device 13b1 of the shunt controller D and the second connection pipe 7b on the load side, and reaches the indoor unit B that is to be heated. It flows in, heat-exchanges with indoor air with the load side heat exchanger 11b, is condensed and liquefied, and the room is heated.

  Furthermore, it is controlled by the degree of supercooling at the outlet of the load side heat exchanger 11b and is slightly depressurized through the flow control device 12b in a fully open state, resulting in an intermediate pressure between the high pressure and the low pressure (intermediate pressure). The refrigerant flows into the bypass pipe 18 through the connection pipe 6b, is depressurized to a low pressure by the third flow rate control device 19, and flows into the first connection pipe 6c on the load side in the second heat exchange section 17. The refrigerant that has exchanged heat and that has exchanged heat with the refrigerant flowing into the second flow rate control device 16 in the first heat exchanging unit 15 reaches the second connection pipe 7. On the other hand, the remaining liquid refrigerant separated by the gas-liquid separator 14 of the shunt controller D is subjected to heat exchange by the first heat exchange unit 15 and the degree of supercooling is increased, and then the difference between the high pressure and the intermediate pressure is constant. As shown by the arrow through the second flow rate control device 16 controlled so as to pass through the check valve 30b1, passes through the first connection pipe 6c on the load side, and flows into the indoor unit C. The refrigerant is decompressed to a low pressure by the flow rate control device 12c controlled by the degree of superheat at the outlet of the load side heat exchanger 11c of the indoor unit C, and exchanges heat with room air in the load side heat exchanger 11c to evaporate. It is gasified and the room is cooled.

  The gas refrigerant enters the second connection pipe 7 via the load-side second connection pipe 7c and the second valve device 13b, and passes through the bypass pipe 18 to the second connection pipe 7. After merging with the heating refrigerant of the indoor unit B that flows in, a circulation cycle is formed which is sucked into the compressor 1 through the second check valve 5b, the four-way switching valve 2, and the accumulator 4, and the cooling main operation is performed. Do.

  At this time, the first valve device 13a1 connected to the indoor unit C to be cooled is closed, 13a2 is opened, and the second valve device 13b1 connected to the indoor unit B to be heated is open, 13b2 is closed. In addition, since the second connection pipe 7 is low pressure and the first connection pipe 6 is high pressure, the refrigerant inevitably flows to the first check valve 5a and the second check valve 5b.

  Since the air conditioning apparatus according to this embodiment is configured as described above, the first connection pipe 6 is always used at a high pressure, and the second connection pipe 7 is always used at a low pressure. Accordingly, the first connection pipe 6 can be designed with a high design pressure, and the second connection pipe 7 can be designed with a low design pressure.

[Detection of pressure loss in gas refrigerant piping]
In the air conditioner configured as described above, a processing procedure such as detecting the condensing pressure of the indoor unit B when gas refrigerant flows into the first connection pipe 6 during heating and heating main operation and pressure loss occurs. Will be described.

FIG. 6 is a diagram illustrating the configuration of the control arithmetic device 70 according to the first embodiment. As shown in FIG. 6, the control calculation device 70 functions as a system that performs condensation pressure detection, and includes an operation control unit 71, a low pressure loss calculation unit 72, a storage unit 73, a high pressure loss loss calculation unit 74, and a condensation pressure calculation unit. 75. The operation control unit 71 controls the refrigerant flow in each operation mode described above. In the present embodiment, the operation of the outdoor unit A, the indoor unit B, and the indoor unit C when the condensation pressure is to be detected is controlled. Here, the degree of supercooling of the refrigerant outlet of the condenser is controlled based on the condensation temperature converted from the condensation pressure calculated by the condensation pressure calculator 75 in particular. The low-pressure pressure loss calculation unit 72 calculates the pressure loss (hereinafter referred to as low-pressure pressure loss) ΔP _L of the low-pressure side refrigerant flowing in the second connection pipe 7. The storage unit 73 stores the ratio of the pipe diameter of the second connection pipe 7 to the first connection pipe 6. High pressure loss calculation unit 74, based on the ratio of pipe diameter to be stored in the low pressure loss and a storage unit 73, the first connecting pipe pressure of the high pressure side of the refrigerant flowing through the 6 (hereinafter referred to as high pressure drop) [Delta] P _H Is calculated. The condensing pressure calculation unit 75 calculates the condensing pressure from the difference between the refrigerant pressure (high pressure) related to the discharge of the compressor 1 and the high pressure loss.

