GB2561096A

GB2561096A - Air conditioner

Info

Publication number: GB2561096A
Application number: GB1806395.8A
Authority: GB
Inventors: Anai Shintaro
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2015-12-24
Filing date: 2015-12-24
Publication date: 2018-10-03
Anticipated expiration: 2035-12-24
Also published as: GB2561096B; GB201806395D0; JPWO2017109906A1; WO2017109906A1; JP6576468B2

Abstract

Provided is an air conditioner that comprises: a coolant circuit in which a compressor, an outdoor heat exchanger, an expansion valve and an indoor heat exchanger are sequentially connected with coolant piping, and which allows a coolant to circulate therearound; and a fan that takes in air that is to undergo heat exchange with the coolant in the indoor heat exchanger. The air conditioner is provided with a control device that performs control so as to cause the compressor to operate at a compressor frequency that satisfies a coolant circulation amount that is required to achieve a blow out temperature of air in the indoor heat exchanger at a set temperature that is set by a user.

Description

(54) Title of the Invention: Air conditioner Abstract Title: Air conditioner (57) Provided is an air conditioner that comprises: a coolant circuit in which a compressor, an outdoor heat exchanger, an expansion valve and an indoor heat exchanger are sequentially connected with coolant piping, and which allows a coolant to circulate therearound; and a fan that takes in air that is to undergo heat exchange with the coolant in the indoor heat exchanger. The air conditioner is provided with a control device that performs control so as to cause the compressor to operate at a compressor frequency that satisfies a coolant circulation amount that is required to achieve a blow out temperature of air in the indoor heat exchanger at a set temperature that is set by a user.

Calculate target evaporation temperature on basts of suction temperature, set temperature, and bypass factor

Calculate evaporation capacity on basis of blown air amount, sucked air enthalpy and bypass factor

Calculate coolant circulation amount on basis of evaporation capacity, evaporator inlet enthalpy and evaporator outlet enthalpy

Adjust compressor frequency

1/6

FIG. 1

FIG. 2

2/6

FIG. 3

FIG. 4

TEMPERATURE Tem

TEMPERATURE To

ATURE Ti

3/6

FIG. 5

4/6

FIG. 6

5/6

FIG. 7

6/6

FIG. 8

ATURE Ti

TEMPERATURE To

DENSING TEMPERATURE Tcm

FIG. 9

ENTHALPY hro' INLET ENTHALPY hri'

DESCRIPTION

Title of Invention

AIR-CONDITIONING APPARATUS

Technical Field [0001]

The present invention relates to an air-conditioning apparatus, and more particularly, to controlling of the blowout temperature of an indoor unit.

Background Art [0002]

In conventional air-conditioning apparatuses, the temperature of an indoor space is controlled by using a refrigeration cycle including, for example, a compressor, a condenser, an expansion valve, an evaporator, and an air-sending device. For example, in a cooling operation, air of the indoor space is cooled by heat exchange between refrigerant that flows in the evaporator and air that is sucked by the air-sending device.

[0003]

In such an air-conditioning apparatus, to adjust the temperature of an indoor space to a predetermined temperature, a target value for the temperature of air blown from an indoor unit is set by a user, and then the actual blowout temperature of the indoor unit is adjusted to the set target temperature.

More specifically, attention is focused on, for example, the difference between the blowout temperature of the indoor unit and the set temperature, which is the target temperature. The frequency of the compressor is controlled to decrease in a case where the difference between the blowout temperature and the set temperature is decreased, and to increase in a case where the difference between the blowout temperature and the set temperature is increased, and, as a result, the blowout temperature is adjusted.

[0004]

In addition, as another method for adjusting the blowout temperature, Patent

Literature 1 discloses a method in which, by adjusting the air amount of a fan of an outdoor unit in response to the outside air temperature or by limiting an increase rate of the frequency of the compressor, the blowout temperature is prevented from significantly diverging from the set temperature.

Citation List

Patent Literature [0005]

Patent Literature 1: Japanese Patent No. 5487171 Summary of Invention Technical Problem [0006]

However, when an air-conditioning apparatus is controlled by focusing only on the difference between the blowout temperature and the set temperature as in a case of the conventional air-conditioning apparatus, response to a temperature change is poor. For example, when a cooling operation is performed while the inlet temperature of the indoor unit is low, the blowout temperature becomes much lower than the set temperature and overshoot is caused, and, as a result, the comfort of a user is impaired.

