JPH0961076A - Heat transfer device and its controlling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a thermal transferring medium to be prevented from being gasified at a pump suction port without increasing cost by a method wherein an increasing rate of condensing capability at a condenser is controlled in response to a liquid surface height, volume and pressure loss of thermal transferring medium present at a pipe between a condenser and a suction port of a pump. SOLUTION: An evaporator 1, a condenser 2, a tank 3 and a pump 4 are connected in sequence by a pipe 5, and refrigerant acting as thermal transferring medium is enclosed in the pipe 5. A freezer 6 is arranged for use in supplying cold heat to the condenser 2, a cold water circulating pipe 7 is arranged between the freezer 6 and the condenser 2 and then the pipe 7 is provided with a pump 8 for controlling a circulation of the cold water and its amount, and with an opening or closing valve 9. Then, the pump 8, the opening or closing valve 9, a liquid surface height sensor 11, a circulating amount measuring device 12 and a memory 21 are connected to a control part 20. The control part 20 calculates differences ΔH, ΔM, and ΔP between a liquid surface height H, a volume M and a pressure loss P and their reference values Hs, Ms and Ps are to multiply a weighted coefficient and then an amount of feeding water of the pump 8 is controlled in response to a sum of differences ΔH, ΔM, and ΔP.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transport device that transports heat by utilizing a phase change of a heat transport medium.

[0002]

2. Description of the Related Art Generally, a temperature difference (sensible heat) of water is used as a medium for transporting heat. An example is cooling water when the exhaust heat from the condenser of the refrigerator is released into the atmosphere using the cooling tower.

However, the use of latent heat (phase change) rather than the use of sensible heat makes it possible to reduce the circulation amount of the heat transport medium. Therefore, recently, a heat transport system utilizing phase change of the heat transport medium has been used. It has been introduced.

As a system for transporting heat by a phase change of a heat transport medium such as a refrigerant (CFC, etc.), an evaporator is installed at a position lower than that of a condenser, and heat transport by natural circulation utilizing a density difference between liquid and vapor. The method is known. However, this method has a constraint that the evaporator must be installed lower than the condenser.

As a general method not subject to this restriction condition, a pump is provided at the outlet of the condenser to obtain a driving force for heat transport, and a compressor is provided at the outlet of the evaporator to provide a driving force for heat transport. There is a way to get it.

However, the method using the compressor requires a larger driving power than the method using the pump and cannot be said to be an effective means. The pump method has less operating power than the compressor method, but the refrigerant may be gasified at the pump inlet. When the refrigerant is gasified, the pump runs idle and heat transfer cannot be continued. Damage to the pump can also occur.

In order to prevent this gasification, the height difference between the position of the condenser and the position of the pump is set to the allowable NPSH specific to the pump.
It is necessary to set it higher than the value. As another means, there is also an example in which a small refrigerator is installed at the pump inlet and the refrigerant is cooled by the refrigerator to keep the refrigerant at the pump inlet always in a liquid state.

[0008]

The example of preventing gasification by using a refrigerator as described above causes an increase in cost and is not a good solution. Even in the example in which the height difference between the position of the condenser and the position of the pump is set to be equal to or higher than the allowable NPSH value peculiar to the pump, when the condensation capacity in the condenser increases rapidly, gasification of the refrigerant is inevitable. .

This is because the pressure of the refrigerant sharply decreases due to the rapid increase of the condensing capacity, and the saturated refrigerant temperature also sharply decreases accordingly, whereas the temperature of the refrigerant at the pump suction port is higher than the pressure in the transmission speed. This is because the rate of decrease is slow due to the slowness. As shown in FIG. 6, the saturated refrigerant temperature becomes lower than the refrigerant temperature several seconds after the rapid increase in the condensation capacity, and the refrigerant is gasified.

[0010] The present invention has been made in view of the above circumstances,
The heat-transporting device of the first to fifth inventions can prevent gasification of the heat-transporting medium at the pump suction port without increasing the cost, thereby continuing appropriate heat-transporting. At the same time, it aims to prevent damage to the pump and improve reliability and safety.

