Steam Jet Refrigeration System | Seminar report Download
In steam jet refrigeration systems, water can be used as the refrigerant. Like air, it is perfectly safe. These systems were applied successfully to refrigeration in the early years of this century.
At low temperatures the saturation pressures are low (0.008129 bar at 4°C) and the specific volumes are high (157.3 m3/kg at 4°C). The temperatures that can be attained using water as a refrigerant are not low enough for most refrigeration applications but are in the range which may satisfy air conditioning, cooling, or chilling requirements. Also, these systems are used in some chemical industries for several processes, e.g. the removal of paraffin wax from lubricating oils.
Note that steam jet refrigeration systems are not used when temperatures below 5°C are required. The main advantages of this system are the utilization of mostly low-grade energy and relatively small amounts of shaft work. here water is used as the refrigerant and the cooling
effect is produced in the steam jet refrigeration continuous cycle by vaporization of a part of the water in the evaporator at a low absolute pressure level.
The steam jet refrigeration system (also known as ejector system refrigeration system) is one of the oldest methods of producing refrigeration effect. The basic components of this system are an evaporator, a compressor device, a condenser and a refrigerant control device. This system
employs a steam injector or booster (instead of mechanical compressor) to compress the refrigerant to the required condenser pressure level. In this system, water is used as the refrigerant. Since the freezing point of water is 0°C, therefore, it cannot be used for applications below 0°C. The steam jet refrigeration system is widely used in food processing plants for precooling of vegetables and concentrating fruit juices, gas plants, paper mills, breweries etc.
Principle of steam jet refrigeration system : –
The boiling point of a liquid changes with change in external pressure. In normal conditions, pressure exerted on the surface of a liquid is the atmospheric pressure. If this atmospheric pressure is reduced on the surface of a liquid, by some means, then the liquid will start boiling at
lower temperature, because of reduced pressure. This basic principal of boiling of liquid at lower temperature by reducing the pressure on its surface is used in steam jet refrigeration system.
The boiling point of pure water at standard atmospheric pressure of 760 mm of Hg is 1 00°C. It may be noted that water boils at 12′C if the pressure on the surface of water is kept at 0.014 bar and at 7′C if the p ressure on the surface of water is 0.01 bar. The reduced pressure on the surface of water is maintained by throttling the steam through the jets or nozzles.
1. Simple construction
2. Vibration free system
3. Highly reliable
4. Low production cost
5. Water is used as a refrigerant which is perfectly safe.
6. Low running cost
7. Load variation quickly adjusted
8. It is suitable for places where steam is available such as process industry, steel plant, petroleum plants, thermal power plants etc.
1. Not suitable for water temperature below 4C.
2. The maintenance of high vacuum in the evaporator is necessary for proper functioning of the system.
3. Since the ejected vapour and motive steam condensed in the condenser, the magnitude of heat transfer is about 3 to 4 times that needed in the vapour compression system per tone per hour.
Thus large size condenser is needed.
4. COP is very low
5. Eff. of ejector is not good.
1. Food processing plant
2. Gas plants
4. Rubber and vulcanizing industries
5. Paper and pulp industries
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