JP2001304699A - Refrigerating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce development cost by shortening the period required in selection of an electric expansion valve at design of an air conditioner. SOLUTION: In an air conditioner (10) for object of design, filling quantity ratio X is obtained by dividing the refrigerant filling quantity of a refrigerant circuit (20) by the specified reference quantity of a refrigerant. A motor-operated expansion valve (36) of a flow coefficient larger than the value being obtained by multiplying an operation value, which is obtained by performing specified operation, using this filling quantity ratio X, by rated cooling capacity (kW) is selected. Hereby, the quantity of a circulating refrigerant in the refrigerant circuit (20) is secured, and the temperature of a refrigerant discharged from a compressor (30) is kept at a prescribed upper limit value or below even under heating overload conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration system having a refrigerant circuit, and more particularly to a selection of an expansion valve in the refrigerant circuit.

[0002]

2. Description of the Related Art Heretofore, a refrigerating apparatus that circulates a refrigerant in a refrigerant circuit to perform a vapor compression refrigeration cycle has been known and is widely used as an air conditioner or the like. The refrigerant circuit includes a compressor, a condenser, a refrigerant expansion mechanism, and an evaporator. As the expansion mechanism, a capillary tube, an expansion valve with a variable opening, or the like is used.

[0003] When selecting an expansion valve in the above-mentioned refrigerating apparatus, conventionally, an expansion valve is selected as follows.
That is, initially the refrigeration system and the operating state rated capacity (the expansion valve differential pressure across the refrigerant density at the expansion valve inlet) on the basis of the derived values of the flow coefficient C _v, the expansion valve having a flow coefficient of this value Choose temporarily. Then, a refrigerant circuit using the provisionally determined expansion valve is configured and an actual machine test is performed, and operation is performed under various conditions to finally determine an expansion valve having a specification that does not cause a problem.

[0004] As for the flow coefficient of a general valve (valve), as shown on page 2006 of “JIS Industrial Dictionary, 4th Edition, edited by the Japan Standards Association,” An experiment is performed by flowing an incompressible fluid through the installed pipe line, and the value is obtained by the following equation. C _v = q _V / (A (2Δp / ρ) ^1/2 ) where q _V is the volume flow rate (m ³ / s), and A is the opening area of the valve
(m ² ), Δp represents the differential pressure (Pa), and ρ represents the density of the fluid (kg / m ³ ). However, unlike the above-described definition formula, the flow coefficient of the expansion valve is generally indicated by a numerical value including the opening area of the expansion valve. This is because it is difficult to strictly quantify the opening area of the expansion valve.

[0005]

As described above, in the conventional selection of the expansion valve, the actual machine test is performed after tentatively determining the rated capacity and the like. In the state where both the room temperature and the outside air temperature are high during operation), the refrigerant discharge temperature of the compressor is often too high, and much effort is often required for trial and error in actual machine tests. For this reason, there has been a problem that it takes a long time to develop a refrigeration apparatus, which causes an increase in development cost.

On the other hand, in recent years, from the viewpoint of preventing global warming,
R32 has attracted attention as a refrigerant in the refrigerant circuit. This R
32 has a slight flammability, but R22, R407C, R
Compared with 410A, it has many advantages such as a lower GWP (global warming potential) and a large refrigerant latent heat due to a large latent heat of vaporization, and an improvement in the COP (coefficient of performance) of the refrigeration system.

However, the specific heat ratio of R32 is smaller than that of the conventional R2.
2, R407C, and R410A. By the way, the specific heat ratio of each refrigerant is 1.
51, R22 1.31, R407C 1.24, R4
10A is 1.36. The physical properties of these refrigerants are based on NIST Refprop Ver.5.

[0008] When the specific heat ratio of the refrigerant increases, the temperature rise width of the refrigerant before and after the compressor increases even if the compression ratio in the compressor is the same. For this reason, when a refrigerant having a specific heat ratio larger than that of the conventional R22, R407C, or R410A, such as R32, is used, in most cases, a problem occurs when an actual machine test is performed using an expansion valve provisionally determined by the conventional method. I will. Therefore, the problem that the man-hour required for selecting the expansion valve is increased and the development cost is increased has been more serious.

The present invention has been made in view of the above points, and has as its object to shorten the period required for selecting an expansion valve and to reduce development costs.

[0010]

A first solution of the present invention is to provide an indoor unit (13) and an outdoor unit (1).
1) is connected by connecting pipes (23, 24) of the refrigerant circuit (20), and the refrigerant charged in the refrigerant circuit (20) is supplied to the compressor (3).
0), a refrigeration system that circulates in the order of condenser, expansion valve (36), and evaporator. And the above connection pipe (23,24)
Is 30 m, the dry bulb temperature of the first air that exchanges heat with the refrigerant in the evaporator is 21 ° C., the wet bulb temperature is 15 ° C., and the dry bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is The refrigerant circuit is designed to have an expansion valve flow coefficient at 28 ° C. and a refrigerant discharge temperature of the compressor (30) maintained at 145 ° C. or less under the limit operation condition where the capacity of the compressor (30) is the maximum capacity. The expansion valve (36) of (20) is configured. That is, the flow coefficient of the expansion valve (36) in the refrigerant circuit (20) is set on the basis of the expansion valve flow coefficient at which the discharge refrigerant temperature of the compressor (30) is maintained at 145 ° C. or lower under the above-mentioned limit operation conditions. Things.

A second solution taken by the present invention is that an indoor unit (13) and an outdoor unit (11) are connected to a refrigerant circuit (2).
A refrigeration unit connected by the communication pipes (23, 24) of (0) and the refrigerant charged in the refrigerant circuit (20) circulates in the order of the compressor (30), the condenser, the expansion valve (36), and the evaporator. Target. And the length of the connecting pipe (23, 24) is 30 m,
The dry bulb temperature of the first air that exchanges heat with the refrigerant in the evaporator is 2
The wet-bulb temperature is 1 ° C., the dry-bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 15 ° C., the dry-bulb temperature is 28 ° C., and the capacity of the compressor (30) is the maximum capacity. The expansion valve (36) of the refrigerant circuit (20) is configured so as to have an expansion valve flow coefficient at which the discharged refrigerant temperature of (30) is maintained at 135 ° C or lower. That is, the flow coefficient of the expansion valve (36) in the refrigerant circuit (20) is set on the basis of the expansion valve flow coefficient at which the discharge refrigerant temperature of the compressor (30) is maintained at 135 ° C. or lower under the above limit operation conditions. Things.

A third solution taken by the present invention is that an indoor unit (13) and an outdoor unit (11) are connected to a refrigerant circuit (2).
A refrigeration unit connected by the communication pipes (23, 24) of (0) and the refrigerant charged in the refrigerant circuit (20) circulates in the order of the compressor (30), the condenser, the expansion valve (36), and the evaporator. Target. And the length of the connecting pipe (23, 24) is 30 m,
The dry bulb temperature of the first air that exchanges heat with the refrigerant in the evaporator is 2
The wet-bulb temperature is 1 ° C., the dry-bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 15 ° C., the dry-bulb temperature is 28 ° C., and the capacity of the compressor (30) is the maximum capacity. The expansion valve (36) of the refrigerant circuit (20) is configured to have an expansion valve flow coefficient that maintains the discharged refrigerant temperature of (30) at 125 ° C. or lower. That is, the flow coefficient of the expansion valve (36) in the refrigerant circuit (20) is set on the basis of the expansion valve flow coefficient at which the discharge refrigerant temperature of the compressor (30) is maintained at 125 ° C. or lower under the above-mentioned limit operating conditions. Things.

A fourth solution taken by the present invention is a refrigeration system in which a refrigerant charged in a refrigerant circuit (20) circulates in the order of a compressor (30), a condenser, an expansion valve (36), and an evaporator. Target. Then, a correlation between a charging ratio obtained by dividing the refrigerant charging amount of the refrigerant circuit (20) by a preset reference refrigerant amount, an expansion valve flow coefficient, and a refrigerant discharge temperature of the compressor (30). The expansion valve (36) of the refrigerant circuit (20) is configured to have a flow coefficient equal to or larger than the value of the expansion valve flow coefficient derived based on the above. That is, the expansion valve in the refrigerant circuit (20) is referred to based on the expansion valve flow coefficient derived based on the correlation between the filling ratio, the expansion valve flow coefficient, and the refrigerant discharge temperature of the compressor (30). The flow coefficient of (36) is set.

