JP2001066011A - Method for controlling flow rate of cooling water in water-cooled air conditioner having absorption refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for controlling the flow rate of cooling water in a water-cooled air conditioner in which the problems of a high temperature regenerator, e.g. pressure increase over atmospheric pressure or corrosion, are avoided by increasing the flow rate of cooling water quickly in response to abrupt variation of load. SOLUTION: When operation is started (S100), a specified flow rate of cooling water is set (S101) and the outlet temperature T is measured at a specified interval (S102). A measured outlet temperature T is then compared with a set temperature T0 and a temperature difference T-T0 (S103), (S105) and if T=T0 (S103), operation is sustained without varying the flow rate and the steps are repeated (S104). Flow rate is decreased if T<T0 (S106) and increased if T>T0 (S107). Flow rate is controlled by controlling the r.p.m. of a cooling water pump in response to a command from a control section. A decision is made whether an operation stop command is present or not (S108) and the operation control is repeated if it does not present (S109) otherwise operation is stopped (S110).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a flow rate of cooling water in a water-cooled air conditioner using an absorption refrigerator, and more particularly to a method for effectively reducing the energy consumption of a cooling water circuit and quickly controlling the outlet temperature. The present invention relates to a driving method that enables the operation.

[0002]

2. Description of the Related Art In FIG. 7, in a conventional water-cooled air conditioner 50 using an absorption chiller, an absorption chiller 51 uses heat pumped from the room during cooling operation and waste heat of a cooling cycle to a cooling water circuit. The heat is radiated from the cooling tower 54 to the outside air via 52. A cooling water pump 53 is provided in the cooling water circuit 52, and forcibly circulates cooling water in the system. As the cooling tower 54, an open type cooling tower utilizing the latent heat of evaporation of water is generally used.

Conventionally, the rated flow rate of the cooling water circuit 52 is set in accordance with the rated (maximum) capacity of the refrigerator, and the cooling water pump 53 is selected correspondingly. In general, the operation of the cooling water pump 53 is always performed at the rated flow rate regardless of the load on the indoor side and the cooling water temperature. Therefore, when the cooling load is small, useless energy is consumed by the cooling water pump 53.

As a method for solving such a problem, Japanese Patent Application Laid-Open No. 60-16272 discloses a method in which a temperature difference between a cooling water outlet and an inlet of a refrigerator, a condenser temperature or a condenser pressure is used as control information. In Japanese Unexamined Utility Model Publication No. 8-159596, it is proposed to control the flow rate of the cooling water by using the solution temperature of the high-temperature regenerator or the inflow temperature of the cooling water as control information to save energy.

However, in an absorption refrigerator, since the heat capacity of each heat exchanger (regenerator, condenser, evaporator, etc.) and absorption solution is large, even if the flow rate of cooling water is changed, the result is an absorption cycle. It takes a considerable amount of time before it appears. Further, since the heat capacity of the cooling water itself is large, even if there is a change in the amount of heat released through the absorption cycle due to, for example, a change in the cooling load, a considerable time delay occurs before the change appears as a change in the cooling water temperature.

In this case, the case where the cooling water flow rate should be reduced is when the cooling load is reduced, and there is no adverse effect even if the flow rate change is slow. However, in the case where the flow rate of the cooling water is to be increased, it is expected that the cooling capacity is required to be increased. Therefore, unless the cooling water flow rate is increased immediately,
A rise in the cooling water temperature causes a rise in the condenser temperature, resulting in a rise in the solution temperature of the high-temperature regenerator. As a result, there is a possibility that the high-temperature regenerator may exceed the atmospheric pressure or may be corroded.

[0007] In recent years, in a building or the like having a large cooling load, a system in which a plurality of absorption chillers are provided and the number of operating units is controlled in accordance with the cooling load has become widespread. In this case, the number of operating units decreases with a decrease in the cooling load, and as a result, the load covered by one refrigerator may suddenly increase. Even in such a case, if the flow rate of the cooling water is not promptly increased, the above-described problem may occur.

[0008]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems, and an object of the present invention is to rapidly increase the flow rate of cooling water in response to a sudden change in load, etc. An object of the present invention is to provide a cooling water flow control method for a water-cooled air conditioner, which can avoid problems such as exceeding atmospheric pressure and corrosion of a regenerator.

[0009]

A first aspect of the present invention is a method for controlling the flow rate of cooling water in a water-cooled air conditioner using an absorption refrigerator, wherein the cooling water temperature at the outlet of the refrigerator (hereinafter referred to as the outlet temperature). ) And a predetermined set temperature (T ₀ )
The cooling water flow rate is increased or decreased based on the temperature difference (T-T ₀ ) to maintain the set temperature, and the flow rate change rate when increasing the flow rate is set to a value larger than the flow rate changing rate when decreasing the flow rate. It is characterized by having done.

