JPH09210475A - Heat transport device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat transport device which can achieve both of the reduction of the circulation flow rate of a heat transport medium, and the reduction of a pump operation power, and by which an energy saving effect can be obtained while displaying the operation power reducing effect, which is a merit for the application of a pump, to the maximum. SOLUTION: The degree of superheat of a refrigerant (heat transport medium) at an evaporator 1 is detected. When this detected degree of superheat is higher than a set value, an expansion valve 5 is controlled in the opening direction, and if the expansion valve 5 is already fully opened, the operation frequency of a pump 4 is increased. When the detected degree of superheat is lower than the set value, the operation frequency of the pump 4 is decreased, and if the operation frequency has already been reduced to an allowable minimum frequency, the expansion valve 5 is controlled in the closing direction.

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, since the circulation flow rate of the heat transport medium can be reduced by utilizing latent heat (phase change) rather than by using sensible heat, recently, a heat transport system utilizing phase change of the heat transport medium has been developed. 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 side of the condenser to obtain a driving force for heat transport, and a compressor or the like is provided at the outlet side of the evaporator to perform heat transport. There is a method of obtaining the driving force of.

Of these two, from the viewpoint of operating power, the method using a pump is advantageous in that it uses less operating power than the method using a compressor. On the other hand, in the heat transport system, the degree of superheat of the heat transport medium in the evaporator is detected, and the circulating flow rate of the heat transport medium during the cycle is adjusted so that the degree of superheat becomes constant.

For example, when the air conditioning load is reduced, the amount of heat exchange in the evaporator is reduced, and all the heat transport medium flowing into the evaporator cannot be completely evaporated. At this time, the degree of superheat changes in the decreasing direction and becomes lower than the set value. When the degree of superheat becomes lower than the set value, the opening degree of the expansion valve during the cycle is reduced to compensate for it, and the circulation flow rate of the heat transport medium is reduced.

When the degree of superheat becomes higher than the set value, the opening degree of the expansion valve during the cycle is increased and the circulation flow rate of the heat transport medium is increased. As means for adjusting the circulation flow rate of the heat transport medium, in addition to the method of changing the opening degree of the expansion valve,
There is a method of providing a bypass path via a flow control valve to change the opening of the flow control valve. In this case, the opening degree of the flow rate control valve is increased, so that part of the heat transport medium circulating in the cycle flows through the bypass path, and the circulation flow rate in the cycle is reduced accordingly. When the opening degree of the flow rate control valve is reduced, the flow rate of the bypass path is reduced, and the circulation flow rate during the cycle is increased accordingly.

[0009]

In the case of obtaining operating power from a pump, when the superheat degree is controlled by adjusting the flow rate by the expansion valve, when the circulating weight is reduced by reducing the opening degree of the expansion valve, it is seen from the pump side. The flow path resistance increases, and the pump head rises as the flow path resistance increases. This state is shown in FIG. That is, as the circulation flow rate of the refrigerant decreases from Q ₂ to Q ₁ due to the reduction in the opening degree of the expansion valve, the pump head increases from H ₁ to H ₂ .

When the head of the pump increases, the driving power increases, and the advantage of using the pump, that is, the effect of reducing the driving power, is impaired. When controlling the superheat degree by adjusting the flow rate by the bypass route, the pump head does not unnecessarily increase when the circulation flow rate decreases,
Therefore, unnecessary increase in driving power does not occur. However, since the flow rate at the pump position does not change, the circulation flow rate is reduced, but it does not lead to a reduction in operating power.

The present invention takes the above circumstances into consideration,
The heat transport device of the first invention can achieve a reduction in the circulation flow rate of the heat transport medium together with a reduction in pump operating power,
The purpose is to maximize the effect of reducing the driving power, which is an advantage of using a pump, and to obtain an energy saving effect.

