CN107906785A - A kind of low temperature natural coldness resource utilizing system and method - Google Patents

Abstract

The invention discloses a low-temperature natural cold source utilization system, which includes a natural cold source system, a refrigeration unit system and a control system. In the cold season, when the wet bulb temperature of the outdoor air reaches a certain level, the refrigerant flowing through the cooling tower is used to directly or indirectly supply cooling to the end of the refrigeration system to provide the cooling load required by industrial production. At other times, the refrigeration unit is turned on to provide cooling. load. The control system automatically controls the operating conditions of the natural cold source system and the refrigeration unit system according to climate changes, so as to meet the requirements of the production process for refrigeration temperature and refrigeration capacity. The invention fully utilizes the low-temperature natural cooling source in winter and can meet the requirement of refrigeration temperature below 0°C in the production process. The system structure is simple, the system efficiency is high, the energy consumption of the refrigeration unit is reduced, and the energy-saving effect is remarkable.

Description

A low-temperature natural cooling source utilization system and method

technical field

The invention belongs to the field of refrigeration and energy saving, in particular to a low-temperature natural cooling source utilization system.

Background technique

Refrigeration is widely used in industrial production process. For example, in the chemical industry, refrigeration technology is required in the process of liquefaction of gas, separation of mixed gas, salt crystallization, degreasing of lubricating oil, cooling of certain chemical reaction processes, absorption of reaction heat and control of reaction speed. In addition, petroleum cracking, synthetic rubber, synthetic resin, fertilizer, natural gas liquefaction, storage and transportation also need refrigeration. At present, most of the traditional industrial production processes use electric compression refrigeration units or absorption refrigeration units for refrigeration, which consume a lot of electricity or steam. There are a lot of natural cold sources in the cold air in the north in winter. When the outdoor wet bulb (or dry bulb temperature) is lower than the refrigeration design temperature and reaches a certain value, the low-temperature cooling solution flowing through the cooling tower can be directly used for buildings or process systems. Provide cooling capacity, that is, use a cooling tower instead of a refrigerator for cooling. This technology makes full use of the outdoor natural cold source, saves the extremely high power consumption of the refrigeration unit, and has great energy-saving potential.

For example, CN201120449431.8 discloses an air-conditioning energy-saving system using natural cold sources, including an indoor heat exchanger and an outdoor heat dissipation system. The chilled water circulation pipeline of the outdoor heat dissipation system is connected with the cold side of the indoor heat exchanger, wherein the The outdoor heat dissipation system includes a chiller, a chilled water pump, a cooling tower, and pipeline constant pressure equipment connected together through pipelines. The cooling tower and the chiller are connected in series through chilled water pipelines. This air-conditioning energy-saving system using natural cooling source starts the cooling tower when the outdoor wet bulb temperature is low, which can use the natural cooling source to reduce the return water temperature of the chilled water and fully reduce the cooling load of the chiller. When the outlet water temperature of the chiller is reached, the chiller can be turned off to realize safe and efficient use of natural cooling sources.

CN201620385131.0 discloses an energy-saving system using natural cold source heat exchange in a data center, which includes an outdoor air system and an indoor air system, the indoor air system is connected to the data center computer room, the outdoor air system and the indoor air system The systems are connected through heat exchangers for heat exchange. The utility model is arranged outside the roof of the data center computer room, which saves the space of the indoor computer room, can run all year round, and reduces the cooling energy consumption of the data center; when the outdoor temperature is low, it can completely use the outdoor natural cold source to cool down, stop the mechanical refrigeration, and achieve high efficiency. energy saving.

CN201521026978.1 discloses a natural cold source heat dissipation system for various data centers, including an outdoor condenser, an indoor evaporator and a thermal superconducting circulation device. The outlet of the outdoor condenser is connected to the indoor evaporator through the thermal superconducting circulation device. The inlet and the outlet of the indoor evaporator are connected to the inlet of the outdoor condenser through pipes to form a closed loop system, which is filled with thermal superconducting materials for heat exchange; the outdoor condenser is an air-cooled condenser or a water-cooled condenser . The utility model utilizes a natural cold source to dissipate heat and can realize heat exchange without ventilation so as to ensure the environmental requirements of the machine room. The system has no high-power power consumption components, which greatly reduces the use time of the air conditioner in the machine room, thereby reducing the power consumption of the machine room; the overall structure is simple , compact, and low manufacturing cost; with the increase of heat exchange, the energy efficiency ratio of the system will increase, and the COP in normal operation is generally higher than that of compression refrigeration, which will minimize the PUE value of the computer room and reduce the input cost of cooling in the computer room.

