JPH062960A - Refrigerating cycle apparatus - Google Patents

Abstract

PURPOSE:To provide a refrigerating cycle apparatus in which excellent coefficient of performance can be realized by regulating subcooling degree to a suitable range irrespective of a load change (refrigerant flow rate change). CONSTITUTION:Load detecting means 9 detects a magnitude of a room cooling load. Subcooling degree control means 6 drives heat absorption control means (damper in this case) 8 in response to the detected magnitude of the load to control heat absorption degree of a condenser 2 to a suitable level (e.g. a range of excellent coefficient of performance or gas refrigerant input preventing range of expansion means).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration cycle apparatus, and more particularly to a refrigeration cycle having no liquid receiver or accumulator tank. (Hereinafter, this is referred to as a receiverless refrigeration cycle).

[0002]

2. Description of the Related Art In a vehicle refrigeration cycle, in a receiver type refrigeration cycle apparatus having a receiver between a condenser and an expansion means, the receiver has a gas-liquid two-phase and only a saturated liquid refrigerant is expanded. Since it is flowing to the means, the degree of subcooling (subcool) before the expansion means is always 0 ° C.

On the other hand, in a receiverless type refrigeration cycle device in which the above receiver is omitted, the subcool is the amount of filled refrigerant,
The coefficient of performance COP fluctuates depending on the refrigerant flow rate of the system (pressure state of the system), the cycle locus on the Mollier diagram changes according to the fluctuation of the subcool, and the coefficient of performance COP fluctuates.

[0004]

In the receiver type refrigeration cycle apparatus described above, since subcooling is not performed (the condenser outlet is on the saturated liquid line), the coefficient of performance is improved by the subcooling even if the refrigerant flow rate fluctuates. I couldn't. In the receiverless refrigeration cycle apparatus, the subcool changes depending on the refrigerant flow rate, and as a result, a good coefficient of performance COP is obtained in a certain subcool range, but there is a problem that the coefficient of performance COP decreases in other subcool ranges. I understood it.

An object of the present invention is to provide a refrigeration cycle apparatus which can realize an excellent coefficient of performance regardless of load fluctuation (refrigerant flow rate fluctuation).

[0006]

A refrigeration cycle apparatus of the present invention is a refrigeration cycle apparatus including a compressor, a condenser, an expansion means and an evaporator, and an endothermic control means for controlling the endothermic ability of the evaporator, Load detection means for detecting the load,
According to the detected load, the heat absorption control means is drive-controlled to adjust the supercooling degree of the condenser to an appropriate level.

In a preferred mode, the heat absorption control means comprises a damper arranged in front of the evaporator. Here, the suitability level refers to a range in which the coefficient of performance is good or a range in which the gas refrigerant can be prevented from flowing into the expansion means.

[0008]

The load detecting means detects the magnitude of the load, and the supercooling degree controlling means drives the heat absorption controlling means according to the detected load magnitude to control the heat absorbing ability of the evaporator. As a result, the degree of supercooling of the condenser can be adjusted to an appropriate level (for example, the good coefficient of performance range or the expansion means gas refrigerant inflow prevention range).
Adjust to.

The inventors of the present invention have experimentally found that the load (refrigerant flow rate), the subcool (supercooling degree), and the coefficient of performance COP are correlated with each other, and the coefficient of performance COP is highest at each load (refrigerant flow rate) level. Subcool has found different things. According to the present invention, the subcool is changed according to the fluctuation of the load (refrigerant flow rate) so that the coefficient of performance COP is always maintained at a good level. This causes load fluctuations (refrigerant flow rate fluctuations)
Regardless of which, a good coefficient of performance can always be achieved.

Further, according to the present invention, the subcool is controlled by controlling the heat absorption capacity of the evaporator. If you do this,
For example, there is an advantage that the structure can be simplified as compared with adjusting the subcool on the condenser side.

