Steady-state off-design thermodynamic performance analysis of a SCCP system

A steady-state model of a small combined cooling and power (SCCP) system, which includes a micro gas turbine (MGT) and a LiBr-H2O single-effect absorption chiller with a cooling tower, is built to investigate the off-design performance of the system. The off-design performance of the compressor and expander of the MGT is described by characteristic maps. Holman correlation is applied to the calculation of heat transfer coefficients of the recuperator, evaporator, condenser, solution heat exchanger, and generator. The heat and mass transfer in the absorber are described according to a physical model based on Nusselt's film theory. The F-LMED method is applied in the cooling tower model. The system is evaluated under different MGT output power and ambient temperature. The effect of the different operation modes of cooling tower is studied. Simulation results show that the performance deterioration of the system is mainly caused by the poor performance of the MGT. The COP and cooling capacity vary smoothly under off-design condition in which the outlet water temperature of the cooling tower remains constant. The effects of the two operation modes of the cooling tower on the cooling capacity of the system do not differ greatly when energy quality is considered.