JP6385568B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner that employs a heat pump system.

  In general, an air conditioner that employs a heat pump system includes a compressor, a condenser, an expansion valve, and an evaporator, pipes that connect these to circulate a refrigerant, and a blower. In the air conditioner, the refrigerant is compressed in the compressor, sent to the condenser as a high-pressure gas state, condensed in the condenser, sent to the expansion valve as a high-pressure liquid state, and expanded and depressurized in the expansion valve. The low-temperature gas-liquid two-phase state is sent to the evaporator, the refrigerant is evaporated in the evaporator, and the low-pressure gas state is sent again to the compressor to adjust the indoor temperature using the refrigeration cycle.

  For example, in the cooling operation, the room is cooled by an evaporator. At this time, in order to exchange heat between the evaporator and room air, the air is configured to pass through the evaporator by a blower.

  In the air conditioner described above, the blast volume is determined by the user. For example, there is a case where it is desired to exert a predetermined air volume and capacity by calculating the indoor heat load. However, when a duct is connected, a desired air flow rate may not be exhibited due to the air path pressure loss of the duct.

  In such a case, conventionally, the amount of air flow that is reduced by calculating the air path pressure loss of the duct in advance is predicted, and the air amount is set to be large. In addition, the amount of air flow is predicted from the load applied to the motor of the blower, and feedback is applied to the motor so as to obtain a predetermined amount of air flow.

JP2003-26977A

  However, when a duct is connected, the desired air flow rate may not be exhibited due to the air path pressure loss of the duct, or complicated control parameters are set so that feedback can be applied in advance based on the relationship between the motor load and air flow rate. There was a need to do.

  For example, in the air conditioner described in Patent Document 1, the relationship between the load (static pressure) of a motor that drives a fan, the current value, and the rotational speed is known in advance, and the air volume is detected and adjusted. However, since it is necessary to grasp the two characteristics of the fan and the motor and to construct a control algorithm, there is a problem that the configuration becomes complicated.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an air conditioner that can be adjusted to a predetermined air volume without grasping duct pressure loss, motor characteristics, and fan characteristics. .

An air conditioner according to the present invention includes a refrigerant circuit in which a compressor that compresses a refrigerant, a condenser that condenses the refrigerant, an expansion valve that depressurizes, and an evaporator that evaporates are connected by a pipe that circulates the refrigerant, and the evaporator A blower that blows air, a temperature sensor that measures a heat exchanger temperature of the evaporator, and a controller that controls the operation of the compressor, the expansion valve, and the blower. Data indicating the relationship between the heat exchange efficiency of the condenser and the evaporator and the amount of blast is stored, and the controller calculates the heat exchanger temperature of the evaporator using the data , and the calculated heat exchanger temperature And according to the result of having compared with the heat exchanger temperature measured with the said temperature sensor, the rotation speed of the said air blower is adjusted and the ventilation volume of the said air blower is changed, It is characterized by the above-mentioned .

  In the air conditioner according to the present invention, the controller can calculate the air flow rate from the heat exchange efficiency and the state of the refrigeration cycle using the table described above, and can adjust the air flow rate based on the calculation result. By providing the blower, it is possible to adjust the air flow to a predetermined level without grasping duct pressure loss, motor characteristics, and fan characteristics.

It is the schematic explaining the structure of the air conditioner which concerns on embodiment of this invention. It is the refrigeration cycle figure (the 1) of the air conditioner which concerns on the same embodiment. It is a flowchart which shows the operation | movement at the time of the cooling operation of the air conditioner which concerns on the embodiment. It is a refrigerating cycle figure (the 2) of the air conditioner concerning the embodiment. It is an air line figure (the 1) of the air conditioner concerning the embodiment. It is an air line figure (the 2) of the air conditioner concerning the embodiment. It is a refrigeration cycle figure (the 3) of the air conditioner concerning the embodiment. It is a refrigeration cycle figure (the 4) of the air conditioner concerning the embodiment.

  Hereinafter, an air conditioner according to an embodiment of the present invention will be described with reference to the drawings. It should be noted that the numerical values and the like appearing in the text are assumed here for convenience of explanation for the operation.

  FIG. 1 is a schematic diagram showing a configuration of an air conditioner according to the present embodiment. This air conditioner includes a refrigerant circuit (composed of a compressor 1, a condenser 2, an expansion valve 3, an evaporator 4 and a pipe 20), a fan 5, a motor 6, a controller 7, a pressure measuring sensor 8, and a temperature measuring sensor 9. To 11 and an intake air state measurement sensor 12.

