JP2008224210A - Air conditioner and operation control method of air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable air conditioner of an opening-closing valve capable of precise temperature/humidity control by a simple means, and capable of reducing the circuit switching of frequent dehumidifying operation and cooling operation, in the air conditioner having the dehumidifying operation and the cooling operation, by arranging a compressor, a first heat exchanger, a reheating heat exchanger, an orifice device and a second heat exchanger. <P>SOLUTION: This air conditioner is provided with a means for detecting the refrigerant state of a first heat exchanger entrance and a reheating exchanger entrance by using a carbon dioxide as a refrigerant, and a means for controlling an air volume of the first heat exchanger, and controls a heat exchange quantity of the reheating heat exchanger by changing a heat exchange quantity of the first heat exchanger. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an air conditioner that performs a dehumidifying operation and a cooling operation, and relates to operation control when a carbon dioxide refrigerant is used.

In a conventional air conditioner having a dehumidifying function, in order to maintain the air-conditioned space in a predetermined temperature and humidity environment, the state of the air to be conditioned is monitored, and which of the operation modes of the cooling operation and the dehumidifying operation is required. Judging and switching the operation mode, the temperature and humidity of the air-conditioned space are adjusted. The switching of each operation mode is performed by changing the refrigerant flow path by opening and closing an on-off valve provided in the refrigerant circuit (see, for example, Patent Document 1).
Japanese Patent Application Laid-Open No. 11-142017 (page 3-4, FIGS. 7 and 8)

  In a conventional air conditioner having a dehumidifying function, when adjusting the temperature and humidity by switching between the dehumidifying operation and the cooling operation of the air conditioner, the difference in the temperature of the non-heat exchange air blown into the room is large. The indoor temperature fluctuates greatly during the dehumidifying operation. For this reason, when trying to control the room temperature to a predetermined temperature, the switching of the on-off valve for switching between the cooling operation mode and the dehumidifying operation mode is frequently performed. Valve failures are likely to occur, leading to a reduction in device reliability.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a highly reliable air conditioner that can obtain an appropriate temperature and humidity environment without frequently switching the operation mode. It is said.

  In the air conditioner according to the present invention, carbon dioxide is used as a refrigerant in the refrigerant circuit having the compressor, the first heat exchanger, the expansion device, the second heat exchanger, and the heat exchanger for reheating, The dehumidifying operation is performed by changing the heat exchange amount of the first heat exchanger to control the heat exchange amount of the reheat heat exchanger disposed on the leeward side of the second heat exchanger.

Since the present invention is configured as described above, it is possible to provide an inexpensive air-conditioning apparatus with stable dehumidifying performance capable of controlling the amount of reheat with simple means.
In addition, it is possible to provide an air conditioner with low switching frequency between the dehumidifying operation and the cooling operation and having a high reliability of the on-off valve.

Embodiment 1 FIG.
FIG. 1 is a refrigerant circuit diagram of an air-conditioning apparatus showing Embodiment 1 of the present invention.
In the figure, the compressor 1, the first heat exchanger 2, the first on-off valve 3, the reheat heat exchanger 4, the expansion device 5, and the second heat exchanger 6 are refrigerants. The first blower 7 sends air to the first heat exchanger 2, and the second blower 8 sends air to the second heat exchanger 6 and the reheat heat exchanger 4. . The second heat exchanger 6 is located on the windward side of the reheat heat exchanger 4.
Further, a bypass pipe 9 branches from the inlet side of the first on-off valve 3 and is connected to the outlet side pipe of the reheater 9 via the second on-off valve 10.

During the dehumidifying operation, the first on-off valve 3 is opened and the second on-off valve 10 is closed, and during the cooling operation, the first on-off valve 3 is closed and the second on-off valve 10 is opened to operate the apparatus. Let

In this refrigerant circuit, carbon dioxide is used as a refrigerant.
For example, as disclosed in JP-A-2002-22299, carbon dioxide operates at a pressure higher than the critical pressure, unlike a refrigerant such as R22. Therefore, carbon dioxide is used in a condenser when a refrigerant such as R22 is used. The corresponding heat exchanger is characterized in that the phase does not change isothermally, and the temperature of the refrigerant decreases toward the outlet of the condenser.