CN201621321744.4 discloses a downflow type phase-change energy storage air conditioner utilizing natural cold sources and peak electricity prices, including a chassis, a first centrifugal fan, an evaporator, a phase-change heat module, and a second centrifugal fan; The first centrifugal fan, evaporator, phase-change heat module, and second centrifugal fan are sequentially installed in the cabinet from top to bottom; The utility model is connected with the compressor; according to the natural environment conditions of different climate zones, the utility model makes full use of the free natural cold source outside, and has high energy utilization efficiency; Release, greatly save the time of turning on the refrigeration compressor during the day, and save power consumption; in areas where peak and valley electricity prices are implemented, make full use of the low electricity price period at night to use the refrigeration compressor to store cold, and release the cold during the daytime high electricity price period, saving a lot of electricity for users. , while shifting the peak power consumption.

CN201520826527.X discloses a heat pump system for heating that utilizes the natural cold source of the atmosphere to increase the subcooling degree of the working fluid. Before entering the throttling element, it needs to pass through at least one of the air-cooled evaporators to exchange heat with the atmosphere with a lower temperature and the low-pressure working medium gas going to the compressor, so that the subcooling degree of the working medium liquid is significantly increased. Enter the throttling element of the other units in the air-cooled evaporator, enter the air-cooled evaporator after throttling and reducing pressure, absorb low-grade heat energy in the atmosphere, and release it to the heating hot water in the water-cooled condenser after raising the temperature; this system makes full use of Atmospheric natural cooling source is used to increase the subcooling degree of the working fluid entering the throttling element, effectively improving the energy efficiency level and reliability of its operation.

CN201420378372.3 discloses a mine cooling system that utilizes natural cold sources in winter for conversion, which includes a natural refrigeration system and a refrigeration unit arranged on the ground and a heat exchange and cooling system arranged underground; wherein the natural refrigeration system is heat exchanged by the ground The heat exchange and cooling system includes high and low pressure heat exchangers installed in the underground, air coolers and fans installed in the underground working face; the cooling tower and the spraying device are connected in parallel on the ground through valves. On the shell side of the heat exchanger; the refrigeration unit is connected in parallel on the tube side of the high and low pressure heat exchanger. The utility model makes full use of the natural cold source in winter. When the temperature on the well is lower than 10°C, the ground natural cooling system is used to cool down. When the temperature on the well is higher than 10°C, the refrigerating unit is started, so as to realize cooling throughout the year, and the operating cost is low. The cooling effect is good, the operating equipment is only the circulating water pump and the water pump of the spraying device, the investment cost is low, and the system operation is stable and reliable.

To sum up, the existing natural cold source utilization technology is generally aimed at data room and other application places that also need cooling in winter. The cooling temperature is higher than 0 ℃, and water is used as the refrigerant. However, the refrigeration temperature in the cooling process of industrial production is often below 0°C, and the refrigeration demand is all year round. Since water freezes below 0°C, the traditional natural cold source utilization technology cannot meet the cooling needs of some industrial production processes.

Contents of the invention

Purpose of the invention: to provide a low-temperature natural cooling source utilization system for the above-mentioned deficiencies in the utilization of existing natural cooling sources. in industrial production.

In order to achieve the above object, the low-temperature natural cold source utilization system provided by the present invention is characterized in that it includes a natural cold source system, a refrigeration unit system and a control system, wherein:

The natural cooling source cooling system includes a brine cooling tower, a low-temperature brine tank, a heat exchanger and a high-temperature brine tank connected in sequence, and the high-temperature brine tank is connected with the brine through a high-temperature brine pump. The natural cooling source cooling system can store cold at night when the daytime temperature does not meet the requirements but the nighttime temperature meets the requirements by setting a low-temperature brine tank and a high-temperature brine tank.