[0007]

Furthermore, with the method disclosed in Patent Literature 1, only the capacity change rates of the devices are adjusted, and thus time is required for the blowout temperature to reach the set temperature when the air-conditioning apparatus is turned on, for example. Consequently, the user may have an impression that cooling performance is poor.

[0008]

In light of the conventional technical problems, the present invention provides an air-conditioning apparatus capable of reducing overshoot that is caused while the blowout temperature is being adjusted to the set temperature and capable of reducing the time required for the blowout temperature to reach the set temperature.

Solution to Problem [0009]

An air-conditioning apparatus of one embodiment of the present invention includes a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are sequentially connected by refrigerant pipes to circulate refrigerant in the refrigerant circuit, an air-sending device configured to suck air that exchanges heat with the refrigerant in the indoor heat exchanger, and a controller configured to operate the compressor at a compressor frequency that satisfies a refrigerant circulation amount required to make a blowout temperature of the air of the indoor heat exchanger reach a set temperature set by a user.

Advantageous Effects of Invention [0010]

As described above, according to one embodiment of the present invention, the refrigerant circulation amount is calculated to make an inlet temperature reach a target blowout temperature, and the com pressor frequency of the compressor is adjusted to satisfy the calculated refrigerant circulation amount and, as a result, overshoot caused while the blowout temperature is being adjusted to the set temperature can be reduced and time required for the blowout temperature to reach the set temperature can be reduced.

Brief Description of Drawings [0011] [Fig. 1] Fig. 1 is a schematic view showing an example of a circuit configuration of an air-conditioning apparatus according to one embodiment of the present invention.

[Fig. 2] Fig. 2 is a pressure-enthalpy (p-h) diagram showing a refrigeration cycle of the air-conditioning apparatus of Fig. 1.

[Fig. 3] Fig. 3 is a flowchart showing an example of the flow of compressor frequency control processing of a compressor in the air-conditioning apparatus of Fig. 1.

[Fig. 4] Fig. 4 is a psychrometric chart showing states of air in an evaporator of the air-conditioning apparatus of Fig. 1.

[Fig. 5] Fig. 5 is a schematic view showing an example of the relationship between a compressor frequency and a blowout temperature in a compressor frequency control of a conventional air-conditioning apparatus.

[Fig. 6] Fig. 6 is a schematic view showing another example of the relationship between the compressor frequency and the blowout temperature in the compressor frequency control of the conventional air-conditioning apparatus.

[Fig. 7] Fig. 7 is a schematic view showing an example of the relationship between a compressor frequency and a blowout temperature in a compressor frequency control of the air-conditioning apparatus of Fig. 1.

[Fig. 8] Fig. 8 is a psychrometric chart showing states of air in an indoor heat exchanger of the air-conditioning apparatus of Fig. 1.

[Fig. 9] Fig. 9 is a p-h diagram showing a refrigeration cycle of the airconditioning apparatus of Fig. 1.

Description of Embodiments [0012]

An air-conditioning apparatus of an embodiment of the present invention will be explained below.

[0013] [Circuit Configuration of Air-conditioning Apparatus]

Fig. 1 is a schematic view showing an example of a circuit configuration of an air-conditioning apparatus according to one embodiment of the present invention.

As shown in Fig. 1, an air-conditioning apparatus 1 includes a compressor 2, an outdoor heat exchanger 3, an expansion valve 4, an indoor heat exchanger 5, a fan 6 as an air-sending device, a motor 7, a controller 10, an outdoor heat exchanger pressure sensor 11, an outdoor heat exchanger outlet temperature sensor 12, an indoor heat exchanger temperature sensor 13, an indoor heat exchanger outlet temperature sensor 14, and an inlet air state sensor 15. The compressor 2, the outdoor heat exchanger 3, the expansion valve 4, and the indoor heat exchanger 5 are connected annularly by refrigerant pipes to form a refrigerant circuit in which refrigerant circulates.

Examples of the refrigerant that circulates in the refrigerant circuit include single component refrigerants such as R-22, refrigerant mixtures such as R-410A, and natural refrigerants such as CO2.

Note that the following explains an example of a circuit configuration in which a cooling operation for cooling air of an indoor space is performed.

[0014]

The compressor 2 sucks and compresses low-temperature low-pressure refrigerant, and then discharges the refrigerant having a high-temperature highpressure gas refrigerant state.

As an example of the compressor 2, for example, an inverter compressor or another device capable of controlling the displacement volume, which is the discharge amount of refrigerant per unit time, by arbitrarily changing a compressor frequency that is a drive frequency, can be used.

