JP2000292025A - Air conditioning system and method for removing gas pool - Google Patents

Abstract

(57) [Summary] In an air conditioning system utilizing natural circulation at least during cooling, when the cooling operation is stopped and then restarted, the time required until cool air is blown out is reduced. SOLUTION: A gas pool removing method in an air conditioning system including a refrigerant circulation system in which an indoor unit and a condenser disposed at a higher position than the indoor unit are connected by a refrigerant liquid pipe and a refrigerant gas pipe. The pressure on the upstream side of the expansion valve provided near the inlet of the refrigerant liquid pipe to the indoor unit is monitored while the cooling operation is stopped. When the pressure becomes lower than the predetermined pressure value, the gas reservoir generated in the refrigerant liquid pipe is removed by opening the expansion valve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioning system utilizing the natural circulation of a refrigerant. More specifically, the present invention relates to an air conditioning system that utilizes natural circulation of a refrigerant at least at the time of cooling, and a gas pool removing method thereof.

[0002]

2. Description of the Related Art As an air conditioning system utilizing the natural circulation of a refrigerant, there is known an air conditioning system schematically shown in FIG. This system includes a refrigerant circulation system in which an indoor unit disposed in each room and an outdoor unit (condenser) 1 provided at a higher position than the indoor unit are connected by refrigerant liquid piping and refrigerant gas piping.

[0003] Refrigerant gas evaporated in an evaporator (not shown) in the indoor unit and deprived of heat in the room rises to the condenser 1 at a high place by the gas pressure. The refrigerant gas is liquefied by discarding heat in the condenser 1 and moves to each indoor unit at a low place by gravity.

In the case of performing air conditioning using the natural circulation of such a refrigerant, generally, when refrigerant liquid enters the refrigerant gas pipe, defective circulation of the refrigerant is caused, and the system does not operate normally. Accordingly, in order to prevent this, in each indoor unit, control as shown in the flowchart of FIG. 2 is performed. This will be described below.

The temperature inside the refrigerant liquid pipe (TL) and the temperature inside the refrigerant gas pipe (TG) are measured by the temperature sensors T provided at the entrance and exit of each indoor unit shown in FIG. 1 (# 1). When the difference (TG-TL) between the measured values is equal to or less than a predetermined value Z (for example, 5 ° C.), it is determined that the refrigerant liquid has entered the gas pipe (the reason will be described later), and the expansion valve is closed. To prevent the coolant liquid from entering the gas pipe any more (# 2 → # 3).
If the difference between the predetermined values is larger than Z, it is considered that the system is operating normally, and the expansion valve is kept open to continue the cooling operation (# 2 → # 4).

In # 2, if TG-TL is equal to or less than the predetermined value Z, the reason for judging that "the refrigerant liquid has entered the gas pipe" is as follows. That is, if no refrigerant liquid has entered the refrigerant gas pipe, the temperature (TG) in the refrigerant gas pipe should be higher than the saturation temperature and therefore higher than the temperature (TL) in the refrigerant liquid pipe. Conversely, if the refrigerant liquid enters the refrigerant gas pipe,
Since the refrigerant liquid having a temperature equal to or lower than the saturation temperature is mixed, the temperature is reduced by that amount. Therefore, if TG-TL is equal to or less than the predetermined value Z, it is determined that the refrigerant liquid has entered the gas pipe.
The predetermined value Z is set according to individual conditions in consideration of a pressure difference between the two pipes, errors of various sensors, and the like.

Although FIG. 1 shows only a refrigerant circulation system in which the refrigerant circulates during cooling, a heating medium circulation system in which a heat medium used during heating circulates is additionally provided. When the heating operation is also performed using natural circulation, an evaporator is provided at a lower place for each indoor unit, and this evaporator and the indoor unit are connected by a heat medium liquid pipe and a heat medium gas pipe. By doing so, a heat medium circulation system is configured.

In the refrigerant circulation system, while the cooling operation of the lowermost indoor unit 2 is stopped (that is, the indoor unit 2
Even when the cooling water is completely stopped or during the heating operation), the pressure in the condenser 1 becomes relatively low because the cooling water is circulating in the condenser 1 provided above.
For this reason, the drop of the refrigerant liquid from the condenser 1 at a high place becomes insufficient, and as a result, in the region 3 near the inlet to the indoor unit 2 in the refrigerant liquid pipe, a gas pool is generated due to a pressure drop. Sometimes. When such gas accumulation occurs, the liquid head pressure drops, and even if the cooling operation is restarted, it takes a long time before the cool air is blown out.

[0009]

Accordingly, a technical problem to be solved by the present invention is that at least in an air-conditioning system utilizing natural circulation at the time of cooling, when the cooling operation is stopped and then restarted, the cooling air is blown out. It is to reduce the required time.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in order to effectively solve the above-mentioned problems.
An "air conditioning system" and a "gas pool removal method" having the following features are provided.

