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EES simulation model for the part load behaviour of single stage H2O/LiBr absorption chillers

Albers, Jan

This simulation model (i.e. the main file AKA_CE_Simulation.EES) calculates the partload behaviour of a single stage H2O/LiBr absorption chiller. For the characterisation of the chiller or heat pump only the heat transfer capabilities (i.e. the UA-values) of five heat exchangers (Desorber, Evaporator, Condenser, Absorber and Solution heat exchanger) and the pumped solution flow rate have to be known. Examplary values are provided in a supplementary library file (i.e. ZAKA_20190721ja.LIB). The heat transfer calculation for the desorber can account for different design configurations where adiabatic sorption processes may occur (e.g. sprayed or irrigated heat exchangers, case A) or not (e.g. flooded heat exchangers, case B). In addition to the differentiation into case A and B there are three possibilities for the heat transfer calculation in ab- and desorber: a) case A or B with temperature independent heat capacity flow rate, b) case A or B with linear temperature dependent heat capacity flow rate, c) case A or B with arbitrary temperature dependent heat capacity flow rate (cell method) Variable internal and external flow rates are possible. But only for the external flow rates the heat transfer coefficients are adapted according to the method described in subsection 2.3.6 of the phd. In parallel to the internal cycle simulation combined with the heat transfer calculation the established and enhanced method of characteristic equations is applied (cf. chapter 3 of the phd). The results of the cycle simulation are plotted in a p-T-diagram and h-xi-diagram. Additional plots which compare the simulated heat flows in evaporator and desorber to the results derived from established and enhanced method as function of the characteristic temperature difference DDt are provided.