In addition to the object of the first invention, the heat-transporting device of the second invention aims to surely obtain the driving force for heat-transporting. The heat transport device of the third invention can achieve reduction of the circulation flow rate of the heat transport medium together with reduction of the pump driving power, and maximizes the driving power reduction effect which is an advantage of using the pump. However, the purpose is to obtain an energy saving effect.

[0013]

According to a first aspect of the present invention, there is provided a heat transport device, in which an evaporator, a condenser, a pump, and an expansion valve are sequentially connected in a pipe, and heat is generated by a phase change of a heat transport medium enclosed in the pipe. For detecting the degree of superheat of the heat transport medium in the evaporator, and if the degree of superheat detected by this detecting means is higher than the set value, it is determined whether the expansion valve is in the fully open state, If it is not in the fully open state, the expansion valve is operated in the opening direction, and if it is in the fully open state, the first control means for increasing the operating frequency of the pump, and the operating frequency of the pump if the degree of superheat detected by the detecting means is lower than a set value. Is a permissible minimum frequency, and if not the permissible minimum frequency, the operating frequency of the pump is lowered, and if the permissible minimum frequency, the second control means for operating the expansion valve in the closing direction.

In the heat transport apparatus of the second invention, the second control means in the first invention is such that when the operating frequency of the pump is the lowest allowable frequency, the maximum lift limit value when the pump head is at the lowest allowable frequency. If the maximum head limit value is reached, the expansion valve is not operated if the maximum valve head has not been reached.

In the heat transfer apparatus of the third invention, the evaporator, the condenser, and the pump are sequentially connected by piping, and a flow control valve is provided between the outlet side of the pump and the outlet side of the condenser. A bypass path is provided, and heat is transported by the phase change of the heat transport medium enclosed in the pipe, and the detection means for detecting the degree of superheat of the heat transport medium in the evaporator and the detection overheat of this detection means If the degree is higher than the set value, it is judged whether the flow control valve is in the fully closed state. If not, the flow control valve is operated in the closing direction, and if it is in the fully closed state, the operating frequency of the pump is raised. If the degree of superheat detected by the control means and the detection means is lower than the set value, it is judged whether the operating frequency of the pump is the allowable minimum frequency. Operate the flow control valve in the opening direction That includes a second control means.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment will be described below with reference to the drawings. The first embodiment corresponds to the first invention and the second invention. As shown in FIG. 1, the evaporator 1, the condenser 2, the tank 3, the pump 4, and the electric expansion valve 5 are sequentially connected by a pipe 6. A refrigerant (for example, CFC) is enclosed in the pipe 6 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 more than the allowable NPSH value specific to the pump. The tank 3 is for temporarily storing the liquid refrigerant from the condenser 2.

A refrigerator 11 is provided for supplying cold heat to the condenser 2, and a pipe 12 for circulating cold water is provided between the refrigerator 11 and the condenser 2. The pipe 12 is provided with a pump 13 and an opening / closing valve 14 for controlling the circulation and amount of cold water. The refrigerator 11 can be applied in various ways such as a vapor compression refrigerator, an absorption refrigerator, and an ice heat storage tank, and indicates all cold heat sources.

The liquid refrigerant sent out from the outlet of the pump 4 flows through the expansion valve 5 to the evaporator 1, where heat is taken from the outside and evaporated. This gas refrigerant then flows to the condenser 2 where it radiates heat to the cold water supplied from the refrigerator 11 and liquefies. 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. In this way, the cold heat released from the refrigerator 11 is transported to the evaporator 1 side.

Further, in the pipe 6 near the delivery port of the pump 4,
The pressure sensor 7 is attached. The pressure sensor 7 detects the pressure of the refrigerant delivered from the pump 4. Pump 4
A pressure sensor 8 is attached to the pipe 6 in the vicinity of the suction port. The pressure sensor 8 detects the pressure of the refrigerant sucked by the pump 4.

