JPH0477217B2 - - 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.

SUMMARY OF THE INVENTION In view of the above-mentioned needs, an object of the present invention is to provide a cold water production device that can cool the cold water to a temperature close to 0° C. without causing freezing damage or the like.

[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. In 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., in order to maintain the cold water temperature at the heat exchanger outlet near 0°C,
A means for detecting the brine temperature at the outlet of the cooler is provided, a means for controlling the capacity of the refrigerator or the heat pump so that the detected value becomes a predetermined temperature, and a means for detecting the temperature of the chilled water at the outlet of the heat exchanger. This cold water production apparatus includes a control device having means for controlling the flow rate of cold water from a cold water supply pump so that the detected value becomes a predetermined temperature.

Next, the present invention will be explained in detail.

In the present invention, brine at a temperature of 0°C or lower is produced using a refrigerator or a heat pump, this brine is passed through a tube of a heat exchanger, and cold water is passed outside the tube to obtain cooled water. In the device, the temperature of the cold water outlet is controlled to be maintained at a temperature close to 0° C. without freezing.

Therefore, based on a predetermined amount of heat exchange, a predetermined cold water inlet temperature, and a cold water flow rate, the refrigerator or heat pump sets the brine temperature so that the cold water outlet temperature is close to 0°C without freezing. Control is performed to maintain the temperature. on the other hand,
Simultaneously with the above control, control on the cold water side is also performed to bring the cold water outlet temperature close to 0°C.

The above-mentioned control on the chilled water side means that a chilled water pump with a variable speed control device is installed on the chilled water inlet side, detects the chilled water outlet temperature, and adjusts the output of the temperature controller so that the chilled water outlet temperature is close to 0°C. This is applied to a variable speed control device to change the chilled water flow rate of the chilled water pump.

Here, the cold water temperature at the heat exchanger outlet is 0°C.
Close to 0 means that there is a part inside the heat exchanger that is close to 0.
Since it is in a so-called supercooled state below .degree. C., a decrease in the amount of heat exchange due to a decrease in the cold water inlet temperature is the condition most likely to cause freezing.

Therefore, in the present invention, when the cold water inlet temperature decreases, first, the cold water pump variable speed device is activated to increase the cold water flow rate, thereby controlling the heat exchanger to be kept constant. If this variable speed device reaches the maximum rotation speed and the cold water inlet temperature shows a tendency to decrease, the cold water to be supplied is mixed with higher temperature cold water from the cold water heat storage tank to maintain the cold water inlet temperature at a predetermined level. control to maintain the temperature at

Another control method is to constantly detect the chilled water inlet temperature, and when the chilled water inlet temperature drops below a predetermined value, the cooling heat amount of the brine cooled by the refrigerator or heat pump is reduced to match the load on the chilled water side. This is a method to control the

Specifically, the capacity control mechanism of a refrigerator or heat pump typically controls the brine temperature (heat exchanger inlet).
When the cold water inlet temperature decreases, the deviation between the predetermined cold water inlet temperature and the actual inlet temperature is given to the brine temperature controller to increase the brine temperature. Control is performed to reduce the amount of cooling heat and thus the amount of heat exchanged with cold water.

〔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, and 7 is a cold water heat storage tank. In the refrigerator or heat pump, 17 represents a cooler and 18 represents a compressor, brine is cooled in the cooler 17, heat exchanged with cold water in a heat exchanger 2, and stored in a brine tank 4. Then, a cycle is performed in which the brine is circulated to the cooler 17 by the brine pump 3. On the other hand, cold water is sent from the high temperature side a of the cold water heat 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 heat storage tank 7. Then, the low temperature side b of this cold water heat storage tank 7
The cold water is sent to the air conditioning loads 9 and 11 by the cold water secondary pumps 8 and 10, and the cold water whose temperature has increased is circulated to the high temperature side a of the cold water heat storage tank 7.

By the way, in such a circulation system, in normal operation, the brine temperature at the outlet of the cooler is detected by the temperature detector 12', and the brine inlet temperature controller 12 instructs the capacity control device 16 to keep this temperature constant. is operated to control the capacity of the compressor 18 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.

Then, move the cold water pump variable speed device 6,
Even if the rotation speed is the maximum, if the cold water inlet temperature detected by the cold water inlet temperature detector 14' shows a tendency to decrease, a command is issued from the cold water inlet controller 14 to turn off the cold water on the high temperature side a of the cold water heat storage tank 7. is mixed by a motor to maintain the cold water inlet temperature at a predetermined temperature.

Another control method is to constantly detect the chilled water inlet temperature with a temperature detector 15', and when the chilled water inlet temperature falls below a predetermined value, the deviation between the predetermined chilled water inlet temperature and the actual inlet temperature is detected. The cold water inlet temperature is read by the cascade integrator 15, and the capacity control device 16 is movably controlled to increase the brine temperature (heat exchanger inlet) by that amount, thereby reducing the heat exchange capacity with the cold water.

〔Effect of the invention〕

In the present invention, cold water close to 0° C. can be produced without freezing. Conventionally, in the air conditioning field, a chilled water circulation system sends 5℃ cold water, returns it at 10℃ from an air conditioner, and cools it again to 5℃ in a refrigerator, but in this case, 10℃ is used.
The temperature difference of -5 = 5℃ was used,
If water at 0℃ can be obtained as in the present invention, 10-0=10
A temperature difference of ℃ 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', 13', 14', 15'...Temperature detector, 12...Brine inlet temperature controller, 1
3... Chilled water outlet controller, 14... Chilled water inlet controller, 15... Chilled water inlet temperature cascade integrator, 16... Capacity control device, 17... Cooler, 18...
Compressor, a...high temperature side, b...low temperature side.

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 a cold water production and cold water heat storage system consisting of cold water circulation system equipment including cold water piping connected to a cold water supply pump, cold water heat storage tank, etc., in order to maintain the cold water temperature at the heat exchanger outlet near 0°C, the cooler A means for detecting the brine temperature at the outlet is provided, a means for controlling the capacity of the refrigerator or the heat pump so that the detected value becomes a predetermined temperature, and a means for detecting the chilled water temperature at the outlet of the heat exchanger is provided, 1. A chilled water production apparatus comprising: a control device having means for controlling the flow rate of chilled water from a chilled water supply pump so that the flow rate of chilled water reaches a predetermined temperature. 2. The chilled water production apparatus according to claim 1, comprising means for detecting the temperature of the chilled water at the inlet of the heat exchanger, and a control device for mixing the chilled waters of different temperatures in the chilled water heat storage tank so that the detected value becomes a predetermined temperature. A cold water production device characterized by also being equipped with. 3. The chilled water production apparatus according to claim 1, further comprising means for detecting the chilled water temperature at the inlet of the heat exchanger, and when the detected value falls below a predetermined temperature, the capacity of the refrigerator or heat pump is reduced to reduce the chilled water inlet. A cold water production device characterized by further comprising a control device that increases the brine temperature by the amount that the temperature decreases.