The heat transport device control method of the sixth aspect of the present invention can prevent gasification of the heat transport medium at the pump suction port before the cost is increased, and thus, appropriate heat transport can be achieved. The purpose is to continue pumping, prevent damage to the pump, and improve reliability and safety.

[0012]

In the heat transport device of the first invention, an evaporator, a condenser, and a pump are sequentially connected by pipes, and heat is transferred by a phase change of a heat transfer medium enclosed in the pipes. Control means for controlling the rate of increase in the condensation capacity of the condenser based on the liquid level height, amount and pressure loss of the heat transport medium existing in the pipe between the condenser and the suction port of the pump. , Are provided.

In the heat transport device of the second invention, an evaporator, a condenser, and a pump are sequentially connected by pipes, and heat is transferred by a phase change of the heat transfer medium enclosed in the pipes. Check the liquid level height detecting means for detecting the liquid level of the heat transport medium existing in the pipe between the condenser and the suction port of the pump, and the pipe length and diameter between the condenser and the suction port of the pump. Calculating the amount of the heat transport medium existing in the stored storage means and the pipe between the condenser and the suction port of the pump by calculating from the detection result of the liquid level height detection means and the stored contents of the storage means. 1 Calculation means, circulation amount measuring means for measuring the amount of heat transport medium circulating through the evaporator, condenser, and pump, and pressure loss of the heat transport medium existing in the pipe between the condenser and the suction port of the pump The measurement result of the circulation amount measuring means and the memory Second obtaining by calculating from the stored contents
Control means for controlling the increasing rate of the condensation capacity in the condenser based on the calculation means, the detection result of the liquid level height detection means, the calculation result of the first calculation means, and the calculation result of the second calculation means. And are equipped with.

In the heat transport device of the third invention, an evaporator, a condenser, and a pump are sequentially connected by pipes, and heat is transferred by a phase change of a heat transfer medium enclosed in the pipes. The standard liquid level height and amount of the heat transfer medium existing in the pipe between the condenser and the pump inlet was stored, and the pipe length and pipe diameter between the condenser and the pump inlet were stored. The storage means, the circulation amount measuring means for measuring the amount of the heat transfer medium circulating through the evaporator, the condenser, and the pump, and the pressure loss of the heat transfer medium existing in the pipe between the condenser and the suction port of the pump are measured. Calculating means for calculating from the measurement result of the circulation amount measuring means and the pipe length and the pipe diameter in the storing means, the liquid level in the storing means, the amount in the storing means, and the calculating means Based on the calculation result of Comprises a control means for controlling the pressure ratio, the.

In the heat transport device of the fourth invention, the circulation amount measuring means in the second or third invention is provided in the pipe between the pump outlet and the evaporator, and circulates from the flow rate of the refrigerant in the pipe. Measure the quantity.

In the heat transport apparatus of the fifth invention, the circulation amount measuring means in the second or third invention detects the operating frequency of the pump and the pressure detecting means for detecting the suction pressure and the discharge pressure of the pump. And means for calculating the circulation amount by calculating the detection result of the pressure detecting means and the detection result of the detecting means.

The heat transport apparatus control method of the sixth aspect of the present invention is a heat transport method in which an evaporator, a condenser, and a pump are sequentially connected by pipes, and heat is transported by a phase change of a heat transport medium enclosed in the pipes. In the device, the rate of increase in the condensation capacity of the condenser is controlled based on the liquid level height, amount, and pressure loss of the heat transport medium existing in the pipe between the condenser and the suction port of the pump.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

[1] Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the evaporator 1, the condenser 2, the tank 3, and the pump 4 are sequentially connected by a pipe 5. A refrigerant (for example, CFC) is enclosed in the pipe 5 as a heat transport medium.

Regarding the position of the condenser 2 and the position of the pump 4, the height difference between them is set to be equal to or higher than the allowable NPSH value peculiar to the pump. A refrigerator 6 is provided for supplying cold heat to the condenser 2, and a pipe 7 for circulating cold water is provided between the refrigerator 6 and the condenser 2. A pump 8 and an opening / closing valve 9 for controlling the circulation and amount of cold water are provided in the pipe 7.
Is provided. As the refrigerator 6, a vapor compression refrigerator,
Various types of applications such as absorption refrigerators and ice heat storage tanks are possible, and all cold heat sources are indicated.