Further, in the pipe 6 near the outlet of the evaporator 1,
Refrigerant state detection means 9 is provided. The refrigerant state detecting means 9 detects the temperature and pressure of the refrigerant in the pipe 6.
On the other hand, the control unit 20 is provided. The expansion valve 5, the pressure sensor 7, the pressure sensor 8, the refrigerant state detecting means 9, the pump 13, the opening / closing valve 14, and the pump operating frequency operating means 21 are connected to the control unit 20.

The pump operating frequency operating means 21 comprises, for example, an inverter circuit for supplying drive power to the motor of the pump 4, and operates the output frequency of the inverter circuit in accordance with a command from the control unit 20. The output frequency of the inverter circuit is referred to below as the operating frequency F of the pump 4.
Called.

The control unit 20 includes the following [1], [2] and [3] as main functional means. [1] Superheat detection means for detecting the degree of superheat of the refrigerant in the evaporator 1 by calculation using the temperature and pressure detected by the refrigerant state detection means 9.

[2] Pump 4 detected by the pressure sensor 7
Measuring means for measuring the difference between the delivery refrigerant pressure of the pump and the suction refrigerant pressure of the pump 4 detected by the pressure sensor 8 as the head of the pump 4.

[3] The operating frequency F of the pump 4 and the opening degree of the expansion valve 5 are controlled so that the degree of superheat detected by the degree of superheat detection means becomes constant at a predetermined set value (for example, 5 ° C.). Control means.

Specifically, (a) when the degree of superheat is higher than a set value, (a) determines whether the expansion valve 5 is in the fully open state, and if not, operates the expansion valve 5 in the opening direction. The first control means for increasing the operating frequency F of the pump 4 in the fully opened state, and (b) when the degree of superheat is lower than the set value, it is judged whether the operating frequency F of the pump 4 is the allowable minimum frequency Fmin, and If it is not the minimum frequency Fmin, the operating frequency F of the pump 4 is lowered, and if it is the allowable minimum frequency Fmin, the expansion valve is measured only when the lift of the pump 4 measured by the measuring means does not reach the maximum lift limit value at the allowable minimum frequency. 5
In the closing direction and does not operate the expansion valve 5 when the maximum lift limit value is reached.

The allowable minimum frequency Fmin is the minimum operating frequency for operating the pump 4 without any trouble. The maximum head limit value is the maximum head that does not hinder the operation of the pump 4, and a plurality of values are predetermined according to the operating frequency F.

Next, the operation of the above configuration will be described with reference to the flowchart of FIG. When the pump 4 is operated, the liquid refrigerant is delivered from the pump 4. This liquid refrigerant flows through the expansion valve 5 set to a predetermined opening degree to the evaporator 1, where heat is taken from the outside to be 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.

During operation, the temperature and pressure of the refrigerant flowing out of the evaporator 1 are detected by the refrigerant state detecting means 9, and the degree of superheat of the refrigerant in the evaporator 1 is detected by calculation using the detection result. Then, the opening degree of the expansion valve 5 and the operating frequency F of the pump 4 are controlled so that the detected degree of superheat becomes constant at a target set value (for example, 5 ° C.).

For example, when the degree of superheat is higher than the set value, the circulating flow rate of the refrigerant is increased to reduce the degree of superheat.
The opening degree of the expansion valve 5 is operated in the opening direction. However, if the expansion valve 5 is already fully opened, the operating frequency F of the pump 4 is operated in the upward direction. When the expansion valve 5 is fully opened and the operating frequency F reaches the maximum allowable operating frequency Fmax, the state is maintained as it is.

When the degree of superheat is lower than the set value, the operating frequency F of the pump 4 is operated downward in order to reduce the circulation flow rate of the refrigerant and increase the degree of superheat. However, if the operating frequency F has already dropped to the allowable minimum operating frequency Fmin, in the case where the lift of the pump 4 measured from the pressure detected by the pressure sensors 7 and 8 has not reached the maximum lift limit value at the allowable minimum frequency. As long as the expansion valve 5 is operated in the closing direction. When the operating frequency F drops to the minimum allowable operating frequency Fmin and the measured lift reaches the maximum lift limit value, the state is maintained as it is.