The cooling system of the refrigerating unit includes an evaporator, a compressor, a condenser, a circulating water pump and a circulating water cooling tower connected in sequence, and the evaporator and the condenser are respectively connected to a throttling device;

The control system automatically controls the operation status of the cooling system of the natural cooling source and the cooling system of the refrigeration unit according to the climate change. When the outdoor wet bulb temperature is 2-3°C lower than the cooling temperature required by the process in winter and transition season, the natural cooling source is turned on. The cooling system is used for cooling, and the refrigeration unit system is turned on for cooling in other time periods.

Specifically, the brine is a fluid with a freezing point lower than 0°C. Wherein, the concentration of the brine is determined according to the refrigeration temperature required by the process.

In some embodiments, the brine is ethylene glycol solution or ammonia water.

Due to the volatility of ethylene glycol solution, ammonia water, etc., if the open cooling tower is directly used for spraying and cooling, a small amount of secondary refrigerant will float into the atmosphere, causing corrosion or pollution to surrounding equipment. The tower adopts a closed cooling tower. In addition, considering that the wet bulb temperature in some areas is low in winter, in order to prevent the spray medium from freezing, the brine cooling tower adopts a dry closed cooling tower type.

The control system monitors and collects outdoor air temperature, humidity, and brine temperature and flow parameters in real time, and adjusts the cooling capacity and cooling temperature of the low-temperature natural cold source utilization system by controlling the frequency conversion of the fan of the brine cooling tower

Specifically, in application, when the outdoor wet-bulb temperature is 2-3°C lower than the cooling temperature required by the process in winter and transitional seasons, the natural cold source system is turned on for cooling, and the refrigeration unit system is turned on for cooling in other time periods. When the natural cooling source system is turned on, the outlet of the brine cooling tower is connected to the brine circulation pump, and the brine is pumped to the low-temperature brine tank by the low-temperature brine after being cooled by the cooling tower. The low-temperature brine enters the high-temperature brine tank after exchanging heat in the heat exchanger, and the high-temperature brine is pumped from the high-temperature brine tank to the brine cooling tower for cooling.

The fan of the brine cooling tower adopts frequency conversion design, and the frequency conversion is carried out according to the outdoor air wet bulb temperature and the brine outlet temperature. The cooling capacity of the brine cooling tower changes with the climate, and an automatic control system is set to meet the regulation requirements under different climate conditions. The automatic control system monitors and collects parameters such as outdoor air temperature, humidity, and brine temperature and flow rate in real time, and adjusts the cooling capacity and cooling temperature of the low-temperature natural cold source utilization system by controlling the brine cooling tower fan frequency conversion.

The present invention further proposes a method for utilizing the above-mentioned system to utilize a low-temperature cold source, comprising the following steps:

(1) From the hot season to the cold season, the natural cold source cooling system is put into operation at night to store cold, and as the weather gets colder, the refrigeration unit gradually reduces load until it is completely shut down;

(2) When all the refrigeration units are out of operation, the air temperature drops further, and the temperature of the brine refrigerant also drops accordingly, causing the temperature of the brine refrigerant to drop below the design refrigeration temperature, the fan of the brine cooling tower reduces the speed through frequency modulation, so as to Ensure that the temperature of the brine is controlled within the required range;

(3) When the refrigerant cooling tower fan is out of operation and the refrigerant temperature still drops below the design refrigeration temperature, add a windshield to the air inlet of the refrigerant cooling tower to prevent the refrigerant from freezing;

(4) As the weather gets warmer, when the temperature of the refrigerant rises above the design cooling temperature, the fan of the refrigerant cooling tower is turned on;

(5) When the fan of the refrigerant cooling tower reaches the rated speed and still cannot meet the requirements, the refrigeration unit is put into operation, and the two systems operate at the same time;

(6) When transitioning from the cold season to the hot season, the natural cooling source cooling system stops running, and all refrigeration units are turned on.

