JP2001336788A - Supercooling water-manufacturing device, and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supercooling water-manufacturing device and method for stably maintaining supercooling water at an optimum temperature (for example, 2 deg.C±0.2 deg.C) for generating ice by a refrigerant, reducing the error in temperature measurement and time constant, accurately maintaining the supercooling water at an outlet, and hence preventing freezing inside for operating stably for a long time. SOLUTION: The steam pressure of liquid refrigerant in a supercooler 1 is detected, and the flow rate of a suction constriction valve V1 and an expansion valve 4 is controlled by an ice generation-controlling device 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercooled water producing apparatus for maintaining supercooled water at an optimum temperature suitable for ice formation using a refrigerant, and a control method thereof.

[0002]

2. Description of the Related Art An ice heat storage system in which cooling water for air conditioning is cooled to supercooling water having a solidification temperature (0 ° C.) or less, and fine ice is precipitated from the supercooling water and provided in a heat storage tank. As means for producing supercooled water applied to this system, Japanese Patent Application Laid-Open Nos.
No. 57925, JP-A-8-313128, and the like have been proposed.

Japanese Patent Application Laid-Open No. Hei 3-271167 discloses a method of controlling a heat pump apparatus for producing supercooled water. As shown in FIG. 4, a shell-and-tube system in which water is supplied to a tube and refrigerant is supplied to a shell. An evaporator of a heat pump device is constituted by the heat exchanger 1 of the mold type, and a heat pump device having a refrigerant circulation cycle formed by returning from the evaporator 1 to the evaporator 1 via the compressor 2, the condenser 3 and the expansion valve 4 is operated. In the meantime, while the liquid refrigerant is present in the shell of the evaporator 1 and the water flowing in the tube is cooled to a temperature of 0 ° C. or less while boiling and evaporating the liquid refrigerant, supercooled water is continuously produced. The temperature of the water before entering the tube 1a of the evaporator is continuously detected, and the capacity of the compressor 2 is controlled based on the detected value so that the refrigerant temperature in the shell 1b is maintained at a predetermined temperature lower than the detected water temperature. Do too It is.

In this control method, the heat transfer in the supercooler (evaporator 1) is performed by boiling heat transfer, so that uniform heat transfer can be performed, and the temperature control is performed by detecting the temperature of water before entering the tube 1a. Since the capacity of the compressor 2 is controlled by the pressure control, the temperature is easily detected.

[0005] Japanese Patent Application Laid-Open No. 6-257925 discloses a "supercooled water producing apparatus". In a similar apparatus, a preheating heat exchanger for heating cold water is provided.
Ice nuclei are melted by a preheat heat exchanger to prevent freezing of the heat transfer tubes in the subcooler. Further, JP-A-8-31312
No. 8 “supercooled water production equipment” is similar equipment,
A reheat pipe is provided in parallel with a water pipe connecting the pump for circulating water in the heat storage tank and the supercooler, and the amount of water in the reheat pipe is controlled so that the water temperature at the inlet of the supercooler becomes constant.

[0006]

SUMMARY OF THE INVENTION Solidification temperature (freezing temperature)
Supercooled water cooled to below has the property of being easily frozen by a slight impact. Therefore, there is a problem that the heat exchanger is easily frozen in the process of producing the supercooled water, and it is difficult to stably operate the supercooled water producing apparatus for a long time.

In particular, it is important to control the temperature of the supercooled water,
Decreasing the temperature of the supercooled water improves the ice generation efficiency, but has the property of freezing when subjected to an impact. Therefore, while using a heat exchanger suitable for the production of supercooled water, the temperature of the produced supercooled water is controlled to an appropriate temperature (for example, 2 ° C. ± 0.2 ° C.), and freezing inside the heat exchanger is performed. Need to be prevented.

However, it has been difficult to measure the temperature of the supercooled water. That is, when the supercooling water temperature is directly measured, ice is generated at the temperature detecting end, and accurate temperature measurement cannot be performed. Further, a radiation thermometer or the like that indirectly measures the temperature of the supercooled water is susceptible to disturbance and has low accuracy (for example, about ± 1 ° C.), so that the above-described high-precision temperature measurement cannot be performed. Furthermore, in the above-described conventional example, the water temperature at the inlet of the subcooler is detected and controlled. However, since the time constant of the temperature measurement is large (around 10 seconds), the measurement delay is large, and even if freezing is detected, it is difficult to cope with the detection. There was a problem that stable operation was not possible with a delay.

