Development of Low Temperature Waste Heat Driven Advanced Adsorption Refrigeration System

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Experiments were conducted on a 3.5 kW rated capacity two-stage, advanced silica gel-water adsorption chiller to determine the influence of operating conditions (water temperatures and water mass flow rates) on cooling capacity and COP. The standard operating temperatures for hot, cooling and chilled water are respectively taken as 55℃, 30℃ and14℃. Experimental temperature profiles of the heat transfer fluid inlets and outlets showed that after 400 s, the hot and the cooling water temperatures approach their respective inlet temperatures. This led us to select the standard adsorption/desorption cycle time as 420 s. The chilled water temperature, however, continues to be lower than the inlet temperature in the whole cycle, which means that there is still cooling energy production. Experiments were performed by varying hot water temperatures between 50 and 64℃ to determine its effect on cooling capacity and COP. Cooling capacity rises as the inlet hot water temperature rises from 50 to 6 … More 0℃ with a cooling water at 30℃. This is because the amount of refrigerant circulation increases due to increased refrigerant desorption with higher driving source temperatures. With hot water temperature variation, the COP peaks between 55 and 58℃ shows that this temperature range is ideal for the chiller to operate effectively. Experiments were conducted on cooling capacity and COP variations with various heat sink temperatures. Both cooling capacity and COP increase with lower cooling water temperatures. This tendency reflects the facts that lower adsorption temperature result in larger amounts of refrigerant being adsorbed. Experimental results for chilled water temperature variations showed that cooling capacity and COP increase linearly with increasing chilled water inlet temperatures. But the delivered chilled water temperature also increases with increasing chilled water inlet temperatures. Experiments were also performed on cooling capacity and COP variations with various flow rates of hot water, cooling water and chilled water. Experimental data indicate that cooling capacity increases steadily with the increase of hot, cooling and chilled water flow rates in the range studied. COP also has the similar tendency of cooling capacity. From the experimental evidence it can be concluded that the advanced two-stage chiller is well suited to utilize low-temperature thermal heat (〜55℃) as the driving source with a cooling source of 30℃. The technological difficulty inherent in operating a cycle with such a small regenerating temperature lift (temperature difference between driving source and sink) is overcome by use of a two-stage chiller. Less