[0015]

Note that the compressor 2 is not limited to the above compressor, and a compressor that operates at a constant drive frequency may be used. When such a compressor is used, the discharge amount of refrigerant can be adjusted, as with a case in which the drive frequency is changed, by, for example, changing the inlet pressure of the refrigerant or by providing the refrigerant circuit with a bypass circuit, which is not shown.

[0016]

The outdoor heat exchanger 3 exchanges heat between the high-temperature high-pressure gas refrigerant and an external fluid. More specifically, in a cooling operation, the outdoor heat exchanger 3 acts as a condenser that rejects heat of the refrigerant to the fluid to condense the refrigerant into high-pressure liquid refrigerant. The external fluid in this case may be, for example, gas such as air or a liquid such as water.

Note that as, in this explanation, the example is used in which a cooling operation is performed, the outdoor heat exchanger 3 will be appropriately referred to as condenser 3 in the explanation below.

[0017]

The expansion valve 4 has a function to decompress and expand the highpressure liquid refrigerant flowing in the refrigerant circuit, to change the refrigerant into low-pressure two-phase gas liquid refrigerant. The expansion valve 4 may be, for example, an electronic expansion valve capable of controlling the opening degree or a capillary tube.

[0018]

The indoor heat exchanger 5 exchanges heat between the low-pressure twophase gas liquid refrigerant and the air of the indoor space (hereinafter appropriately referred to as indoor air). More specifically, in a cooling operation, the indoor heat exchanger 5 acts as an evaporator that evaporates the refrigerant into low-pressure gas refrigerant and cools the indoor air by the evaporation heat generated at that time.

Note that as, in this explanation, the example is used in which a cooling operation is performed, the indoor heat exchanger 5 will be appropriately referred to as evaporator 5 in the explanation below.

[0019]

The fan 6 is provided close to the evaporator 5. The fan 6 is driven by the motor 7 and supplies, to the evaporator 5, air that is used in heat exchange in the evaporator 5. In addition, the fan 6 sends information that indicates the air blow amount of air supplied to the evaporator 5 to the controller 10, which will be described below.

As the fan 6, for example, a sirocco fan or a plug fan may be used. In addition, as a method for sucking air, a pushing method or a pulling method may be used, for example.

[0020]

The outdoor heat exchanger pressure sensor 11 is provided to the refrigerant pipe on the refrigerant inflow side of the outdoor heat exchanger 3 and measures outdoor heat exchanger pressure, which is the pressure of the refrigerant flowing into the outdoor heat exchanger 3. The information that indicates the measured outdoor heat exchanger pressure is sent to the controller 10 described below.

Note that as, in this explanation, the example is used in which a cooling operation is performed, the outdoor heat exchanger pressure sensor 11 will be referred to as condenser pressure sensor 11 and the outdoor heat exchanger pressure will be referred to as condenser pressure in the explanation below.

[0021]

The outdoor heat exchanger outlet temperature sensor 12 is provided to the refrigerant pipe on the refrigerant outflow side of the outdoor heat exchanger 3 and measures outdoor heat exchanger outlet temperature, which is the temperature of the refrigerant flowing out from the outdoor heat exchanger 3. The information that indicates the measured outdoor heat exchanger outlet temperature is sent to the controller 10.

Note that as, in this explanation, the example is used in which a cooling operation is performed, the outdoor heat exchanger outlet temperature sensor 12 will be referred to as condenser outlet temperature sensor 12 and the outdoor heat exchanger outlet temperature will be referred to as condenser outlet temperature in the explanation below.

[0022]

The indoor heat exchanger temperature sensor 13 is provided to the refrigerant pipe on the refrigerant inflow side of the indoor heat exchanger 5 and measures indoor heat exchanger temperature, which is the temperature of the refrigerant flowing into the indoor heat exchanger 5. The information that indicates the measured indoor heat exchanger temperature is sent to the controller 10.

Note that as, in this explanation, the example is used in which a cooling operation is performed, the indoor heat exchanger temperature sensor 13 will be referred to as evaporator temperature sensor 13 and the indoor heat exchanger temperature will be referred to as evaporator temperature in the explanation below. [0023]

The indoor heat exchanger outlet temperature sensor 14 is provided to the refrigerant pipe on the refrigerant outflow side of the indoor heat exchanger 5 and measures indoor heat exchanger outlet temperature, which is the temperature of the refrigerant flowing out from the indoor heat exchanger 5. The information that indicates the measured evaporator outlet temperature is sent to the controller 10.