By the way, when the air conditioning load decreases, the heat exchange amount of the evaporator 1 decreases, and all the refrigerant flowing into the evaporator 1 cannot be completely evaporated. At this time, the degree of superheat changes in the decreasing direction and becomes lower than the set value.

When the degree of superheat becomes lower than the set value, the operating frequency of the pump 4 is operated downward as described above. In this way, the operating frequency of the pump 4 is lowered, so that the circulation flow rate of the refrigerant is reduced to a state commensurate with the air conditioning load. The head of the pump 4 decreases as the circulation flow rate decreases.

That is, as shown in FIG. 3, as the circulation flow rate of the refrigerant decreases from Q ₂ to Q ₁ , the pump 4 head decreases from H ₂ to H ₁ contrary to the conventional case. Thus, by achieving the reduction of the circulation flow rate of the refrigerant in the direction of lowering the head of the pump 4, there is no need to increase the pump operating power, on the contrary, the operating power can be reduced, and the advantage of using the pump 4 is obtained. The energy saving effect can be obtained while maximizing the effect of reducing the driving power.

Further, by controlling the set value of the superheat degree to be constant, the evaporation of the refrigerant in the evaporator 1 can be almost finished near the outlet of the evaporator 1. Therefore, it is possible to perform efficient and efficient air conditioning with an optimum capacity that always corresponds to the air conditioning load, and to perform stable and lean operation.

Moreover, since the pump 4 is operated within a range in which the lift does not exceed the maximum lift limit value, the driving force for heat transport can be reliably obtained without any hindrance to the operation of the pump 4.
Next, a second embodiment will be described. The second embodiment corresponds to the third invention. In the drawings, FIG.
The same parts as those of the above are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 4, a bypass path 32 is connected between the pipe 6 on the outlet side of the pump 4 and the pipe 6 on the outlet side of the condenser 2 via a flow rate control valve 31. The bypass path 32 is for bypassing a part of the refrigerant sent from the pump 4 to the outlet side of the condenser 2, and the bypass amount can be adjusted by changing the opening degree of the flow rate adjusting valve 31.

The expansion valve 5, the refrigerant state detecting means 9, the pump 13, the opening / closing valve 14, the pump operating frequency operating means 21, and the flow rate adjusting valve 31 are connected to the control section 20. The pressure sensors 7 and 8 do not need to be provided and are removed.

The control unit 20 has the following [1] and [2] as main functional means. [1] Superheat detection means for detecting the degree of superheat of the refrigerant in the evaporator 1 by calculation using the temperature and pressure detected by the refrigerant state detection means 9.

[2] The opening degree of the flow rate control valve 31 and the operating frequency F of the pump 4 are controlled so that the degree of superheat detected by the degree of superheat detection means becomes constant at a preset value (for example, 5 ° C.). Control means to do.

Specifically, (a) when the degree of superheat is higher than a set value, the control means determines whether or not the flow rate control valve 31 is in the fully closed state, and if it is not in the fully closed state, the flow rate control valve 31 is closed. If the superheat degree is lower than the set value, the operating frequency F of the pump 4 is the allowable minimum frequency Fmin. If it is not the minimum allowable frequency Fmin, lower the operating frequency F of the pump 4 and set the minimum allowable frequency Fmi.
If n, it comprises a second control means for operating the flow rate control valve 31 in the opening direction.

Next, the operation of the above configuration will be described with reference to the flowchart of FIG. During operation, the temperature and pressure of the refrigerant flowing out of the evaporator 1 are detected by the refrigerant state detecting means 9, and the degree of superheat of the refrigerant in the evaporator 1 is detected by calculation using the detection result. Then, the opening degree of the flow rate control valve 31 and the operating frequency F of the pump 4 are controlled so that the detected degree of superheat becomes constant at a target set value (for example, 5 ° C.). The expansion valve 5 is set to a predetermined opening.

