20 September 2011

ENERGY AND EXERGY ANALYSIS OF DOUBLE EFFECT (PARALLEL AND SERIES FLOW) ABSORPTION CHILLER SYSTEMS


In this paper, three double effect absorption chiller system models are developed. One is for parallel flow and the two are for series flow. These flow directions refer to the solution flowing from the absorber to the regenerators. Given the same amount of cooling
capacity and the same set of environmental conditions (room, condensing and regenerating
temperatures), the temperature, enthalpy, entropy, mass flow rate, and lithium bromide mass fraction in each component of the three absorption systems are presented, together with the exergy destruction calculations. The results show, as expected, that the exergy destruction/losses in the system reduce the system COPs compared to those of reversible cycles. Examining the exergy destruction in detail, it can be seen that the losses in the
generator, absorber, and heat exchangers are significantly larger than those in evaporator, condenser and expansion valves. The series flow configuration, with the solution flowing to
the low temperature regenerator, has the highest COP and exergetic efficiency, but is also most vulnerable to crystallization formation. From the combined analyses, the double effect
parallel flow absorption chiller is the best in terms of system performance and avoidance of crystallization.