A fifth solution taken by the present invention is that an indoor unit (13) and an outdoor unit (11) are connected to a refrigerant circuit (2).
A refrigeration unit connected by the communication pipes (23, 24) of (0) and the refrigerant charged in the refrigerant circuit (20) circulates in the order of the compressor (30), the condenser, the expansion valve (36), and the evaporator. Target. And the length of the connecting pipe (23, 24) is 30 m,
The dry bulb temperature of the first air that exchanges heat with the refrigerant in the evaporator is 2
The operating conditions at which the wet-bulb temperature is 1 ° C., the wet-bulb temperature is 15 ° C., the dry-bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 28 ° C., and the capacity of the compressor (30) is the maximum capacity are defined as the critical operating conditions. A charge ratio obtained by dividing the refrigerant charge of the refrigerant circuit (20) by a preset reference refrigerant amount, an expansion valve flow coefficient,
The expansion valve (36) of the refrigerant circuit (20) has a flow coefficient that is equal to or greater than the value of the expansion valve flow coefficient derived based on the correlation with the refrigerant temperature discharged from the compressor (30) under the above-mentioned limit operating conditions. Is constituted. That is, the refrigerant circuit (20) is determined based on the expansion valve flow coefficient derived based on the correlation between the filling ratio, the expansion valve flow coefficient, and the refrigerant temperature discharged from the compressor (30) under the limit operating conditions. ), The flow coefficient of the expansion valve (36) is set.

A sixth solution taken by the present invention is that an indoor unit (13) and an outdoor unit (11) are connected to a refrigerant circuit (2).
A refrigeration unit connected by the communication pipes (23, 24) of (0) and the refrigerant charged in the refrigerant circuit (20) circulates in the order of the compressor (30), the condenser, the expansion valve (36), and the evaporator. Target. The first air that exchanges heat with the refrigerant in the evaporator has a dry bulb temperature of 27 ° C. and a wet bulb temperature of 19 ° C. The second air that exchanges heat with the refrigerant in the condenser has a dry bulb temperature of 35 ° C. The operating conditions in which the capacity of the machine (30) is a predetermined rated capacity are the standard operating conditions, and the standard operating conditions in the reference circuit, which is a refrigerant circuit (20) in which the length of the connecting pipes (23, 24) is 5 m, are used. When the refrigeration cycle is performed, the amount of refrigerant that must be charged into the reference circuit to completely convert the refrigerant into a liquid phase at the inlet of the expansion valve (36) of the reference circuit is set in advance as the reference refrigerant amount. The length of the connecting pipe (23, 24) is 30
m, the dry bulb temperature of the first air that exchanges heat with the refrigerant in the evaporator is 21 ° C., the wet bulb temperature is 15 ° C., the dry bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 28 ° C., Compressor (30)
The operating condition where the capacity of the
The correlation between the charging ratio obtained by dividing the refrigerant charging amount of the refrigerant circuit (20) by the reference refrigerant amount, the flow coefficient of the expansion valve, and the refrigerant temperature discharged from the compressor (30) under the above-mentioned limit operating conditions is shown. The expansion valve (3) of the refrigerant circuit (20) has a flow coefficient equal to or greater than the value of the expansion valve flow coefficient derived based on the
6) is configured. That is, the refrigerant circuit (20) is determined based on the expansion valve flow coefficient derived based on the correlation between the filling ratio, the expansion valve flow coefficient, and the refrigerant temperature discharged from the compressor (30) under the limit operating conditions. ), The flow coefficient of the expansion valve (36) is set.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the refrigerant filled in the refrigerant circuit (20) has a larger specific heat ratio than R22. It is composed of substances.

According to an eighth aspect of the present invention, in any one of the first to sixth aspects, the refrigerant filled in the refrigerant circuit (20) is constituted by a single refrigerant of R32. Is what is done.

According to a ninth solution of the present invention, an indoor unit (13) and an outdoor unit (11) are connected to a refrigerant circuit (2).
A refrigeration unit connected by the communication pipes (23, 24) of (0) and the refrigerant charged in the refrigerant circuit (20) circulates in the order of the compressor (30), the condenser, the expansion valve (36), and the evaporator. The refrigerant filled in the refrigerant circuit (20) is a refrigerant composed of a single R32 refrigerant. The first air that exchanges heat with the refrigerant in the evaporator has a dry bulb temperature of 27 ° C., the wet bulb temperature is 19 ° C., and the second air that exchanges heat with the refrigerant in the condenser.
Refrigerant circuit (20) in which the operating condition that the dry bulb temperature of the air is 35 ° C. and the capacity of the compressor (30) is a predetermined rated capacity is set as the standard operating condition, and the length of the connecting pipe (23, 24) is 5 m. When the refrigeration cycle under the standard operating conditions is performed in the reference circuit, the amount of refrigerant that must be charged into the reference circuit in order to completely convert the refrigerant into a liquid phase at the inlet of the expansion valve (36) of the reference circuit. Is set in advance as a reference refrigerant amount, the refrigeration capacity exhibited by the operation under the standard operation conditions in the refrigerant circuit (20) is defined as a rated refrigeration capacity (kW), and the flow coefficient of the expansion valve is An expression in which a value obtained by dividing the refrigerant charge amount by the reference refrigerant amount is expressed as X
(1.02443 · X ² −3.79638 · X + 3.88706) · 10 ^{-2 The} calculated value is multiplied by the rated refrigeration capacity and is equal to or greater than the value obtained.

The tenth solution taken by the present invention is that the indoor unit (13) and the outdoor unit (11) are connected by connecting pipes (23, 24) of a refrigerant circuit (20), and the refrigerant circuit ( 20) A refrigeration system in which the refrigerant filled in the compressor circulates in the order of a compressor (30), a condenser, an expansion valve (36), and an evaporator,
The refrigerant to be filled in the refrigerant circuit (20) is intended to be composed of a single refrigerant of R32. The dry air temperature of the first air that exchanges heat with the refrigerant in the evaporator is 27 ° C.
Operating conditions in which the wet bulb temperature is 19 ° C., the dry bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 35 ° C., and the capacity of the compressor (30) is a predetermined rated capacity, When performing a refrigeration cycle under the standard operating conditions in a reference circuit which is a refrigerant circuit (20) having a length of the communication pipes (23, 24) of 5 m, refrigerant is supplied to an inlet of an expansion valve (36) of the reference circuit. The amount of refrigerant that must be charged into the reference circuit in order to completely make it into a liquid phase is set in advance as a reference refrigerant amount, and the refrigeration capacity exhibited by the refrigerant circuit (20) operating under the standard operating conditions is rated. The refrigerating capacity (kW), the flow coefficient of the expansion valve, a value obtained by dividing the refrigerant charge of the refrigerant circuit by the reference refrigerant amount is represented by X
(1.20720 · X ² −4.21152 · X + 4.17078) · 10 ^{-2 The} calculated value is multiplied by the rated refrigeration capacity and is equal to or greater than the value obtained.

An eleventh solution taken by the present invention is that an indoor unit (13) and an outdoor unit (11) are connected by connecting pipes (23, 24) of a refrigerant circuit (20), and the refrigerant circuit ( 20) A refrigeration system in which the refrigerant filled in the compressor circulates in the order of a compressor (30), a condenser, an expansion valve (36), and an evaporator,
The refrigerant to be filled in the refrigerant circuit (20) is intended to be composed of a single refrigerant of R32. The dry air temperature of the first air that exchanges heat with the refrigerant in the evaporator is 27 ° C.
Operating conditions in which the wet bulb temperature is 19 ° C., the dry bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 35 ° C., and the capacity of the compressor (30) is a predetermined rated capacity, When performing a refrigeration cycle under the standard operating conditions in a reference circuit which is a refrigerant circuit (20) having a length of the communication pipes (23, 24) of 5 m, refrigerant is supplied to an inlet of an expansion valve (36) of the reference circuit. The amount of refrigerant that must be charged into the reference circuit in order to completely make it into a liquid phase is set in advance as a reference refrigerant amount, and the refrigeration capacity exhibited by the refrigerant circuit (20) operating under the standard operating conditions is rated. The refrigerating capacity (kW), the flow coefficient of the expansion valve, a value obtained by dividing the refrigerant charge of the refrigerant circuit by the reference refrigerant amount is represented by X
(1.39816 · X ² −4.66544 · X + 4.48651) · 10 ^{-2 The} calculated value is multiplied by the rated refrigeration capacity and is equal to or larger than the value obtained by multiplying the calculated value.

According to a twelfth solution of the present invention, in the eighth, ninth, tenth or eleventh solution, the refrigerant filled in the refrigerant circuit (20) is a single refrigerant of R32. Instead, it is composed of a mixed refrigerant containing 75% by mass or more of R32.

-Operation- In each of the above solutions, the refrigeration system (10) is connected to the refrigerant circuit (2).
0) is provided. The refrigerant circuit (20) is configured as a closed circuit and is filled with refrigerant. In this refrigerant circuit (20),
A compressor (30), a condenser, an expansion valve (36), and an evaporator are provided. When the compressor (30) is driven, the compressor (30)
Refrigerant circulates in the order of the condenser, the expansion valve (36), and the evaporator while changing phase, and a vapor compression refrigeration cycle is performed.