Note that as, in this explanation, the example is used in which a cooling operation is performed, the indoor heat exchanger outlet temperature sensor 14 will be referred to as evaporator outlet temperature sensor 14 and the indoor heat exchanger outlet temperature will be referred to as evaporator outlet temperature in the explanation below.

[0024]

The inlet air state sensor 15 is provided close to the indoor heat exchanger 5 and measures dry-bulb temperature and wet-bulb temperature of the air flowing into the indoor heat exchanger 5. The information that indicates the measured dry-bulb temperature and wet-bulb temperature is sent to the controller 10.

Note that, when wet-bulb temperature cannot be measured, relative humidity may be measurable so that the controller 10 can calculate the wet-bulb temperature on the basis of the air properties, which will be described later, that are stored in the controller 10.

[0025]

The controller 10 is formed of, for example, software that is executed on an arithmetic device, such as a microcomputer and a central processing unit (CPU), and hardware such as a circuit device that performs control functions, which will be described later, and controls the entire air-conditioning apparatus 1. For example, the controller 10 controls the drive frequency of the compressor 2, the rotation frequency and activation and deactivation of the fan 6, the opening degree of the expansion valve 4 and other operation states on the basis of the operation information of the air-conditioning apparatus 1 received from various sensors and operation contents instructed by a user.

[0026]

Furthermore, the controller 10 has a read-only memory (ROM) (not shown) as a storage unit, and information for performing various kinds of processing in the present embodiment is stored in advance in the ROM.

Examples of the various kinds of information stored in the ROM include air property information, refrigerant property information, arithmetic expressions for capacity, and bypass factor information.

[0027]

The air property information indicates properties of air that exchanges heat with refrigerant in the evaporator 5. The air property information is formed of, for example, a table in which the temperature, humidity, density, enthalpy and other properties of air are correlated with each other, and with which the density and the enthalpy are determined by the temperature and the humidity.

Note that, when a density value and an enthalpy value are required for the temperature and the humidity of the air that are not described in the table of the air property information, these values can be obtained by interpolating values in the table, for example.

[0028]

The refrigerant property information indicates properties of the refrigerant flowing in the refrigerant circuit. The refrigerant property information is formed of, for example, a table in which the temperature, pressure, density, enthalpy and other properties of refrigerant are correlated with each other, and with which the density and the enthalpy are determined by the temperature and the pressure.

Note that, when a density value and an enthalpy value are required for the temperature and the pressure of the refrigerant that are not described in the table of the refrigerant property information, these values can be obtained by interpolating values in the table, for example.

[0029]

The arithmetic expressions for capacity are arithmetic expressions for calculating required values in performing various kinds of processing in the present embodiment. Specific arithmetic expressions stored in the ROM will be described later.

The bypass factor information indicates the proportion of the amount of air that, when air passes through the evaporator 5, passes over without directly contacting the evaporator 5 to the blow amount of air supplied by the fan 6. A bypass factor BF is determined by the blow amount of air supplied to the evaporator 5 by the fan 6. For example, as the air blow amount increases, the bypass factor BF increases.

[0030]

The controller 10 calculates a com pressor frequency that satisfies a refrigerant circulation amount Gr that is required to make the blowout temperature reach a set temperature, on the basis of the pressure information and temperature information sent from the various sensors 11 to 15 and the various information described above such as refrigerant property information. Then, the controller 10 controls the compressor 2 on the basis of the calculated compressor frequency.

[0031]

Fig. 2 is a p-h diagram showing a refrigeration cycle of the air-conditioning apparatus of Fig. 1.

The state of the refrigerant at point a in Fig. 2 indicates the state of the refrigerant at point a in Fig. 1. Similarly, the states of the refrigerant at points b to d in Fig. 2 indicate the states of the refrigerant at points b to d in Fig. 1, respectively. [0032]

A condenser pressure Pern, which is the pressure of the refrigerant at point b, is measured by the condenser pressure sensor 11.

On the basis of the condenser pressure Pern, the controller 10 refers to the table of the refrigerant property information stored in the ROM and can obtain a temperature associated with the condenser pressure Pern as a condenser temperature.

[0033]

A condenser outlet temperature, which is the temperature of the refrigerant at point c, is measured by the condenser outlet temperature sensor 12.

On the basis of the condenser outlet temperature and the condenser temperature obtained as described above, the controller 10 can calculate a degree of subcooling SCm.

[0034]

An evaporator temperature Te, which is the temperature of the refrigerant at point d, is measured by the evaporator temperature sensor 13.