By performing such control, when the outlet temperature is increasing due to an increase in cooling load or the like, the flow rate can be rapidly increased, and the outlet temperature can be rapidly reduced. Thereby, problems such as exceeding the atmospheric pressure and corrosion of the high-temperature regenerator can be effectively avoided.

In this case, the rate of change is the absolute value of the temperature difference (| T
−T ₀ |) is desirable (claim 2).

This makes it possible to quickly change the flow rate according to the difference between the current temperature (T) and the set temperature (T ₀ ).

According to a third aspect of the present invention, the absorption refrigerator includes a high-temperature regenerator, and when the high-temperature regenerator exceeds a predetermined temperature, the cooling water flow rate is maximized. This is the cooling water control method to be set.

With this control, corrosion of the high-temperature regenerator over atmospheric pressure or high temperature can be more reliably avoided.

According to a fourth aspect of the present invention, in the above method, the absorption chiller comprises a plurality of absorption chillers each having a cooling water circuit, and the number of operating the absorption chillers is increased or decreased according to the cooling load. The cooling water control method is characterized in that the cooling water flow rate is set to a maximum for a predetermined time when the number of operating vehicles is reduced.

In a system in which the number of operating units is controlled according to the cooling load, even if the load covered by one refrigerator increases rapidly, the flow rate of the cooling water can be quickly increased.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. Note that the same components are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 is a diagram showing a first embodiment of a water-cooled air conditioner according to the present invention. In the figure, a water-cooled air conditioner 1 includes an absorption refrigerator 2, a cooling tower 3, a cooling water outgoing pipe 5.
A cooling water circuit 7 including a cooling water return pipe 6 and a cooling water pump 4, a control unit 9, and an inverter control device 16 are main components.

The absorption refrigerator 2 is a known double-effect absorption refrigerator, and includes a high-temperature regenerator, a low-temperature regenerator, a condenser, an evaporator, an absorber, a high-temperature heat exchanger, a low-temperature heat exchanger, and the like. Although it is a component, illustration is omitted except for the high-temperature regenerator 10. Further, description of the operation of the refrigerator main body will be omitted.

The high-temperature regenerator 10 has a burner 13 as a heating source.
And the city gas supply line 15 as its fuel
Supplies city gas.

In the cooling water return pipe 6, a cooling water pump 4
Is provided. Further, a temperature sensor 12 is provided near the outlet of the refrigerator 2 in the cooling water outgoing pipe 5, and measures the outlet temperature (T).

The control unit 9 is a computer system including a CPU, a ROM, a RAM, and the like. The controller 9 takes in data of the outlet temperature T, and based on the information, outputs the cooling water pump 4.
Is configured to perform the rotation speed control. That is, the rotation speed of the cooling water pump 4 is controlled by the inverter control device 16 based on a command from the control unit 9 and is set to a predetermined cooling water flow rate.

Although the control unit 9 is provided outside the refrigerator in FIG. 1, it may be built in the refrigerator.

The controller 9 calculates the rate of change of the flow rate of the cooling water according to the set temperature (T ₀ ) and the measured outlet temperature (T).

In this case, when T <T ₀ , the flow rate change rate per unit time (dG / dt) is the absolute value of the temperature difference (| T
−T ₀ |) and is expressed by the following equation.

DG / dt = (T−T ₀ ) · R (1) Here, R is a constant, and its value can be determined according to the absorption refrigerator or the heat capacity of the cooling water. In the equation (1), since T−T ₀ <0, dG / dt <0, that is, the flow rate decreases. When T> T ₀ , it is expressed by the following equation.

DG / dt = n · (T−T ₀ ) R (2) where n is a constant greater than 1, and can be determined according to the characteristics of the water-cooled air conditioner. In equation (2),
Since T−T ₀ > 0, dG / dt> 0, that is, an increase in the flow rate.

By setting the flow rate change rate as shown in the equations (1) and (2), when T> T ₀ , the same temperature difference (absolute value) is n n compared to when T <T _0. Gives twice the rate of flow change. That is, the flow rate increase is performed at a speed n times faster than the flow rate decrease.

FIG. 2 is a flowchart showing a method for controlling the flow rate of the cooling water according to this embodiment. 1 and 2, a method for controlling the flow rate of cooling water according to the present invention will be described.

When the operation is started (S100), the flow rate of the cooling water is initialized to a predetermined flow rate (S101). The set flow rate may be set to, for example, a rated (maximum) capacity.

