JPH08313001A - Air-conditioning system - Google Patents

Abstract

PURPOSE: To improve the responsiveness of a temperature control in a refrigerant circulation type air-conditioning system. CONSTITUTION: In this air-conditioning system wherein a refrigerant condensed in an outdoor machine 1 is sent to a plurality of indoor machines 2, evaporated in each indoor machine 2 and returned to the outdoor machine 1, while the degree of opening of an expansion valve 4 interposed in a branch refrigerant piping 3 on the upstream side of each indoor machine 2 is controlled so that a refrigerant temperature difference between the outlet and the inlet of the indoor machine 2 be a prescribed value, a means for changing a control target value of the temperature difference in accordance with the quantity of air of a fan 6 of the indoor machine 2 is provided. Accordingly, the refrigerant temperature difference (degree of overheat) between the outlet and the inlet to be a control target of the expansion valve 4 is changed over simultaneously with a changeover of the quantity of air of the fan which comes to be a sudden change of a load, and therefore the expansion valve 4 makes an immediate response without waiting for a change of a refrigerant temperature in an evaporation coil 8 and can cope with the sudden change of the load.

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 of a type in which a refrigerant is circulated from an outdoor unit to an indoor unit during cooling.

[0002]

2. Description of the Related Art In this type of air conditioning system, FIG.
As shown in FIG. 1, the outdoor unit 1 that operates as a condenser during cooling
, The liquid refrigerant is gravity flowed down to the indoor unit 2 that operates as an evaporator, or is pressure-fed using a pump, is evaporated in the evaporation coil 7 of each indoor unit 2 and is returned to the outdoor unit 1 as a refrigerant vapor. The temperature difference (superheat degree) detected by the refrigerant temperature sensors 5a and 5b provided at the inlet and the outlet of the indoor unit 2 for the opening degree of the expansion valve 4 provided on the upstream side of each indoor unit 2.
Is controlled to be a constant value. This is because the heat exchange is effectively performed by changing the state of the refrigerant liquid at an appropriate location in the evaporation coil 7, and the evaporation of the refrigerant becomes active in the indoor unit 2 having a large indoor load. This is to prevent the refrigerant from flowing unevenly to the indoor unit 2 having a small indoor load due to an increase in the refrigerant circulation resistance.

[0003]

Conventionally, in this type of system, it takes a considerable amount of time for the temperature sensors 5a and 5b to detect a change in the load as a change in the temperature of the refrigerant. It is not easy to control the expansion valve 4 so as to cause a state change at an appropriate position in the evaporation coil 7 of the indoor unit 2, and the response of the expansion valve 4 is delayed when the room temperature rises or the air volume increases (by manual operation). However, since the evaporation of the refrigerant occurs at the upstream side of the evaporation coil 7, the temperature of most of the coil 7 rises, and the cooling capacity decreases, and also when the room temperature drops or the air volume decreases. When the response of the expansion valve 4 is delayed, the supply of the refrigerant becomes excessive and the liquid refrigerant is mixed in the return pipe,
In addition to obstructing the flow of the gas refrigerant and hindering circulation, there is a shortcoming that the amount of liquid refrigerant on the feed pipe side is insufficient. There was a problem that caused. Therefore, conventionally, the number of locations where the refrigerant temperature sensor is installed in the indoor unit 2 is increased, a room temperature sensor is used together, or the ratio of the amount of refrigerant used to the load is increased.
Various measures have been taken, but the satisfactory results commensurate with the cost have not been obtained. The present invention aims to solve the above problems at a relatively low cost.

[0004]

In the present invention, as shown in FIGS. 1 and 2, a plurality of indoor units 2 are provided with a refrigerant condensed in an outdoor unit 1.
To the outdoor unit 1, and the opening degree of the expansion valve 4 installed in the branch refrigerant pipe 3 on the upstream side of each indoor unit 2 In the air-conditioning system that controls the temperature difference of the refrigerant in (1) to be a predetermined value, a means for changing the control target value of the temperature difference according to the air volume of the fan 6 of the indoor unit 2 is provided. .