There is also a problem that it is difficult to maintain the conditions for ice formation. That is, the relationship between the temperature of the supercooler and the temperature of the supercooled water is not constant, and varies depending on operating conditions and aging. Therefore, it has been difficult to maintain the temperature of the supercooled water at a temperature suitable for ice formation.

Further, in a subcooler that uses brine instead of a refrigerant, a device for cooling the brine is required in addition to the subcooler, so that the equipment becomes large, and the maintenance and management of the brine concentration is required, and the operating cost is reduced. There is a problem in that the merit of an ice heat storage system that stores heat in the form of ice by using nighttime electric power for daytime cooling demand is reduced.

The present invention has been made to solve the various problems described above. That is, an object of the present invention is to stably maintain supercooled water at an optimum temperature (for example, 2 ° C. ± 0.2 ° C.) suitable for ice formation by using a refrigerant, and to reduce the temperature measurement error and time. It is an object of the present invention to provide a supercooled water producing apparatus and a control method thereof, wherein the constant is small, the supercooled water at the outlet can be maintained with high precision, and thereby the freezing inside can be prevented and the stable operation can be performed for a long time. .

[0012]

According to the present invention, a compressor (2), a condenser (3) and an expansion valve are provided from a shell (1b) of a subcooler (1) comprising a shell-and-tube heat exchanger. (4) a heat pump device forming a refrigerant circulation cycle returning to the shell through the shell; and a chilled water circulating device for circulating chilled water into the tube (1a) of the subcooler. In a supercooled water producing apparatus for continuously producing supercooled water by boiling and evaporating the water flowing in the tube to a temperature below the freezing point, the vapor pressure of the liquid refrigerant in the shell (1b) is detected. An apparatus for producing supercooled water, comprising: an ice generation control device (10) for controlling this;

Further, according to the present invention, the shell (1) of the subcooler (1) comprising a shell and tube type heat exchanger is provided.
b) a heat pump device that forms a refrigerant circulation cycle returning to the shell via the compressor (2), the condenser (3) and the expansion valve (4), and the tube (1) of the subcooler.
a) a method for controlling a supercooled water producing apparatus for continuously producing supercooled water by cooling a water flowing in a tube of an evaporator to a temperature below a freezing point, comprising: And a control method of the supercooled water producing apparatus, characterized in that the vapor pressure of the liquid refrigerant in the shell (1b) is detected and controlled within a certain range.

According to the above-described apparatus and method of the present invention, the supercooling is performed by controlling the temperature of the supercooler in a stable manner, instead of directly controlling the temperature of the supercooled water by directly measuring the temperature of the supercooled water. Since this is an indirect method for stabilizing the water temperature, it is possible to avoid using an unstable and short-life temperature detector (for example, a thermocouple) for measuring the temperature of the supercooled water. When the temperature inside the subcooler is directly measured, the temperature of the local refrigerant gas atmosphere is measured, but by measuring the saturated vapor pressure, the boundary between the refrigerant gas inside the subcooler and the refrigerant liquid is measured. The temperature of the surface can be measured with high accuracy.

According to a preferred embodiment of the present invention, a vapor pressure detector P3 for detecting the vapor pressure of the liquid refrigerant in the shell (1b), and a vaporized refrigerant from the shell (1b) to the compressor (2). A suction throttle valve V1 for controlling the flow rate,
The steam pressure signal detected by the steam pressure detector P3 is input to the ice generation control device (10), and the flow rate of the suction throttle valve V1 and the expansion valve (4) is controlled by the ice generation control device. That is, the saturated vapor pressure corresponding to the saturated vapor temperature of the liquid refrigerant in which ice is optimally generated is preset, and the suction throttle valve and the expansion valve are set so that the refrigerant temperature corresponding to the saturated vapor pressure becomes the optimal temperature for ice generation. Control valves simultaneously. With this configuration and method, it is possible to stably control the temperature of the refrigerant corresponding to the saturated vapor pressure to a temperature optimum for ice formation.

Further, the condenser (3) is connected to an expansion valve (4).
Temperature detector T4 for detecting the temperature of the liquid refrigerant flowing to
And a condensed liquid temperature control device (12) for controlling the condenser so as to keep the temperature of the liquid refrigerant constant, so as to keep the temperature of the liquid refrigerant supplied from the condenser within a constant range. With this configuration and method, it is possible to stabilize the temperature of the liquid refrigerant supplied from the condenser and maintain the condition in which the subcooler functions optimally.

