Experimental Study of a Bubble Pump Operating with a Set of Parallel Lift Tubes and a Binary Solution of R134a-DMAC

An alternative utilization of a compressor or a mechanical pump in the traditional refrigeration cycles is the diffusion absorption refrigeration (DAR) cycle operating with a bubble pump to circulate the binary working fluid. The bottle neck of the DAR cycle is the bubble pump and its performance is determined by the amount of separated refrigerant leaving the bubble pump and the circulation ratio (i.e., the ratio between the mass flow rates of separated refrigerant and rich solution). This work investigated the possibility of increasing bubble pump performance by using a set of parallel bubble pump lift tubes. A modular experimental continuous system was designed to characterize the performance of three parallel bubble pump lift tubes with an environmentally friendly binary solution of R134a-DMAC. The dependence of the number of bubble pump lift tubes and various operating conditions (i.e., refrigerant mass concentration and heat input) on the amount of the desorbed refrigerant was determined. The results showed that in comparison to a single lift tube, the use of two or three parallel lift tubes when the bubble pump was operated with optimum heat input could double or triple, correspondingly, the amount of desorbed refrigerant.