That is, the liquid refrigerant sent from the outlet of the pump 4 takes heat from the outside in the evaporator 1 and evaporates. This gas refrigerant then flows to the condenser 2 where it radiates heat to the cold water from the refrigerator 6 and liquefies it. The liquid refrigerant is taken into the suction port of the pump 4 via the tank 3 and is again sent from the outlet of the pump 4 toward the evaporator 1.

Thus, the cold heat released from the refrigerator 6 is transported to the evaporator 1 side. The tank 3 is for temporarily storing the liquid refrigerant from the condenser 2. A liquid level detector 11 is connected in parallel with the tank 3. The liquid level detector 11 detects the liquid level H of the refrigerant (liquid) existing in the pipe 5 between the condenser 2 and the suction port of the pump 4.

A circulation amount measuring device 12 is provided in the pipe 5 between the outlet of the pump 4 and the evaporator 1. The circulation amount measuring device 12 measures the flow rate of the refrigerant in the pipe 5, that is, the amount of the refrigerant circulating through the evaporator 1, the condenser 2, the tank 3, and the pump 4.

On the other hand, a controller 20 is provided. The control unit 20 includes the pump 8, the on-off valve 9, and the liquid level height detector 1
1, and the circulation amount measuring device 12 are connected, and a storage means such as a memory 21 is connected. In the memory 21, the length and diameter of the pipe 5 between the condenser 2 and the suction port of the pump 4 are stored in advance, and the capacity of the tank 3 is stored in advance. The stored pipe length, pipe diameter, and tank capacity are data at the time of design.

The control unit 20 is equipped with the following functional means. (1) The amount M of the refrigerant existing in the pipe 5 between the condenser 2 and the suction port of the pump 4, the detection result H of the liquid level height detector 11 and the stored contents of the memory 21 (pipe length, pipe diameter, First calculating means for calculating by calculating from the tank capacity).

(2) The pressure loss P of the refrigerant existing in the pipe 5 between the condenser 2 and the suction port of the pump 4 is measured by the circulation amount measuring device 1
Second calculation means for calculating and obtaining from the measurement result of No. 2 and the stored contents (pipe length, pipe diameter) of the memory 21.

(3) Detection result H of the liquid level detector 11,
Control means for controlling the increasing rate of the condensation capacity in the condenser 2 based on the calculation result M of the first calculation means and the calculation result P of the second calculation means. Specifically, the amount of water sent by the pump 8, that is, the amount of cold water flowing from the refrigerator 6 to the condenser 2 is controlled.

Next, the operation of the above configuration will be described. When the pump 4 is operated, the liquid refrigerant is delivered from the pump 4. This liquid refrigerant flows to the evaporator 1, where heat is taken from the outside and evaporated. The gas refrigerant flowing out from the evaporator 1 flows into the condenser 2, where heat is released to the cold water from the refrigerator 6 and liquefied. The liquid refrigerant is taken into the suction port of the pump 4 via the tank 3 and is again sent from the outlet of the pump 4 toward the evaporator 1.

By the way, even when the height difference between the position of the condenser 2 and the position of the pump 4 is set to be equal to or higher than the allowable NPSH value peculiar to the pump, when the condensing capacity of the condenser 2 rapidly increases, for example, a refrigerator. When the temperature of the cold water supplied from 6 to the condenser 2 sharply drops, or when the amount of cold water supplied from the refrigerator 6 to the condenser 2 sharply increases,
The liquid refrigerant may be gasified at the suction port of the pump 4.

The factors that determine whether the liquid refrigerant is gasified at the suction port of the pump 4 are the liquid level height H and the amount M of the refrigerant existing in the pipe 5 between the condenser 2 and the pump 4 suction port. , Pressure loss P.

The liquid level height H of the refrigerant is the liquid level height detector 1
1 is detected. The amount M of the refrigerant is calculated and calculated from the liquid level height H detected by the liquid level height detector 11 and the stored contents (pipe length, pipe diameter, tank capacity) of the memory 21.

The pressure loss P of the refrigerant corresponds to the pipe resistance and is calculated from the circulation amount measured by the circulation amount measuring device 12 and the stored contents (length and diameter of the pipe 5) of the memory 21. Desired. The table below summarizes under what conditions these three factors H, M and P cause gasification.