[0005]

In the conventional structure, when the air volume of the fan 6 is switched to "strong", for example, the amount of heat given from the air to the coil is first increased by the contact between the fins of the evaporation coil 7 and the air. The liquid level of the internal refrigerant drops, the temperature difference detected by the refrigerant temperature sensors 5a and 5b at the inlet and outlet of the evaporator 8 increases, and the detected output expands by an amount deviating from a preset control target value. The opening of the valve 4 is proportionally controlled in the "open" direction, but there is a time delay due to thermal inertia from the time when the fan air volume is switched to the time when the expansion valve 4 is activated, and the time when the air volume is switched. The opening of the expansion valve 4 changes only continuously despite the discontinuity of the load on the fan 6. Therefore, the liquid level of the refrigerant in the evaporating coil 7 is similar to that of the air volume switching of the fan 6. Can't keep up with sudden changes in load There was a point. On the other hand, according to the configuration of the present invention, when the air volume of the fan 6 is switched,
At the same time, the control target value of the expansion valve 4 is also switched, so that the refrigerant temperature difference at that time largely deviates from the control target value, and therefore the opening degree of the expansion valve 4 is discontinuously and significantly modified. It is possible to cope with a sudden change in load caused by switching the fan air volume.

[0006]

FIG. 1 shows an embodiment of an air conditioning system according to the present invention. The outdoor unit 1 is, for example, an absorption refrigerator 1a.
And a cooling tower 1b, and is installed at a position higher than any of the plurality of indoor units 2 such as on the rooftop of a building, and the refrigerant liquid condensed by the condenser of this outdoor unit 1 (for example, alternative Freon) R22, R134A, etc.) is allowed to naturally flow down to the plurality of indoor units 2 through the refrigerant pipe 8 on the sending side by its own weight, the refrigerant is evaporated in each indoor unit 2, and the outdoor unit is passed through the refrigerant pipe 7 on the returning side. Reflux to 1. Further, in each indoor unit 2, the indoor air sucked by the fan 6 is cooled by the evaporation coil 7 and blown out into the room.
The refrigerant temperature sensors 5a and 5b provided at the inlet and outlet of the evaporation coil 7 monitor the temperature rise in the evaporation coil 7 and proportionally control the opening of the expansion valve 4 with this detection output. It is controlled so that the evaporation of the refrigerant is completed at an appropriate place inside. Reference numeral 11 is a control device.

On the other hand, the air volume of the fan 6 is automatically set according to the indoor temperature, that is, the output of the temperature sensor provided at the air inlet to the indoor unit 2, but compulsorily when the manual changeover switch is operated. It can be switched to three levels of "strong", "medium", and "weak", and the control target value of the above-described superheat degree (temperature difference at the inlet and outlet) can be switched to three levels according to the fan air volume. There is. FIG. 2 shows the relationship between the air volume of the fan 6 and the target value of the degree of superheat of the indoor unit 2.

In FIG. 2, when the indoor cooling load does not fluctuate much, the fan 6 ventilates with an air volume of "medium," for a change in room temperature within a certain range.
Output change of the refrigerant temperature sensors 5a, 5b (superheat degree: 7.5 ° C)
(Deviation from), the change in the opening of the expansion valve 4 in proportion to
The temperature is controlled so that the room temperature maintains a constant value. Here, when the room temperature rises beyond a certain range, the fan air volume is automatically switched to "strong", and thereby the target superheat degree is switched to 5.0. Therefore, the expansion valve 4
The degree of opening, which has been controlled in the vicinity of a superheat of 7.5 ° C until now, is controlled in the opening direction by the amount corresponding to 2.5 ° C all at once, so that it can quickly respond to a sudden change in the fan air volume. In this respect, in the conventional method in which the switching of FIG. 2 is not performed, when the temperature difference first exceeds the target value of 7.5 ° C. due to an increase in the fan air volume, the temperature difference starts to increase, which corresponds to the amount exceeding 7.5 ° C. Since the opening degree of the expansion valve 4 was changed as much as it is, even though the cooling load was increased significantly after the fan air volume was switched, the deviation from 7.5 ° C was still small immediately after the switching. Due to this, the response of the expansion valve 4 is extremely slow. However, in the method of the present invention, the target degree of superheat is 5.0 ° C immediately after switching.
Since it switches to, the deviation from the target increases all at once,
The expansion valve 4 responds immediately without waiting for the temperature rise of the refrigerant, and can respond to a sudden change in load.