In particular, the first to third, fifth, sixth, and ninth embodiments
In each of the eleventh to eleventh solving means, the indoor unit (13) and the outdoor unit (11) are provided in the refrigeration system (10).
The indoor unit (13) and the outdoor unit (11) are connected by communication pipes (23, 24) of the refrigerant circuit (20).

When the object is cooled by the refrigerating device (10), the heat absorption of the refrigerant in the evaporator is used. For example, an evaporator is provided in the indoor unit (13), and the refrigerant absorbs heat from the object in the evaporator. On the other hand, the outdoor unit (11) is provided with a compressor (30) and a condenser. The expansion valve (36) may be provided in either the indoor unit (13) or the outdoor unit (11).

When the object is heated by the refrigerating device (10), that is, when the refrigerating device (10) is used as a heat pump, the heat radiation of the refrigerant in the condenser is used.
For example, a condenser is provided in the indoor unit (13), and the refrigerant radiates heat to the object in the condenser. On the other hand, the outdoor unit (11) is provided with a compressor (30) and an evaporator. The expansion valve (36) is the indoor unit (13)
Alternatively, it may be provided in any of the outdoor unit (11).

In the first, second, and third solving means, the predetermined operating condition is determined as the limit operating condition. The limit operating conditions are that the connection pipes (23, 24) are relatively long and the first air that exchanges heat with the refrigerant in the evaporator and the second air that exchanges heat with the refrigerant in the condenser. Is a relatively high temperature,
Further, the operating condition is such that the compressor (30) is operated at the maximum capacity. That is, the limit operating condition is an operating condition in which the temperature of the refrigerant discharged from the compressor (30) tends to be the highest.

In particular, when the refrigeration system (10) is configured as an air conditioner, this limit operation condition corresponds to a so-called heating overload condition, and the compressor (30) is the most conceivable operation condition.
This is an operating condition in which the discharged refrigerant temperature becomes higher. That is, since the condensation temperature of the refrigerant in the condenser is high and the degree of superheat of the refrigerant at the outlet of the evaporator is high, the compressor (3
The temperature of the refrigerant discharged from 0) increases.

Under the above limit operating conditions, it is necessary to ensure the maximum amount of refrigerant circulating in the refrigerant circuit (20), and therefore the opening of the expansion valve (36) is maximized. Therefore, if the flow coefficient of the expansion valve (36) is too small, the refrigerant circulation amount will be insufficient even when the expansion valve (36) is fully opened, and the temperature of the refrigerant discharged from the compressor (30) may be too high. If the temperature of the discharged refrigerant is excessively raised, troubles such as deterioration of the refrigerant and refrigerating machine oil and damage to the compressor motor are caused.

Therefore, in the first solving means, the flow coefficient of the expansion valve (36) is determined so that the temperature of the refrigerant discharged from the compressor (30) does not exceed 145 ° C. even under the above-mentioned limit operating conditions. In other words, the expansion valve (36) having a flow coefficient that maintains the refrigerant discharge temperature of the compressor (30) at 145 ° C. or lower under the limit operation condition is adopted. Therefore, even when the refrigeration cycle is performed under the limit operation condition, the circulation amount of the refrigerant in the refrigerant circuit (20) is sufficiently ensured, and the temperature of the refrigerant discharged from the compression does not exceed 145 ° C.

In the second solution, the flow coefficient of the expansion valve (36) is determined so that the temperature of the refrigerant discharged from the compressor (30) does not exceed 135 ° C. even under the above-mentioned limit operating conditions. In other words, the expansion valve (36) having a flow coefficient that ensures that the refrigerant discharged from the compressor (30) under the limit operating conditions is maintained at 135 ° C or lower. For this reason, even when the refrigeration cycle is performed under the limit operation condition, the refrigerant circulation amount in the refrigerant circuit (20) is sufficiently ensured, and the temperature of the refrigerant discharged from the compression does not exceed 135 ° C.

In the third solution, the flow coefficient of the expansion valve (36) is determined so that the temperature of the refrigerant discharged from the compressor (30) does not exceed 125 ° C. even under the above-mentioned limit operating conditions. In other words, the expansion valve (36) having a flow coefficient that allows the refrigerant discharged from the compressor (30) to maintain the temperature of the refrigerant at 125 ° C. or lower under the limit operation condition is adopted. For this reason, even when the refrigeration cycle is performed under the limit operation condition, the refrigerant circulation amount in the refrigerant circuit (20) is sufficiently ensured, and the temperature of the refrigerant discharged from the compression does not exceed 125 ° C.

In the fourth, fifth, and sixth solving means, the correlation between the filling ratio, the expansion valve flow coefficient, and the refrigerant temperature discharged from the compressor (30) is obtained in advance, and the correlation is determined. The expansion coefficient of the expansion valve (36) in the refrigerant circuit (20) is determined based on the expansion valve flow coefficient derived based on the relationship. For example, the expansion valve (36) of the refrigerant circuit (20) is selected such that the expansion coefficient of the expansion valve (36) is equal to or greater than the value of the derived expansion valve flow coefficient. The filling ratio is
This is a value obtained by dividing the amount of refrigerant charged in the refrigerant circuit (20) by a predetermined reference refrigerant amount.

In particular, in the fifth and sixth solving means, the correlation between the filling ratio, the expansion valve flow coefficient, and the refrigerant temperature discharged from the compressor (30) under the above-mentioned limit operating conditions is quantified in advance. I do. By determining the expansion coefficient of the expansion valve (36) based on the expansion valve flow coefficient derived on the basis of the relationship between the three, the discharge refrigerant temperature of the compressor (30) can be set to a predetermined value even under the above-mentioned limit operating conditions. The expansion valve (36) that can be maintained below the value is selected.

Further, in the sixth solution, the contents of the reference refrigerant amount for obtaining the filling ratio are embodied. First, predetermined operating conditions are set as standard operating conditions. These standard operating conditions are the standard operating conditions when the first air is cooled by the refrigerating device (10). For example, when the refrigerating device (10) is configured as an air conditioner, the conditions of the first air and the second air under the standard operating conditions are JIS B 8615-1: 199.
It corresponds to the standard cooling condition specified in 9.

The reference refrigerant amount is defined as follows. That is, the reference refrigerant amount is set in advance by setting a refrigerant circuit (20) having a connecting pipe (23, 24) having a length of 5 m as a reference circuit, and circulating the refrigerant in the reference circuit to perform a refrigeration cycle. , Determined experimentally. Then, when the refrigeration cycle is performed in the reference circuit under the standard operating conditions, the minimum amount of refrigerant that must be charged into the reference circuit because all of the refrigerant becomes a liquid phase at the inlet of the expansion valve (36). , A reference refrigerant amount.

In the seventh and eighth solutions, the refrigerant circuit (20) is filled with a refrigerant having a specific heat ratio higher than R22. Specifically, in the eighth solution, a refrigerant of a single component consisting only of R32 is charged into the refrigerant circuit (20). Here, when a refrigerant having a large specific heat ratio is used, even if the compression ratio in the compressor (30) is the same, the width of temperature rise accompanying compression becomes large. That is, as the specific heat ratio of the refrigerant increases, the temperature of the refrigerant discharged from the compressor (30) increases. On the other hand, by using the expansion valve (36) having a predetermined flow coefficient as in the first to sixth solving means, even if a refrigerant having a specific heat ratio larger than R22 is used, the compressor can be used. The temperature of the discharged refrigerant of (30) can be maintained at a predetermined value or less.

In the ninth, tenth, and eleventh means, when the refrigerant to be charged into the refrigerant circuit (20) is a single refrigerant of R32, the filling ratio, the expansion valve flow coefficient, The correlation with the refrigerant temperature discharged from the compressor (30) under the above limit operation condition is specifically expressed by a mathematical expression. At that time, in each of these solutions, a predetermined rated refrigeration capacity is determined. This rated refrigeration capacity is obtained by expressing the refrigeration capacity that is exhibited when the refrigeration cycle is performed under the standard operating conditions in the refrigeration circuit (20) of the refrigeration system (10) to be designed in kW (kilowatt). It is.

More specifically, in the ninth to eleventh solutions, the above-mentioned standard operating conditions, the reference refrigerant amount, and the rated refrigeration capacity are determined, and then the expansion valve (3
The flow coefficient of 6) is derived as follows. First, the refrigeration capacity of the design target is set in advance, and its value matches the rated refrigeration capacity. Further, the amount of refrigerant to be charged into the refrigerant circuit (20) is also predetermined in the design stage. A value obtained by dividing the refrigerant charge amount by the reference refrigerant amount is defined as X, and the calculated value is obtained by substituting the value X into a predetermined mathematical formula. By multiplying the calculated value by the rated refrigeration capacity, an expansion valve flow coefficient required in the refrigerant circuit (20) is obtained. And
By adopting an expansion valve (36) having a flow coefficient equal to or greater than the derived expansion valve flow coefficient, an expansion valve (36) having appropriate specifications is selected.