Furthermore, a chilled water temperature detector T1 and a chilled water pressure detector P1 for detecting the temperature and pressure of the chilled water supplied to the subcooler (1), and a heater installed upstream of the subcooler And a circulating pump, and a chilled water system controller (14) for controlling the heater and the circulating pump so as to keep the temperature and pressure of the chilled water supplied to the subcooler constant. Is maintained within a certain range, and the cold water inlet temperature is kept constant. With this configuration and method, by keeping the pressure of the water supplied to the subcooler constant,
The flow condition under which the subcooler functions optimally can be maintained. In addition, even if minute ice blocks remain in the cold water sucked from the heat storage water tank, the ice blocks become cores of ice and are prevented from freezing inside the supercooler by supplying the cold water inlet temperature at a constant temperature. be able to.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In the drawings, common parts are denoted by the same reference numerals. FIG. 1 is an overall configuration diagram of a supercooled water production device of the present invention. As shown in this figure, the supercooled water production device of the present invention includes a heat pump device and a cold water circulation device. The heat pump device includes a compressor 1, a condenser 3 and an expansion valve 4 from a shell 1 b of a subcooler 1 composed of a shell and tube heat exchanger.
To form a refrigerant circulation cycle returning to the shell 1b. The chilled water circulation device includes a heat storage water tank 11, a heater H, and a circulation pump P, and circulates and supplies cold water from the heat storage water tank 11 into the tube 1a of the supercooler 1. With this configuration, the supercooled water producing apparatus continuously produces supercooled water by boiling and evaporating the liquid refrigerant in the shell 1b of the evaporator 1 to cool the water flowing in the tube to a temperature below the freezing point. It has become.

In the present invention, the subcooler 1 is a liquid-filled heat exchanger filled with liquid refrigerant to a level that fills the inside of the tube 1a, and does not use brine. The heat storage water tank 11 stores a mixture of water and ice produced by the supercooler 1.

The apparatus for producing supercooled water according to the present invention includes an ice generation controller 10, a condensate temperature controller 12, a chilled water controller 14, and a general controller 16. The general control device 16 centrally controls the ice generation control device 10, the condensate temperature control device 12, and the chilled water system control device 14 so as to stably operate the subcooler 1, and centrally monitors the operation state of each device. Note that the general control device 16 is not indispensable, and may be independently controlled by each control device.

The supercooler 1 is provided with a vapor pressure detector P3 for detecting the vapor pressure of the liquid refrigerant in the shell 1b. Further, the heat pump device includes a suction throttle valve V1 for controlling the flow rate of the evaporated refrigerant from the shell 1b to the compressor 2. With this configuration, a saturated vapor pressure corresponding to the saturated vapor temperature of the liquid refrigerant at which ice is optimally generated is set in advance,
The steam pressure signal detected by the steam pressure detector P3 is input to the ice generation control device 10, and the ice generation control device 10 detects the vapor pressure of the liquid refrigerant in the shell 1b and detects the suction throttle valve V1.
And the flow rate of the expansion valve 4 are simultaneously controlled, whereby the vapor pressure of the liquid refrigerant is controlled within a certain range, and the refrigerant temperature corresponding to the saturated vapor pressure is controlled to be an optimum temperature for ice formation.

For example, when the refrigerant temperature becomes higher than the set temperature, the saturated vapor pressure becomes higher. Therefore, by opening the suction throttle valve V1 and increasing the suction amount of the compressor 2, the vapor pressure of the liquid refrigerant in the shell 1b is reduced. Lowering the temperature to the optimum range. Similarly, even if the flow rate of the expansion valve 4 is reduced, the shell 1 b
Lowering the vapor pressure of the liquid refrigerant while maintaining the amount of evaporation in the
The temperature can be returned to the optimal range. The suction throttle valve V1 and the expansion valve 4 are preferably controlled simultaneously. When the refrigerant temperature is lower than the set temperature, the control is reversed.