Next, the control system of this refrigerant circuit will be described.
The first temperature sensor 11a is connected to the inlet side pipe of the first heat exchanger 2, and the second temperature sensor 12a and the first pressure sensor 13a are connected to the outlet side pipe of the first heat exchanger 2 again. A third temperature sensor 11b is attached to the outlet side pipe of the heat exchanger 4 for heat, and a fourth temperature sensor 12b and a second pressure sensor 13b are attached to the outlet side pipe of the second heat exchanger 6. Yes.
Furthermore, these sensors are electrically connected to the information processing unit 14a of the control device 14, and information on each sensor is sent to the information processing unit 14a for information processing, and actuator processing is performed based on the processed information. The part 14 b controls the first blower 7, the second blower 8, the throttle device 5, the first on-off valve 3, and the second on-off valve 10. That is, the information processing unit 14a calculates the enthalpy of the refrigerant from information obtained from the pressure sensors 13a and 13b and the temperature sensors 11a, 11b, 12a, and 12b, and the actuator control unit 14b receives information from the information processing unit 14a. Based on this, the rotation speed of the first blower 7 is controlled.

FIG. 2 is a Ph diagram representing the operation of the refrigeration cycle of the air conditioner of the present invention, where the horizontal axis indicates the refrigerant enthalpy h, the vertical axis indicates the magnitude of the refrigerant pressure P, T is an isotherm, C is a critical point.
In the figure, during the dehumidifying operation, the high-temperature and high-pressure refrigerant compressed by the compressor 1 flows into the first heat exchanger 2, where it is in a state R3 where heat is radiated by the input of the compressor. The refrigerant in the state R3 flows into the heat exchanger 4 for reheating, where it dissipates heat to the air, so that the state R4 is obtained. The refrigerant is decompressed by the expansion device 5 and enters the gas-liquid two-phase state R5. In the second heat exchanger 6, the refrigerant takes heat from the air and evaporates to become a gas single-phase refrigerant R1, and is sucked into the compressor 1 again to complete the refrigeration cycle.

Next, a method for controlling the reheat capacity will be described.
Since the carbon dioxide refrigeration cycle normally operates at a critical pressure or higher, if the refrigerant temperature and refrigerant pressure are detected at the outlet of the first heat exchanger 2, the refrigerant enthalpy of the portion can be determined. The pressure Pcm at the outlet of the first heat exchanger 2 is detected by the pressure sensor 13a, the temperature Tcm is detected by the temperature sensor 12a, and the enthalpy Hcm in R3 is calculated by the information processing unit 14a. The information processing unit 14a stores in advance an approximate expression H = f (P, T) for obtaining the enthalpy H of the refrigerant from the pressure P and the temperature T.

  Also at the outlet of the second heat exchanger 6, the refrigerant pressure Peo is detected by the pressure sensor 13b, and the refrigerant temperature Teo is detected by the temperature sensor 12b. From the obtained detection result, the information processor 14a Refrigerant enthalpy Heo is calculated.

  Further, from the refrigerant temperature Tco at the outlet of the reheat heat exchanger 4 and the refrigerant pressure Pcm at the outlet of the first heat exchanger 2, the refrigerant enthalpy Hco at the outlet of the reheat heat exchanger 4 is converted into the first heat exchanger 2. From the refrigerant temperature Tcin at the inlet and the refrigerant pressure Pcm at the outlet of the first heat exchanger 2, the refrigerant enthalpy Hcin at the inlet of the first heat exchanger 2 is calculated by the information processing unit 14a.

  Here, the difference Hcm-Hcin of each refrigerant enthalpy obtained from the above calculation is the condensation heat exchange amount in the first heat exchanger 2, and Hcm-Hco is the reheat heat exchange amount in the reheat heat exchanger 4, Hco-Heo represents the evaporation heat exchange amount in the second heat exchanger 6.

Since the refrigerant enthalpy at the outlet of the reheat heat exchanger 4 and the outlet of the first heat exchanger 2 can be easily detected due to the characteristics of the carbon dioxide refrigerant, for example, by changing the air volume of the first blower 7, the condensation heat exchange By controlling the amount, it becomes possible to freely change the ratio of the reheating ability and the evaporation ability. Thereby, reheat capability can be controlled precisely and the blowing temperature in a dehumidification operation can be changed actively.
Below, the control method in the case of changing freely the ratio of the reheat capability of an air conditioning apparatus and evaporation capability is demonstrated.

