SUMMARY

Heat actuated adsorption heat pumps offer the opportunity to improve overall energy efficiency in waste heat applications by eliminating parasitic shaft work losses accompanying traditional vapor compression cycles. Adsorption heat pumps are intermittent devices, which induce cooling by adsorbing refrigerant in a sorption bed heat/mass exchanger until the adsorbent reaches saturation. Because adsorption chiller operation is periodic, transient models must be used to predict performance. In this thesis, such models are developed at the adsorbent particle level, heat/mass exchanger component level and system level. Refrigerant diffusion at the particle level is modeled using the Fickian diffusion equation, which is compared with the commonly used Linear Driving Force (LDF) approximation. It is shown that error associated with the LDF diffusion approximation is a function of adsorbent particle radius, particle diffusivity, cycle time, and operating temperatures. At the component level, the sorption rate depends strongly on adsorbent temperature, so annular-finned tubes are used to improve the thermal coupling between the adsorbent and heat stream. A distributed parameter sorption bed simulation is developed, which tracks temperature and refrigerant distributions in the finned tube and adsorbent layer. Unlike in steady-state absorption systems, the efficiency of adsorption heat pumps is shown to depend strongly on the inert bed mass. Thus, there exists an ideal fin density which improves sorption rate and cooling power without wholly sacrificing coefficient of performance. System-level chiller operation is simulated for different working pairs and sorption bed configurations using lumped parameter conservation equations solved by the forward difference method. The various models presented in this work provide fundamental insights into adsorption heat pump operation, which are needed to realize the potential of these systems for waste heat applications.