JPS6220463B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling a refrigeration cycle, for example, a refrigeration cycle of a room air conditioner, and more particularly to a method of controlling a refrigeration cycle with the aim of improving the coefficient of performance during intermittent operation. It is.

First, a conventional refrigeration cycle control method and its drawbacks will be explained using the refrigeration cycle of a room air conditioner as an example.

Figure 1 is a cycle configuration diagram of the refrigeration cycle of a room air conditioner. Figure 2 is a pressure balance diagram showing the pressure balance after the compressor is stopped. Figure 3 is the same as Figure 1. It is a Mollier diagram showing the operating point of such a refrigeration cycle.

In FIG. 1, a high-temperature, high-pressure gas refrigerant compressed by a compressor 1 exchanges heat with outside air in a condenser 2 and discharges the heat to the outside air, becoming a high-pressure liquid refrigerant. This high-pressure liquid refrigerant becomes a low-temperature two-phase refrigerant in the pressure reducer 3, exchanges heat with indoor air in the evaporator 4 to cool the room, and returns to the compressor 1 to complete the cycle.

If there is sufficient cooling capacity, the refrigeration cycle is operated intermittently, but conventionally, when the refrigeration cycle is stopped, the compressor 1 is stopped and at the same time the condensed water adhering to the evaporator 4 is stopped. The evaporator blower 6 was also stopped to prevent re-evaporation into the indoor air. Note that 5 is a condenser blower.

By the way, when the above-mentioned refrigeration cycle is in a steady operating state, for example, assuming that the compressor 1 is a high-pressure chamber type rotary compressor, the compressor 1
It is generally known that 70 to 75% of the amount of refrigerant sealed in the entire refrigeration cycle is collected on the high-pressure side from 1 to 3 to the pressure reducer 3.

Now, when the refrigeration cycle in the steady state of operation is stopped (that is, when the compressor 1 is stopped), the pressure 7 on the high pressure side becomes as shown in FIG.
It starts to descend from P _d , while the pressure decreaser
The pressure 8 on the low pressure side up to P _s begins to rise. Then, after a time t _b after the compressor 1 is stopped, the pressure 7 on the high pressure side and the pressure 8 on the low pressure side become the balance pressure P
Balance and become equal at _b . The time t _b from stopping the compressor 1 until pressure balance is normally 2.5 to 3 minutes, as the JIS startup test specifies 3 minutes.
It is set to 3 minutes.

When the operation of the refrigeration cycle is represented on the Mollier diagram in Figure 3, the compression process is from state 11 to state 12, the condensation process is from state 12 to state 13, the decompression process is from state 13 to state 14, and the evaporation process is from state 14. 14
, the state is 11. When the refrigeration cycle is stopped, the condensing pressure P _d and the evaporating pressure P _s each approach the balance pressure P _b . Also, the temperature on the high pressure side after pressure balance is between the compression end temperature T _d and the saturation temperature T _b at the balance pressure, so all the high pressure side is superheated gas refrigerant (refrigerant in range A in Figure 3). It will be filled with. At this time, the total amount of superheated gas refrigerant on the high pressure side is about 10 to 15% of the total, so 80 to 80% of the refrigerant that was on the high pressure side when operating in the steady state described above
This means that after the compressor 1 is stopped, 85% of the water has flowed into the low pressure side through the pressure reducer 3 before the pressure is balanced.

Most of the refrigerant flowing into the low pressure side is a low enthalpy liquid refrigerant, and its temperature is the saturation temperature of the pressure on the low pressure side, which is gradually increasing.

Therefore, although the liquid refrigerant flowing into the low pressure side can exchange heat with indoor air and can be used as cooling capacity, conventionally, as described above,
At the same time as the compressor 1 is stopped, the evaporator blower 6
Since the liquid refrigerant was also stopped, there was a drawback that the cooling capacity of the liquid refrigerant was not utilized at all.

The present invention eliminates the above-mentioned drawbacks of the prior art,
The purpose of the present invention is to provide a refrigeration cycle control method that effectively utilizes the cooling capacity of the refrigerant that flows into the low-pressure side after the compressor is stopped, and improves the coefficient of performance during intermittent operation.

A feature of the present invention is that in a method for controlling a refrigeration cycle that includes at least a compressor, a condenser, an evaporator, and an evaporator blower that blows air to the evaporator, during intermittent operation, after the compressor is stopped, the evaporator A method for controlling a refrigeration cycle in which an evaporator blower is operated only until the cooling capacity of the low-enthalpy refrigerant flowing into the evaporator becomes approximately equal to the cooling capacity due to re-evaporation of condensed water adhering to the evaporator. It is in.

More specifically, in the method of controlling the refrigeration cycle of a room air conditioner, during intermittent operation,
After the refrigeration cycle is stopped, the evaporator blower is operated only until the refrigerant temperature of the evaporator becomes approximately equal to the wet bulb temperature of the indoor air, and then the evaporator blower is stopped until the refrigeration cycle is restarted. This is designed to improve the coefficient of performance of the refrigeration cycle while minimizing re-evaporation of condensed water adhering to the evaporator into the indoor air.