Beneficial effect: compared with the prior art, the present invention has the following advantages:

(1) Make full use of the cooling capacity of the outdoor natural cooling source in winter, reduce the energy consumption of the refrigeration unit, and have better energy-saving benefits;

(2) The medium with low freezing point such as brine, ethylene glycol solution, and ammonia water is used as the secondary refrigerant, which can meet the refrigeration temperature requirements below 0°C during the production process;

(3) The refrigerant cooling tower adopts the form of a dry closed cooling tower to avoid the influence of the spray medium on the surrounding environment caused by the drift or volatilization;

(4) The automatic control system is adopted to adjust the operating status of the system in real time according to climate changes, so as to maximize the utilization rate of the natural cold source system and maximize the energy-saving benefits;

(5) A low-temperature brine tank and a high-temperature brine tank are installed, which can store energy and balance the temperature and flow of the brine, so that the system can operate stably.

(6) The structure of the present invention is simple and practical, and has strong versatility, which can be used not only in the design of new systems, but also in the transformation of existing systems.

Description of drawings

Fig. 1 is a schematic diagram of a low-temperature natural cooling source utilization system, in which: 1. brine cooling tower, 2. low-temperature brine pump, 3. low-temperature brine tank, 4. heat exchanger, 5. high-temperature load Refrigerant tank, 6. High temperature brine pump, 7. Evaporator, 8. Compressor, 9. Condenser, 10. Throttling device, 11. Circulating water pump, 12. Circulating water cooling tower, 13 Brine circulation Pump.

Detailed ways

The invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but not as a limitation to the utility model.

As shown in Figure 1, when the outdoor wet-bulb temperature in winter and transitional seasons is 2-3°C lower than the cooling temperature required by the process, the high-temperature brine is cooled by the brine cooling tower 1 and reaches the cooling temperature required by the process, and then is carried by the low-temperature load. The refrigerant pump 2 sends to the low-temperature brine tank 3 . After the low-temperature brine is exchanged with the process heat fluid in the heat exchanger 4 , the temperature of the brine rises and enters the high-temperature brine tank 5 . The high-temperature brine is sent from the high-temperature brine tank 5 by the high-temperature brine pump 6 to the brine cooling tower 1 for cooling.

As shown in Figure 1, when the outdoor wet bulb temperature in hot season is higher than the refrigeration temperature required by the process, the natural cooling source system stops running, the refrigeration unit is turned on, and the high-temperature brine enters the evaporator 7 of the refrigeration unit from the high-temperature brine tank 5 The temperature is lowered, and then sent into the low-temperature brine tank 3 by the brine circulation pump 13 . After the low-temperature brine is exchanged with the process heat fluid in the heat exchanger 4, the temperature of the brine rises and enters the high-temperature brine tank 5, forming a refrigeration cycle. If there is a peak-to-valley price difference in the electricity price, the low-temperature brine tank 3 can be used to store cold with low-valley electricity at night, so as to reduce the operating cost of the refrigerating unit.

The secondary refrigerant includes fluids with a lower freezing point such as ethylene glycol solution and ammonia water. The concentration is determined according to the refrigeration temperature required by the process and combined with local climate conditions to ensure that it does not freeze in the coldest climate. In order to prevent the spray medium from escaping or volatilizing and the spray medium from freezing, the brine cooling tower 1 adopts a dry closed cooling tower. The fan of brine cooling tower 1 is designed with frequency conversion, and frequency conversion is performed according to the wet bulb temperature of outdoor air and the outlet temperature of brine.