In the ninth solution, the correlation between the filling ratio and the expansion valve flow coefficient when the discharge refrigerant temperature of the compressor (30) is set to 145 ° C. under the above-mentioned limit operating conditions is determined by the filling ratio. Is represented as X by the following formula. (1.02443 · X ² −3.79638 · X + 3.88706) · 10 ^-2 The calculated value is derived by substituting the value of the known filling ratio X into this equation. The calculated value derived based on this formula represents a value obtained by dividing the expansion valve flow coefficient by the rated cooling capacity, that is, the expansion valve flow coefficient per 1 kW of the rated cooling capacity.
Then, the derived operation value is multiplied by the rated cooling capacity, and an expansion valve having a flow coefficient equal to or higher than the obtained value is connected to the refrigerant circuit (2).
0) The expansion valve (36). An expansion valve with this specification (3
By adopting 6), the temperature of the refrigerant discharged from the compressor (30) is 145 ° C. even under the above-mentioned limit operating conditions.
It is kept below.

[0040] In the tenth solution, the discharge refrigerant temperature of the compressor (30) under the above-mentioned limit operating condition is set to 135 ° C.
The correlation between the filling ratio and the expansion valve flow coefficient in the case of と し た is expressed by the following formula, where X is the filling ratio. (1.20720 · X ² −4.21152 · X + 4.17078) · 10 ⁻² The calculated value is derived by substituting the value of the known filling ratio X into this equation. The calculated value derived based on this formula represents a value obtained by dividing the expansion valve flow coefficient by the rated cooling capacity, that is, the expansion valve flow coefficient per 1 kW of the rated cooling capacity.
Then, the derived operation value is multiplied by the rated cooling capacity, and an expansion valve having a flow coefficient equal to or higher than the obtained value is connected to the refrigerant circuit (2).
0) The expansion valve (36). An expansion valve with this specification (3
By adopting 6), the temperature of the refrigerant discharged from the compressor (30) is 135 ° C. even under the above-mentioned limit operating conditions.
It is kept below.

In the eleventh solution, the refrigerant discharged from the compressor (30) under the above-mentioned limit operating condition is set to a temperature of 125 ° C.
The correlation between the filling ratio and the expansion valve flow coefficient in the case of と し た is expressed by the following formula, where X is the filling ratio. (1.39816 · X ² −4.66544 · X + 4.48651) · 10 ^-2 The calculated value is derived by substituting the value of the known filling ratio X into this equation. The calculated value derived based on this formula represents a value obtained by dividing the expansion valve flow coefficient by the rated cooling capacity, that is, the expansion valve flow coefficient per 1 kW of the rated cooling capacity.
Then, the derived operation value is multiplied by the rated cooling capacity, and an expansion valve having a flow coefficient equal to or higher than the obtained value is connected to the refrigerant circuit (2).
0) The expansion valve (36). An expansion valve with this specification (3
By adopting 6), the temperature of the refrigerant discharged from the compressor (30) is 125 ° C. even under the above-mentioned limit operating conditions.
It is kept below.

In the twelfth solution, the refrigerant circuit (2
The refrigerant charged in 0) is constituted by a mixed refrigerant containing 75% by mass or more of R32. That is, the refrigerant circuit (20) is filled with a mixed refrigerant having a concentration of R32 of 75% by mass or more and less than 100% by mass. And the ninth, tenth, and eleventh
The equation shown in the solution means is that the refrigerant in the refrigerant circuit (20) is R
The present invention is applicable not only to the case of using a single refrigerant of 32 but also to the case of using a mixed refrigerant containing 75% by mass or more of R32.

[0043]

According to the present invention, the expansion valve (36) is taken into consideration in consideration of the refrigerant temperature discharged from the compressor (30) under the above-mentioned limit operating conditions.
Is determined. In other words, instead of selecting the expansion valve (36) in consideration of the rated capacity as in the past, consideration is given to operation under critical operating conditions where there is a great risk that the refrigerant discharged from the compressor (30) will excessively rise. The expansion valve (36) is selected.

Therefore, the expansion valve (36) having a flow coefficient capable of securing a sufficient amount of the circulating refrigerant even under the limit operation condition can be accurately selected from the beginning of the development. Therefore, even if the actual machine test is performed thereafter, it is sufficient to simply confirm that there is no problem, and the man-hour for selecting the expansion valve (36) by trial and error becomes almost unnecessary. As a result, the time required for selecting the expansion valve (36) can be significantly reduced, and the development cost can be reduced.

In particular, according to the ninth, tenth, and eleventh means for solving the problems, the expansion valve (36) having a flow coefficient capable of maintaining the temperature of the refrigerant discharged from the compressor (30) at a predetermined value or less even under the above-mentioned limit operating conditions. ) Can be accurately selected by performing an operation using a known value at the design stage. For this reason, the development man-hour of the refrigeration system (10) can be further reduced, and the development cost can be more reliably reduced.

[0046]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the present embodiment, the refrigeration apparatus according to the present invention is applied to an air conditioner (10). The air conditioner (10) switches between a cooling operation and a heating operation.

As shown in FIG. 1, the air conditioner (10)
A refrigerant circuit (20) is provided. This refrigerant circuit (20)
It is configured as a closed circuit and is filled with a single-component refrigerant composed of R32. Note that R32 is 7 for the refrigerant circuit (20).
A mixed refrigerant containing 5% by mass or more may be charged.

The refrigerant circuit (20) comprises an outdoor circuit (21),
It is composed of an indoor circuit (22), a liquid side communication pipe (23), and a gas side communication pipe (24). The outdoor circuit (21) is provided in an outdoor unit (11) that is an outdoor unit. This outdoor unit (11) is provided with an outdoor fan (12). On the other hand, the indoor circuit (22) is provided in an indoor unit (13) that is an indoor unit. This indoor unit (13)
An indoor fan (14) is provided. The liquid side communication pipe (23) and the gas side communication pipe (24) constitute a communication pipe.

The outdoor circuit (21) includes a compressor (30),
Four-way switching valve (33), outdoor heat exchanger (34), receiver (3
5) and an electric expansion valve (36) are provided. Also,
The outdoor circuit (21) includes a bridge circuit (40), a liquid-side stop valve (25), and a gas-side stop valve (26).

In the outdoor circuit (21), the compressor (3
The discharge port (32) of (0) is connected to the first port of the four-way switching valve (33). The second port of the four-way switching valve (33) is connected to one end of the outdoor heat exchanger (34).
The other end of the outdoor heat exchanger (34) is connected to a bridge circuit (40). The bridge circuit (40) includes a receiver (35), an electric expansion valve (36), and a liquid-side shutoff valve (2
5) and are connected. This will be described later. The suction port (31) of the compressor (30) is connected to the third port of the four-way switching valve (33). The fourth port of the four-way switching valve (33) is connected to the gas side shut-off valve (26).

The bridge circuit (40) is connected to the first conduit (4
1), the second pipe (42), the third pipe (43), and the fourth pipe (44) are connected in a bridge shape. In this bridge circuit (40), the outlet end of the first pipe (41) is connected to the outlet end of the second pipe (42), and the inlet end of the second pipe (42) is connected to the third pipe (43). ), And connected to the third pipe (4
The inlet end of 3) is connected to the inlet end of the fourth conduit (44),
The outlet end of the pipe (44) is connected to the inlet end of the first pipe (41).

Each of the first to fourth conduits (41 to 44) is provided with one check valve. The first conduit (41) is provided with a check valve (CV-1) that allows only the flow of the refrigerant from the inlet end to the outlet end. The second pipe (42) is provided with a check valve (CV-2) that allows only the flow of the refrigerant from the inlet end to the outlet end. Third pipe (4
3) is provided with a check valve (CV-3) that allows only the flow of the refrigerant from the inlet end to the outlet end. The fourth pipe (44) is provided with a check valve (CV-4) that allows only the flow of the refrigerant from the inlet end to the outlet end.

The other end of the outdoor heat exchanger (34) is connected to the inlet end of the first conduit (41) in the bridge circuit (40) and to the fourth end.
It is connected to the outlet end of the pipe (44). The outlet end of the first conduit (41) and the outlet end of the second conduit (42) in the bridge circuit (40) are connected to the upper end of a receiver (35) formed in a cylindrical container shape. The lower end of the receiver (35) is connected to a bridge circuit (4) via an electric expansion valve (36).
0) at the inlet end of the third conduit (43) and the fourth conduit (4
4) Connected to the inlet end. The inlet end of the second pipe (42) and the outlet end of the third pipe (43) in the bridge circuit (40) are connected to the liquid-side shutoff valve (25).