  First, the functions of the members constituting the refrigerant circuit and the peripheral members will be described. The compressor 1 sucks low-pressure gas refrigerant and compresses it into a high-pressure gas refrigerant. Here, the compressor 1 may be capable of arbitrarily changing the operating frequency by inverter control, or may be a constant speed that cannot change the operating frequency.

  The condenser 2 condenses the refrigerant in a high-pressure gas state into a refrigerant in a high-pressure liquid state by exchanging heat with an external fluid. Here, the external fluid used for heat exchange may be a gas such as air or a liquid such as water.

  The expansion valve 3 expands and decompresses the high-pressure liquid refrigerant into the low-pressure gas-liquid two-phase refrigerant. Needless to say, it can be replaced if there is a similar effect. For example, an electronic expansion valve or a capillary tube may be used.

  The evaporator 4 evaporates the low-pressure gas-liquid two-phase refrigerant flowing from the expansion valve 3 into a low-pressure gas refrigerant by exchanging heat with air, and returns the refrigerant to the compressor.

  The fan 5 is for sending air to the evaporator 4 for heat exchange between the air and the low-pressure gas-liquid two-phase refrigerant of the evaporator 4. Needless to say, the same effect can be substituted. For example, the type of fan may be a sirocco fan or a plug fan. Further, a push-in method or a pulling method may be used.

  The motor 6 is for driving the fan 5. In the present embodiment, the motor is capable of controlling the rotational speed for adjusting the air flow rate, but it is needless to say that the motor can be replaced if the same effect can be obtained.

  Next, the function of each sensor will be described. The pressure measuring sensor 8 measures the pressure of the condenser 2. The temperature measuring sensor 9 measures the outlet temperature of the condenser 2. The temperature measuring sensor 10 measures the heat exchanger temperature Te of the evaporator 4. The temperature measuring sensor 11 measures the outlet temperature of the evaporator 4.

  The intake air state measurement sensor 12 measures the dry bulb temperature and the wet bulb temperature of the air flowing into the evaporator 4. If the wet bulb temperature cannot be measured, the relative humidity may be measured, and the wet bulb temperature may be calculated based on the air physical property data stored in the memory (not shown) of the controller 7.

  Next, the configuration and function of the controller 7 will be described. The controller 7 is constituted by a microcomputer, and data indicating air physical properties, refrigerant physical properties, and capacity calculation formulas are stored in a non-volatile memory or the like, and the heat exchange efficiency ε and the air flow rate GA as shown in Table 1 below are stored. Table data indicating the relationship is stored.

  The controller 7 is obtained from the sensors 8 to 12 in order to create the refrigerant circulation amount Gr according to the predetermined refrigeration cycle (entrance / entrance enthalpy of the evaporator 4 and outlet enthalpy of the evaporator 4) and capacity shown in FIG. The compressor 1 and the expansion valve 3 are controlled based on the pressure / temperature data, the blown air amount is calculated, and the fan 5 is driven by controlling the motor 6 until a predetermined blown air amount is obtained.

  Needless to say, the controller 7 can be replaced by a device other than the microcomputer as long as the same effect can be obtained. Moreover, the controller 7 may be provided in either the indoor unit or the outdoor unit, or may be provided in both.

  Next, how to obtain various values displayed in the refrigeration cycle diagram shown in FIG. 2 will be described. The controller 7 calculates the condenser temperature based on the refrigerant physical property data stored in the memory, based on the condenser pressure PCm obtained by the pressure measuring sensor 8. The controller 7 calculates the degree of supercooling SCm based on the condenser outlet temperature and the condenser temperature obtained by the temperature measuring sensor 9.

  Based on the heat exchanger temperature Te obtained by the temperature measuring sensor 10, the controller 7 calculates the evaporator pressure Pe using the refrigerant physical property data stored in the memory. The evaporator pressure Pe is used for calculating the refrigerant circulation amount Gr.

The refrigerant circulation amount Gr is expressed by the following equation (1) by the displacement volume V of the compressor 1 and the density ρ of the refrigerant to be compressed.

Gr = V × ρ ----- (1)
Here, the displacement volume V of the compressor is determined by the compressor used, and the density ρ of the refrigerant to be compressed is calculated from the refrigerant physical property data stored in the memory by the controller 7 based on the evaporator pressure Pe.

The controller 7 calculates the degree of superheat SHm based on the evaporator outlet temperature obtained by the temperature measurement sensor 11 and the heat exchanger temperature Te described above. Further, the controller 7 calculates the intake air enthalpy based on the air dry bulb temperature, the wet bulb temperature obtained by the intake air state measurement sensor 12 and the air physical property data stored in the memory.