The outlet temperature (T) is measured at predetermined time intervals (S102). Then the temperature difference between the outlet temperature measurement value (T) and the set temperature _{(T 0) (T-T} 0) is compared (S1
03, S105).

If T = T ₀ (S103), the operation is continued without changing the flow rate, and the above steps are repeated (S104).

When T <T ₀ , the flow rate is reduced based on the rate of change shown in equation (1) (S106). Also, T> T ₀
In the case of (1), the flow rate is increased by the change rate shown in the equation (2) (S107). As described above, the flow rate change rate (absolute value) in this case is k times larger than when T <T ₀ .

The flow rate can be increased or decreased by a command from the control unit 9.
This is performed by controlling the rotation speed of the cooling water pump 4.

It is determined whether an operation stop command has been issued (S10).
8) As long as there is no stop command, the above operation control is repeated (S109). If there is an operation stop command, the operation is stopped (S110).

FIG. 3 is a diagram showing a second embodiment of the present invention. This embodiment differs from the first embodiment in that the temperature of the solution (TH) of the high-temperature regenerator is also taken in and the flow rate of the cooling water is controlled. That is, in the water-cooled air conditioner 30 in FIG. 3, the temperature sensor 17 measures the solution temperature of the high-temperature regenerator, and the information is taken into the control unit 9.

FIG. 4 is a flowchart showing a method for controlling the flow rate of the cooling water according to this embodiment. FIG. 4 shows only the steps to be added between S102 and S103 in the steps of FIG. 3, and the steps before and after are the same as those in FIG.

Following the measurement of the outlet temperature (T) (S102), the solution temperature (T
H) is measured (S201).

The solution temperature (TH) and a predetermined upper limit temperature (TH
_L ) is compared (S202), and is equal to or higher than the upper limit temperature (TH ≧ T).
_HL ), the cooling water flow rate is set to the maximum (S2).
03). When the temperature is lower than the upper limit temperature (TH <TH _L ), FIG.
The control is performed according to the steps from S102 onward (S2).
04).

As the value of TH _L , for example, 180 ° C. which may cause corrosion of the high-temperature regenerator may be used.

In the present embodiment, the high-temperature regenerator solution temperature is used as the management information in order to avoid an abnormally high temperature. However, the present invention is not limited to this, and other heat exchangers, for example, a condenser temperature can be used. is there.

FIG. 5 is a diagram showing a third embodiment of the present invention. The present embodiment is different from the above embodiment in that the present embodiment is configured by a plurality of absorption refrigerators and cooling water circuits. That is, the water-cooled air conditioner 20
Are two absorption refrigerators 2a and 2b, and a cooling tower 3a
.3b, cooling water outgoing pipes 5a and 5b, cooling water returning pipes 6a and 6b
And two cooling water circuits including cooling water pumps 4a and 4b.

The chilled water circuit side includes an indoor unit 21, a chilled water pump 25, a chilled water forward pipe 22, and a chilled water return pipe 23. On the outgoing pipe side, the refrigerator 2a-side branch pipe 22a and the refrigerator 2b-side branch pipe 22b join at a junction 22c, and the cold water forward pipe 2
2 and is led to the indoor unit 21. On the return pipe side, the cold water return pipe 23 branches at the branch point 23c, and the branch pipe 2 on the refrigerator 2a side.
3a and the branch pipe 23b on the refrigerator 2b side.

Temperature sensors 27 and 28 are provided in the path of the cold water outgoing pipe 22 and the cold water returning pipe 23, and measure the cold water outgoing temperature T2 and the cold water returning temperature T3, respectively. A flow meter (not shown) is provided in the chilled water path to measure the chilled water flow rate. These measured values are configured to be taken into the number control panel 26. The number control panel 26 is configured to calculate the cooling load from the product of the chilled water return temperature difference (T3-T2) and the chilled water flow rate, and to control the number of refrigerators operated based on this information.

Next, a method for controlling the flow rate of cooling water in the present embodiment will be described. FIG. 6 is a conceptual diagram showing the operation number control of the absorption chillers 2a and 2b according to the cooling load.
In the figure, the horizontal axis shows the cooling load, and the vertical axis shows the refrigerator output with the maximum value being 200. In the figure, part A is assigned to the refrigerator 2a, and part B is assigned to the refrigerator 2b. Thus, when the cooling load is less than 100, the refrigerator 2
It can be seen that the cooling is performed by the single-unit operation of a and the two-unit operation is performed when the cooling load exceeds 100. Therefore, when the cooling load decreases from L2 to L1, the output of the refrigerator 2a becomes P1
From P2 to P2.

