Study and analysis of the diϱusion absorption refrigeration machine in search of technological solutions to further extend its limits

Abstract

Diϱusion absorption refrigeration (DAR) is a reliable cooling system, especially in conditions where conventional refrigeration systems are not convenient. Since it operates without any mechanical components, the DAR refrigerator is silent, making it suitable for quiet environments. The evaporation process in DAR systems notably aϱects their operation. However, few studies have focused on this speciϧc issue. In this work, a numerical investigation was conducted using CONVERGE CFD software and the RANS approach to analyze the evaporator region of a DAR system operating with an ammonia/water mixture and using hydrogen or helium as an inert gas. The aim was to validate an accurate CFD model by analyzing the ϩow behavior and thermal parameters within the evaporator for an ammonia/hydrogen gas mixture ϧrst, and then to examine the use of helium instead of hydrogen as the pressure equalizer. For this purpose, an experimental bench was prepared. The computational results showed high agreement with the experimental data, with slight deviations often remaining under 3%. The study also investigated the eϱect of ammonia presence at the hydrogen inlet, speciϧcally at 5% and 10% ratios. The results demonstrated that the average temperature deviation was less than 1% when using 5% ammonia. A total pressure of 5 bars was found to be appropriate for the DAR system when helium replaces hydrogen. This study sheds light on the evaporation process, which is crucial for enhancing the design and operational eϫciency of DAR systems. The validated numerical model will be of great use for this purpose.