On the basis of the evaporator temperature Te, the controller 10 refers to the table of the refrigerant property information and can obtain a pressure associated with the evaporator temperature Te as an evaporator pressure Pe.

[0035]

An evaporator outlet temperature, which is the temperature of the refrigerant at point a, is measured by the evaporator outlet temperature sensor 14.

On the basis of the evaporator outlet temperature and the evaporator temperature Te calculated as described above, the controller 10 can calculate a degree of superheat SHm.

[0036] [Operations of Air-conditioning Apparatus]

Next, operations of the air-conditioning apparatus 1 having the abovementioned configuration will be explained. In this example, the flow of the refrigerant in a cooling operation mode will be explained.

[0037]

First, low-temperature low-pressure refrigerant is compressed by the compressor 2 into high-temperature high-pressure gas refrigerant, and is discharged from the compressor 2.

The high-temperature high-pressure gas refrigerant discharged from the compressor 2 flows into the condenser 3, and condenses into high-pressure liquid refrigerant in a subcooling state while rejecting heat by exchanging heat with outside air, and flows out from the condenser 3.

[0038]

The high-pressure liquid refrigerant that flows out from the condenser 3 is expanded and decompressed by the expansion valve 4 into low-temperature lowpressure two-phase gas-liquid refrigerant, and flows into the evaporator 5.

The low-temperature low-pressure two-phase gas-liquid refrigerant that flows into the evaporator 5 receives heat by exchanging heat with indoor air and evaporates, thereby cooling the indoor air, and then becomes low-temperature lowpressure gas refrigerant and flows out from the evaporator 5.

The low-temperature low-pressure gas refrigerant that flows out from the evaporator 5 is sucked into the compressor 2.

[0039] [Control of Compressor Frequency]

Next, control of the compressor frequency of the compressor 2 in the airconditioning apparatus 1 will be explained.

When a set temperature, which is a target value for the temperature of air blowing out from an indoor unit, is set by a user, the air-conditioning apparatus 1 according to the present embodiment calculates a refrigerant circulation amount required to make the blowout temperature of the evaporator 5 provided in the indoor unit promptly reach the set temperature. Then, a compressor frequency that satisfies the obtained refrigerant circulation amount is calculated, and the compressor frequency of the compressor 2 is adjusted to the obtained compressor frequency. [0040]

Fig. 3 is a flowchart showing an example of the flow of compressor frequency control processing of the compressor 2 in the air-conditioning apparatus 1 of Fig. 1.

Fig. 4 is a psychrometric chart showing states of air in the evaporator 5 of the air-conditioning apparatus 1 of Fig. 1.

In this explanation, a case is assumed where the compressor frequency of the compressor 2 is continuously controlled and the processing of the flowchart of Fig. 3 is cyclically repeated. For example, the processing shown in Fig. 3 is repeated at predetermined time intervals.

[0041]

First, in step S1, the controller 10 calculates an evaporating temperature (hereinafter appropriately referred to as target evaporating temperature) Tern, which is a target temperature for the evaporator 5. The target evaporating temperature Tern indicates the temperature at point C that is an intersection of a saturation curve and an extension line connecting point A indicating an inlet temperature and point B indicating a blowout temperature (hereinafter appropriately referred to as target blowout temperature), which is a set temperature set by a user as a target temperature.

The target evaporating temperature Tern can be calculated on the basis of formula (1), which is an arithmetic expression stored in the ROM, by using an inlet temperature Ti, a set temperature To, and a bypass factor BF determined by an air blow amount Ga.

[Formula 1]

Tern = (To - Ti x BF)/(1 - BF) -(1) [0042]

Note that the inlet temperature Ti is the temperature of air that exchanges heat with the refrigerant in the evaporator 5 and can be obtained on the basis of the information indicating dry-bulb temperature sent from the inlet air state sensor 15.

The set temperature To is a target blowout temperature set by a user.

The bypass factor BF is a value determined on the basis of the air blow amount Ga of the fan 6 and can be obtained by referring to the bypass factor information stored in the ROM on the basis of the information indicating the air blow amount Ga sent from the fan 6.

[0043]

Next, in step S2, the controller 10 calculates an evaporation capacity Qe required to make the inlet temperature reach the target blowout temperature.

The evaporation capacity Qe can be calculated on the basis of formula (2), which is an arithmetic expression stored in the ROM, by using the air blow amount

Ga, an intake air enthalpy hai, a saturated air enthalpy hae, and the bypass factor BF.

