JPH0477216B2 - - 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,
Means for detecting the chilled water temperature at the outlet of the heat exchanger and means for detecting the brine temperature at the outlet of the evaporator of the refrigerator or heat pump are provided, and the chiller or A control device having means for controlling the capacity of the heat pump, and means for controlling the capacity of the refrigerator or the heat pump to decrease and increase the brine temperature when the brine temperature detection means reaches a predetermined lower limit temperature. This is a cold water production device.

Next, the present invention will be explained in detail.

In the present invention, the lower limit of the brine temperature at the brine inlet of the heat exchanger is determined by conducting an actual machine test in advance and determining the lower limit of the brine temperature at the brine inlet of the heat exchanger based on the results. It is controlled by a control device, but the brine inlet temperature is also detected at the same time, and when the brine inlet temperature reaches the predetermined lower limit temperature mentioned above, the capacity control means is switched from chilled water outlet temperature control to brine inlet temperature control to stop the brine. It raises the temperature slightly.

With the above basic control, it is possible to produce cold water at a temperature close to 0° C. without freezing even if load fluctuations occur.

Furthermore, in the present invention, taking into account sudden load fluctuations due to the followability of the control device, when the brine inlet temperature reaches the lower limit value and switching to brine inlet temperature control, the cold water flow rate is temporarily forcibly increased. For this purpose, a variable control device is installed at the cold water inlet of the heat exchanger.
Freezing can be prevented. in this case,
It is necessary to install a device that can control the rotation speed of the cold water pump.

Similarly, the same effect can be obtained by temporarily forcibly increasing the cold water inlet temperature instead of increasing the flow rate. This method involves mixing cold water with a temperature higher than the planned cold water inlet temperature. For this,
It is preferable to consider the temperature distribution within the cold water heat storage tank and provide a means for mixing the cold water in the hottest part.

[Effect]

In the present invention, brine at about -3°C 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. ,
This cold water outlet is controlled to be kept at a temperature close to 0°C to freeze it.

By the way, if we consider the case where cold water freezes,
The cold water outlet temperature is determined by heat transfer between the cold water and the ice surface.
Maintains 0℃ even when frozen. However, brine
Frozen ice inhibits heat transfer, reducing the amount of heat exchange and lowering the brine temperature.
This will further promote freezing.

Therefore, in the present invention, the brine inlet temperature is detected as well as the cold water outlet temperature, and control is performed to prevent the cold water from freezing based on the brine temperature.

〔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 cold water outlet temperature of the heat exchanger 2 is detected by the detector 12.
The capacity of the compressor 18 of the refrigerator 1 is controlled so as to keep the cold water temperature close to 0°C. For this reason, the capacity control device 16 is operated by commands from the chilled water outlet temperature controller 13.

On the other hand, the lower limit of the brine inlet temperature is determined in advance by an actual machine test at a temperature at which the cold water does not freeze, and the brine inlet temperature is detected by the detector 14. Then, due to some abnormality, the detected value becomes
When the temperature falls below a predetermined lower limit, the capacity control of the compressor is switched from control based on the cold water outlet temperature to control using the brine inlet temperature controller 15 to slightly increase the brine temperature and avoid freezing. Furthermore, in this case, at the same time,
By controlling the variable speed control device 6, the cold water 1
Freezing can be effectively avoided by increasing the capacity of the next pump and temporarily increasing the flow rate of 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 drawings]

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... Chilled water outlet temperature detector, 13... Chilled water outlet temperature controller, 14... Brine inlet temperature detector, 15... Brine inlet temperature controller, 16... Capacity control device, 17... Cooler, 18...
Compressor, a...high temperature side of the heat storage tank, b...low temperature side of the heat storage tank.

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 a cold water circulation system consisting of cold water pipes connected to 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, Means for detecting the chilled water temperature at the outlet of the heat exchanger and means for detecting the brine temperature at the outlet of the evaporator of the refrigerator or heat pump are provided, and the temperature of the chiller or heat pump is determined according to the output of the chilled water temperature detecting means. and means for controlling the capacity of the refrigerator or heat pump to increase the brine temperature by decreasing the capacity of the refrigerator or heat pump when the brine temperature detection means reaches a predetermined lower limit temperature. Cold water production equipment. 2. The chilled water production apparatus according to claim 1, further comprising a control device that increases the flow rate of chilled water for a predetermined period of time when the brine temperature detection means reaches a predetermined lower limit temperature. 3. The chilled water production apparatus according to claim 1 or 2, further comprising a control device that increases the chilled water temperature for a predetermined time by mixing high temperature chilled water when the brine temperature detection means reaches a predetermined lower limit temperature. A cold water production device characterized by: