Evaluation of Transient Behavior of a Single-Effect Absorption Chiller

This paper deals with the dynamic simulation of a single-effect LiBr-H2O absorption chiller. The thermodynamic properties were taken from the EES software and the simultaneous differential equations were solved in MATLAB environment. The effect of quality on the concentration of solution at the exit points of generator and absorber is taken into account. This effect was ignored in the previous works by assuming that the concentrations of solution at the generator and absorber were equal to the corresponding concentrations at the exit points of those components. The variation of parameters such as coefficient of performance, second law efficiency, enthalpy, and mass flow rate versus time is of interest in this research. Some of the results obtained from the parametric study are: As the pressure difference between the generator and absorber decreases, the solution mass flow rate at the exit point of the absorber will increase, and the solution mass flow rate at the exit point of the generator will decrease. The solution mass in the generator decreases when the solution mass in the absorber is increased, in spite of increasing the solution mass flow rate entering the generator and decreasing the solution mass flow rate leaving the generator. Rich solution leaves the generator at a higher rate than the weak solution. In spite of that, an increase in the heat transfer rate of the generator leads to an increase in the concentration of rich solution. A decrease in the generator pressure, and an increase in the concentration of rich solution lead to an increase in the temperature of generator. Absorbing the refrigerant at a higher rate leads to a decrease in the quality of solution in the absorber and an increase in the rate of heat exchange in the absorber. An increase in the rate of heat exchange in the generator and a decrease in the rate of heat exchange in the evaporator reduce the COP and the second law efficiency.