An investigation on heat transfer characteristics in a thermosiphon desorber at sub-atmospheric pressure

Abstract In the air conditioning and refrigeration market, air conditioners using mechanical compressors have become very common, leading to a significant increase in electricity consumption and contributing to the power crisis that many countries are facing. The emergence and development of absorption chillers in general, and absorption chillers without using liquid pumps in particular, provide effective cooling capabilities, energy savings, and environmental friendliness through the reuse of waste energy at low temperatures. However, improving the efficiency of absorption chillers without using liquid pumps remains a challenging problem. This paper delves into the study of the heat transfer characteristics of the thermosiphon desorber (in absorption chillers without using liquid pumps). The mass flow rate of the hot water supplied to the desorber device is varied, combined with different heights of the riser tubes (z V = 0.25 m and z V = 0.7 m). A model is formulated by simultaneously solving mass, energy, and momentum equations to calculate the heat transfer coefficient for single-phase and two-phase flows. Subsequently, an assessment is made of the heat flow and pressure drop in the riser tube of the thermosiphon desorber.