[0032]

[Table 1]

That is, when the liquid level height H of the refrigerant is low,
Easy to gasify. When the amount M of the refrigerant is large, it is easy to gasify.
When the pressure loss P of the refrigerant is large, it is easy to gasify. In consideration of these gasification-prone conditions, reference values Hs, Ms, and Ps are set for the three factors H, M, and P, respectively, and these reference values are stored in the internal memory of the control unit 20 in advance.

In the control section 20, the difference ΔH between the liquid level height H, the amount M, the pressure loss P and the reference values Hs, Ms and Ps, respectively,
ΔM and ΔP are obtained, and the differences ΔH, ΔM, and ΔP are multiplied by their own weighting factors. Each weighting factor is also stored in advance in the internal memory of the control unit 20.

Then, the sum of the differences ΔH, ΔM, and ΔP, which have been respectively multiplied by the weighting factors, is obtained, and the water supply amount of the pump 8 is controlled according to the sum. That is, when the refrigerant is likely to be gasified at the suction port of the pump 4, the amount of water sent by the pump 8 is suppressed, and thus the rate of increase in the condensation capacity of the condenser 2 is suppressed.

For example, when the temperature of the cold water supplied from the refrigerator 6 to the condenser 2 suddenly drops from 12.5 ° C to 7.5 ° C, if nothing is done as it is, as shown in FIG. After several seconds, the saturated refrigerant temperature becomes lower than the refrigerant temperature at the pump suction port, and the refrigerant gasifies.

On the other hand, if the water supply amount of the pump 8 is suppressed as described above, the rate of decrease of the refrigerant pressure at the pump inlet becomes slower, and the rate of decrease of the saturated refrigerant temperature becomes slower accordingly. Therefore, as shown in FIG. 2, a situation in which the saturated refrigerant temperature becomes lower than the refrigerant temperature is avoided, and thus gasification of the refrigerant at the pump suction port can be prevented.

In FIG. 2, the influence of the liquid level height H of the refrigerant and the influence of the pressure loss P of the refrigerant appear in the temperature difference (the difference between the saturated refrigerant temperature and the refrigerant temperature) at the portion A in the figure. As the liquid level height H is higher and the pressure loss P is smaller, the figure A
The temperature difference between the parts becomes large, and the gasification of the refrigerant at the pump inlet can be prevented.

The influence of the amount M of the refrigerant appears in the time of the portion B in the figure (the time taken for the temperature of the refrigerant to decrease). The smaller the amount M, the shorter the time of the portion B in the drawing, and the gasification of the refrigerant at the pump suction port can be prevented.

As described above, whether or not the refrigerant is likely to be gasified at the suction port of the pump 4 is judged from the liquid level height H, the amount M, and the pressure loss P of the refrigerant. The idling operation of the pump 1 is avoided by suppressing the gasification of the refrigerant by suppressing the increase rate of the condensation capacity in the vessel 2. Therefore, appropriate heat transport can be continued, damage to the pump 4 can be prevented, and reliability and safety can be improved. Moreover, since it is not necessary to use a small refrigerator as in the conventional case, the cost does not increase.

[2] A second embodiment will be described. Second
The embodiment deals with the case where the liquid surface height detector 11 cannot be attached, and the piping configuration is the same as that of the first embodiment except that the liquid surface height detector 11 is not provided.

In the memory 21, the length and diameter of the pipe 5 between the condenser 2 and the suction port of the pump 4 are stored in advance, and the capacity of the tank 3 is stored in advance.
The standard liquid level height Ha and the amount Ma of the refrigerant existing in the pipe 5 between the pump and the suction port of the pump 4 are stored in advance. The standard liquid level height Ha is data at the time of design or actual measurement data at the time of normal operation. The standard amount Ma can be calculated from the standard liquid level height Ha, the pipe length, the pipe diameter, and the tank capacity.

The control unit 20 has the following functional means. (1) The pressure loss P of the refrigerant existing in the pipe 5 between the condenser 2 and the suction port of the pump 4 is calculated from the measurement result of the circulation amount measuring device 12 and the stored contents (pipe length, pipe diameter) of the memory 21. The calculation means to be obtained.