That is, the air-conditioning system of the present invention comprises an "indoor unit" and a "condenser located higher than the indoor unit".
It includes a refrigerant circulation system connected by a “refrigerant liquid pipe” and a “refrigerant gas pipe”. And, "detection means for detecting whether or not the cooling operation is actually operating" and "the refrigerant liquid piping are provided on the upstream side of the expansion valve provided near the inlet to the indoor unit, and the refrigerant liquid piping "A pressure sensor for measuring pressure" and "comparison means for comparing the pressure measured by the pressure sensor with a predetermined pressure value when it is determined that the cooling operation is not actually performed by the detection means" and "comparison by the comparison means. Valve opening means for opening the expansion valve when it is determined that the pressure is lower than the predetermined pressure. "

In this system, "the pressure on the upstream side of the expansion valve provided near the inlet of the refrigerant liquid piping to the indoor unit is
During the cooling operation is stopped, monitoring is performed, and when the pressure becomes lower than a predetermined pressure value, the expansion valve is opened, thereby removing a gas pool generated in the refrigerant liquid pipe. it can.

Therefore, when the cooling operation utilizing the natural circulation of the refrigerant is stopped (ie, when the indoor unit is completely stopped or when the indoor unit is performing the heating operation), the refrigerant liquid pipe If a gas reservoir occurs upstream of the expansion valve provided near the entrance to the indoor unit, the gas reservoir is quickly removed by opening the expansion valve,
Next, when restarting the cooling operation, a sufficient liquid head pressure is secured at the position of the expansion valve. Therefore, when the cooling operation is restarted, the time required until the cool air is actually blown can be reduced as compared with the conventional case.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 3 is a schematic diagram showing an air conditioning system showing one embodiment of the present invention, and corresponds to FIG. The difference from the conventional example of FIG. 1 is that a pressure sensor P for detecting the pressure in the refrigerant liquid pipe is provided near the entrance to the indoor unit 21 located at the lowest position.

Although not shown, the air-conditioning system also has a circulation system for heating by natural circulation. Therefore, an evaporator (not shown) is located at a position lower than the indoor unit 21. Is installed. FIG. 4 shows a control flowchart in this system.

First, it is confirmed at # 11 whether "cooling mode" or "heating mode" is selected as the operation mode of the indoor unit 21. The present invention monitors the pressure on the upstream side of the expansion valve in the refrigerant liquid pipe while the cooling operation is stopped, and opens the expansion valve when the pressure decreases to a degree that would cause gas accumulation. The accumulated gas is released to the indoor unit side. Therefore, "cooling mode is confirmed at $ 11" and "the indoor unit fan is ON at $ 21 (that is,
When it is confirmed that the indoor unit is operating), the cooling operation is actually in operation, so that the "gas accumulation removal control" is not performed. In this case,
It is preferable to perform "control for preventing refrigerant liquid from entering the refrigerant gas pipe" as described with reference to FIG.

In other cases, since at least the cooling operation is not actually performed, the routine proceeds to # 12, where "gas accumulation removal control" is started. Even if the "cooling mode" is confirmed in # 11, if the "fan is determined to be OFF" in # 21, the indoor unit stores the "cooling mode". It means that actual driving is not being performed.

From # 12, the description will be made of the "gas accumulation removal control". However, as can be understood from the above description, the system proceeds to # 12 only when the cooling operation is not actually performed. It should be noted that this is,
This is because the control of the present invention "monitors the pressure in the refrigerant liquid pipe while the cooling operation is stopped, thereby shortening the time required for blowing the cold air when the cooling operation is restarted."

In the "gas pool removal control", first, at # 12, the pressure upstream of the expansion valve installed in the lowermost indoor unit 21 shown in FIG. 3 is measured. And this measured value P1
Is compared with a predetermined pressure value X at # 13. Predetermined pressure value X
Is a value that is assumed to cause gas accumulation when the pressure in the refrigerant liquid pipe is smaller than this value X, and can be set to, for example, 8 kgf / cm ² . ♯13
If it is determined that the measured value P1 is equal to or larger than X, it is considered that no gas pool has occurred, and the expansion valve is kept closed (# 14).

If it is determined in step # 13 that the measured value P1 is smaller than X, it is preferable to open the expansion valve because "gas accumulation removal control" is required. However, in natural circulation systems, this "gas pool removal control"
Therefore, priority should be given to "preventing the refrigerant liquid from entering the gas pipe". Therefore, first, the refrigerant liquid is set in the same manner as described in the conventional example (see # 2 in FIG. 2). The temperature in the pipe (TL) and the temperature in the refrigerant gas pipe (TG) are measured and compared (# 31). The difference between these measurements (T
If (G-TL) is equal to or less than the predetermined value Y (for example, 5 ° C.), the process proceeds to # 14, and the expansion valve is closed.

