JPH0477218B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a chilled water production apparatus, and more particularly to an efficient chilled water production apparatus that can be used for cooling in air conditioning, industrial process cooling, and the like.

[Conventional technology]

When producing chilled water using a refrigerator or a heat pump, the lower limit of the chilled water temperature has conventionally been 5° C. due to concerns about damage to heat transfer tubes due to freezing of the water.
In the field of air conditioning, a common cycle is to send cold water at 5 to 7 degrees Celsius to an air conditioner, exchange heat with cold air, raise the temperature to about 10 to 12 degrees Celsius, and return. Also, even when using a heat storage device, the effective temperature difference for heat storage is 10℃ - 5℃ or 12℃
The temperature was in the range of -5°C to 7°C.

On the other hand, in the industrial field, the temperature of the liquid to be cooled varies depending on the process, but the most commonly used temperature range is called mild brine. mild·
The brine is an ethylene glycol aqueous solution, a propylene glycol aqueous solution, a calcium chloride aqueous solution, or the like. These antifreezes are used at temperatures ranging from about 5°C to -30°C.

[Problem to be solved by the invention]

In the field of air conditioning, it is desired to save energy and reduce equipment costs by increasing the temperature difference of circulating water used for air conditioning, reducing the amount of circulating water, and reducing the diameter of transport pipes. Furthermore, there are restrictions on the size of heat storage tanks installed in the basements of urban buildings.
If the heat storage capacity can be increased while keeping the size the same, it is possible to use late-night electricity at a lower price, so it is hoped that such heat storage devices will become more widespread.

Furthermore, in industrial applications, it has become clear that energy can be saved and maintenance management can be made easier by replacing antifreeze, which has poor heat transfer, high liquid viscosity, and corrosive properties, with water as much as possible.

However, in the prior art, increasing the degree of cooling of the cold water causes the problem of damage to the heat transfer tube due to freezing, and the temperature of the cold water cannot be lowered sufficiently.

Therefore, in view of the above-mentioned needs, the present invention provides an apparatus for producing cold water that is just on the verge of freezing between 5°C and 0°C, which was previously thought to be unusable. It is an object of the present invention to provide a chilled water production device that can quickly thaw and continue operation without causing any problems.

[Means to solve the problem]

The present invention provides equipment for a brine circulation system consisting of a refrigerator or a heat pump, a heat exchanger for brine and cold water, brine piping connecting the two, a brine circulation pump, a brine tank, etc., and a brine circulation system connected to the heat exchanger. A monitoring means for operating a cold water production and cold water heat storage device consisting of cold water circulation system equipment consisting of cold water piping, a cold water supply pump, a cold water heat storage tank, etc., while maintaining the cold water temperature at the heat exchanger outlet near 0°C. As a detection method, the frozen state of cold water inside the heat exchanger is detected by either or both of a decrease in temperature difference between the heat exchanger inlet and outlet on the brine side and an increase in pressure loss at the heat exchanger inlet and outlet on the chilled water side. means, and when the detection means detects an abnormality,
As a means for raising the brine temperature and thawing, a suction capacity control mechanism for the compressor and a bypass mechanism connecting the condenser and the evaporator are provided in the refrigerator or heat pump, and a means for closing the suction capacity control mechanism. and a control means comprising means for forcing hot gas to flow from the condenser to the evaporator.

As described above, the present invention provides a method for thawing the freezing phenomenon inside the heat exchanger in a short time and allowing operation to continue when the detection means for detecting the frozen state of cold water inside the heat exchanger detects an abnormality. , a suction capacity control mechanism for a compressor, a condenser, and an evaporator are connected in the refrigerator or heat pump as a means of reducing the brine cooling capacity of the refrigerator or heat pump and increasing the temperature of the brine to thaw it. This chilled water production apparatus is provided with a control means comprising a bypass mechanism for closing the suction capacity control mechanism, and a means for forcing hot gas to flow from the condenser to the evaporator.

Next, the present invention will be explained in detail.

In the cold water production apparatus of the present invention, brine at a temperature of 0°C or lower is produced using a refrigerator or a heat pump, and this brine is passed through a tube of a heat exchanger, and cold water is passed outside the tube to cool the cold water. It is a device that lowers the cold water outlet temperature to 0 without freezing.
It is controlled to keep the temperature close to ℃.