  Next, processing performed by the control arithmetic device 70 will be described. When at least one of the indoor unit B and the indoor unit C performs heating, the operation control unit 71 causes the air conditioner to perform a full heating operation or a heating main operation.

The low-pressure pressure loss calculation unit 72 converts the saturation temperature related to detection by the temperature sensor 22 provided at the outlet of the third flow rate control device 19 of the bypass pipe 18 to the saturation pressure Pe based on the physical properties of the refrigerant. Then, the low pressure side pressure loss ΔP _L (ΔP _L = Pe−PSL) is calculated from the difference between the low pressure PSL related to the detection of the pressure sensor 21 provided in the suction portion of the compressor 1 and the saturation pressure Pe.

  Here, the pressure sensor 21 is normally provided to measure the pressure on the low pressure side when the air conditioning apparatus capable of simultaneous heating and cooling according to the present embodiment performs pressure control operation. By diverting, the number of sensors (detection means) can be reduced.

A low side pressure loss [Delta] P _L which low pressure loss calculating section 72 calculates, for the first connection pipe 6, the value of the second connection pipe 7 storage unit 73 the ratio of the pipe diameter stored in, the high pressure loss [Delta] P _H is high pressure loss calculating section 74 calculates. Here, the ratio of the pipe diameter of the second connection pipe 7 to the first connection pipe 6 is determined at the connection port of the first connection pipe 6 and the second connection pipe 7 of the outdoor unit A. Therefore, the value is unique to the model of the outdoor unit A.

  In general, the pressure loss ΔP can be calculated by the following Darcy's Formula. Here, λ is Darcy's pipe friction coefficient, L is the pipe length, D is the pipe inner diameter, ρ is the specific gravity of the refrigerant, U is the average flow velocity, and L is the pipe length of the connection pipe.

Based on the formula (1), the high pressure loss ΔP _H and the low pressure loss ΔP _L in the first connection pipe 6 and the second connection pipe 7 are expressed by the following formulas (2) and (3), respectively. Here, the subscript relating to the high pressure is H, and the subscript relating to the low pressure is L. The pipe lengths of the first connection pipe 6 and the second connection pipe 7 are both L.

Here, in the heating only operation and the heating main operation, the gas-liquid two-phase refrigerant flows through the second connection pipe 7, so that the pressure loss generally increases as compared with the single-phase operation. This can be considered as an increase in the tube friction coefficient λ. The refrigerant circulation amount Gr can be expressed by a high-pressure side parameter and a low-pressure side parameter, respectively, as in the following equations (4) and (5).

The pressure loss ratio RDP between ΔP _H and ΔP _L is expressed by the following equation (6).

The pipe inner diameters D _H and D _L are values determined by the pipe specifications of the first connection pipe 6 and the second connection pipe 7, respectively. Further, the refrigerant density ρ _H on the high pressure side can be calculated based on the high pressure PSH detected by the pressure sensor 20 provided at the compressor outlet in FIG. 1 and the temperature detected by the temperature sensor 23. The refrigerant density ρL on the low-pressure side can be calculated using the enthalpy calculated from the temperature of the liquid refrigerant detected by the temperature sensor 22 and the temperature sensor 24 provided at the inlet of the flow control device 19. The ratio λ _H / λ _L between λ _H and λ _L is the high pressure related to the piping specifications of the first connecting pipe 6 and the second connecting pipe 7 and the detection of the pressure sensor 20 provided at the discharge portion of the compressor 1. It is determined by the refrigerant physical property on the high pressure side obtained from the pressure PSH and the temperature detected by the temperature sensor 23 and the refrigerant physical property on the low pressure side obtained from the temperature of the temperature sensor 22 and the temperature sensor 24. From the above, RDP can be calculated.