(2) Liquid level height Ha and amount M in the memory 21
Control means for controlling the increasing rate of the condensation capacity in the condenser 2 based on a and the calculation result P of the calculation means. Specifically, the amount of water sent by the pump 8, that is, the amount of cold water flowing from the refrigerator 6 to the condenser 2 is controlled.

The operation is the same as that of the first embodiment except that the standard liquid level height Ha is used in place of the liquid level height H and the standard amount Ma is used in place of the amount M. The liquid level height and amount are treated as constants, and the rate of increase in the capacity of the condenser 2 is expressed as a function of the circulation amount measured by the circulation amount measuring device 12.

Also in this case, it is possible to prevent the gasification of the refrigerant in advance and avoid the idling operation of the pump 1, so that proper heat transport can be continued and the pump 4 can be prevented from being damaged. [3] A third embodiment will be described.

In the third embodiment, as shown in FIG.
A frequency detector 13 is provided instead of the circulation amount measuring device 12. The frequency detector 13 detects the operating frequency f of the pump 4. The operating frequency f is the frequency of the drive power supplied to the drive motor (not shown) of the pump 4,
The higher the rotational speed of the pump 4, the greater the amount of refrigerant delivered.

Further, the pressure sensor 3 is provided at the suction port of the pump 4.
1. A pressure sensor 32 is attached to the delivery port of the pump 4. The pressure sensor 31 detects the suction pressure of the pump 4. The pressure sensor 32 detects the discharge pressure of the pump 4.

The detection result of the frequency detector 13, the detection result of the pressure sensor 31, and the detection result of the pressure sensor 32 are sent to the control unit 20. The control unit 20 obtains a difference between the detection result of the pressure sensor 31 and the detection result of the pressure sensor 32, and calculates the pressure difference and the detection result of the frequency detector 13 to calculate the evaporator 1, the condenser 2, and the tank 3. , And the amount of refrigerant circulating through the pump 4. That is, the calculation means of the control unit 20, the frequency detector 13, and the pressure sensors 31, 3
2 constitutes a circulation amount measuring means.

The configuration and operation are the same as those of the second embodiment except that the circulation amount is measured using the frequency detector 13 as described above. [4] Modifications In each of the above-described embodiments, the tank 3 is provided between the condenser 2 and the pump 4, but the present invention can be carried out in the same manner even if the tank 3 is not provided. The capacity data of the tank 3 is excluded.

In each of the examples, the water supply amount of the pump 8 was controlled as the condensing capacity of the condenser 2.
It is also possible to control the refrigerating capacity of the refrigerator 6 as indicated by broken line arrows and to keep the water supply amount of the pump 8 constant.

In each of the embodiments, the cold water is supplied from the refrigerator 6 to the condenser 2. However, as shown in FIG. 5, the condenser in the refrigerator 6 may be used as it is as the condenser 2. . In this case, the refrigerating capacity of the refrigerator 6 is controlled as the condensing capacity of the condenser 2.

[0053]

As described above, according to the present invention, in the heat transport device of the first to fifth inventions, the liquid level height of the heat transport medium existing in the pipe between the condenser and the suction port of the pump is high. Well,
Since the rate of increase in the condensation capacity of the condenser is controlled based on the amount and pressure loss, it is possible to prevent gasification of the heat transfer medium at the pump inlet without increasing the cost. This makes it possible to continue appropriate heat transfer, prevent damage to the pump, and improve reliability and safety.

The heat transport device control method according to the sixth aspect of the present invention is based on the liquid level height, amount and pressure loss of the heat transport medium existing in the pipe between the condenser and the suction port of the pump. Since the rate of increase in the condensation capacity is controlled, it is possible to prevent gasification of the heat transfer medium at the pump inlet without increasing the cost, and to continue appropriate heat transfer. At the same time, damage to the pump can be prevented, and reliability and safety can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment.

FIG. 2 is a diagram showing a relationship between a refrigerant temperature and a saturated refrigerant temperature in each example.

FIG. 3 is a diagram showing a configuration of a second embodiment.

FIG. 4 is a diagram showing a configuration of a third embodiment.

FIG. 5 is a diagram showing a configuration of a modified example of each embodiment.