[0011]

FIG. 1 shows an embodiment of the refrigeration cycle apparatus of the present invention.
Shown in. This refrigeration cycle apparatus is of a receiverless type, and comprises a vehicle engine driven compressor 1, a condenser 2, an expansion valve 3, an evaporator 4 and a compressor 1 which are connected by a refrigerant pipe. It constitutes a part. The compressor 1 is of fixed capacity type, but may be of variable capacity type.

At the outlet of the evaporator 4, a temperature sensitive cylinder 5 for detecting the temperature of the refrigerant is provided, and the temperature sensitive cylinder 5 detects the temperature of the refrigerant at the outlet of the evaporator 4. The detected change in the refrigerant temperature is converted into a change in the pressure of the refrigerant enclosed in the tube 51, and the diaphragm type expansion valve 3 is controlled by the change in the pressure to superheat the refrigerant SH from the evaporator 4.
Is controlled to a predetermined set value. If the superheat degree SH is lower than the set value, the expansion valve 3 is throttled, whereby the evaporator 4
The amount of refrigerant flowing into the evaporator 4 is reduced, the amount of liquid refrigerant stored in the evaporator 4 is reduced, and 100% of the gas refrigerant is discharged at the outlet of the evaporator 4.
And the superheat degree SH becomes a predetermined value. On the contrary, the degree of superheat SH
Is higher than a set value (for example, 0 to several degrees Celsius), the expansion valve 3 is opened, whereby the amount of refrigerant flowing into the evaporator 4 is increased, and the amount of liquid refrigerant stored in the evaporator 4 is increased. -The liquid refrigerant reaches the vicinity of the outlet of the evaporator 4, and the evaporator 4
The degree of superheat SH at the outlet of is decreased.

A technique for adjusting the opening degree of the expansion valve 3 according to the refrigerant condition at the outlet of the evaporator 4 to maintain the superheat degree SH at the outlet of the evaporator 4 at a constant level is well known, and a further addition is made. The description is omitted. The feature of this embodiment is that a damper (load detecting means in the present invention) 8 is provided in front of the evaporator 4 in the air-conditioning duct 7, and a load sensor (heat absorption in the present invention) formed of a pressure sensor is provided at the outlet of the condenser 2. A control means 9 is provided, and the controller (subcooling degree control means in the present invention) 6 controls the opening and closing of the damper 8 according to the output signal of the load sensor 9.
The damper 8 is a rotary damper driven by a motor (not shown), and when the damper 8 is closed, the wind to the upstream half of the evaporator 4 is shut off.

The control operation of the controller 6 will be described below with reference to the flowchart of FIG. First, the pressure Pc at the outlet of the condenser 2 is determined by the output signal of the load sensor 9.
Is read (100). Next, read capacitor 2
It is checked whether the pressure Pc at the outlet of the valve is less than or equal to a predetermined value Pct (104), and if it is less than that, the damper 8 is closed (106) as a low load (low refrigerant flow rate) and the process returns to step 100. Return to 100. When the damper 8 is closed, the evaporation capacity of the evaporator 4 is reduced and the amount of liquid refrigerant stored in the evaporator 4 is increased.
As a result, the amount of liquid refrigerant stored in the condenser 2 is reduced, which reduces the liquid cooling capacity of the condenser 2, and as a result, the subcool (degree of supercooling) of the liquid refrigerant discharged from the condenser 2 is reduced.

That is, in this embodiment, when the load (refrigerant flow rate) is small and the condensing pressure of the condenser 2 is low, the damper 8 is closed to reduce the heat absorption capacity of the evaporator 4, and thereby the evaporator 4 is reduced. The amount of liquid refrigerant stored in the condenser 2 is reduced, the amount of liquid refrigerant stored in the condenser 2 is reduced, and the liquid cooling capacity of the condenser 2 is reduced.
The sub-cooling of the liquid refrigerant that comes out is reduced.

In this way, low load (low refrigerant flow rate)
The coefficient of performance COP of the cycle can be improved. Next, the magnitude of the load (refrigerant flow rate) and the coefficient of performance C
The relationship between OP and subcool (supercooling degree) will be described in detail below. First, the relationship between the load (cooling load) and the refrigerant flow rate will be described.