The cooling capacity of the brine cooling tower 1 varies with the climate, and the system operation strategy of the present invention is:

(1) From the hot season to the cold season, the natural cold source cooling system is put into operation at night to store cold, and as the weather gets colder, the refrigeration unit gradually reduces load until it is completely shut down;

(2) When all the refrigeration units are out of operation, the air temperature drops further, and the temperature of the brine refrigerant also drops accordingly, causing the temperature of the brine refrigerant to drop below the design refrigeration temperature, the fan of the brine cooling tower reduces the speed through frequency modulation, so as to Ensure that the temperature of the brine is controlled within the required range;

(3) When the refrigerant cooling tower fan is out of operation and the refrigerant temperature still drops below the design refrigeration temperature, add a windshield to the air inlet of the refrigerant cooling tower to prevent the refrigerant from freezing;

(4) As the weather gets warmer, when the temperature of the refrigerant rises above the design cooling temperature, the fan of the refrigerant cooling tower is turned on;

(5) When the fan of the refrigerant cooling tower reaches the rated speed and still cannot meet the requirements, the refrigeration unit is put into operation, and the two systems operate at the same time;

(6) When transitioning from the cold season to the hot season, the natural cooling source cooling system stops running, and all refrigeration units are turned on.

The above-mentioned embodiments are only one of the more preferred specific implementation modes of the present invention, and ordinary changes and substitutions performed by those skilled in the art within the scope of the technical solution shall be included in the protection scope of the present invention.

Claims (7)

1. a kind of low temperature natural coldness resource utilizing system, it is characterised in that including natural cooling source system, refrigeration unit system and control System, wherein：

The natural cooling source cooling system includes refrigerating medium cooling tower, low temperature refrigerating medium tank, heat exchanger and the height being sequentially connected Warm refrigerating medium tank, the high temperature refrigerating medium tank are connected by high temperature coolant pump with refrigerating medium cooling tower；

The refrigeration unit cooling system includes evaporator, compressor, condenser, water circulating pump and the recirculated water being sequentially connected Cooling tower, the evaporator and condenser are connected with throttling arrangement respectively；

The control system according to climate change to natural cooling source cooling system and refrigeration unit cooling system operation conditions into Row automatically controls, and when wet-bulb temperature is less than 2~3 DEG C of technological requirement cryogenic temperature outside winter and conditioning in Transition Season room, it is cold to open nature Source cooling system is freezed, and other times section unlatching refrigeration unit system is freezed.

2. low temperature natural coldness resource utilizing system according to claim 1, it is characterised in that the refrigerating medium is less than for freezing point 0 DEG C of fluid.

3. low temperature natural coldness resource utilizing system according to claim 1, it is characterised in that the refrigerating medium is molten for ethylene glycol Liquid or ammonium hydroxide.

4. low temperature natural coldness resource utilizing system according to claim 1, it is characterised in that the refrigerating medium cooling tower uses Sealed cooling tower.

5. low temperature natural coldness resource utilizing system according to claim 4, it is characterised in that the refrigerating medium cooling tower uses Dry type sealed cooling tower.

6. low temperature natural coldness resource utilizing system according to claim 1, it is characterised in that the refrigerating medium cooling tower 1 Wind turbine carries out frequency conversion according to outdoor air wet bulb temperature and refrigerating medium outlet temperature.

7. a kind of claim 1~6 any one of them low temperature natural coldness resource utilizing system carries out low temperature natural coldness resource utilizing Method, it is characterised in that include the following steps：

(1) cold season being transitioned into by the hot season, natural cooling source cooling system night puts into operation, carries out cold-storage, as weather turns cold, system The gradual off-load of cold group is until all stop transport；

(2) after refrigeration unit is all stopped transport, temperature further declines, and refrigerant temperature also declines therewith, causes refrigerating medium temperature When degree is down to below design cryogenic temperature, the wind turbine of refrigerating medium cooling tower reduces rotating speed by frequency modulation, to ensure refrigerant temperature Control is in claimed range；

(3) it is cold in refrigerating medium when refrigerant temperature is still down to below design cryogenic temperature after refrigerating medium blower fan of cooling tower is stopped transport But the mode such as tower air inlet increase wind shield prevents refrigerating medium from freezing；

(4) when rising to more than design cryogenic temperature with the warm refrigerant temperature of weather turn, then the wind of refrigerating medium cooling tower is opened Machine；

(5) when the wind turbine of refrigerating medium cooling tower reaches rated speed, when still cannot meet the requirements, refrigeration unit input fortune OK, two systems are run at the same time；

(6) when being transitioned into the hot season by cold season, natural cooling source cooling system is out of service, and refrigeration unit is all turned on.