Here, a method for controlling the reheat capacity to 40% of the evaporation capacity will be described.
In order to control the ratio to 40%, the following expression (1) or (2) needs to be satisfied.
(Hcm-Hco) / (Heo-Hco) = 0.4 (1)
When the equation (1) is transformed, Hcm = 0.4 × (Heo−Hco) + Hco (2)
First, each refrigerant enthalpy is calculated by the information processing unit 14a from the detection values of each pressure sensor and temperature sensor.
Here, if Hcm> 0.4 × (Heo−Hco) + Hco, the rotation speed of the first blower 7 is increased by the actuator controller 14b. On the other hand, if Hcm <0.4 × (Heo−Hco) + Hco, the actuator controller 14b decreases the rotation speed of the first blower 7 until the formula (1) or (2) is established. By repeating the above operation, the target ratio can be adjusted to 40%.

The ratio between the reheating capacity and the evaporation capacity has a limit value (lower limit) as a characteristic of the apparatus, and assuming that it is 40%, the reheating capacity can be changed in a range of 40 to 100%. Conversely, the cooling capacity can be controlled at a capacity of 0 to 60%.
In addition, although the rotation speed of the air blower was controlled in this Embodiment, it is possible to control reheat capability freely also by the method of controlling an expansion apparatus or a heat-transfer area.

FIG. 3 is an operation flow diagram of the air-conditioning apparatus showing Embodiment 1 of the present invention, and shows a flow of the switching method of the dehumidifying operation and the cooling operation shown above and the method for adjusting the blown air temperature during the dehumidifying operation. It is a thing.
In the figure, when the dehumidifying operation of the air conditioner is started (step S1), the indoor intake air temperature is detected to determine whether it is within the target range (step S2). If not, the ratio (Hcm-Hco) / (Heo-Hco) of the reheat capacity and the evaporation capacity is confirmed (step S3), and the value is the limit reheat ratio (set in advance as the apparatus) It is determined whether it is larger than the lower limit (step S4). If it is smaller, the operation is switched to the cooling operation mode (step S5). If it is larger, the operation is continued in the dehumidifying operation mode (step S6). If it is determined in step 6 that the dehumidifying operation is to be continued, it is determined whether or not the indoor intake air temperature is higher than the set target value (step S7). If it is higher, the current first heat exchanger 2 outlet temperature is determined. A lower target temperature is set (step S8), the air volume of the first blower 7 that blows air toward the first heat exchanger 2 toward this target value is increased (step S8), and the reheat amount is accordingly increased. The indoor blowing air temperature decreases and the indoor intake air temperature is determined again (step S2), and the air temperature adjustment operation is repeated. In step S7, if the indoor intake air temperature is lower than the set target value, a target temperature higher than the current first heat exchanger 2 outlet temperature is set (step S10), and the target value is reached. The air volume of the first blower 7 that blows air to the first heat exchanger 2 is decreased (step S11), the amount of reheat increases accordingly, the indoor blown air temperature rises, and the indoor intake air temperature is determined again. Performing (step S2) air temperature adjustment operation is repeated.

  As described above, in the present invention, since the ratio of the reheating ability and the evaporation ability can be freely changed, the temperature of the air-conditioned space can be adjusted by adjusting the blown air temperature in most of the dehumidifying operation range. In addition, dehumidifying performance with a wide adjustment range of the blown air temperature can be obtained. Therefore, since the rapid temperature change due to the rise of the blowing temperature is eliminated as in the conventional air conditioner, the degree of necessity for the cooling operation is reduced, and the switching between the dehumidifying operation and the cooling operation of the air conditioner is greatly reduced. To do. As a result, the failure probability of the on-off valve is reduced, and the reliability of the device is improved.