The indoor circuit (22) is provided with an indoor heat exchanger (37). One end of the indoor circuit (22) is connected to a liquid side closing valve (25) via a liquid side communication pipe (23). The other end of the indoor circuit (22) is connected to a gas-side shut-off valve (26) via a gas-side communication pipe (24). That is,
The liquid side communication pipe (23) and the gas side communication pipe (24) are provided from the outdoor unit (11) to the indoor unit (13). After the installation of the air conditioner (10), the liquid-side stop valve (25) and the gas-side stop valve (26) are always kept open.

The compressor (30) is of a closed type. Specifically, the compressor (30) includes a rolling piston-type compression mechanism and an electric motor that drives the compression mechanism housed in a cylindrical housing. The refrigerant sucked from the suction port (31) is directly introduced into the compression mechanism. The refrigerant compressed by the compression mechanism is once discharged into the housing and then sent out from the discharge port (32). The illustration of the compression mechanism and the electric motor is omitted.

Electric power is supplied to the electric motor of the compressor (30) through an inverter (not shown). When the output frequency of the inverter is changed, the number of revolutions of the motor changes, and the capacity of the compressor changes. That is, the compressor (30) has a variable capacity.

The outdoor heat exchanger (34) is composed of a cross-fin type fin-and-tube heat exchanger. The outdoor heat exchanger (34) has an outdoor fan (12)
Supplies outdoor air. This outdoor heat exchanger (3
4) heat exchange between the refrigerant in the refrigerant circuit (20) and the outdoor air. The outdoor heat exchanger (34) functions as a condenser during the cooling operation, and functions as an evaporator during the heating operation.

The indoor heat exchanger (37) is constituted by a cross-fin type fin-and-tube heat exchanger. The indoor heat exchanger (37) includes an indoor fan (14).
Supplies indoor air. This indoor heat exchanger (3
7) heat exchange between the refrigerant in the refrigerant circuit (20) and the indoor air. Further, the outdoor heat exchanger (34) functions as an evaporator during the cooling operation and functions as a condenser during the heating operation.

The four-way switching valve (33) has a state where the first port and the second port communicate with each other and the third port and the fourth port communicate with each other (a state shown by a solid line in FIG. 1). The state is switched to a state in which the first port and the fourth port communicate with each other and the second port and the third port communicate with each other (a state shown by a broken line in FIG. 1). By the switching operation of the four-way switching valve (33),
The direction of circulation of the refrigerant in the refrigerant circuit (20) is reversed.

-Operation-The operation of the air conditioner (10) will be described. The air conditioner (10) switches between the cooling operation and the heating operation by reversing the circulation direction of the refrigerant in the refrigerant circuit (20).

<< Cooling operation >> During the cooling operation, the four-way switching valve (33) is switched to the state shown by the solid line in FIG. 1, the electric expansion valve (36) is adjusted to a predetermined opening, and the outdoor fan (12) And the indoor fan (14) is operated. In this state, the refrigerant circulates in the refrigerant circuit (20), and the refrigeration cycle is performed using the outdoor heat exchanger (34) as a condenser and the indoor heat exchanger (37) as an evaporator.

Specifically, the discharge port (3) of the compressor (30)
The refrigerant discharged from 2) is sent to the outdoor heat exchanger (34) through the four-way switching valve (33). In the outdoor heat exchanger (34), the refrigerant radiates heat to outdoor air and condenses. The condensed refrigerant flows into the receiver (35) through the first pipe (41) of the bridge circuit (40). The refrigerant flowing out of the receiver (35) is decompressed by the electric expansion valve (36), and then flows from the third pipe (43) of the bridge circuit (40) to the liquid-side communication pipe (2).
It is sent to the indoor heat exchanger (37) through 3).

In the indoor heat exchanger (37), the refrigerant absorbs heat from indoor air and evaporates. That is, in the indoor heat exchanger (37), the indoor air taken into the indoor unit (13) radiates heat to the refrigerant. Due to this heat radiation, the temperature of the indoor air decreases, and low-temperature conditioned air is generated. The generated conditioned air is
The air is supplied from the indoor unit (13) to the room and used for cooling.

The refrigerant evaporated in the indoor heat exchanger (37) flows through the gas side communication pipe (24) and the four-way switching valve (33), and is sucked into the compressor (30) from the suction port (31). Compressor (3
0) compresses the sucked refrigerant and discharges it again (32)
Discharge from.

<< Heating Operation >> During the heating operation, the four-way switching valve (33) is switched to the state shown by the broken line in FIG. 1, the electric expansion valve (36) is adjusted to a predetermined opening, and the outdoor fan (12) And the indoor fan (14) is operated. In this state, the refrigerant circulates in the refrigerant circuit (20), and a refrigeration cycle is performed using the indoor heat exchanger (37) as a condenser and the outdoor heat exchanger (34) as an evaporator.

Specifically, the discharge port (3) of the compressor (30)
The refrigerant discharged from 2) is sent from the four-way switching valve (33) to the indoor heat exchanger (37) through the gas side communication pipe (24). In the indoor heat exchanger (37), the refrigerant radiates heat to the indoor air and condenses. In other words, in the indoor heat exchanger (37),
Indoor air taken into the indoor unit (13) is heated by the refrigerant. This heating raises the temperature of the indoor air,
Warm conditioned air is produced. The generated conditioned air is supplied indoors from the indoor unit (13) and used for heating.

The refrigerant condensed in the indoor heat exchanger (37) is transferred to the liquid side communication pipe (23) and the second pipe (42) of the bridge circuit (40).
And flows into the receiver (35). Receiver (35)
The refrigerant flowing out of the outlet is depressurized by the electric expansion valve (36), and then sent to the outdoor heat exchanger (34) through the fourth pipe (44) of the bridge circuit (40). In the outdoor heat exchanger (34), the refrigerant absorbs heat from outdoor air and evaporates.

The refrigerant evaporated in the outdoor heat exchanger (34) passes through the four-way switching valve (33) and is drawn into the compressor (30) from the suction port (31). The compressor (30) compresses the sucked refrigerant and discharges the refrigerant again from the discharge port (32).

-Selection of Electric Expansion Valve-The basic principle for selecting the electric expansion valve (36) of the refrigerant circuit (20) in the air conditioner (10) will be described. In the present embodiment, instead of determining the flow coefficient of the electric expansion valve (36) based on the rated cooling capacity (rated refrigeration capacity) as in the related art, the limit at which the discharged refrigerant temperature of the compressor (30) becomes the highest is set. The electric expansion valve (36) is selected by obtaining a flow coefficient such that the discharged refrigerant temperature is equal to or lower than the predetermined upper limit value even under the operating conditions.

The basic concept will be described. First, the relationship between the amount of refrigerant charged in the refrigerant circuit (20) and the dryness of the refrigerant at the inlet of the electric expansion valve (36) under marginal operation conditions, and the dryness of the refrigerant at the entrance of the electric expansion valve (36) under marginal operation conditions And the relationship between the refrigerant circulation amount in the refrigerant circuit (20),
The relationship between the refrigerant circulation amount in the refrigerant circuit (20) and the refrigerant temperature discharged from the compressor (30) is quantified. Then, based on these relationships, an expansion valve flow coefficient that can ensure a sufficient amount of refrigerant circulation is determined so that the discharge refrigerant temperature of the compressor (30) is maintained at or below the upper limit value even under the limit operating conditions. The electric expansion valve (36) is selected based on the value.

Here, the above-mentioned limit operation conditions are the following operation conditions. That is, the liquid side and gas side communication pipes (2
3, 24) is set to 30 m, and during the heating operation, the dry bulb temperature of the outdoor air is 21 ° C and the wet bulb temperature is 1
The operating conditions are such that the operating frequency of the compressor (30) is 5 ° C., the dry-bulb temperature of the indoor air is 28 ° C., and the operating frequency of the compressor (30) is the maximum frequency. The indoor and outdoor air conditions in the limit operation condition correspond to a so-called heating overload condition in which both the indoor air and the outdoor air have a relatively high temperature during the heating operation. The limit operating condition is an operating condition in which the temperature of the refrigerant discharged from the compressor (30) is the highest, and is an operating condition in which the refrigerant circulation amount in the refrigerant circuit (20) must be maximized.

The “relationship between the amount of refrigerant charged in the refrigerant circuit (20) and the dryness of the refrigerant at the inlet of the electric expansion valve (36) under the limit operating conditions” is represented as a graph shown in FIG. How FIG. 3 is obtained will be described.