Before entering into the description of the embodiments, the basic matters of the present invention will be explained using FIGS. 4 to 6.

Figures 4 to 6 are for explaining the basic matters of the present invention, and Figure 4 is for explaining the surface condition of the evaporator on the low pressure side after the compressor is stopped. The psychrometric diagram, Figure 5, is a cooling capacity change diagram showing the change in the cooling capacity of the refrigeration cycle when the evaporator blower continues to operate even after the compressor is stopped. FIG. 2 is a cooling capacity change diagram showing the cooling capacity shown in the figure divided into cooling capacity due to low enthalpy refrigerant flowing into the evaporator and cooling capacity due to re-evaporation of condensed water.

In FIG. 4, the vertical axis shows absolute humidity, the horizontal axis shows temperature, 9 shows the saturation line, and 10 shows the isohumid bulb temperature line.

When the compressor is stopped, the evaporator surface temperature increases from the temperature T _e in the steady operating state to the saturation temperature T _b of the refrigerant in the balanced state. When the compressor is stopped and the evaporator surface is wet with condensed water, the surface state moves from state a to state b (surface state at pressure balance) on the saturation line 9, and then dries. Then, along the isohumid bulb temperature line 10, the indoor air condition at that time reaches c. In this process, from state a to state d (evaporator surface temperature T _o at this time) where the absolute humidity is almost equal to the absolute humidity of state c, there is no re-evaporation of condensed water on the evaporator surface; Re-evaporation is performed from subsequent state d to state b.

In connection with the evaporator surface condition shown in Figure 4 above, the evaporator blower continues to operate even after the compressor is stopped, and the cooling capacity of the low enthalpy refrigerant that has flowed into the evaporator is utilized. FIG. 5 shows the change in cooling capacity of the refrigeration cycle.

In FIG. 5, the vertical axis is the cooling capacity, the horizontal axis is the time scale, and 15 indicates the change in the cooling capacity.

Range B of the cooling capacity 15 is the range of cooling capacity due to the low enthalpy refrigerant flowing into the evaporator from state a to state d in FIG. Range D, which is the sum of the cooling capacity by the low enthalpy refrigerant and the cooling capacity by re-evaporation of condensed water, is the range of the cooling capacity obtained by re-evaporation of condensed water in state b. Note that t _b is the time from when the compressor is stopped until the pressure is balanced.

FIG. 6 shows the cooling capacity shown in FIG. 5 divided into cooling capacity R due to low enthalpy refrigerant flowing into the evaporator and cooling capacity W due to re-evaporation of condensed water. In FIG. 6, the vertical axis represents cooling capacity, and the horizontal axis represents time.

The cooling capacity R due to the low enthalpy refrigerant flowing into the evaporator decreases with time, and the balance time t
It becomes zero at _b . In addition, the cooling capacity W due to re-evaporation of condensed water starts when the evaporator surface temperature reaches the temperature T _o (see Figure 4), and the time t _o has elapsed since the compressor stopped, and the evaporation This continues until the surface of the vessel is completely dry. The cooling capacity W obtained by reevaporation of this condensed water cannot be the actual cooling capacity because the condensed water needs to be recovered from the indoor air again when the refrigeration cycle is started next time.

Therefore, when the time integral value ∫ ^t ₀ (R-W) dt of the cooling capacity in Fig. 6 almost reaches the maximum, that is, d/dt ∫ ^t ₀ (R-W) dt = R-W≒0. Then, the maximum performance can be achieved by stopping the evaporator blower at the time t _f when the cooling capacity R due to the low enthalpy refrigerant flowing into the evaporator becomes almost equal to the cooling capacity W due to re-evaporation of condensed water. It can be seen that the coefficients are obtained.

For the reasons explained above, even after the compressor is stopped during intermittent operation, the cooling capacity of the low enthalpy refrigerant that flows into the evaporator is reduced by the re-evaporation of the condensed water adhering to the evaporator. By operating the evaporator blower only until the cooling capacity is approximately equal to the cooling capacity, the cooling capacity of the low enthalpy refrigerant can be used, the actual cooling capacity can be increased, and the coefficient of performance of the refrigeration cycle can be improved. .

Then, at the time t _f when the cooling capacity R of the low-enthalpy refrigerant flowing into the evaporator becomes equal to the cooling capacity W of the re-evaporation of condensed water, the refrigerant temperature T _R of the evaporator rises and the humidity of the indoor air increases. This is when the temperature matches the bulb temperature T _W .

Examples will be described below based on the basic matters of the present invention described above.

FIG. 7 is a block diagram of a control device used to implement a method for controlling the refrigeration cycle of a room air conditioner stationer according to an embodiment of the present invention, and FIG. It is a coefficient of performance diagram showing the coefficient of performance of the implemented refrigeration cycle in comparison with the coefficient of performance of the refrigeration cycle that implemented the conventional control method.