Embodiment 2. FIG.
In a normal dehumidification cycle, the reheat capacity is increased by the input of the compressor, and the blown air temperature is inevitably higher than the intake air temperature of the dehumidifier. The suction and blowout air temperatures of the devices are almost equal, and it is possible to remove only the humidity.
Below, in order to make the suction air temperature and blowing temperature of a dehumidification apparatus the same, the method to control so that a reheat capability and an evaporation capability become equal is demonstrated.

In order for the reheating ability and the evaporation ability to be equal, the following equation (3) needs to be satisfied.
Heo = Hcm (3)
First, the refrigerant pressure Pcm and refrigerant temperature Tcm at the outlet of the first heat exchanger 2 and the refrigerant pressure Peo and refrigerant temperature Teo at the outlet of the second heat exchanger 6 are detected, and the enthalpy Hcm and Heo are calculated by the information processing unit 14a. To do.
If Heo <Hcm, the rotation speed of the first blower 7 is increased by the actuator controller 14b. Conversely, if Heo> Hcm, the actuator controller 14b decreases the rotational speed of the first blower 7 and repeats the above operations until Expression (3) is satisfied.

  In addition, by reducing the air volume of the first blower 7 in the first heat exchanger 2 and controlling it to Heo <Hcm, it is possible to perform a heating-like dehumidifying operation with a high blowing temperature. Conversely, by increasing the air volume of the first blower 7 and controlling it to Heo> Hcm, it is possible to perform air-conditioning dehumidification with a low blowing temperature.

Embodiment 3 FIG.
FIG. 4 is a refrigerant circuit diagram of the air-conditioning apparatus showing Embodiment 3 of the present invention.
In the figure, a fourth on-off valve 2a is provided on the inlet side of the first heat exchanger 2, and a second bypass circuit 16 bypasses the first heat exchanger 2 from the inlet side of the fourth on-off valve 2a. Is branched and connected to the outlet pipe of the first heat exchanger 2 via the third on-off valve 16a.
Normally, the fourth on-off valve 2a is open and the third on-off valve 16a is closed. However, in the case where the outdoor air temperature to be heat-exchanged in the first heat exchanger 2 is low, the first blower Even if 7 is not operated, the refrigerant is cooled and condensed, and as a result, the reheat capability during the dehumidifying operation may be insufficient. In such a case, the fourth on-off valve 2a is closed and the third on-off valve 16a is opened so that the refrigerant does not pass through the first heat exchanger 2, thereby reducing the heat loss in the condensing part. As a result, sufficient reheating capability can be secured. In order to reduce heat radiation in the piping of the second bypass circuit 16, measures such as heat insulation of the piping portion are further effective.

Embodiment 4 FIG.
FIG. 5 is a refrigerant circuit diagram of the air-conditioning apparatus according to Embodiment 4 of the present invention, and includes a first check valve 17 at the outlet of the reheater 10 and a second counter at the outlet of the first heat exchanger 2. A stop valve 18 is provided. By these check valves, the refrigerant bypasses the reheat heat exchanger 4 and passes through the first bypass circuit 9, and the first heat exchanger 2 is bypassed and the second bypass circuit 16 is bypassed. When passing, it is possible to prevent backflow into the reheat heat exchanger 4 and the first heat exchanger 2 after passing through each bypass circuit, and a stable refrigeration cycle can be supplied without a shortage of refrigerant.

It is a refrigerant circuit figure of the air harmony device showing Embodiment 1 of the present invention. It is a Ph diagram showing operation | movement of the refrigerating cycle of the air conditioning apparatus which shows Embodiment 1 of this invention. It is an operation | movement flowchart of the air conditioning apparatus which shows Embodiment 1 of this invention. It is a refrigerant circuit figure of the air conditioning apparatus which shows Embodiment 3 of this invention. It is a refrigerant circuit figure of the air conditioning apparatus which shows Embodiment 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor, 2 1st heat exchanger, 2a 4th on-off valve, 3 1st on-off valve, 4 reheat heat exchanger, 5 expansion device, 6 2nd heat exchanger, 7 1st Blower, 8 Second blower, 9 First bypass circuit, 10 Second on-off valve, 11a, 11b, 12a, 12b Temperature sensor, 13a, 13b Pressure sensor, 14 Controller, 14a Information processing unit, 14b Actuator control 15a, refrigerant flow direction during cooling operation, 15b refrigerant flow direction during dehumidification operation, 16 second bypass circuit, 16a third on-off valve, 17 first check valve, 18 second check valve valve.