The refrigerant charge in the refrigerant circuit (20) is divided by a predetermined reference refrigerant amount and generalized. The value obtained by dividing the refrigerant charge amount by the reference refrigerant amount is defined as a charge amount ratio. The reason why this filling ratio is used is to obtain an applicable relationship regardless of the capacity of the air conditioner (10).

Here, the reference refrigerant amount is as follows. That is, the liquid side and gas side communication pipes (23, 24)
Consider a refrigerant circuit assuming a length of 5 m, and use this as a reference circuit. When a refrigeration cycle is performed under predetermined standard operating conditions in this reference circuit, the electric expansion valve (3
6) The minimum amount of refrigerant that must be charged into the reference circuit in order for all the refrigerant to be in the liquid phase at the inlet is defined as the reference refrigerant amount. This reference refrigerant amount is obtained in advance by a test.

The above standard operating conditions are defined in JIS B 8615-
This corresponds to the standard cooling condition specified in 1: 1999. Specifically, during the cooling operation, the dry bulb temperature of the indoor air is 27 ° C., the wet bulb temperature is 19 ° C., the dry bulb temperature of the outdoor air is 35 ° C., and the operating frequency of the compressor (30) is the rated frequency. There are certain operating conditions.

On the other hand, the dryness of the refrigerant at the inlet of the electric expansion valve (36) under the above-mentioned limit operation conditions is extremely difficult to measure, and is quantified as follows.

When the refrigerant flowing through the electric expansion valve (36) is completely in a liquid phase (that is, the dryness is zero), the volume flow rate of the liquid refrigerant passing through the electric expansion valve (36) is represented by Q _L (m ³ / h). The liquid refrigerant quantity Q _L is calculated by Equation (1). Q _L = 2.736 · C _V (ΔP / G) ^1/2 Equation (1) C _V : Flow coefficient of electric expansion valve ΔP: Differential pressure before and after electric expansion valve (kPa) G: At inlet of electric expansion valve liquid refrigerant density (-) Further, the volume flow rate of refrigerant passing through the motor-operated expansion valve (36) and Q _F (m ³ / h) in certain operating conditions. This liquid refrigerant amount Q _F
Is determined by equation (2). Q _F = 3600 · V · x · η _V · ρ _S · ρ _L Equation (2) V: Cylinder volume of the compression mechanism in the compressor (m ³ ) x: Operating frequency of the compressor (1 / s) η _V : Volumetric efficiency of compression mechanism (-) ρ _S : Density of refrigerant sucked into compressor (kg / m ³ ) ρ _L : Density of refrigerant at inlet of electric expansion valve (kg / m ³ )

Under the above-mentioned limit operating conditions, the refrigerant circuit (20)
The experiment for performing the refrigeration cycle is performed by changing the refrigerant charge of the refrigerant circuit (20) as a parameter. Through this experiment, the values of ΔP, G, ρ _S , and ρ _L for each refrigerant charge amount are measured or calculated based on the measured values and the physical properties of the refrigerant. Then, the value obtained by dividing the Q _F in Q _L, i.e. the electric expansion valve (36) coolant volume flow at the inlet ratio Q _F / Q
_L is determined for each refrigerant charge.

[0079] On the other hand, as shown in FIG. 2, the liquid product ratio in the gas-liquid two-phase refrigerant is consistent with the refrigerant volumetric flow ratio Q _F / Q _L. This point is disclosed in “Refrigeration Mechanical Engineering Handbook” (5th edition), page 405, table 5.11, issued by Asakura Shoten. By using this relationship, a liquid volume ratio corresponding to each refrigerant charge, which is the above-mentioned experimental parameter, can be obtained. The liquid volume ratio of the gas-liquid two-phase refrigerant is a value obtained by dividing “the volume of the liquid refrigerant contained in the gas-liquid two-phase refrigerant” by “the total volume of the gas-liquid two-phase refrigerant”. Therefore, a liquid volume ratio of 1.0 means that all refrigerants are in a liquid phase,
A liquid volume ratio of zero means that all the refrigerant is in the gas phase.

If the liquid volume ratio of the gas-liquid two-phase refrigerant is obtained,
The dryness of the gas-liquid two-phase refrigerant can be calculated using equation (3). Dryness fraction _{= (1-α) ρ g} / [α · ρ l + (1-α) ρ g] ... Equation (3) alpha: Liquid product ratio [rho _l: Density of saturated liquid (kg / m ³⁾ ρ _g : Density of saturated gas (kg / m ³ )

From the above, it is possible to determine the dryness of the refrigerant corresponding to each of the refrigerant filling amounts, which are the above experimental parameters.
Then, as shown in FIG. 3, a relationship between the filling amount ratio and the dryness of the refrigerant at the inlet of the electric expansion valve (36) is obtained.

The above-mentioned “Electric expansion valve (3
6) The relationship between the dryness of the refrigerant at the inlet and the amount of refrigerant circulated in the refrigerant circuit (20) "is shown as a graph shown in FIG. 4. How FIG. 4 is obtained will be described.

As described above, the degree of dryness of the refrigerant at the inlet of the electric expansion valve (36) under the above-mentioned limit operation conditions is determined by the experiment under the above-mentioned limit operation conditions, the equations (1) to (3), and the relationship shown in FIG. Quantified based on

[0084] On the other hand, the refrigerant circulation amount in the refrigerant circuit (20) includes an electric expansion valve (36) all the refrigerant at the inlet is assumed to be a liquid phase, in the formula (1), C _V, [Delta] P, and G Is calculated by setting each value of. Here, the refrigerant circulation amount is expressed as a mass flow rate per hour. Also, in order to generalize regardless of the capacity of the air conditioner (10), a value obtained by dividing the refrigerant circulation amount by the rated cooling capacity is used. The rated cooling capacity is the cooling capacity obtained when the compressor (30) is operated at the rated frequency under the above-described standard cooling conditions, expressed in kW (kilowatt).

Then, as shown in FIG. 4, the flow coefficient C _V
Is used as a parameter to obtain the relationship between the dryness of the refrigerant at the inlet of the electric expansion valve (36) and the amount of refrigerant circulated per 1 kW of the rated cooling capacity. Here, the value of the flow coefficient C _V is also
It is generalized by dividing by the rated cooling capacity.

The “relationship between the amount of circulating refrigerant in the refrigerant circuit (20) and the temperature of refrigerant discharged from the compressor (30)” is represented by a graph shown in FIG. How FIG. 5 is obtained will be described.

The amount of circulating refrigerant in the refrigerant circuit (20) is calculated based on experiments under the above-mentioned limit operating conditions and on the basis of equation (1). Note that, also here, the refrigerant circulation amount is generalized by dividing by the rated cooling capacity. Meanwhile, the compressor (30)
Is derived based on known refrigerant physical properties in consideration of actual measured values obtained by experiments under the above-mentioned limit operating conditions and operating characteristics of the compressor (30) such as a compression ratio. Then, as shown in FIG. 5, the relationship between the refrigerant circulation amount per 1 kW of the rated cooling capacity and the temperature of the refrigerant discharged from the compressor (30) is obtained.

As described above, as shown in FIG. 3, FIG. 4, and FIG. 5, the above relation can be quantified. By using these relationships, as shown in FIG. 6, the relationship between the filling ratio and the refrigerant temperature discharged from the compressor (30) is quantified using the flow coefficient C _V per 1 kW of the rated cooling capacity as a parameter. it can.

Further, here, for the sake of convenience in determining the flow coefficient C _V of the electric expansion valve (36), the relationship of FIG. 6 is rewritten as shown in FIG. That is, the relationship is shown between the filling ratio X and the flow coefficient C _V per 1 kW of the rated cooling capacity, with the temperature of the refrigerant discharged from the compressor (30) as a parameter.

The relationship when the temperature of the refrigerant discharged from the compressor (30) is 125 ° C. is shown as a dashed line in FIG.
The flow coefficient C _V per 1 kW of the rated cooling capacity in this case is calculated by using the filling amount ratio X as (1.39816 · X ² −4.66544 ·
X + 4.48651) · 10 ^-2 Then, when a certain filling rate X is determined, a value obtained by multiplying the calculated value obtained by substituting the value of the filling rate X into the above equation by the cooling rated capacity of the air conditioner (10) is equal to or more than the value obtained. Electric expansion valve with flow coefficient (3
By selecting 6), the discharge refrigerant temperature of the compressor (30) is maintained at 125 ° C. or less even under the above-mentioned limit operating conditions.

The relationship when the discharge refrigerant temperature of the compressor (30) is 135 ° C. is shown as a solid line in FIG. 7, and in this case, the flow coefficient C _V per 1 kW of the rated cooling capacity.
Is calculated using the filling ratio X (1.20720 · X ² −4.21152 · X +
4.17078) · 10 ^-2 . Then, a certain filling amount ratio X
Is determined, the electric expansion valve having a flow coefficient equal to or greater than the value obtained by multiplying the calculated value obtained by substituting the value of the filling amount ratio X into the above equation and the rated cooling capacity of the air conditioner (10). By selecting (36), the temperature of the refrigerant discharged from the compressor (30) is maintained at 135 ° C. or less even under the above-mentioned limit operating conditions.