If the load increases, the evaporation rate will increase accordingly.
The amount of refrigerant evaporated in the evaporator 4 increases, the outlet pressure of the evaporator 4 increases, and the outlet pressure of the condenser 2 increases. The refrigerant flow rate increases in proportion to the pressure increase. Therefore, if the pressure Pc at the outlet of the condenser 2 is detected, the load (refrigerant flow rate)
I understand. The load may be detected by the pressure of other parts, or can be estimated by detecting the temperature.

Next, the relationship between the subcool and the amount of refrigerant stored in the condenser 2 and the evaporator 4 will be described. The subcool is generated by supercooling the condensed liquid refrigerant on the downstream side of the condenser 2 (or on the subcool condenser additionally provided on the downstream side of the condenser 2). Therefore, it is understood that the subcool (degree of subcooling) depends on the amount of liquid refrigerant that accumulates in the downstream of the condenser 2. In the receiverless type refrigeration cycle apparatus, the refrigerant storage amount of the condenser 2 can be controlled by adjusting the refrigerant storage amount of the evaporator 4, and by adjusting the refrigerant storage amount of the evaporator 4. The subcool can be adjusted.

Next, the relationship between the subcool, the coefficient of performance COP, and the load (refrigerant flow rate) will be described. According to the experiment, as shown in FIG. 3, the subcool at the highest value of the coefficient of performance COP varies depending on the size of the load, and the subcool at the highest coefficient of performance COP is small at low load and large at high load. Further, for example, when R134a is used as the refrigerant, the subcool at the highest coefficient of performance COP is, for example, 2 when the load is low.
It was found that the temperature was up to 3 ° C., for example, 8 ° C. under medium load, and 15 to 16 ° C. under high load.

That is, since the condensing temperature in the condenser 2 is sufficiently high at the time of high load (large refrigerant flow rate) shown by the solid line in the Mollier diagram of FIG. 4, the subcool is set to be large so that the heat absorption amount Q1 per same work amount AL1. Is increased and the coefficient of performance is improved. However, even in this case, the refrigerant temperature itself at the outlet of the condenser 2 has a limit due to heat transfer conditions such as cooling air temperature. Therefore, in order to increase the subcool, the condensing pressure of the condenser 2 must be increased. , If the subcool is made too large, the work A of the compressor 1
L1 increases, and the coefficient of performance COP = heat absorption amount Q1 / AL1 decreases. That is, when the load is high, the coefficient of performance CO
There is a subcool value that maximizes P.

Similarly, at a low load (small refrigerant flow rate) indicated by a broken line in the Mollier diagram of FIG. 4, if the subcool is increased, the heat absorption amount Q2 per work amount AL2 is improved and the coefficient of performance is improved. However, even in this case, the refrigerant temperature at the outlet of the condenser 2 itself has a limit due to heat transfer conditions such as cooling air temperature, and therefore the condensing temperature (ie, condensing pressure) of the condenser 2 must be increased in order to increase the subcool. As a result, the work amount AL2 of the compressor 1 increases,
The coefficient of performance COP = heat absorption Q2 / AL2 decreases. After all, since the condensation temperature itself of the condenser 2 is low at a low load (small refrigerant flow rate), the burden of increasing the condensation pressure and the work amount AL2 of the compressor 1 to increase the heat absorption amount Q2 by the sub-cooling is large. At a lower subcool value, the coefficient of performance COP = heat absorption amount Q2 / AL2 is the highest.

When the experimental results shown in FIG. 3 are summarized, the coefficient of performance C
The maximum value of OP becomes one characteristic line L in which the subcool increases in proportion to the increase of the load (refrigerant flow rate) (see FIG. 5). Here, if the subcool value at the time of high load (large refrigerant flow rate) is adjusted so that the coefficient of performance COP becomes the highest by adjusting the amount of refrigerant charged in the cycle, the load (refrigerant is As the flow rate decreases, the subcool deviates from the maximum coefficient of performance line L as shown by the broken line L'in FIG. In other words, since the liquid refrigerant is sufficiently stored in the condenser 2, the subcool is large,
The condensation pressure of the condenser 2, that is, the compressor 1
Has a large amount of work.

