23 September 2011

EXPERIMENTAL RESULTS AND MODEL CALCULATIONS OF A HYBRID ADSORPTION-COMPRESSION HEAT PUMP BASED ON A ROOTS COMPRESSOR AND SILICA GEL-WATER SORPTION


Thermally driven sorption systems can provide significant energy savings,
especially in industrial applications. The driving temperature for operation of such systems
limits the operating window and can be a barrier for market-introduction. By adding a
compressor, the sorption cycle can be run using lower waste heat temperatures.
ECN has recently started the development of such a hybrid heat pump. The final goal is to
develop a hybrid heat pump for upgrading lower (<100°C) temperature industrial waste heat to above pinch temperatures. The paper presents the first measurements and model calculations of a hybrid heat pump system using a silica gel water system combined with a Roots type compressor. From the measurements can be seen that the effect of the compressor is dependent on where in the cycle it is placed. When placed between the evaporator and the sorption reactor, it has a considerable larger effect compared to the compressor placed between the sorption reactor and the condenser. The latter hardly improves the performance compared to purely heatdriven operation. This shows the importance of studying the interaction between all components of the system. The model, which shows reasonable correlation with the measurements, could proof to be a valuable tool to determine the optimal hybrid heat pump configuration.