FIG. 6 is a diagram showing a relationship between a refrigerant temperature and a saturated refrigerant temperature in a conventional device.

[Explanation of symbols]

1 ... Evaporator, 2 ... Condenser, 3 ... Tank, 4 ... Pump, 5
... Piping, 6 ... Refrigerator, 7 ... Piping, 8 ... Pump, 9 ... Open / close valve, 11 ... Liquid level height detector, 12 ... Circulation amount measuring device, 13
... frequency detector, 20 ... control unit, 21 ... memory (storage means), 31 ... pressure sensor, 32 ... pressure sensor.

Front page continuation (72) Inventor Kazuo Chiba 1-34 Roppongi, Minato-ku, Tokyo Inside NTT Ft. Stock companies NTT FACILITIES

Claims (6)

[Claims] 1. A heat-transporting device in which an evaporator, a condenser, and a pump are sequentially connected by piping, and heat is transported by a phase change of a heat-transporting medium enclosed in the piping, wherein suction of the condenser and the pump A heat transfer medium characterized by comprising a control means for controlling the rate of increase in the condensation capacity of the condenser based on the liquid level height, amount, and pressure loss of the heat transfer medium existing in the pipe between the mouth and the port. apparatus. 2. A heat transport device in which an evaporator, a condenser, and a pump are sequentially connected in a pipe, and heat is transported by a phase change of a heat transport medium enclosed in the pipe, and suction of the condenser and the pump. A liquid level height detecting means for detecting the liquid level height of the heat transport medium existing in the pipe between the mouth and the storage means for storing the pipe length and the pipe diameter between the condenser and the suction port of the pump. And a first calculation for calculating the amount of the heat transport medium existing in the pipe between the condenser and the suction port of the pump from the detection result of the liquid level height detection means and the stored contents of the storage means. Means, circulation amount measuring means for measuring the amount of the heat transport medium circulating through the evaporator, the condenser, and the pump, and the heat transport medium existing in the pipe between the condenser and the suction port of the pump. The pressure loss of the Second calculation means obtained by calculation from the measurement result and the storage content of the storage means, the detection result of the liquid level height detection means, the calculation result of the first calculation means, and the calculation result of the second calculation means. And a control means for controlling an increasing rate of the condensation capacity of the condenser based on the above. 3. An evaporator, a condenser, and a pump are sequentially connected by pipes, and a heat transport device for transporting heat by a phase change of a heat transport medium enclosed in the pipes, wherein the condenser and the pump are sucked. Storage means for storing the standard liquid level height and amount of the heat transfer medium existing in the pipe between the mouth and the pipe length and pipe diameter between the condenser and the suction port of the pump; Circulation amount measuring means for measuring the amount of the heat transport medium circulating through the evaporator, the condenser, and the pump, and the pressure loss of the heat transport medium existing in the pipe between the condenser and the suction port of the pump. Is calculated from the measurement result of the circulation amount measuring means and the pipe length and the pipe diameter in the storage means, the liquid level in the storage means, the amount in the storage means, and the calculation Based on the calculation result of the means, Serial condenser, and a control means for controlling the rate of increase in condensation capacity of the by equipped with a heat transport apparatus according to claim. 4. The heat transport apparatus according to claim 2 or 3, wherein the circulation amount measuring means is provided in a pipe between the delivery port of the pump and the evaporator, and measures the flow rate of the refrigerant in the pipe. A heat transport device characterized by measuring the amount of circulation. 5. The heat transport apparatus according to claim 2 or 3, wherein the circulation amount measuring means detects an operating frequency of the pump, and suction pressure and discharge pressure of the pump. A heat transport device comprising: a pressure detection means; and a calculation means for calculating a circulation amount by calculating a detection result of the pressure detection means and a detection result of the detection means. 6. A heat-transporting device in which an evaporator, a condenser, and a pump are sequentially connected by piping, and heat is transported by a phase change of a heat-transporting medium sealed in the piping, wherein a condenser and a suction port of the pump are provided. A method for controlling a heat-transporting device, characterized in that the rate of increase in the condensation capacity of the condenser is controlled based on the liquid level height, the amount, and the pressure loss of the heat-transporting medium existing in the pipe between them.