Cleanroom cooling solutions

Cooling Solutions

Refrigeration program should be based on the cooling requirements (cooling consumption, cooling mode, chilled water temperature, etc.), the construction area of the water source (water temperature, water quality, water quantity, etc.) and power supply, heat source preparation party and technical and economic comparison. Both require better economic indicators and consider the local possibilities.

The selection of the refrigeration unit is the central part of the process of determining the refrigeration program, the main types of refrigeration units are as follows.

1、Compression type refrigeration unit

Compression refrigeration units include three types: piston (reciprocating), centrifugal and screw.

Piston (reciprocating) compression refrigeration device is the main equipment is piston refrigeration compressor, commonly used work ammonia (NH3), Freon & mdash; 12, 22 (F & mdash; 12, 22). This type of equipment driven by an electric motor, easy to use, a variety of products to meet the requirements of various types of air conditioning supply cold, is widely used. But a large investment, high cost of equipment, power consumption, maintenance and management is more complex.

The main equipment of centrifugal compression refrigeration device is centrifugal refrigeration compressor, commonly used work is Freon & mdash; 11, 113, 114 (F-11, 113, 114). The machine and piston refrigeration compressor principle is the same, but it only rotary motion, than the piston type smooth operation, small vibration, less parts, often with the evaporator, condenser combination as one, compact equipment covers an area of small. Centrifugal refrigeration compressor refrigeration capacity is larger, so only when the air conditioning consumption is larger, this type of equipment is used.

The main equipment of the screw-type compression refrigeration unit is a screw-type refrigeration compressor, the commonly used work material is Freon —12, 22, ammonia (F-12, 22, R717). The current production of screw refrigeration compressor and piston type, although the efficiency is slightly lower, but because of its simple structure, small size, high suction coefficient, low exhaust temperature, single-stage compression ratio, insensitive to wet travel, small exhaust pulsation, less wear parts, column repair cycle, the refrigeration capacity can be steplessly adjusted and other advantages, so in a variety of refrigeration devices are more widely used. Generally in (120—800)x105kJ＼h capacity range of refrigeration devices with this machine has a better technical and economic indicators.

2、Absorption refrigeration unit

Absorption refrigeration units use thermal energy to cool. Common are ammonia & mdash; water absorption refrigeration device and water & mdash; lithium bromide aqueous solution absorption refrigeration device. The former is suitable for low-temperature refrigeration; the latter is suitable for air-conditioning supply cooling, making more than 4 ℃ air-conditioning or process with cold water. Lithium bromide absorption refrigeration in the water as the work material, lithium bromide aqueous solution as the absorbent. It has the following advantages.

It has great adaptability to the pressure of steam heat source, when the steam pressure is 0.02—0.1MPa, single lithium bromide absorption chiller can be used, when the steam pressure is 6.0—1.0MPa, double-effect lithium bromide chiller can be used.

Secondly, the equipment is simple, basically a combination of heat exchanger, easy to manufacture, except for small power shield pump, vacuum pump, no moving parts, so the vibration is small, smooth operation; the equipment works under vacuum, the work material is odorless, non-toxic, harmless to people, safe to use, simple operation and management; easy to realize the automation of equipment operation, the cooling capacity can be automatically adjusted in the range of 10% to 100%; the cooling water Even if the water temperature reaches 37-38℃, the equipment can still operate normally; save electricity, the electricity consumption of lithium bromide refrigerator is only about 5% of that of compressor refrigerator under the same condition of single machine cooling capacity, which is very suitable for the area where the power supply is tight and the heat source is sufficient. However, lithium bromide absorption refrigeration also has shortcomings and limitations, mainly because lithium bromide aqueous solution is strongly corrosive to metal in contact with air, once it is corroded, it will not only affect the heat transfer effect and reduce the service life, but also cause damage to the equipment, so the equipment must be strictly sealed, and great attention should be paid to the operation and management.

3、Steam injection refrigeration unit

Steam jet refrigeration device is also a kind of equipment that uses thermal energy for refrigeration, with water as the refrigerant and steam as the refrigeration power. The pressure of steam requires 0.2—0.8MPa, its main advantages are: equipment working under vacuum, except for the pump, no rotating parts; refrigerant is water, harmless to people, safe to use, simple operation; equipment is simple, easy to manufacture, general mechanical plant or machine shop can be processed and manufactured; equipment a small investment, and can be installed outdoors, saving civil construction costs; can use industrial It can use the waste heat in industrial enterprises or heating boilers in industrial enterprises to supply heat and heating in winter and steam and cooling in summer.

The main disadvantage of steam injection cooling is the low efficiency, and it is not economical to set up a special boiler and use a small heating boiler to supply steam. It can be used when the chilled water temperature is above 5°C and is more economical above 100°C. Its efficiency changes with the chilled water temperature, the lower the chilled water temperature, the greater the steam consumption and the lower the efficiency. In addition, the cooling water is very large, the same conditions of single-unit cooling capacity, steam injection chillers require cooling water is about 1.5 times for the compressed or brominated absorption type, which is not suitable for the region of water tension.