  In addition, it cannot be overemphasized that the refrigerant | coolant used for an air conditioner should just use a refrigerating cycle. For example, a single refrigerant such as R22, a mixed refrigerant such as R410A, or a natural refrigerant such as CO2 may be used.

  Further, the air conditioner does not need to be configured only by the members shown in FIG. For example, a liquid reservoir (accumulator) may be provided to protect the compressor 1, or an oil separator may be provided to recover the refrigerator oil.

  Next, based on FIG. 3, operation | movement of the air conditioner which concerns on this Embodiment is demonstrated. FIG. 3 is a flowchart showing the flow of processing during the cooling operation of the air conditioner.

  The controller 7 determines whether or not the set air flow rate is obtained based on the preset evaporation capacity Qe and the air flow rate GA (steps S1 to S3), and when the controller 7 is away from the set air flow rate (step S4). No), the air flow rate is adjusted, and the refrigeration cycle is changed so as to satisfy the evaporation capacity Qe (steps S5 to S7).

The evaporation capacity Qe is expressed by the following equation (2) using the refrigerant circulation amount Gr and the evaporator inlet / outlet enthalpy difference ΔHr.

Qe = Gr × ΔHr ------ (2)
Here, the evaporator inlet / outlet enthalpy difference ΔHr is a value limited by the refrigerant, and therefore, in the following, a case where R410A is used is shown as an example. ΔHr is generally about 150 to 200 kJ / kg from the viewpoint of unit protection. Therefore, ΔHr is controlled to be, for example, 175 kJ / kg.

The standard outdoor temperature is about 35 ° C., and when the condenser 2 is placed outdoors and installed to exchange heat with air, the temperature of the condenser 2 is 35 for heat exchange. More than ℃ is necessary. Although it is better that there is a temperature difference, the condenser pressure PCm is preferably about 30 kgf / Cm2G from the viewpoint of unit protection. At this time, the temperature of the condenser is about 50 ° C.

The evaporator outlet enthalpy Hro is also limited by the refrigerant. From the viewpoint of unit protection, the pressure and superheat range are almost the same value, which is about 425 KJ / kg.

As a result of the above, the evaporator inlet enthalpy Hri can be determined,
Hri = Hro−ΔHr
= 425KJ / kg-175KJ / kg
= 250KJ / kg
It becomes. Since PCm is 30 kgf / Cm2G, the refrigerant temperature at the outlet of the condenser needs to be 31 ° C.

That is, since the temperature of the condenser 2 was 50 ° C., the target degree of supercooling SCm is
SCm = 50 ° C.-31 ° C. = 19 ° C.
It becomes.

  The target superheat degree SHm is preferably about 2 to 5 ° C. from the viewpoint of unit protection. Here, it is set to 2 ° C.

If the evaporation capacity Qe is, for example, 28 kW, then Gr = Qe / ΔHr
= 28kW / 175kJ / kg
= 0.16 kg / s
Therefore, the compressor 1 may be controlled to satisfy this Gr. For example, in the case of a rotational speed control type, the frequency may be changed.

  There is only one refrigeration cycle in which the above-described state is established. Until this refrigeration cycle is reached, the controller 7 is operated based on the data of the pressure measurement sensor 8 and the temperature measurement sensors 9 to 11 to control the compressor 1 and the expansion valve 3, and the heat exchanger temperature at that time is set to Te. And FIG. 4 shows the refrigeration cycle at this time.

The temperature difference required to bring the refrigerant circulation amount Gr flowing into the evaporator to the state of the superheat degree SHm is determined by the heat exchange efficiency ε. This is because the higher the efficiency of the heat exchanger, the more refrigerant can be evaporated. Further, the efficiency of the heat exchanger is determined by the size of the heat exchanger and the amount of air blown. The larger the heat exchanger and the greater the amount of blast, the higher the efficiency of the heat exchanger. The efficiency of the heat exchanger is expressed by GA × ε from the heat exchange efficiency ε and the air flow rate GA.

  The evaporation capacity is represented by the following formula (3) using the heat exchange efficiency.

Qe = GA × ε × ΔhA ----- (3)
Here, Qe is the evaporation capacity, GA is the air flow rate, ε is the heat exchange efficiency, and ΔhA is the air enthalpy difference.

  As shown in the air diagram of FIG. 5, the enthalpy difference is the enthalpy difference when the air in state A becomes the air in state C, indicating that the sucked air is completely cooled to the heat exchanger temperature. ing. However, in reality, all of the sucked air is not cooled to the heat exchanger temperature, and only the state B in FIG. 5 is obtained. At this time, the enthalpy difference between the state A and the state B is represented by ε × ΔhA.