The relationship when the refrigerant temperature discharged from the compressor (30) is 145 ° C. is shown as a broken line in FIG. 7, and in this case, the flow coefficient C _V per 1 kW of the rated cooling capacity.
Is calculated using the filling ratio X (1.02443 · X ² −3.79638 · X +
3.88706) · 10 ^-2 Then, a certain filling amount ratio X
Is determined, the electric expansion having a flow coefficient equal to or higher than the value obtained by multiplying the calculated value obtained by substituting the value of the filling amount ratio X into the above equation by the rated cooling capacity value of the air conditioner (10). Valve (36)
Is selected, the temperature of the refrigerant discharged from the compressor (30) is maintained at 145 ° C. or lower even under the above-mentioned limit operating conditions.

The selection of the electric expansion valve (36) with reference to FIG. 7 will be described by way of an example. For example, an air conditioner having a rated cooling capacity of 14 kW, the reference refrigerant amount of 2.4 kg, and an additional charging amount of refrigerant of 0.24 kg when the length of the liquid side and gas side communication pipes (23, 24) is 30 m. In (10), consider the case where the electric expansion valve (36) is selected. In this case, even if 15% of the refrigerant charged in the refrigerant circuit (20) leaks, the compressor (30) under the above-mentioned limit operating conditions
Is required to be maintained at 135 ° C. or lower.

In this case, the filling ratio X is (2.4 + 0.24) ·
(1-0.15) /2.4 = 0.94. From the relationship shown by the solid line in FIG. 7, the value on the vertical axis when the filling ratio X is 0.94,
That is, when the flow coefficient C _V per 1 kW of the rated cooling capacity is read, it is 0.0128. Then, when this read value is multiplied by the rated cooling capacity, it becomes 0.0128 × 14 = 0.18. Therefore, if the motor-operated expansion valve (36) having a flow coefficient C _V of 0.18 or more is selected, the above-mentioned requirement is satisfied.

-Effects of Embodiment- In this embodiment, the compressor (3
The flow coefficient of the electric expansion valve (36) is determined in consideration of the discharged refrigerant temperature of 0). In other words, instead of selecting the motor-operated expansion valve (36) in consideration of the rated capacity as in the past, consideration is given to operation under critical operating conditions where there is a great danger that the refrigerant refrigerant discharged from the compressor (30) will rise excessively. The electric expansion valve (36) is selected.

Therefore, the electric expansion valve (36) having a flow coefficient capable of ensuring a sufficient refrigerant circulation amount even under the limit operation condition is
It will be possible to select accurately from the beginning of development. For this reason,
Even if the actual machine test is performed thereafter, it is sufficient to simply confirm that no problem occurs, and the man-hour for selecting the electric expansion valve (36) by trial and error becomes almost unnecessary. As a result, the time required for selecting the electric expansion valve (36) can be significantly reduced, and the development cost can be reduced.

In particular, according to the present embodiment, by using the relationship as shown in FIG. 7, for the air conditioner (10) having all the rated cooling capacities, the discharge refrigerant temperature of the compressor (30) can be obtained even under the above-mentioned limit operating conditions. It is possible to accurately select an electric expansion valve (36) having a flow coefficient capable of maintaining the pressure at or below a predetermined limit value from an early stage of development. For this reason, the number of development steps of the air conditioner (10) can be further reduced, and the development cost can be more reliably reduced.

In the present embodiment, the specific heat ratio is higher than that of R22, which has been conventionally used as a refrigerant.
R32 in which the temperature of the discharged refrigerant of 0) becomes high is used as the refrigerant. However, according to the present embodiment, as described above, it is possible to select the electric expansion valve (36) in consideration of the operation state under the above-mentioned limit operation condition. Therefore, even when such R32 is used as a refrigerant, it is possible to select an appropriate electric expansion valve (36), and to reduce the number of development steps and the development cost of the air conditioner (10). Can be.

Further, according to the present embodiment, the electric expansion valve (3) according to the rated cooling capacity of the air conditioner (10) to be designed is designed.
The flow coefficient of 6) can be assumed in advance. For this reason, the specification (flow coefficient) of the electric expansion valve (36) applied to each model can be assumed in advance corresponding to the product lineup of the air conditioner (10). Therefore, the electric expansion valve (36) of the specification corresponding to the product lineup of the air conditioner (10) can be preliminarily lined up, and the electric expansion valve (36) most suitable for the specification of each model can be selected. Becomes

-Modification of Embodiment-In this embodiment, the selection of the motor-operated expansion valve (36) has been described. However, the above-described selection method uses an expansion valve other than the motor-operated expansion valve (36), for example, a thermo-sensitive expansion valve. The present invention is also applicable to a type expansion valve.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an air conditioner according to an embodiment.

FIG. 2 is a relationship diagram showing a relationship between a refrigerant volume flow rate ratio and a liquid volume ratio of a gas-liquid two-phase refrigerant.

FIG. 3 is a relationship diagram showing a relationship between a filling ratio X and a refrigerant dryness before an electric expansion valve.

FIG. 4 shows the degree of dryness of refrigerant before an electric expansion valve, the amount of refrigerant circulated per 1 kW of rated cooling capacity, and 1 kW of rated cooling capacity.
It is a relationship diagram showing the relationship of the flow coefficient per hit.

FIG. 5 is a relationship diagram showing a relationship between a refrigerant circulation amount per 1 kW of rated cooling capacity and a refrigerant temperature discharged from a compressor.

FIG. 6 is a relationship diagram showing a relationship between a filling ratio X, a refrigerant discharge temperature of a compressor, and a flow coefficient per 1 kW of rated cooling capacity.

FIG. 7 is a relationship diagram showing a relationship between a charging rate X, a refrigerant discharge temperature of a compressor, and a flow coefficient per 1 kW of a rated cooling capacity.

[Explanation of symbols]

 (10) Air conditioner (refrigerator) (11) Outdoor unit (outdoor unit) (13) Indoor unit (indoor unit) (20) Refrigerant circuit (23) Liquid side communication pipe (communication pipe) (24) Gas side Connecting pipe (connecting pipe) (30) Compressor (36) Electric expansion valve

Claims (12)