When the check in # 31 is cleared (that is, when it is determined that the refrigerant liquid has not entered the gas pipe), the gas reservoir in the liquid pipe is removed by opening the expansion valve (# 34). However, before that, it is determined at # 32 whether or not the heating operation is actually performed. If the heating operation is in operation, the fan of the indoor unit is switched to the Lo operation, and the expansion valve is opened (# 33 → # 34). this is,
If the expansion valve is opened unconditionally despite the actual operation of the heating operation, the refrigerant circulates into the warm air required for heating, causing the cold air to flow in and reducing the heating efficiency.
This is for minimizing the intrusion of the cool air. On the other hand, when the heating operation is not actually performed, the indoor unit 21 immediately below is not performing cooling or heating (during stop), so that the expansion valve is opened and the gas reservoir is removed as it is. (♯32 → ♯34).

FIGS. 5 and 6 show the results of the system of the present invention (FIG. 5) and the conventional system (FIG. 6) when the cooling operation is resumed after the cooling operation is stopped for a certain period of time. "ON / OFF state", "opening degree of solenoid valve", "pressure in refrigerant liquid pipe", and "temperature of air blown from indoor unit". Both figures are drawn on the same scale, and by comparing the two, the effect of the control method of the present invention can be clearly understood.

Comparing the two figures when the cooling operation is stopped, according to the present invention (FIG. 5), when the pressure in the refrigerant liquid pipe is reduced, the gas reservoir is removed by opening the solenoid valve, whereby the same effect is obtained. It can be seen that the pressure has returned to a predetermined value or higher. This ensures a sufficient liquid head pressure on the upstream side of the solenoid valve when the cooling operation is restarted. On the other hand, in the case of FIG. 6, even if the pressure in the refrigerant liquid pipe has decreased, the refrigerant liquid is left as it is, so that it can be seen that a sufficient liquid head pressure cannot be secured when the cooling operation is restarted. .

As a result of such a difference, in the present invention, the time required for the blow-out temperature to be actually 15 ° C. or less from the time when the cooling operation is restarted and the fan in the indoor unit is turned on is only three minutes. It has become. In contrast, in the system of FIG. 6, it takes 19 minutes to obtain the same blowing temperature. Also, when comparing the opening of the valve at the time of restarting the cooling operation, in the present invention (FIG. 5), the opening of the valve is relatively small because a sufficient liquid head pressure has already been secured at that time. Thus, it can be seen that in the system of FIG. 6, the valve needs to be widely opened because the liquid head pressure is insufficient.

In the above-described embodiment, the pressure monitoring of the refrigerant liquid pipe is performed only for the indoor unit disposed at the lowest position among the plurality of indoor units. May be controlled in the same manner.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a conventional air conditioning system that performs cooling using natural circulation.

FIG. 2 is a flowchart illustrating control for preventing refrigerant liquid from entering a refrigerant gas pipe in the air conditioning system of FIG. 1;

FIG. 3 is a schematic diagram illustrating an air conditioning system according to an embodiment of the present invention.

FIG. 4 is a flowchart illustrating control in the air conditioning system of FIG. 3;

FIG. 5 is an explanatory diagram illustrating a change in the blow-out temperature and the like when the cooling operation is restarted after the cooling operation is stopped for a certain time in the system of the present invention.

FIG. 6 is an explanatory diagram corresponding to FIG. 5 of a conventional system.

[Explanation of symbols]

 1,11 Condenser 2,21 Lowermost indoor unit 3 Area where gas accumulation occurs

Claims (2)

[Claims] An air conditioning system including a refrigerant circulation system in which an indoor unit (21) and a condenser (11) disposed at a higher position than the indoor unit (21) are connected by a refrigerant liquid pipe and a refrigerant gas pipe. Detecting means for detecting whether or not the cooling operation is actually performed; anda refrigerant liquid pipe is provided upstream of an expansion valve provided near an inlet of the refrigerant liquid pipe to the indoor unit (21). A pressure sensor for measuring pressure, a comparing means for comparing the pressure measured by the pressure sensor with a predetermined pressure value when it is determined that the cooling operation is not actually performed by the detecting means, And an opening means for opening the expansion valve when it is determined to be smaller than the above. 2. An air conditioning system including a refrigerant circulation system in which an indoor unit (21) and a condenser (11) disposed at a higher position than the indoor unit (21) are connected by refrigerant liquid piping and refrigerant gas piping. The pressure on the upstream side of the expansion valve provided near the inlet of the liquid pipe to the indoor unit (21) is monitored throughout the period in which the cooling operation is stopped, and when the pressure becomes lower than a predetermined pressure value, A gas reservoir removal method, comprising removing a gas reservoir generated in a refrigerant liquid pipe by opening an expansion valve.