The objective of this work is to develop a simulation model for an ammonia/water absorption chiller in order to calculate the chiller capacity and coefficient of performance (COP) at varying operating conditions as they typically appear in solar thermal cooling applications. Therefore a market available chiller has been tested in the laboratory at different steady state and transient operating conditions. For steady state operation two simulation models, the first based on the "characteristic equation" for absorption chillers and the second based on mass, species and energy balances, have been set up and coherently used. The ΔΔT model (based on the "characteristic equation") did not provide proper results compared to the measured values and the model based on mass, species and energy balances. With the resulting simulation model, the control of the absorption chiller has been optimized and a database of cooling capacity and COP values for different operating conditions of external temperature levels and volume flow rates has been generated. Using this database a third simulation model based on characteristic curves has been set up. To identify the crucial effects of the transient operating behavior on the thermal capacities and COP, this has also been experimentally investigated. Dynamic simulation models have been set up to consider effects of thermal masses and charge or discharge of solution/refrigerant accumulators. Relevant influences have been integrated in the characteristic curve model. Final results of the transient simulation show a good agreement with measured values over a test period.
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