AbstractA mathematical model for the descriotion of the steady and the transient behavior of" a lithium bromide-water absorotion chiller is developed. This model is particularly important for the study of control requirements and is Convenient for the mathematical formulation of the control problem. Both a conceptual approach, that is, using the proper energy balance and heat transfer equations, and an empirical approach, that is curvefitting of the operating data, are used in develooing the model. The steady state part of the model is expressed as functions of the operating conditions (temperatures of the hot water input, the chilled water and the cooling water) and is derived by curvefits to the 0gerating data supplied by the manufacturer. The transient Dart of the model is expressed as a set of differential equations and is formulated by making use of the basic eyua Lions of energy and heat transfer. Finally, the derived model is used in the simulation of the chiller for different variations in the input hot water temperature and the results are compared with some available experimental data.