Claims (9)

A compressor, a first heat exchanger, an expansion device, a second heat exchanger, a reheat heat exchanger, and a blower, using carbon dioxide as a refrigerant, sucked by the blower, and the second An air conditioner that performs a dehumidifying operation in which air cooled and dehumidified in a heat exchanger is heated and blown out in the reheat heat exchanger disposed on the leeward side of the second heat exchanger. An air conditioner that controls the heat exchange amount of the reheat heat exchanger by changing the heat exchange amount of the heat exchanger. 2. The air conditioner according to claim 1, wherein the heat exchange amount of the first heat exchanger is controlled by changing an amount of air passing through the first heat exchanger. First detection means for detecting the refrigerant state at the first heat exchanger outlet, second detection means for detecting the refrigerant state at the second heat exchanger outlet, the first detection means, The air conditioner according to claim 2, further comprising a control unit that processes information obtained from the second detection unit and controls the operation of the blower. First detection means for detecting refrigerant state at the inlet and outlet portions of the first heat exchanger, second detection means for detecting refrigerant state at the second heat exchanger outlet portion, and reheater outlet portion And a control means for controlling the operation of the blower by processing information obtained from the first detection means, the second detection means, and the third detection means. The air conditioning apparatus according to claim 2. A first bypass circuit for bypassing the reheat heat exchanger, a first on-off valve provided in the first bypass circuit, and a second on-off valve provided on the inlet side of the reheat heat exchanger; The air conditioning apparatus according to claim 2, comprising: A first bypass circuit for bypassing the reheat heat exchanger, a first on-off valve provided in the first bypass circuit, and a second on-off valve provided on the inlet side of the reheat heat exchanger, And a second bypass circuit for bypassing the first heat exchanger, a third on-off valve provided in the second bypass circuit, and a fourth on-off valve provided on the inlet side of the first heat exchanger And an air conditioner according to claim 2. A compressor, a first heat exchanger, an expansion device, a second heat exchanger, a reheat heat exchanger, and a blower, using carbon dioxide as a refrigerant, sucked by the blower, and the second An operation control method for an air conditioner that performs a dehumidifying operation in which air cooled and dehumidified in a heat exchanger is heated and blown out in the reheat heat exchanger disposed on the leeward side of the second heat exchanger. Detecting the intake air temperature; increasing the first heat exchanger air volume if the intake air temperature is higher than a target value; decreasing the first heat exchanger air volume if the temperature is lower; An operation control method for an air conditioner, comprising: an adjustment step for adjusting to a target value. A compressor, a first heat exchanger, an expansion device, a second heat exchanger, a reheat heat exchanger, and a blower, using carbon dioxide as a refrigerant, sucked by the blower, and the second An operation control method for an air conditioner that performs a dehumidifying operation in which air cooled and dehumidified in a heat exchanger is heated and blown out in the reheat heat exchanger disposed on the leeward side of the second heat exchanger. A detection step for detecting the intake air temperature; a reheat amount is calculated from the intake air temperature; and if the reheat amount is equal to or less than a predetermined value, a determination step for causing the refrigerant to bypass the reheater and perform a cooling operation; When the determination step exceeds a predetermined value, the first heat exchanger air volume is increased if the intake air temperature is higher than a target value, and the first heat exchanger air volume is decreased if the intake air temperature is lower than the target value. Adjustment step to adjust to the value and Operation control method of the air conditioning apparatus characterized in that it has. The compressor, the first heat exchanger, the second heat exchanger, the expansion device, and the reheat heat exchanger are sequentially connected, and the second heat exchanger and the first heat exchange are connected. A refrigerant circuit arranged in parallel, a carbon dioxide refrigerant sealed in the refrigerant circuit, a first blower for blowing air to the first heat exchanger, and a wind passing through the second heat exchanger And an air conditioner having a second blower that blows air to the second heat exchanger so as to pass through the reheat heat exchanger, wherein the amount of heat exchange of the first heat exchanger is adjusted Then, the heat exchange amount of the heat exchanger for reheating is adjusted.

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