[Claims] An indoor unit (13) and an outdoor unit (11) are connected by connecting pipes (23, 24) of a refrigerant circuit (20), and a refrigerant filled in the refrigerant circuit (20) is a compressor. (30) A refrigeration apparatus which circulates in the order of a condenser, an expansion valve (36), and an evaporator, wherein the length of the communication pipe (23, 24) is 30 m, and the length of the refrigeration apparatus is 30 m, which exchanges heat with a refrigerant in the evaporator. The dry-bulb temperature of 1 air is 21 ° C, the wet-bulb temperature is 15 ° C, the dry-bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 28 ° C, and the capacity of the compressor (30) is the maximum capacity. A refrigeration system in which the expansion valve (36) of the refrigerant circuit (20) is configured to have an expansion valve flow coefficient such that the refrigerant discharge temperature of the compressor (30) is maintained at 145 ° C. or less under the limit operation conditions. . 2. An indoor unit (13) and an outdoor unit (11) are connected by connecting pipes (23, 24) of a refrigerant circuit (20), and a refrigerant filled in the refrigerant circuit (20) is a compressor. (30) A refrigeration apparatus which circulates in the order of a condenser, an expansion valve (36), and an evaporator, wherein the length of the communication pipe (23, 24) is 30 m, and the length of the refrigeration apparatus is 30 m, which exchanges heat with a refrigerant in the evaporator. The dry-bulb temperature of 1 air is 21 ° C, the wet-bulb temperature is 15 ° C, the dry-bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 28 ° C, and the capacity of the compressor (30) is the maximum capacity. A refrigeration system in which the expansion valve (36) of the refrigerant circuit (20) is configured to have an expansion valve flow coefficient at which the temperature of refrigerant discharged from the compressor (30) is maintained at 135 ° C. or lower under the limit operation conditions. . 3. An indoor unit (13) and an outdoor unit (11) are connected by connecting pipes (23, 24) of a refrigerant circuit (20), and a refrigerant filled in the refrigerant circuit (20) is a compressor. (30) A refrigeration apparatus which circulates in the order of a condenser, an expansion valve (36), and an evaporator, wherein the length of the communication pipe (23, 24) is 30 m, and the length of the refrigeration apparatus is 30 m, which exchanges heat with a refrigerant in the evaporator. The dry-bulb temperature of 1 air is 21 ° C, the wet-bulb temperature is 15 ° C, the dry-bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 28 ° C, and the capacity of the compressor (30) is the maximum capacity. A refrigeration system in which the expansion valve (36) of the refrigerant circuit (20) is configured to have an expansion valve flow coefficient at which the refrigerant discharged from the compressor (30) is maintained at 125 ° C. or lower under the limit operation conditions. . 4. A refrigeration system in which a refrigerant filled in a refrigerant circuit (20) circulates in the order of a compressor (30), a condenser, an expansion valve (36), and an evaporator, wherein the refrigerant circuit (20) The expansion valve is derived based on a correlation between a charging ratio obtained by dividing a refrigerant charging amount of the compressor by a preset reference refrigerant amount, an expansion valve flow coefficient, and a refrigerant discharge temperature of the compressor (30). A refrigeration apparatus in which the expansion valve (36) of the refrigerant circuit (20) is configured to have a flow coefficient equal to or larger than the value of the flow coefficient. 5. An indoor unit (13) and an outdoor unit (11) are connected by connecting pipes (23, 24) of a refrigerant circuit (20), and a refrigerant charged in the refrigerant circuit (20) is a compressor. (30) A refrigeration apparatus which circulates in the order of a condenser, an expansion valve (36), and an evaporator, wherein the length of the communication pipe (23, 24) is 30 m, and the length of the refrigeration apparatus is 30 m, which exchanges heat with a refrigerant in the evaporator. The dry-bulb temperature of 1 air is 21 ° C, the wet-bulb temperature is 15 ° C, the dry-bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 28 ° C, and the capacity of the compressor (30) is the maximum capacity. The operating condition is defined as a critical operating condition, a charging ratio obtained by dividing the refrigerant charging amount of the refrigerant circuit (20) by a preset reference refrigerant amount, an expansion valve flow coefficient, and a compressor under the critical operating condition. (30) to have a flow coefficient equal to or greater than the value of the expansion valve flow coefficient derived based on the correlation with the discharged refrigerant temperature And a refrigeration system in which the expansion valve (36) of the refrigerant circuit (20) is configured. 6. An indoor unit (13) and an outdoor unit (11) are connected by connecting pipes (23, 24) of a refrigerant circuit (20), and a refrigerant filled in the refrigerant circuit (20) is a compressor. (30) A refrigeration apparatus that circulates in the order of a condenser, an expansion valve (36), and an evaporator, wherein the dry air temperature of the first air that exchanges heat with the refrigerant in the evaporator is 2
The operating conditions in which the wet bulb temperature is 7 ° C., the dry bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 35 ° C., and the capacity of the compressor (30) is a predetermined rated capacity are standard operating conditions. The refrigerant circuit (2
0) When the refrigeration cycle is performed under the standard operating conditions in the reference circuit, the refrigerant must be charged into the reference circuit in order to completely convert the refrigerant into a liquid phase at the inlet of the expansion valve (36) of the reference circuit. The amount is set in advance as a reference refrigerant amount, the length of the connection pipe (23, 24) is 30 m, the dry bulb temperature of the first air that exchanges heat with the refrigerant in the evaporator is 21 ° C., and the wet bulb temperature is 15 ° C. Operating conditions in which the dry-bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 28 ° C. and the capacity of the compressor (30) is the maximum capacity are defined as marginal operating conditions, and the refrigerant in the refrigerant circuit (20) An expansion valve flow derived based on a correlation between a charging ratio obtained by dividing the charging amount by the reference refrigerant amount, an expansion valve flow coefficient, and a refrigerant temperature discharged from the compressor (30) under the above-mentioned limit operating conditions. In order to have a flow coefficient equal to or greater than the coefficient value, the refrigerant circuit ( 20) expansion valve (3
6) The refrigeration system that is composed. 7. The refrigerating apparatus according to claim 1, wherein the refrigerant filled in the refrigerant circuit (20) is made of a substance having a specific heat ratio larger than that of R22. 8. The refrigeration apparatus according to claim 1, wherein the refrigerant filled in the refrigerant circuit (20) is a single refrigerant of R32. 9. The indoor unit (13) and the outdoor unit (11) are connected by connecting pipes (23, 24) of a refrigerant circuit (20), and the refrigerant filled in the refrigerant circuit (20) is a compressor. (30) A refrigeration apparatus that circulates in the order of a condenser, an expansion valve (36), and an evaporator, wherein the refrigerant filled in the refrigerant circuit (20) is constituted by a single refrigerant of R32, The dry bulb temperature of the first air that exchanges heat with the refrigerant in the evaporator is 2
The operating conditions in which the wet bulb temperature is 7 ° C., the dry bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 35 ° C., and the capacity of the compressor (30) is a predetermined rated capacity are standard operating conditions. The refrigerant circuit (2
0) When the refrigeration cycle is performed under the standard operating conditions in the reference circuit, the refrigerant must be charged into the reference circuit in order to completely convert the refrigerant into a liquid phase at the inlet of the expansion valve (36) of the reference circuit. The amount is set in advance as a reference refrigerant amount, the refrigeration capacity exhibited by the operation under the standard operating conditions in the refrigerant circuit (20) is defined as a rated refrigeration capacity (kW), and the flow coefficient of the expansion valve is The value obtained by dividing the refrigerant charging amount of the above by the reference refrigerant amount is represented by X, and the calculated value derived based on the equation (1.02443 · X ² −3.79638 · X + 3.88706) · 10 ⁻² is the above rating. A refrigeration system that has a value equal to or higher than the value obtained by multiplying the refrigeration capacity. 10. An indoor unit (13) and an outdoor unit (11) are connected by connecting pipes (23, 24) of a refrigerant circuit (20), and a refrigerant filled in the refrigerant circuit (20) is a compressor. (30) A refrigeration apparatus that circulates in the order of a condenser, an expansion valve (36), and an evaporator, wherein the refrigerant filled in the refrigerant circuit (20) is constituted by a single refrigerant of R32, The dry bulb temperature of the first air that exchanges heat with the refrigerant in the evaporator is 2
The operating conditions in which the wet bulb temperature is 7 ° C., the dry bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 35 ° C., and the capacity of the compressor (30) is a predetermined rated capacity are standard operating conditions. The refrigerant circuit (2
0) When the refrigeration cycle is performed under the standard operating conditions in the reference circuit, the refrigerant must be charged into the reference circuit in order to completely convert the refrigerant into a liquid phase at the inlet of the expansion valve (36) of the reference circuit. The amount is set in advance as a reference refrigerant amount, the refrigeration capacity exhibited by the operation under the standard operating conditions in the refrigerant circuit (20) is defined as a rated refrigeration capacity (kW), and the flow coefficient of the expansion valve is The value obtained by dividing the refrigerant charging amount of the above by the reference refrigerant amount is represented by X, and the calculated value derived based on the expression (1.20720 · X ² −4.21152 · X + 4.17078) · 10 ⁻² is the above-mentioned rating. A refrigeration system that has a value equal to or higher than the value obtained by multiplying the refrigeration capacity. 11. An indoor unit (13) and an outdoor unit (11) are connected by connecting pipes (23, 24) of a refrigerant circuit (20), and a refrigerant filled in the refrigerant circuit (20) is a compressor. (30) A refrigeration apparatus that circulates in the order of a condenser, an expansion valve (36), and an evaporator, wherein the refrigerant filled in the refrigerant circuit (20) is constituted by a single refrigerant of R32, The dry bulb temperature of the first air that exchanges heat with the refrigerant in the evaporator is 2
The operating conditions in which the wet bulb temperature is 7 ° C., the dry bulb temperature of the second air that exchanges heat with the refrigerant in the condenser is 35 ° C., and the capacity of the compressor (30) is a predetermined rated capacity are standard operating conditions. The refrigerant circuit (2
0) When the refrigeration cycle is performed under the standard operating conditions in the reference circuit, the refrigerant must be charged into the reference circuit in order to completely convert the refrigerant into a liquid phase at the inlet of the expansion valve (36) of the reference circuit. The amount is set in advance as a reference refrigerant amount, the refrigeration capacity exhibited by the operation under the standard operating conditions in the refrigerant circuit (20) is defined as a rated refrigeration capacity (kW), and the flow coefficient of the expansion valve is The value obtained by dividing the refrigerant charging amount of the above by the reference refrigerant amount is expressed as X, and the calculated value derived based on the expression (1.39816 · X ² −4.66544 · X + 4.48651) · 10 ^-2 is the above rating. A refrigeration system that has a value equal to or higher than the value obtained by multiplying the refrigeration capacity. 12. The refrigeration apparatus according to claim 8, 9, 10 or 11, wherein the refrigerant filled in the refrigerant circuit (20) is a mixture containing 75% by mass or more of R32 instead of a single refrigerant of R32. A refrigeration device composed of a refrigerant.