FIG. 2 is a Mollier diagram of the refrigerant used in the present invention. In this figure, the horizontal axis is pressure and the vertical axis is temperature. From this Mollier chart, it is understood that the refrigerant temperature corresponding to the saturated vapor pressure of the liquid refrigerant accurately corresponds to the refrigerant temperature.
Therefore, in the temperature measurement using a thermocouple, etc., only the local temperature is known, and the error of the temperature measurement and the influence of the time constant are large, but the saturated vapor pressure is representative of the interface temperature between the gas phase and the liquid layer. It can be seen that the error and the time constant are small and are not affected by local temperature variations.

Further, in FIG. 1, the heat pump device is provided between the condenser 3 and the expansion valve 4 with a refrigerant temperature detector T4 for detecting the temperature of the liquid refrigerant flowing from the condenser 3 to the expansion valve 4. Further, the condensed liquid temperature control device 12 controls the condenser 3 so as to keep the temperature of the liquid refrigerant detected by the refrigerant temperature detector T4 constant. This control can be performed, for example, by adjusting the flow rate of the cooling water with the flow rate control valve V4.

The chilled water circulating device has a chilled water temperature detector T for detecting the temperature and pressure of the chilled water supplied to the subcooler 1.
1 and a chilled water pressure detector P1, a heater H and a circulation pump P installed upstream of the subcooler 1. The chilled water control device 14 monitors the state of the chilled water circulation device, and determines the temperature T1 and the pressure P1 of the chilled water supplied to the subcooler 1.
Is controlled so that is within a certain range.

FIG. 3 is a diagram showing an embodiment of the present invention.
In this figure, the horizontal axis represents time from about 8:40 am to about 13:00 pm, and the vertical axis represents temperature and pressure. Also,
Each line in the figure represents the cooling water pressure of the subcooler 1, the cooling water flow rate, the central temperature of the subcooler 1, the cooling water inlet temperature, the internal pressure of the subcooler 1, and the expansion valve. At the outlet pressure. From this figure, the internal pressure of the subcooler 1 and
It can be seen that there is a correlation between the directly measured temperature. Also, the measured value of the internal pressure is very stable,
It can be seen from this figure that the measurement can be performed with high accuracy. Further, in the temperature measurement, a time delay of the measurement occurs due to the influence of the protective tube or the like, but since there is no time delay in the pressure measurement, the temperature change in the subcooler 1 can be more accurately known.

As described above, the present invention improves the supercooling water temperature control method, and does not use the direct method of measuring the supercooling water temperature and stably controlling the supercooling water temperature, but the method of controlling the supercooler refrigerant temperature. An indirect system that stabilizes the supercooling water temperature by performing stable control is adopted. When the temperature inside the subcooler is directly measured, the temperature of the local refrigerant gas atmosphere is measured, but by measuring the saturated vapor pressure, the boundary between the refrigerant gas inside the subcooler and the refrigerant liquid is measured. The surface temperature could be measured accurately.

Also, a saturated steam temperature control in the supercooler is adopted, and a saturated steam pressure corresponding to a saturated steam temperature at which ice is generated optimally is set, and a refrigerant temperature corresponding to the saturated steam pressure is optimal for ice formation. A method was adopted in which the suction throttle valve and the expansion valve were simultaneously controlled so as to reach a desired temperature. Furthermore, in order to stabilize the condition of the cold water supplied to the subcooler, the pressure and temperature of the water supplied to the subcooler are kept constant, thereby maintaining the flow condition under which the supercooler functions optimally. And

Further, the temperature of the liquid refrigerant supplied from the condenser is stabilized, and the condition that the supercooler functions optimally is maintained. Furthermore, by adopting a shell and tube type heat exchanger that does not use brine, the basic principle of a conventional chilled water production apparatus can be applied as it is.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention.

[0031]

As described above, the apparatus for producing supercooled water and the control method thereof according to the present invention have the following features. (1) An ice heat storage facility using ice that has a higher heat storage effect than water. The size of the entire apparatus is reduced, the degree of freedom of the apparatus is increased, and the construction cost is reduced. (2) A supercooler that does not use brine can be put to practical use, and a heat exchanger for cooling brine is not required. Thus, the entire apparatus can be downsized, the degree of freedom of the apparatus can be increased, and the construction cost can be reduced. (3) Since no brine is used, it is not necessary to manage the brine, so that the operating unit price is reduced and the nighttime electric power utilization effect can be sufficiently obtained. (4) By stabilizing the conditions of water and refrigerant supplied to the subcooler, it is possible to eliminate the effects of changes in weather conditions and deterioration over time, so that it is suitable for operation of the supercooler. Conditions are maintained and efficient operation is possible.