  As described above, the efficiency of the heat exchanger is determined by the size of the heat exchanger and the air flow rate. The relationship between the heat exchange efficiency ε and the blown air amount GA can be grasped in advance by desk calculations or tests. The relationship as shown in Table 1 is obtained for each heat exchanger, and the data of the table is stored in the memory of the controller 7 to determine the air flow rate. It is not necessary to be concerned with the table as shown in Table 1, and it may be given by an approximate expression.

It is assumed that the evaporation capacity Qe is 28 kW and the air flow rate GA is 60 m3 / min. From Table 1 above, the controller 7 calculates that ε is 0.69. At this time, ΔhA is ΔhA = Qe / (GA × ε)
= 28kW / ((60m3 / min / 60 / 0.83m3 / kg) × 0.69)
= 33.7kJ / kg
It becomes. Here, the reason for dividing by 60 and 0.83 m 3 / kg is to convert the volume flow rate into a mass flow rate in units. 0.83 m3 / kg is a specific volume of general air.

It is assumed that the state A of the intake air is found to be 27 ° C. dry bulb and 19 ° C. wet bulb by the intake air state measurement sensor 12. At this time, the enthalpy hAA in the state A can be calculated as 53.8 kJ / kg by the controller 7 from the air physical properties.
hAC = hAA−ΔhA
= 53.8 kJ / kg-33.7 kJ / kg
= 20.1kJ / kg
It becomes. From the air physical property data stored in the memory of the controller 7, the heat exchanger temperature Te_cal can be calculated to be 5.8 ° C. The air diagram at this time is shown in FIG.

  Here, Te obtained by the intake air state measurement sensor 12 is compared with Te_cal obtained by calculation. From the accuracy of a general temperature sensor, when the difference between Te and Te_cal is 0.5 ° C. or more, it is determined that the air flow rate is different from the set value. Of course, since the accuracy differs depending on the sensor, a value other than 0.5 ° C. may be used as the determination value.

  If the refrigeration cycle as shown in FIG. 7 is stable and Te is 5 ° C., Te_cal is 5.8 ° C., and thus the value is 0.8 ° C. lower. This indicates that the efficiency of the heat exchanger is lower than that obtained from the set air flow rate. That is, the actual air flow rate is smaller than the set air flow rate, and it is necessary to increase the air flow rate by increasing the rotational speed of the fan 5.

Conversely, if it is stable in the refrigeration cycle as shown in FIG. 8 and Te is 7 ° C., it is 1.2 ° C. higher, so the efficiency of the heat exchanger is higher than that obtained from the set air flow rate. In other words, it is necessary to lower the rotational speed of the fan 5 to reduce the air flow rate.

  Since the refrigeration cycle is changed by changing the air flow rate, the air flow rate can be adjusted to the set value by checking the value of Te each time.

  In the present embodiment, only the evaporator is described, but it goes without saying that the air flow rate can be adjusted in the same way even if it is a condenser.

DESCRIPTION OF SYMBOLS 1 Compressor 2 Condenser 3 Expansion valve 4 Evaporator 5 Fan 6 Motor 7 Controller 8 Pressure measurement sensor 9-11 Temperature measurement sensor 12 Suction air condition measurement sensor

Claims (4)

A refrigerant circuit in which a compressor that compresses the refrigerant, a condenser that condenses the refrigerant, an expansion valve that depressurizes, and an evaporator that evaporates are connected by piping for circulating the refrigerant;
A blower for blowing air to the evaporator;
A temperature sensor for measuring the heat exchanger temperature of the evaporator;
A controller for controlling the operation of the compressor, the expansion valve and the blower, and
In the memory of the controller, data indicating the relationship between the heat exchange efficiency of the condenser and the evaporator and the blast volume is stored.
The controller is
Calculate the evaporator heat exchanger temperature using the data ,
According to the result of comparing the calculated heat exchanger temperature and the heat exchanger temperature measured by the temperature sensor, the rotational speed of the blower is adjusted to change the blower amount of the blower <br / > Air conditioner characterized by that. A suction air temperature sensor for measuring a suction air temperature which is a temperature of air flowing into the evaporator;
The controller's memory further stores air properties,
The controller is
The heat exchanger temperature of the evaporator is calculated based on the data, the set evaporation capacity, the set air flow rate, the air properties, and the intake air temperature measured by the intake air temperature sensor.
The air conditioner according to claim 1. The air conditioner according to claim 1 or 2 , wherein the fan is directly connected to a fan and a motor. The air conditioner according to claim 1 or 2 , wherein the blower has a fan and a motor indirectly connected via a pulley or a belt.

Images