For example, when the degree of superheat is higher than the set value, the circulating flow rate of the refrigerant is increased to reduce the degree of superheat.
The opening degree of the flow rate control valve 31 is operated in the closing direction. When the opening degree of the flow rate control valve 31 decreases, the amount of the refrigerant sent from the pump 4 and flowing into the bypass path 32 decreases, and the amount of the refrigerant flowing to the evaporator 1 increases accordingly.

However, if the flow rate control valve 31 is already fully closed, the operating frequency F of the pump 4 is operated in the upward direction. When the flow rate adjusting valve 31 is fully closed and the operating frequency F reaches the maximum allowable operating frequency Fmax, the state is maintained as it is.

When the degree of superheat is lower than the set value, the operating frequency F of the pump 4 is operated in the downward direction in order to reduce the circulation flow rate of the refrigerant and increase the degree of superheat. However, if the operating frequency F has already dropped to the allowable minimum operating frequency Fmin, the opening degree of the flow control valve 31 is operated in the opening direction. When the operating frequency F drops to the allowable minimum operating frequency Fmin and the flow rate control valve 31 is fully opened, the state is maintained as it is.

When the air conditioning load decreases, the heat exchange amount of the evaporator 1 decreases and all the refrigerant flowing into the evaporator 1 cannot be completely evaporated. At this time, the degree of superheat changes in the decreasing direction and becomes lower than the set value.

When the degree of superheat becomes lower than the set value, the operating frequency of the pump 4 is operated downward as described above. In this way, the operating frequency of the pump 4 is lowered, so that the circulation flow rate of the refrigerant is reduced to a state commensurate with the air conditioning load. The head of the pump 4 decreases as the circulation flow rate decreases.

That is, as in the case of the first embodiment, as shown in FIG. 3, as the circulation flow rate of the refrigerant decreases from Q ₂ to Q ₁ , the head of the pump 4 decreases from H ₂ to H ₁ . Become. Thus, by achieving the reduction of the circulation flow rate of the refrigerant in the direction of lowering the head of the pump 4, there is no need to increase the pump operating power, on the contrary, the operating power can be reduced, and the advantage of using the pump 4 is obtained. The energy saving effect can be obtained while maximizing the effect of reducing the driving power.

Further, by controlling the set value of the superheat degree to be constant, the evaporation of the refrigerant in the evaporator 1 can be almost finished in the vicinity of the outlet of the evaporator 1. Therefore, it is possible to perform efficient and efficient air conditioning with an optimum capacity that always corresponds to the air conditioning load, and to perform stable and lean operation.

Although the tank 3 is provided between the condenser 2 and the pump 4 in each of the above-described embodiments, the present invention can be similarly implemented even when the tank 3 is not provided. Moreover, although the case where the number of the evaporators 1 is one has been described, the same can be applied to the case where a plurality of the evaporators 1 are connected in parallel. Further, the refrigerator 11 and the condenser 2 may be integrated. Other,
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.

[0051]

As described above, according to the present invention, the heat transport device of the first invention detects the superheat degree of the heat transport medium in the evaporator, and when the detected superheat degree is higher than the set value. In the case of operating the expansion valve in the opening direction, if the expansion valve is already fully open, the operating frequency of the pump is increased, while if the detected superheat is lower than the set value, the operating frequency of the pump is decreased.
When the operating frequency has already dropped to the allowable minimum frequency, the expansion valve is operated in the closing direction, so that the circulation flow rate of the heat transport medium can be reduced together with the reduction of the pump operating power. The energy saving effect can be obtained while maximizing the effect of reducing the driving power, which is an advantage.