Therefore, the supercooled water producing apparatus and the control method of the present invention stably maintain the supercooled water at an optimum temperature (for example, 2 ° C. ± 0.2 ° C.) suitable for ice formation by using a refrigerant. And the temperature measurement error and time constant are small, and the supercooled water at the outlet can be maintained with high accuracy. This prevents internal freezing and enables stable operation for a long time. Has the effect.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an apparatus for producing supercooled water according to the present invention.

FIG. 2 is a Mollier diagram of a refrigerant used in the present invention.

FIG. 3 is a diagram showing an embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional supercooled water producing apparatus.

[Explanation of symbols]

1 heat exchanger (evaporator), 1a tube, 1b shell, 2 compressor, 3 condenser, 4 expansion valve, 10 ice generation control device, 11 heat storage water tank, 12 condensate temperature control device, 14 cold water system control device, V1 suction throttle valve, V2
V5 flow control valve, F1 flow meter, P circulation pump, P
1 Cold water pressure detector, P3 Steam pressure detector, T1, T
2 Cold water temperature detector, T3, T4 Refrigerant temperature detector, H
Heater

Claims (8)

[Claims] 1. A compressor (2) from a shell (1b) of a subcooler (1) comprising a shell and tube heat exchanger,
A heat pump device forming a refrigerant circulation cycle returning to the shell via a condenser (3) and an expansion valve (4); and a chilled water circulating device for circulating chilled water into the tube (1a) of the supercooler, In a supercooled water producing apparatus for continuously producing supercooled water by boiling and evaporating a liquid refrigerant in a shell of an evaporator to cool water flowing in a tube to a temperature below a freezing point, the liquid in the shell (1b) An apparatus for producing supercooled water, comprising: an ice generation control device (10) for detecting and controlling the vapor pressure of a refrigerant. 2. A vapor pressure detector P3 for detecting a vapor pressure of the liquid refrigerant in the shell (1b), and a suction throttle valve V1 for controlling a flow rate of the vaporized refrigerant from the shell (1b) to the compressor (2). The steam pressure signal detected by the steam pressure detector P3 is input to the ice generation control device (10), and the flow rate of the suction throttle valve V1 and the expansion valve (4) is controlled by the ice generation control device. The supercooled water producing apparatus according to claim 1, wherein the apparatus is controlled. 3. A refrigerant temperature detector T4 for detecting a temperature of a liquid refrigerant flowing from the condenser (3) to an expansion valve (4), and a condenser for controlling the condenser to keep the temperature of the liquid refrigerant constant. The apparatus for producing supercooled water according to claim 1, further comprising a liquid temperature control device (12). 4. A chilled water temperature detector T1 and a chilled water pressure detector P1 for detecting the temperature and pressure of chilled water supplied to the subcooler (1), and a heater installed upstream of the subcooler. And a circulating pump, and a chilled water control device (14) for controlling the heater and the circulating pump so as to keep the temperature and pressure of the chilled water supplied to the subcooler constant. The supercooled water producing apparatus according to item 1. 5. A compressor (2) from a shell (1b) of a subcooler (1) comprising a shell-and-tube type heat exchanger,
A heat pump device forming a refrigerant circulation cycle returning to the shell via a condenser (3) and an expansion valve (4); and a chilled water circulating device for circulating chilled water into the tube (1a) of the supercooler, A method for controlling a supercooled water producing apparatus for continuously producing supercooled water by cooling water flowing in a tube of an evaporator to a temperature below a freezing point, wherein a vapor pressure of a liquid refrigerant in a shell (1b) is reduced. A method for controlling a supercooled water producing apparatus, comprising detecting and controlling this within a certain range. 6. A suction vapor pressure corresponding to a saturated vapor temperature of a liquid refrigerant in which ice is optimally generated is set in advance, and a suction throttle is set so that a refrigerant temperature corresponding to the saturated vapor pressure becomes an optimal temperature for ice generation. The control method for the supercooled water producing apparatus according to claim 5, wherein the valve and the expansion valve are simultaneously controlled. 7. The method according to claim 5, wherein the temperature of the liquid refrigerant supplied from the condenser is kept within a certain range. 8. The control of the supercooled water producing apparatus according to claim 5, wherein the pressure of the water supplied to the supercooler is maintained within a certain range and the temperature of the cold water inlet is kept constant. Method.