[Formula 2]

Qe = Ga x (hae - hai) x (1 - BF) - (2) [0044]

Note that the intake air enthalpy hai indicates the enthalpy of air sucked by the evaporator 5 and can be obtained by referring to the table of the air property information stored in the ROM on the basis of the inlet temperature Ti.

Furthermore, the saturated air enthalpy hae indicates the enthalpy of saturated air in the evaporator 5 and can be obtained by referring to the table of the air property information on the basis of the target evaporating temperature Tern calculated in step S1.

[0045]

Next, in step S3, the controller 10 calculates a refrigerant circulation amount Gr required to make the inlet temperature reach the target blowout temperature.

The refrigerant circulation amount Gr can be calculated on the basis of formula (3), which is an arithmetic expression stored in the ROM, by using the evaporation capacity Qe calculated in step S2, an evaporator inlet enthalpy hri and an evaporator outlet enthalpy hro.

[Formula 3]

Gr = Qe/(hro - hri) -(3) [0046]

Note that the evaporator inlet enthalpy hri indicates the enthalpy of the refrigerant flowing into the evaporator 5. The evaporator inlet enthalpy hri can be calculated by referring to the table of the refrigerant property information stored in the ROM on the basis of the condenser pressure Pern measured by the condenser pressure sensor 11 and the condenser outlet temperature measured by the condenser outlet temperature sensor 12.

The evaporator outlet enthalpy hro indicates the enthalpy of the refrigerant flowing out from the evaporator 5. The evaporator outlet enthalpy hro can be calculated by referring to the table of the refrigerant property information on the basis of the evaporator pressure Pe calculated on the basis of the evaporator temperature measured by the evaporator temperature sensor 13 and the table of the refrigerant property information, and the evaporator outlet temperature measured by the evaporator outlet temperature sensor 14.

[0047]

In this case, the refrigerant circulation amount Gr can be calculated also on the basis of the design specifications of the compressor 2.

The refrigerant circulation amount Gr based on the design specifications of the compressor 2 can be calculated on the basis of formula (4), which is an arithmetic expression stored in the ROM, by using a displacement volume V of the compressor 2 and a density p of the refrigerant compressed by the compressor 2.

[Formula 4]

Gr = V x p -(4) [0048]

The density p of the refrigerant can be obtained by referring to the table of the refrigerant property information and, more specifically, is the density associated with the evaporator pressure Pe.

The displacement volume V is the discharge amount of the refrigerant discharged from the compressor 2 per unit time. For example, when the compressor 2 is a reciprocating compressor, the displacement volume V is determined by the product of the number of cylinders, the volume of the cylinders, and the rotation frequency, which are design specifications. The information indicating the displacement volume V is stored in advance in the ROM of the controller 10.

[0049]

In addition, as the displacement volume V of the compressor 2 is determined on the basis of the rotation frequency, the displacement volume V can be changed by changing the com pressor frequency, which is proportional to the rotation frequency. Thus, by adjusting the compressor frequency of the compressor 2, the refrigerant circulation amount Gr can be adjusted to a predetermined amount.

[0050]

Consequently, in step S4, the controller 10 calculates and adjusts the compressor frequency of the compressor 2 so that the refrigerant circulation amount Gr equals the refrigerant circulation amount Gr calculated in step S3.

Consequently, in the air-conditioning apparatus 1 according to the present embodiment, the blowout temperature of the evaporator 5 can be brought close to the set temperature and overshoot is not caused.

[0051]

As described above, in the present embodiment, the refrigerant circulation amount Gr required to make the inlet temperature of air in the evaporator 5 reach the target blowout temperature is calculated, and the compressor frequency of the compressor 2 is adjusted to satisfy the calculated refrigerant circulation amount Gr. Consequently, overshoot that is caused while the blowout temperature is being adjusted to the set temperature can be reduced.

[0052] [About Reach Time]

A reach time required for the blowout temperature to reach the set temperature will be explained.

Fig. 5 is a schematic view showing an example of the relationship between a compressor frequency and a blowout temperature in a compressor frequency control of a conventional air-conditioning apparatus. Fig. 6 is a schematic view showing another example of the relationship between the com pressor frequency and the blowout temperature in the compressor frequency control of the conventional airconditioning apparatus.

Fig. 7 is a schematic view showing an example of the relationship between the compressor frequency and the blowout temperature in the com pressor frequency control of the air-conditioning apparatus of Fig. 1.

