ADVANCED MODULAR SIMULATION OF ABSORPTION SYSTEMS

A computer code has been developed for simulation of absorption systems at steady state in a flexible and modular form, making it possible to investigate various cycle configurations with different working fluids. The code is based on unit subroutines containing the governing equations for the system's components. The components are linked together by a main program according to the user's specifications to form the complete system. When all the equations have been established, a mathematical solver routine is employed to solve them simultaneously. Property subroutines contained in a separate database serve to provide thermodynamic properties of the working fluids. The code is user-oriented and requires a relatively simple input containing the given operating conditions and the working fluid at each state point. The user conveys to the computer an image of the cycle by specifying the different components and their interconnections. Based on this information, the program calculates the temperature, flow rate, concentration, pressure and vapour fraction at each state point in the system and the heat duty at each unit, from which the coefficient of performance may be determined. This paper describes the code and its operation, and discusses some typical results. Significant improvements have been introduced into the present version relative to earlier versions. Particular attention has been devoted to the mathematical portion of the code in order to enhance its convergence capability with large and complex cycles. Simulation results are described for LiBr-H2O triple-effect cycles, LiCl-H2O solar-powered open absorption cycles and ammonia-water single-effect and GAX cycles.