In this case, in FIG. 5 again, upon receiving the operation stop information of the refrigerator 2b from the number control panel 10, the control unit (not shown) of the refrigerator 2a performs cooling so as to maximize the cooling water flow rate. The rotation speed of the water pump 4a is controlled. Thereby, it is possible to avoid exceeding the atmospheric pressure due to an abnormally high temperature of the high temperature regenerator (not shown) of the refrigerator 2a.

After the cooling water flow is operated at the maximum for a predetermined time, normal cooling water flow control is performed again according to the flow of FIG.

In the present embodiment, the number of absorption chillers is two. However, the number of chillers is not limited to this, and it goes without saying that the same control can be performed by using three or more chillers.

In the above embodiments, city gas is used as the fuel for the refrigerator. However, other fuels, for example, kerosene and electricity, can be used, and various kinds of exhaust heat can be used.

Although an example has been described in which water is used as the cooling medium, the present invention is not limited to this, and another cooling medium can be used.

[0051]

According to the present invention, in the cooling water flow rate control of the absorption refrigerator, the flow rate change rate is set to a larger value when increasing the flow rate than when decreasing the flow rate.
Problems such as exceeding atmospheric pressure and corrosion of the high-temperature regenerator can be effectively avoided.

According to the second aspect of the present invention, the temperature of the high-temperature regenerator can be controlled in more detail.

According to the third aspect of the present invention, it is possible to more reliably prevent the high-temperature regenerator from corroding due to exceeding the atmospheric pressure or high temperature.

According to the fourth aspect of the present invention, in the method of controlling the number of operating units according to the cooling load, even if the load covered by one refrigerator increases rapidly, the cooling water flow rate is quickly increased. It became possible to increase.

[Brief description of the drawings]

FIG. 1 is a diagram showing an absorption refrigerator according to a first embodiment.

FIG. 2 is a diagram showing a flow chart for controlling the flow rate of cooling water according to the first embodiment.

FIG. 3 is a diagram showing an absorption refrigerator according to a second embodiment.

FIG. 4 is a diagram illustrating a flow of controlling a flow rate of cooling water according to a second embodiment.

FIG. 5 is a diagram showing an absorption refrigerator according to a third embodiment.

FIG. 6 is a diagram showing number control according to a third embodiment.

FIG. 7 is a view showing a conventional absorption refrigerator.

[Explanation of symbols]

1. Water-cooled air conditioner, 2.2a. 2b ... Absorption refrigerator,
3. Cooling tower, 4.4a, 4b ... Cooling water pump, 5.5a
5b: Cooling water outgoing pipe, 6.6a, 6b: Cooling water return pipe, 9
... Control unit, 10 ... High temperature regenerator, 11 ... Temperature sensor, 15
... City gas supply line, 13 ... Burner, 16 ... Inverter control device, 21 ... Indoor unit, 22 ... Chilled water outgoing pipe, 23 ... Chilled water return pipe, 25 ... Chilled water pump, 27/28 ... Temperature sensor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Osamu Shibata 1-5-20 Minato-ku, Tokyo Tokyo Gas Co., Ltd. In-house F-term (reference) 3L093 AA01 BB11 BB18 BB22 BB26 BB29 CC00 CC07 DD09 EE14 EE17 EE25 EE30 GG02 HH00 HH14 JJ00 JJ06 KK05

Claims (4)

[Claims] 1. A method for controlling a flow rate of a cooling water in a water-cooled air conditioner using an absorption refrigerator, comprising: a measurement value (T) of a cooling water temperature (hereinafter referred to as an outlet temperature) at a refrigerator outlet; The cooling water flow rate is increased or decreased based on the temperature difference (T−T ₀ ) from the temperature (T ₀ ) to maintain the set temperature, and the flow rate when the flow rate change rate when increasing the flow rate is decreased. A method for controlling a flow rate of cooling water, wherein the cooling water flow rate is set to a value larger than a change rate. 2. The method according to claim 1, wherein the rate of change of the flow rate is an absolute value (|
The cooling water control method according to claim 1, wherein the cooling water control method is proportional to (T−T ₀ |). 3. The absorption refrigerator has a high temperature regenerator, and when the high temperature regenerator exceeds a predetermined temperature,
3. The cooling water control method according to claim 1, wherein the cooling water flow rate is set to a maximum. 4. The absorption chiller according to claim 1, wherein the absorption chiller includes a plurality of absorption chillers each having a cooling water circuit, and the number of operating the absorption chillers depends on a cooling load. A cooling water control method, wherein the cooling water flow rate is increased or decreased, and the cooling water flow rate is set to a maximum for a predetermined time when the number of operating vehicles is reduced.