Experimental study on a novel pumpless absorption refrigeration system using R134a/DMF as working pair

To address the challenges related to corrosion, sealing, additional electrical energy consumption, and the limited adaptability imposed by the electrically-driven solution pump to small-scale absorption refrigeration cycle (ARC) system, a pumpless module based on the switching valves method (SVM) is designed and constructed for an ARC system. The pumpless operation is realized based on thermal-gravity-driven mechanism by employing a corresponding valve-assembly among three vessels, which effectively substitutes for the electrical solution pump. R134a/DMF is employed as the working pair to maintain the necessary pressure differential for efficient solution pumping process. The overall performance of the system is studied. Experimental results show that the system operating parameters fluctuate periodically, and the fluctuation induces periodic variations in heat input and cooling capacity in the range of 0.95∼1.76 kW and 0.27∼0.79 kW, respectively. For the system the maximum cooling capacity of 0.79 kW and the average cooling capacity of 0.33 kW are achieved under the conditions of valve opening of 32°, average hot oil temperature of 116.9°C, heat sink temperature of 30.9°C, cooling source temperature of 25.9°C, and cycle time of 300 s, while the average COP of 0.28 is achieved at the cycle time of 420 s under the same conditions. The pumpless module is validated feasible as a promising alternative to solution pump, especially for small-scale system.