To this end, the refrigerator or heat pump maintains the brine temperature at which the cold water outlet temperature is close to 0°C without freezing, based on a predetermined amount of heat exchange, a predetermined cold water inlet temperature, and a cold water flow rate, and maintains this temperature. It is controlled so that

At the same time, the cold water side is also controlled to bring the cold water outlet temperature close to 0°C. To control this chilled water side, a chilled water pump with a variable speed control device is installed, and the temperature of the chilled water outlet from the heat exchanger is detected and the output of the temperature controller is adjusted to a variable speed so that the chilled water outlet temperature is close to 0°C. The flow rate of cold water from the cold water pump is changed and controlled by the control device.

In this type of control, if the chilled water temperature at the heat exchanger outlet is close to 0°C, a part of the heat exchanger is in a so-called supercooled state below 0°C, which is a condition that is likely to cause freezing. ing.

Therefore, even if it freezes, it can be thawed quickly without causing an accident or failure of the equipment, and it can be returned to 0°C.
If cold water is available nearby, the process of producing cold water near 0°C will be possible.

To prevent accidents from freezing, a shell-and-tube heat exchanger is used, and cold water is passed outside the tubes, and brine (antifreeze) is passed inside the tubes. Accidents such as tube rupture can be prevented. In this case, it is possible that the ice adhering to the outer surface of the tubes could grow between the tubes and bend the tubes, but such accidents can occur because there is no means to detect freezing, leaving the ice unprotected. This is what happens when you let it grow.

The present invention attempts to quickly thaw the frozen state by detecting the initial frozen state, and the detection of the initial frozen state is difficult because the pressure loss at the cold water inlet and outlet of the heat exchanger increases due to freezing. and a means of detecting a reduction in the temperature difference between the brine inlet and outlet of the heat exchanger due to a reduction in the amount of heat exchanged due to ice degrading the heat transfer from the brine to the cold water in the event of freezing. Or, it is intended to detect freezing.

Furthermore, if freezing is detected, the capacity control mechanism of the refrigerator or heat pump must be operated within a range that allows stable operation in order to maintain the brine side at a temperature of 0°C or higher and thaw it from the inside of the tube as a means of quickly releasing the freezing. The hot gas bypass valve is forcibly throttled to a low output (low cooling capacity), and at the same time the hot gas bypass valve is forcibly opened to maintain the low output.

On the other hand, at the same time, as a thawing measure from the cold water side, means for temporarily forcibly increasing the flow rate of cold water supplied to the heat exchanger to improve the heat transfer coefficient and thaw the ice;
There are also means for increasing the cold water inlet temperature.

A specific means for thawing from the cold water side is to set the cold water pump at a variable speed and provide a control means to forcibly set the rotation speed to the maximum when freezing is detected. Furthermore, in order to increase the inlet temperature of the cold water, a mixing device such as a three-way valve for forcibly mixing the high-temperature cold water in the cold water heat storage tank may be provided.

〔Example〕

The present invention will be specifically described below with reference to the drawings, but the present invention is not limited to these embodiments.

Embodiment 1 FIG. 1 is a schematic flow diagram of a cold water production apparatus showing an embodiment of the present invention.

In FIG. 1, 1 is a refrigerator or a heat pump, 2 is a heat exchanger between brine and cold water, 7 is a cold water heat storage tank, 21 is a cooler (evaporator), 22 is a compressor,
23 is a capacity control mechanism, 24 is a hot gas bypass valve, and 25 is a condenser.

In operation of this equipment, the brine is
1, heat exchange is performed with cold water in a heat exchanger 2, and stored in a brine tank 4.
A cycle is taken in which the brine is circulated to the cooler 21 by the brine pump 3. On the other hand, the cold water is sent from the high temperature side a of the cold water storage tank 7 to the heat exchanger 2 by the cold water primary pump 5, where it is cooled by brine and returned to the low temperature side b of the cold water storage tank 7. Then, the cold water on the low temperature side b of the cold water heat storage tank 7 is sent to the air conditioning loads 9, 11 by the cold water secondary pumps 8, 10, and the cold water whose temperature has increased by being effectively used is sent to the cold water heat storage tank 7.
is circulated to the high temperature side a.

By the way, in such a circulation system, in normal operation, the temperature detector 12' detects the brine temperature at the outlet of the cooler, and the brine temperature controller 12 commands the capacity control mechanism 23 to keep this temperature constant. It is moved to control the capacity of the compressor 22 of the refrigerator 1. On the other hand, the chilled water outlet temperature of the heat exchanger is detected by the temperature detector 13', and the chilled water outlet controller 13 commands to operate the variable speed control device 6 to maintain this temperature near 0°C. This is to adjust the flow rate of cold water of the primary pump 5.

In such normal operation, the temperature at the brine inlet and brine outlet of the heat exchanger 2 and/or the pressure at the cold water inlet and cold water outlet of the heat exchanger 2 are constantly detected 14 and 15, and the detected brine If the temperature difference and/or cold water pressure difference is abnormal compared to normal operating values, this indicates that freezing has started inside the heat exchanger, and the following steps should be taken to promptly thaw it. I do.

