High COP Exhaust Driven Vapour Absorption Chiller
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The methods for exhaust recovery in Vapour absorption Chillers are highlighted below –
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Conventional Cycle: In the conventional double effect vapour absorption chillers, to achieve the best performance, the Absorbent temperature in double effect generator will be around 160°C. Since the heat exchange is between gases to solution, an approach of ~20°C is necessary so that the area required for generator is optimum. Thus the temperature of exhaust gases leaving the generator is restricted to 180°C and thereby limiting the exhaust heat recovery.
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Ineffective Cycle: Few vapour absorption chiller manufacturers use the heat content of exhaust gases leaving at 180°C in a heat recovery unit to heat hot water. This hot water is then used in a single effect generator as heat source for providing chilling. Since the machine is a combination of single effect and double effect generator the coefficient of performance is lower than a double effect cycle.
- Thermax High COP cycle: To achieve more heat recovery from exhaust gas and achieve higher COP, the Thermax cycle makes use of a specially designed low finned steel tube heat exchanger which preheats the absorbent being carried to generator and in turn recovers heat from exhaust gas and drops the temperature down to 130°C. Since the heat gets recovered in the double effect portion, the COP is higher and thus the refrigeration capacity is improved.
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