[0053]

As shown in Fig. 5, in a conventional technique, attention is focused on the difference in temperature between a blowout temperature and a set temperature and, when a period of time in which this temperature difference is present exceeds a temperature difference time period t that is set in advance, the compressor frequency is changed. For example, when a period of time in which the blowout temperature is lower than the set temperature exceeds the temperature difference time period t, the compressor frequency is reduced. In addition, when a period of time in which the blowout temperature is higher than the set temperature exceeds the temperature difference time period t, the compressor frequency is increased.

By repeatedly changing the compressor frequency in such a manner, the blowout temperature is gradually brought close to the set temperature while the amount of overshoot is decreasing. Then, the blowout temperature eventually reaches the set temperature after a time period Ti has elapsed from the start of operation of the compressor, and becomes stable.

[0054]

Meanwhile, in a case in which the compressor frequency is changed repeatedly, when the rate of increase in compressor frequency is increased, the speed for bringing the blowout temperature close to the set temperature can be increased. However, in such a case, the blowout temperature increases or decreases rapidly in a short period of time and, because the blowout temperature exceeds or falls below the set temperature, the amount of overshoot is increased.

To solve the abovementioned problem, as shown in Fig. 6, a method is proposed in which the rate of increase in compressor frequency is reduced compared with that of the conventional technique to reduce the amount of overshoot of the blowout temperature.

In such a case, the speed for bringing the blowout temperature close to the set temperature is reduced compared with that of the conventional technique but the difference in temperature between the blowout temperature and the set temperature in the temperature difference time period t can be reduced. Consequently, the amount of overshoot can be reduced and a time period required for the blowout temperature to reach the set temperature and to become stable can be shortened to a time period T2, which is shorter than the abovementioned time period Ti.

However, even in this case, it is difficult to make the blowout temperature reach the set temperature without causing overshoot.

[0055]

Meanwhile, by setting the compressor frequency by using the abovementioned method in the present embodiment, the blowout temperature can reach the set temperature without causing overshoot and then can be stabilized, as shown in Fig.

7. In this configuration, a period of time required for the blowout temperature to reach the set temperature and then to become stable after the start of operation of the compressor 2 can be shortened to a time period T3, which is shorter than each of the abovementioned time periods Ti and T2.

As described above, in the present embodiment, the period of time required for the blowout temperature to reach the set temperature can be further shortened without limiting the rate of increase in compressor frequency.

[0056]

Note that, in the abovementioned example, adjustment processing of the compressor frequency for the air-conditioning apparatus 1 capable of performing a cooling operation is explained; however, the same processing can be applied to an air-conditioning apparatus capable of performing a heating operation.

[0057]

Fig. 8 is a psychrometric chart showing states of air in the indoor heat exchanger 5 of the air-conditioning apparatus 1 of Fig. 1.

Fig. 9 is a p-h diagram showing a refrigeration cycle of the air-conditioning apparatus 1 of Fig. 1.

In a case of performing a heating operation, a refrigerant circuit is formed so that the side for sucking refrigerant and the side for discharging refrigerant of the compressor 2 in the air-conditioning apparatus 1 show in Fig. 1 are switched, and that the indoor heat exchanger 5 acts as a condenser and the outdoor heat exchanger 3 acts as an evaporator.

[0058]

As with the case of the target evaporating temperature described above, the controller 10 calculates, on the basis of formula (5), a target condensing temperature Tern in the indoor heat exchanger 5 acting as a condenser.

[Formula 5]

Tern = (To - Ti x BF)/(1 - BF) - (5) [0059]

Then, the controller 10 calculates a condensing capacity Qc required to make the inlet temperature reach the target blowout temperature To on the basis of formula (6).

[Formula 6]

Qc = Ga x Cp x (Tc - Ti) x (1 - BF) = Ga x (Tc-Ti) x (1 - BF) -(6)

Cp shown above represents the specific heat of air at constant pressure and can be omitted because this value does not affect on the calculation result under an environment where the air-conditioning apparatus 1 is used.

[0060]

Next, the controller 10 calculates a refrigerant circulation amount Gr required to make the inlet temperature Ti reach the target blowout temperature To on the basis of formula (7) by using the calculated condensing capacity Qc, a condenser inlet enthalpy hri' and a condenser outlet enthalpy hro'.

[Formula 7]

Gr= Qc/(hro' - hri') - --(7) [0061]

Then, as with the case of a cooling operation, the controller 10 calculates and adjusts the compressor frequency of the compressor 2 so that the refrigerant circulation amount Gr calculated on the basis of the above formula (4) equals the refrigerant circulation amount Gr calculated on the basis of the formula (7).