In FIG. 7, 16 is a thermistor-type device that is installed on the windward side of the evaporator so as not to touch the evaporator and so that condensed water is constantly replenished, and that detects the wet bulb temperature of the indoor air. wet bulb temperature detector,
17 is an A/D that converts the indoor air wet bulb temperature T _W detected by the wet bulb temperature detector 16 into a digital signal;
A converter 18 is a thermistor-type refrigerant temperature detector that is installed in a heat-insulated manner on a part of the refrigerant pipe of the evaporator that does not have fins and detects the refrigerant temperature of the evaporator, and 19 is a refrigerant temperature detector 18. Converts the refrigerant temperature T _R of the evaporator detected by A/ to a digital signal.
A D converter 20 compares the digital signals from both A/D converters 17 and 19, and calculates T within a predetermined error range.
a comparator 21 which emits a signal when _W matches T _R (i.e. when T _R becomes approximately equal to T _W );
is a microcomputer that issues a relay cutoff signal in response to a signal from the comparator 20, and 22 is a relay that stops the evaporator blower 6 in response to a relay cutoff signal from the microcomputer 21.

With this configuration, the evaporator blower 6
does not stop when the compressor (not shown) is stopped, and the refrigerant temperature T _R of the evaporator detected by the refrigerant temperature sensor 18 rises, causing the indoor air humidity detected by the wet bulb temperature sensor 16 to rise. It stops when the temperature almost matches the bulb temperature T _W . That is, the evaporator blower 6 stops after approximately time t _f (see FIG. 6) has elapsed since the compressor stopped.

When the coefficient of performance of the refrigeration cycle controlled in this way is compared with that of the conventional refrigeration cycle, the 8th
It will look like the figure.

In Fig. 8, the horizontal axis represents operating time/(operating time + stop time), and the vertical axis represents the coefficient of performance during intermittent operation/the coefficient of performance during continuous operation. The coefficients are shown as solid lines. On the other hand, when the conventional refrigeration cycle compressor is stopped and the evaporator blower is stopped at the same time, the coefficient of performance is as shown by the broken line. In either case, the coefficient of performance decreases as the operating time ratio decreases, but in this example, the rate of decrease is small;
This has the desired effect.

As described in detail above, according to the present invention, in a method for controlling a refrigeration cycle that includes at least a compressor, a condenser, an evaporator, and an evaporator blower that blows air to the evaporator, the compressor is not operated during intermittent operation. After the evaporator is stopped, the evaporator blower is operated only until the cooling capacity of the low enthalpy refrigerant that has flowed into the evaporator becomes approximately equal to the cooling capacity of the re-evaporation of condensed water adhering to the evaporator. Therefore, it is possible to provide a refrigeration cycle control method that effectively utilizes the cooling capacity of the refrigerant that flows into the low-pressure side after the compressor is stopped and improves the coefficient of performance during intermittent operation.

[Brief explanation of the drawing]

Figure 1 is a cycle configuration diagram of the refrigeration cycle of a room air conditioner. Figure 2 is a pressure balance diagram showing the pressure balance after the compressor is stopped. Figure 3 is the same as Figure 1. The Mollier diagram and FIGS. 4 to 6 showing the operating points of the refrigeration cycle are for explaining the basic matters of the present invention,
Figure 4 is an psychrometric diagram to explain the surface condition of the evaporator on the low-pressure side after the compressor has been stopped, and Figure 5 is the operation of the evaporator blower even after the compressor has been stopped. Fig. 6 is a cooling capacity change diagram showing changes in the cooling capacity of the refrigeration cycle when the refrigeration cycle is continued. FIG. 7, which is a cooling capacity change diagram divided into cooling capacities due to water re-evaporation, is a diagram showing cooling capacity changes according to an embodiment of the present invention.
A block diagram of a control device used to implement a method for controlling the refrigeration cycle of a room air conditioner,
FIG. 8 is a coefficient of performance diagram showing a comparison of the coefficient of performance of a refrigeration cycle using the control method according to FIG. 7 with that of a refrigeration cycle using a conventional control method. 1... Compressor, 2... Condenser, 4... Evaporator, 6... Evaporator blower, 16... Wet bulb temperature detector, 18... Refrigerant temperature detector, 22... Relay.

Claims (1)

[Scope of Claims] 1. A method for controlling a refrigeration cycle equipped with at least a compressor, a condenser, an evaporator, and an evaporator blower for blowing air to the evaporator, wherein during intermittent operation, after stopping the compressor, The evaporator blower is operated only until the cooling capacity of the low-enthalpy refrigerant flowing into the evaporator becomes approximately equal to the cooling capacity of the re-evaporation of condensed water adhering to the evaporator. refrigeration cycle control method. 2. The evaporator blower is operated only after the compressor is stopped until the temperature of the refrigerant in the evaporator becomes approximately equal to the wet bulb temperature of indoor air. refrigeration cycle control method.