If RDP is calculated, ΔP _H = ΔP _L × RDP, so that the high pressure loss calculator 74 can calculate the high pressure loss ΔP _H from the low pressure loss ΔP _L calculated by the low pressure loss calculator 72. . Next, the condensing pressure calculating unit 74, it is possible to calculate the condensing pressure in the indoor heat exchanger 11 of the indoor unit according to the heating by subtracting the high pressure loss [Delta] P _H from the high pressure PSH. And the operation control part 71 controls the supercooling degree of the indoor unit 11 used as a condenser based on the temperature which detects the temperature sensors 25b and 25c, and the condensation temperature converted from the condensation pressure.

  Here, as shown in the equation (6), the calculation of the condensation pressure has no dependency on the refrigerant circulation amount Gr, which is the operating capacity of the compressor 1, and thus is not affected by the performance variation of the compressor 1. It becomes possible to calculate the condensation pressure of the indoor unit 11 relating to heating with high accuracy.

  In the above processing in the system, the first connection pipe 6 and the second connection pipe 7 are calculated to have the same length. However, the first connection pipe 6 and the second connection pipe are calculated. When the lengths of 7 are different, the condensation pressure can be calculated with higher accuracy by multiplying the ratio of the pipe lengths to the RDP.

Further, in the above processing in the system, in calculating λ _L , the dryness of the refrigerant flowing through the second connection pipe 7 is about 0.2 in the all-heating operation and hardly changes. The two-phase multiplication factor representing the pressure loss may be constant. On the other hand, in the heating-main operation, the dryness of the refrigerant flowing through the second connection pipe 7 varies from about 0.2 to 0.9 depending on the ratio of the number of indoor units that are performing cooling. Therefore, the condensation pressure can be calculated with higher accuracy by calculating the two-phase multiplication coefficient according to the dryness.

In the above processing, the low pressure pressure loss calculation unit 72 calculates the low pressure loss ΔP _L on the assumption that both ends of the second connection pipe 7 are at the same height. In an actual air conditioner, the end of the second connection pipe 7 often has a height difference, and a head difference due to the height difference often occurs. Therefore, for example, data related to the height difference of the connecting pipe 7 is input externally, and the pressure drop due to the head difference is corrected with respect to the low pressure loss ΔP _L to calculate the condensation pressure with higher accuracy. be able to.

  As described above, according to the system related to the control arithmetic device 70 in the present embodiment, the refrigerant of the air conditioner, for example, from the low pressure loss in the first refrigerant pipe 6 and the high pressure loss in the second refrigerant pipe 7. It is possible to detect the condensing pressure excluding the influence of pressure loss and the like in the piping. And since the operation control part 71 can perform supercooling control based on the proper condensing temperature converted from the condensing pressure, for example, when the volume of the condenser, the path shape, and the connecting pipe length change significantly. Even so, it is possible to perform supercooling control with high accuracy. For this reason, it is possible to suppress hunting and refrigerant noise in the flow control device and to realize an efficient operation state.

  Also, for example, even if it is difficult to detect the condensation temperature by inserting a temperature sensor etc. due to the laminated structure of the plates, such as a plate heat exchanger, the condensation can be done with a simple configuration without using the temperature sensor etc. The pressure can be calculated.

Embodiment 2. FIG.
FIG. 8 is a diagram illustrating the configuration of the control arithmetic device 70 and the like according to the second embodiment. In the present embodiment, for example, it is assumed that a notification unit 80 that performs auditory and visual notification using a speaker, a display, or the like is provided. In addition, the control arithmetic device 70 has a notification processing unit 76 for determining that the refrigerant of the air conditioner is insufficient and notifying the notification means 80 of it.

  For example, in the case of a heating only operation or a heating main operation in which the indoor heat exchangers 11b and 11c are condensers, the notification processing unit 76 determines the temperature at the outlet of the indoor heat exchanger 11 related to the detection of the temperature sensor 25 and the above-described temperature. The temperature difference with the condensation temperature converted from the condensation pressure calculated by the process is calculated. If the temperature difference is smaller than the predetermined value or the temperature at the outlet of the indoor heat exchanger 11 is larger, the air conditioner assumes that the refrigerant is superheated gas at the outlet of the indoor heat exchanger 11. It is determined that the refrigerant is insufficient, and the informing means 80 is informed that the refrigerant is insufficient. As a result, for example, a refrigerant shortage due to refrigerant leakage in the refrigerant circuit can be appropriately notified, and safety and reliability can be improved.