[0009]

As described above, according to the configuration of the present invention, when the fan air volume is changed, which causes a sudden change in the load, the degree of refrigerant superheat (the inlet / outlet temperature) of the evaporation coil 7, which is the control target of the expansion valve 4, is simultaneously obtained. Since the difference) can also be switched, the opening degree of the expansion valve 4 can be greatly corrected immediately without waiting for a change in the refrigerant temperature due to a sudden change in the load, and it is possible to immediately respond to a discontinuous change in the load due to the switching of the fan air volume. There is an advantage that you can.

[Brief description of drawings]

FIG. 1 is a schematic system diagram of an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the present invention.

FIG. 3 is a schematic system diagram of a conventional example.

[Explanation of symbols]

 1 Outdoor Unit 2 Indoor Unit 3 Branched Refrigerant Pipe 4 Expansion Valve 5a Indoor Unit Inlet Temperature Sensor 5b Indoor Unit Outlet Temperature Sensor 6 Fan 7 Evaporation Coil 8 Sending Side Refrigerant Pipe 9 Return Side Refrigerant Pipe 10 Outdoor Unit Outlet Temperature Sensor 11 Control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (71) Applicant 390003333 Shinko Industrial Co., Ltd. 1-4-5 Minamimorimachi, Kita-ku, Osaka-shi, Osaka (71) Applicant 000003621 Takenaka Corporation, Honmachi, Chuo-ku, Osaka-shi, Osaka 4-1-113 (72) Inventor Noboru Kobayashi 4-1-2 Hiranocho, Chuo-ku, Osaka City Osaka Gas Co., Ltd. (72) Inventor Tsuyoshi Okumura 4-1-2, Hiranocho, Chuo-ku, Osaka Gas Co., Ltd. (72) Inventor Seiichiro Fujimaki 1-5-20 Kaigan, Minato-ku, Tokyo Tokyo Gas Co., Ltd. (72) Inventor Koji Matsubara 19-18 Sakurada-cho, Atsuta-ku, Nagoya City Toho Gas Co., Ltd. ( 72) Inventor Shinji Tonmiya 4-28 Mita, Minato-ku, Tokyo Within Yazaki Corporation (72) Inventor Yasutoshi Yoshida 1-4-5, Minamimorimachi, Kita-ku, Osaka Shinko Industrial Co., Ltd. In the company (72) Inventor Nozomu Kusumoto 4-13 Hommachi, Chuo-ku, Osaka City Stock company Takenaka Corporation

Claims (2)

[Claims] 1. A refrigerant condensed in an outdoor unit is sent to a plurality of indoor units, and the refrigerant is evaporated in each indoor unit to be returned to the outdoor unit, and is also installed in a branch refrigerant pipe on the upstream side of each indoor unit. In an air-conditioning system that controls the opening of the expansion valve so that the temperature difference of the refrigerant at the inlet and outlet of the indoor unit becomes a predetermined value, the control target value of the temperature difference is set according to the air volume of the fan of the indoor unit. An air conditioning system provided with means for changing. 2. The outdoor unit is installed at a high place so that the refrigerant naturally circulates to each indoor unit by its own weight.
Air conditioning system as described.