The present embodiment has been made in order to solve this problem. When the load is lower than a predetermined value, the damper 8 is closed to increase the amount of liquid refrigerant stored in the evaporator 4, thereby increasing the amount of the condenser 2. The amount of liquid refrigerant stored is reduced, the subcool of the condenser 2 is reduced, the condensing pressure of the condenser 2 is reduced, the work of the compressor 1 is reduced, and the coefficient of performance COP is kept at the maximum value.

The amount of heat transfer area reduction by shutting off the evaporator 4 by the damper 8 is limited to such an extent that the subcool at the time of low load is excessively reduced and bubbles are not mixed in the expansion valve 3. 6 shows the internal state of the evaporator 4 when the damper 8 is open, and FIG. 7 shows the internal state of the evaporator 4 when the damper 8 is closed. The load (refrigerant flow rate) may be detected by detecting the pressure or temperature of discharge or suction of the compressor 1 or by detecting the outlet temperature of the condenser 2.

From another point of view of the operation of this embodiment, assuming that the refrigerant flow rate that achieves the highest coefficient of performance COP at low load (small refrigerant flow rate), the liquid in the condenser 2 at high load (large refrigerant flow rate). By opening the damper 8, the drawback of the prior art that the amount of refrigerant storage is reduced, the subcool cannot be sufficiently taken, and the temperature of the liquid refrigerant in front of the expansion valve 3 cannot be sufficiently lowered is solved. (Modification) Another embodiment is shown in FIG. In this mode, a film damper 9 is used instead of the damper 8.

The film type damper 9 has winding rollers 91 and 92 driven by a motor (not shown), and a film 9 having both ends fixed to the winding rollers 91 and 92.
3 and the film 93 is an opening window 9 for predetermined ventilation.
Have four. The motor is driven according to the load by the controller 6 shown in FIG.
Thus, the winding amount of the film 93 is adjusted, and the area in which the opening window 94 overlaps the evaporator 4 is adjusted. By doing so, the heat transfer area of the evaporator 4 can be linearly changed, and the highest coefficient of performance COP can always be achieved. That is, the overlapping area between the evaporator 4 and the opening window 94 may be increased as the load (refrigerant flow rate) is reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a refrigeration cycle device of the present invention,

2 is a flowchart showing the operation of the controller of FIG.

FIG. 3 is a characteristic diagram showing the relationship between load, coefficient of performance, and subcool,

4 is a Mollier diagram of the refrigeration cycle apparatus of FIG. 1,

FIG. 5 is a characteristic diagram showing the relationship between load, coefficient of performance, and subcool,

FIG. 6 is a state diagram showing a state inside the evaporator when the damper is opened,

FIG. 7 is a state diagram showing a state inside the evaporator when the damper is closed,

FIG. 8 is a block diagram showing another aspect,

[Explanation of symbols]

1 is a compressor, 2 is a condenser (condenser), 3 is expansion means (expansion valve), 4 is an evaporator (evaporator), 5 is a sensor, 6 is a controller (supercooling degree control means), and 8 is a damper. (Heat absorption control means), 9 is a load sensor (load detection means)

Claims (2)

[Claims] 1. A refrigeration cycle apparatus comprising a compressor, a condenser, an expansion means and an evaporator, an endothermic control means for controlling the endothermic ability of the evaporator, a load detecting means for detecting a load, and a detected load. And a subcooling degree control means for driving and controlling the heat absorption control means to adjust the subcooling degree of the condenser to an appropriate level. 2. The refrigeration cycle apparatus according to claim 1, wherein the heat absorption control means comprises a damper arranged on the front surface of the evaporator.