  The condensing pressure detection system of the present invention and the air conditioner to which the present invention is applied are not limited to the configuration of the embodiment described above, and various modifications can be made without departing from the gist of the present invention.

  Further, as an example of equipment to which the system of the present invention can be applied, in addition to a refrigeration air conditioner, the present invention is also applied to other refrigeration cycle devices such as refrigerators, dehumidifiers, heat pump water heaters, showcases, etc. Can be configured.

  DESCRIPTION OF SYMBOLS 1 Compressor, 2 way switching valve, 3 Heat source side heat exchanger, 4 Accumulator, 5a 1st check valve, 5b 2nd check valve, 5c 3rd check valve, 5d 4th check valve , 6 First connection pipe, 6b, 6c Load side first connection pipe, 7 Second connection pipe, 7b, 7c Load side second connection pipe, 11b, 11c Indoor heat exchanger, 12b, 12c Flow control device, 13a1, 13a2, 13b1, 13b2 Valve device, 14 Gas-liquid separator, 15 First heat exchange unit, 16 Second flow control device, 17 Second heat exchange unit, 18 Bypass piping, 19 First 3 flow control device, 30a1, 30a2, 30b1, 30b2 check valve, 20, 21 pressure sensor, 22, 23, 24, 25 temperature sensor, 70 control operation device, 71 operation control unit, 72 low pressure pressure loss calculation unit, 73 Memory , 74 high pressure loss calculating section, 75 the condensation pressure calculating unit, 76 notification unit, 80 notification unit, A outdoor unit, B, C indoor unit, D branch controller.

Claims (7)

A compressor that compresses the refrigerant; a condenser that condenses the refrigerant by heat exchange; a flow rate control device that adjusts the pressure of the condensed refrigerant; and the refrigerant and air that are depressurized to exchange heat. A condensing pressure detection system for detecting a condensing pressure of a refrigeration cycle apparatus that constitutes a refrigerant circuit by pipe connection to an evaporator for evaporating
A low-pressure pressure loss calculation unit for calculating a pressure loss of a low-pressure refrigerant pipe serving as a low-pressure side refrigerant pipe in the refrigerant circuit;
A high pressure loss that calculates a pressure loss of the high pressure refrigerant pipe based on a cross sectional area ratio of the high pressure refrigerant pipe and the low pressure refrigerant pipe that is a high pressure side refrigerant pipe in the refrigerant circuit and a pressure loss of the low pressure refrigerant pipe An arithmetic unit;
A condensation pressure detection system comprising: a condensation pressure calculation unit that subtracts the high pressure loss from the pressure on the discharge side of the compressor and calculates a condensation pressure in the condenser.   2. The condensation according to claim 1, further comprising an operation control unit that controls a degree of supercooling of a refrigerant outlet of the condenser based on a condensation temperature converted from a condensation pressure calculated by the condensation pressure calculation unit. Pressure detection system.   The said high pressure pressure loss calculating part correct | amends the pressure loss of the said high pressure refrigerant | coolant piping based on ratio of the pipe length of the said low pressure refrigerant | coolant piping and the said high pressure refrigerant | coolant piping. Condensation pressure detection system.   The said high-pressure-pressure-loss calculating part correct | amends the pressure loss of the said high-pressure refrigerant | coolant piping based on the dryness of the refrigerant | coolant which flows through the said low-pressure refrigerant | coolant piping. Condensation pressure detection system.   5. The condensation pressure detection according to claim 1, wherein the high-pressure pressure loss calculation unit corrects a pressure loss of the high-pressure refrigerant pipe based on a height difference of the low-pressure refrigerant pipe. system. Condenser outlet temperature detection means for detecting the temperature of the refrigerant at the refrigerant outlet of the condenser;
When it is determined that the temperature difference between the condensation temperature based on the condensation pressure calculated by the condensation pressure calculation unit and the temperature related to the detection by the condenser outlet temperature detection means is equal to or less than a predetermined value, the air conditioner has insufficient refrigerant. The condensation pressure detection system according to claim 1, further comprising: a notification processing unit that notifies the notification unit that the information is being performed.   A refrigeration cycle system having the condensing pressure detection system according to any one of claims 1 to 6.

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