The Advantages and Disadvantages of Six Chillers
1. Screw chiller
The screw chiller is a chiller with various forms of screw compressors as the host. It is an assembled refrigeration device composed of screw refrigeration compressor, condenser, evaporator, thermal expansion valve, oil separator, automatic control components and instruments. At present, screw chillers are more and more widely used in the field of refrigeration and air conditioning in my country, and their typical cooling capacity ranges from 700 to 1000 kW.
advantage:
1. Simple structure, few moving parts, few wearing parts and long service life.
2. The circular motion is stable, and there is no "surge" phenomenon during low-load operation.
3. High compression ratio and high EER value.
4. It can be adjusted steplessly in the range of 10%~100%, with high efficiency and significant power saving at partial load.
5. Not sensitive to wet stroke.
shortcoming:
1. The price is higher than the piston type. The capacity of the single machine is smaller than that of the centrifugal type, and the rotation speed is lower than that of the centrifugal type.
2. The lubricating oil system is more complicated and the fuel consumption is large.
3. The noise of the large-capacity unit is higher than that of the centrifugal type.
4. High machining accuracy and assembly accuracy are required.
2. Piston chiller
The piston chiller is a chiller with a piston compressor as the main engine. The unit is composed of refrigeration compressors, condensers, evaporators, thermal expansion valves, etc., and is equipped with automatic energy regulation and automatic safety protection devices. The piston compressor device system is relatively simple, and this type of compressor is generally used more in low temperature conditions!
advantage:
1. Wide range of applicable pressures and strong maintainability.
2. With multi-head, high-speed multi-cylinder, the performance can be improved.
3. The material is simple, the general metal material can be used, the processing is easy, and the cost is low.
shortcoming:
1. There are many parts and wearing parts.
2. The compression ratio is low, the cooling capacity of a single unit is small, and the cylinder unloading adjustment cannot be adjusted steplessly.
3. The subordinate reciprocates up and down, the vibration is larger, and the quality index per unit cooling capacity is larger.
4. Very sensitive to liquid shock.
3. Modular chiller
It is composed of multiple modular chiller units in parallel. The multi-loop work is coordinated and controlled by a microcomputer, and each compressor can independently adjust the energy. The modular unit can be composed of up to 13 units. The modular chiller is equipped with a computer monitoring system to control the entire unit. According to the size of the load, start and stop each compressor regularly or change the high-speed operation to low-speed operation, including each independent refrigeration system and the whole machine operation.
advantage:
1. According to the change of cooling load, adjust the number of modules in operation at any time, so that the output cooling capacity and air conditioning load can be optimally matched to reduce energy consumption.
2. The parallel operation of multiple compressors is guaranteed.
3. Light weight, small size, saving construction area.
4. The modular combination provides the maximum spare capacity for the refrigeration system, and it is very simple and easy to expand the capacity of the unit.
shortcoming:
1. High requirements for water quality, once the scale is blocked, it will affect the heat transfer of the condenser and the evaporator.
2. The cost is high, the parts are many, the wearing parts are many, and the maintenance cost is high. ?
3. The compression ratio is low, and the cooling capacity of a single unit is small.
4. The adjustment performance of the single head under partial load is poor, and stepless adjustment cannot be performed.
5. The quality index of unit cooling capacity is relatively large.
4. Centrifugal chiller
The centrifugal chiller is cooled by freon refrigerant evaporating and absorbing the heat of the refrigerant water in the evaporator, and the freon wet vapor after evaporating and absorbing heat is compressed into high temperature and high pressure gas by the compressor, which becomes liquid after being condensed by the water-cooled condenser. Throttled by the expansion valve into the evaporator for recirculation. Thus, 7~12°C cold water is prepared for air conditioning at the end of the air conditioner.
advantage:
1. The impeller speed is high, the gas transmission volume is large, and the single machine capacity is large.
2. Fewer wearing parts, reliable operation, compact structure, stable operation, small vibration and low noise.
3. The quality index of unit cooling capacity is small.
4. The refrigerant is not mixed with lubricating oil, and the heat transfer performance of the evaporator and the condenser is good.
5. The EER value is high, and it can be adjusted steplessly within 10%~100%.
shortcoming:
1. The single-stage compressor will have a "surge" phenomenon at low load, and run smoothly at full load.
2. Strict requirements for material strength, machining accuracy and manufacturing quality.
3. When the operating conditions deviate from the design conditions, the efficiency decreases rapidly, and the cooling capacity decreases faster than the piston type with the decrease of the evaporating temperature.
4. Centrifugal negative pressure system, the outside air is easy to intrude, and there is a danger of chemical change and corrosion of the pipeline.
5. Water source heat pump unit
A heat pump type integral water-air or water-water air conditioner that uses water as a heat source and can perform a cooling/heating cycle. It uses water as a heat source for heating and water as a heat rejection source for cooling. Cold (hot) air or cold (hot) air is produced by using water circulating in common pipes, water drawn from wells and lakes or rivers, or water circulating in underground coils as cold (heat) sources water equipment. It includes a heat exchange device on the user side, a compressor, and a heat exchange device on the heat source side, with single cooling or cooling and heating functions.
advantage:
1. Energy saving, heat can be recovered when running in winter.
2. One machine has multiple operations and runs stably.
3. The environmental effect is significant.
4. High energy efficiency ratio.
shortcoming:
1. It is limited by the available water source conditions and the geographical structure of the water layer.
2. The system is prone to the phenomenon of water stringing between the source side and the load side.
3. Influenced by energy policies and fuel prices in different regions and countries.
4. The one-time investment and operating costs are relatively high.
6. Lithium bromide absorption chiller
Lithium bromide absorption refrigerator is mainly composed of generator, condenser, evaporator, absorber, heat exchanger, circulating pump and so on. In lithium bromide absorption refrigeration, water is used as the refrigerant and lithium bromide is used as the absorbent.
advantage:
1. Fewer moving parts, low failure rate, smooth movement, low vibration and low noise;
2. The processing is simple, the operation is convenient, and it can realize 10%~100% stepless adjustment;
3. The lithium bromide solution is non-toxic and has no destructive effect on the ozone layer;
4. The waste heat can be used. Waste heat and other low-grade thermal energy;
5. Low operating cost and good safety;
6. Powered by heat energy, less electricity consumption.
shortcoming:
1. The service life is shorter than that of the compression type;
2. Power saving is not energy saving, steam consumption is large, and thermal efficiency is low;
3. The unit operates under vacuum for a long time, and the outside air is easy to invade. If the air invades, the cooling capacity will be attenuated, so strict sealing is required, which will bring inconvenience to manufacturing and use;
4. The exhaust heat load of the unit is larger than that of the compression type, and the requirements for the quality of the cooling water are higher;
5. Lithium bromide solution is strongly corrosive to carbon steel, which affects the life and performance of the unit.
