| The adsorption refrigeration, which has zero ODP and very little greenhouse effect, is a good opportunity to replace the CFCs or HCFCs refrigeration. Compared to absorption refrigeration, adsorption refrigeration has no distillation (ammonia-water system), corrosion or crystallization (lithium bromide-water system) problem. Meanwhile, adsorption refrigeration has lower equipment cost and more effective when low grade thermal energy, such as solar energy and the waste heat from an engine, acts as the driving heat source. Due to the instability and intermittence of waste heat and solar energy, varying heat source is an unavoidable problem when the adsorption refrigeration is applied in waste heat recovery, solar energy utilization etc. Therefore, it is necessary to research the operating performance of the adsorption chiller under varying heat source and further optimize the control strategy.Based on the former achievements of the adsorption refrigeration, the dynamic mathematical model of a silica gel-water adsorption chiller was built by means of lumped parameters method. Matlab-Simulink is used as the tool to realize the modularized simulation of this chiller. Effects of the hot water tank capacity, the cycle time, the mass recovery time and the initial hot water temperature on the performance of the chiller powered by solar energy were analyzed. And, the operating performance of this chiller driven by solar energy and stable heat source were compared. The simulation results indicated that when the chiller was driven by solar energy, a smaller hot water tank capacity is better for improving the performance of the chiller; when hot water tank capacity is bigger, the appropriate extension of operating time can help to boost refrigerating performance of the chiller.By analyzing the effects of operating parameters on performance of this adsorption chiller, the reasonable operation mode of this chiller driven by solar energy was proposed, and the corresponding control system was designed. The control system was composed of AT89C51 which is the key unit, relays, TLC1543 and MAX232. The operating control and data acquisition functions were realized. The signals recorded included temperatures, pressures and flowrates. In addition, an optimal controlling strategy, which was called varying cycle control method, was also proposed for the chiller driven by solar energy. By this method, the average refrigerating capacity is increased by 5.4%. |
PDF Full Text Request