First, as a quick thawing method, the capacity control mechanism 23 of the refrigerator 1 is forced to the extent that stable operation can continue in order to keep the brine at a temperature of 0°C or higher and thaw it from the inside of the tube of the heat exchanger. At the same time, the condenser 2
Hot gas bypass valve 24 from 5 to evaporator 21
open and maintain low output.

Next, as a thawing means from the cold water side, the variable speed control device 6 is operated to set the cold water primary pump to the maximum rotation speed, and the cold water flow rate is temporarily increased to improve the heat transfer coefficient and defrost. Furthermore, in order to raise the inlet temperature of the cold water and thaw it, the cold water in the higher temperature section a in the cold water heat storage tank 7 is forcibly mixed with a mixing device such as a three-way valve.

As mentioned above, not only the operation on the brine side, but also
By appropriately combining operations on the cold water side, even if the inside of the heat exchanger freezes, it can be quickly thawed before an accident occurs to the equipment.

〔Effect of the invention〕

In the present invention, since a freeze detection means is provided, a frozen state can be detected at an early stage, and cold water close to 0° C. can be produced without causing an accident or failure of the device.

Conventionally, in the air conditioning field, a cold water circulation system sends cold water at 5°C, returns it at 10°C from an air conditioner, and cools it again to 5°C in a refrigerator, but in this case, 10-5 = 5°C.
Therefore, if water at 0°C can be obtained as in the present invention, a temperature difference of 10 - 0 = 10°C can be used.

As mentioned above, in the present invention, twice the temperature difference can be used compared to the conventional one, so from the following equation,
The amount of circulating water is reduced to half, and the pump power (conveying power) is reduced by half.
This has the effect of making it possible to reduce the pipe diameter.

Q=G×△T×γ×h……(1) (Q: heat exchange amount, △T: temperature difference, G: circulation amount, γ: specific gravity of fluid, h: specific heat of fluid) On the other hand, heat storage capacity By replacing G in equation (1) with the amount of water held in the heat storage tank, the temperature difference ΔT that can be effectively used increases, and the heat storage capacity can also be increased.

[Brief explanation of the drawing]

FIG. 1 is a schematic flow diagram of a cold water production apparatus showing an embodiment of the present invention. 1... Refrigerator or heat pump, 2... Heat exchanger,
3...Brine pump, 4...Brine tank, 5...
Cold water primary pump, 6... variable speed control device, 7... cold water heat storage tank, 8, 10... cold water secondary pump, 9, 11...
Air conditioning load, 12...Brine inlet (cooler outlet) temperature controller, 13...Cold water outlet temperature controller, 12', 13'...Temperature detector, 14...Brine temperature difference detector, 15...Cold water pressure difference detector, 21...
Cooler (evaporator), 22... Compressor, 23... Capacity control mechanism, 24... Hot gas bypass valve, 25... Condenser.

Claims (1)

[Scope of Claims] 1. Brine circulation system equipment consisting of a refrigerator or heat pump, a heat exchanger between brine and cold water, brine piping connecting the two, a brine circulation pump, a brine tank, etc., and a heat exchanger. In order to maintain the temperature of cold water at the outlet of the heat exchanger near 0℃ in cold water production and cold water heat storage equipment, which consists of cold water circulation system equipment consisting of cold water piping connected to the cold water supply pump, cold water heat storage tank, etc. As a means of monitoring the freezing state of cold water inside the heat exchanger, the freezing state of the cold water inside the heat exchanger can be determined by either or both of a decrease in the temperature difference between the heat exchanger inlet and outlet on the brine side and an increase in pressure loss at the heat exchanger inlet and outlet on the chilled water side. A suction capacity control mechanism for a compressor, a condenser and A chilled water production apparatus comprising a bypass mechanism connecting an evaporator, a control means comprising a means for closing the suction capacity control mechanism, and a means for forcing hot gas to flow from the condenser to the evaporator. 2. The chilled water production apparatus according to claim 1, further comprising a control means for forcibly increasing the flow rate of chilled water supplied to the heat exchanger in order to promote thawing from the chilled water side when the detection means detects an abnormality. Cold water production equipment. 3. The chilled water production apparatus according to claim 1 or 2, in order to promote thawing from the cold water side when the detection means detects an abnormality, a means for mixing cold water of different temperatures in the cold water heat storage tank is provided, and heat exchange is performed. A cold water production device comprising a control means for increasing the temperature of cold water supplied to a container.