Consequently, overshoot that is caused while the blowout temperature of the indoor heat exchanger 5 is being adjusted to the set temperature can be reduced also in an air-conditioning apparatus capable of performing a heating operation.

[0062]

One embodiment of the present invention is explained above; however, the present invention is not limited to the abovementioned embodiment of the present invention, and various modifications and applications are enabled within the scope of the present invention.

For example, the configuration of the air-conditioning apparatus 1 is not limited to the configuration illustrated in Fig. 1, and may be provided with an accumulator for protecting the compressor 2 or an oil separator for recovering refrigerating machine oil. Furthermore, the air-conditioning apparatus may be provided with, for example, a refrigerant flow switching device that switches between a cooling operation and a heating operation by switching the direction of refrigerant flow.

Reference Signs List [0063] air-conditioning apparatus 2 compressor 3 outdoor heat exchanger

4 expansion valve 5 indoor heat exchanger 6 fan 7 motor 10 controller outdoor heat exchanger pressure sensor 12 outdoor heat exchanger outlet temperature sensor 13 indoor heat exchanger temperature sensor 14 indoor heat exchanger outlet temperature sensor 15 inlet air state sensor

Claims

CLAIMS [Claim 1]

An air-conditioning apparatus comprising:

a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are sequentially connected by refrigerant pipes to circulate refrigerant in the refrigerant circuit;

an air-sending device configured to suck air that exchanges heat with the refrigerant in the indoor heat exchanger; and a controller configured to operate the compressor at a compressor frequency that satisfies a refrigerant circulation amount required to make a blowout temperature of the air of the indoor heat exchanger reach a set temperature set by a user.
[Claim 2]

The air-conditioning apparatus of claim 1 further comprising:

an outdoor heat exchanger pressure sensor configured to measure an outdoor heat exchanger pressure that is a pressure of the refrigerant flowing into the outdoor heat exchanger;

an outdoor heat exchanger outlet temperature sensor configured to measure an outdoor heat exchanger outlet temperature that is a temperature of the refrigerant flowing out from the outdoor heat exchanger;

an indoor heat exchanger temperature sensor configured to measure an indoor heat exchanger temperature that is a temperature of the refrigerant flowing into the indoor heat exchanger;

an indoor heat exchanger outlet temperature sensor configured to measure an indoor heat exchanger outlet temperature that is a temperature of the refrigerant flowing out from the indoor heat exchanger; and an inlet air state sensor configured to measure an inlet temperature of the air flowing into the indoor heat exchanger, wherein the controller includes a storage unit configured to store a bypass factor that is associated with an air blow amount of the air-sending device and refrigerant property information of the refrigerant, and wherein the controller is configured to calculate the refrigerant circulation amount required to make the blowout temperature reach the set temperature on a basis of the inlet temperature of the air of the indoor heat exchanger, the set temperature, the outdoor heat exchanger pressure, the outdoor heat exchanger outlet temperature, the indoor heat exchanger temperature, the indoor heat exchanger outlet temperature, the bypass factor, and the refrigerant property information, and calculate the compressor frequency that satisfies the refrigerant circulation amount that is calculated.
[Claim 3]

The air-conditioning apparatus of claim 2, wherein, in a cooling operation, the controller is configured to calculate an evaporating temperature that is a target on a basis of the inlet temperature, the set temperature, and the bypass factor, calculate an evaporation capacity required to make the inlet temperature reach a target blowout temperature on a basis of the air blow amount, an intake air enthalpy, a saturated air enthalpy, and the bypass factor, calculate a refrigerant circulation amount required to make the inlet temperature reach the target blowout temperature on a basis of the evaporation capacity that is calculated, an evaporator inlet enthalpy, and an evaporator outlet enthalpy, and calculate the com pressor frequency that satisfies the refrigerant circulation amount that is calculated.
[Claim 4]

The air-conditioning apparatus of claim 3, wherein the controller is configured to calculate the intake air enthalpy on a basis of the inlet temperature, calculate the saturated air enthalpy on a basis of the evaporating temperature, calculate the evaporator inlet enthalpy on a basis of a condenser pressure that is the outdoor heat exchanger pressure, a condenser outlet temperature that is the outdoor heat exchanger outlet temperature, and the refrigerant property information, and calculate the evaporator outlet enthalpy on a basis of an evaporator pressure obtained by using an evaporator temperature that is the indoor heat exchanger

5 temperature and the refrigerant property information, an evaporator outlet temperature that is the indoor heat exchanger outlet temperature, and the refrigerant property information.