In the heat transport apparatus of the second invention, in the first invention, when the detected superheat degree is lower than the set value, when the operating frequency of the pump has already dropped to the allowable minimum frequency, the pump head is allowed. Since the expansion valve is operated in the closing direction only when the maximum lift limit value at the lowest frequency is not reached, in addition to the object of the first invention, a driving force for heat transport can be reliably obtained.

The heat transport device of the third invention detects the superheat degree of the heat transport medium in the evaporator, and when the detected superheat degree is higher than the set value, the flow control valve is operated in the closing direction, If the flow control valve is already fully closed, raise the pump operating frequency.On the other hand, if the detected superheat is lower than the set value, lower the pump operating frequency, and if the operating frequency is already at the allowable minimum frequency, set the flow rate. Since the control valve is operated in the opening direction, the circulation flow rate of the heat transport medium can be reduced together with the reduction of the pump operating power, and the advantage of using the pump is that the operating power reducing effect is maximized. The energy saving effect can be obtained while exhibiting excellent performance.

[Brief description of drawings]

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

FIG. 2 is a flowchart for explaining the operation of the first embodiment.

FIG. 3 is a diagram showing a relationship among a refrigerant circulation flow rate, a pump operating frequency, and a pump head in each example.

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

FIG. 5 is a flowchart for explaining the operation of the second embodiment.

FIG. 6 is a diagram showing a relationship among a refrigerant circulation flow rate, a pump operating frequency, and a pump head in a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Evaporator 2 ... Condenser 3 ... Tank 4 ... Pump 6 ... Piping 7 ... Refrigerator 8 ... Piping 9 ... Pump 10 ... Open / close valve 11 ... Refrigerant state detection means 20 ... Control part 21 ... Pump operating frequency operation means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shisei Makoto 1-33, Roppongi 4-chome, Minato-ku, Tokyo (NTT Facilities) (72) Inventor Kazuo Chiba 4-chome, Roppongi, Minato-ku, Tokyo No. 33 Stock Company NTT Facilities

Claims (3)

[Claims] 1. A heat-transporting device, in which an evaporator, a condenser, a pump, and an expansion valve are sequentially connected in a pipe, and heat is transported by a phase change of a heat-transporting medium sealed in the pipe, wherein When the superheat degree of the heat transport medium is detected, and when the superheat degree detected by the detector is higher than a set value, it is determined whether the expansion valve is in the fully open state. If not, the expansion valve is operated in the opening direction. However, if it is in the fully open state, the first control means for increasing the operating frequency of the pump, and if the detected superheat degree of the detecting means is lower than a set value, it is determined whether the operating frequency of the pump is the minimum allowable frequency,
The heat-transporting device further comprises: second control means for lowering the operating frequency of the pump if it is not the minimum allowable frequency, and operating the expansion valve in the closing direction if it is the minimum allowable frequency. 2. The heat transport apparatus according to claim 1, wherein the second control means, when the operating frequency of the pump is the lowest allowable frequency, the pump head reaches the maximum head limit value at the lowest allowable frequency. A heat transport device characterized in that the expansion valve is operated in the closing direction only when it is not present, and the expansion valve is not operated when the maximum lift limit value is reached. 3. An evaporator, a condenser, and a pump are sequentially connected by piping, and a bypass path is provided between the pump outlet side and the condenser outlet side via a flow rate control valve, and the inside of the piping is connected. In a heat transport device that transports heat by phase change of the enclosed heat transport medium, a detection unit that detects a superheat degree of the heat transport medium in the evaporator, and a detected superheat degree of this detection unit is higher than a set value. Determining whether the flow rate control valve is in a fully closed state, and operating the flow rate control valve in a closing direction if not in a fully closed state, and increasing the operating frequency of the pump in a fully closed state, When the detection degree of superheat of the detection means is lower than a set value, it is determined whether the operating frequency of the pump is the minimum allowable frequency,
The heat-transporting device further comprises: second control means for lowering the operating frequency of the pump if it is not the lowest allowable frequency, and operating the flow control valve in the opening direction if it is the lowest allowable frequency.