The experimental characterization of a lithium bromide–water absorption chiller and the development of a calibrated model

Abstract

Small-scale solar air conditioning systems based upon thermally activated chillers offer great potential for cooling houses with minimal demands upon the central electrical system. Building performance simulation can be used to assess the potential of the technology and to explore the impact of system design (e.g. type and area of solar collectors, volume of hot and cold thermal stores, operating strategies), but only if appropriate models calibrated with accurate and reliable data are available. Experiments were conducted on a commercially available lithium bromide–water absorption chiller under a controlled set of operating conditions. Instrumentation was selected, calibrated, and installed in order to derive quantities of interest at acceptable levels of measurement uncertainty. Over this range of experiments, the cooling capacity varied from 6.9kW to 40.5kW, and the thermal coefficient of performance ranged from 0.56 to 0.83. A quasi-steady-state model suitable for use in building performance simulations that expressed the chiller’s performance was developed. Based upon statistical significance testing, it was found that the rates of heat transfer to both the generator and the evaporator could be expressed as linear functions of the generator inlet temperature, absorber/condenser inlet temperature, and flow rate of water to the generator. The validity of the calibrated model was then tested using measurements from a disjunct experiment whose data were not used to calibrate the model.