Experimental And Simulation Study On Double Film Heat And Mass Transfer Process In The Ammonia/Water Gax Cycle

Absorption refrigeration is an energy saving refrigeration technology and an effective approach to utilize low grade heat as driving power and its working fluid is natural cryogen. So, more and more scholars paid attention to absorption refrigeration.Most scholars focus on an effective technique to improve the performance of absorption cycle. Now, three ways are usually taken in absorption refrigeration cycle to make system more efficient:First, try to research and find new working fluid with better natural property; Second, improve absorption cycle construction to get multi-stage and effect and more excellent internal energy integration; Third, enhance efficiency of heat and mass transfer of key process of absorption cycle to reduce resistance of heat and mass transfer.In this study, experimental and simulating research on double film separation of GAX cycle is carried out. There are two parts in this study: Heat integration for ammonia separation column of GAX and Experiment study on double film separation.In heat integration study, Aspen Plus simulator was used to simulate water-ammonia separation system in GAX absorption refrigeration cycle. The mothed of setting middle reboiler was proposed, and the simulation of GAX ammonia separation was studied. The efficiency of heat exchanger, the position of inlet-outlet and flow rate of side product all affected the operating cost of the separator. The analysis of heat integration indicate that the energy loss of separation and heat exchange decline by setting middle reboiler. As the result, the heat duty of bottom and top of separator decreased by 10.51% and 13.45% respectively, and efficiency of heat integration increased 12.87%.In double film separation study, a new ammonia-water double film separator is carried out. Falling film is taken in separation side and climbing film is taken in annular side, heat transfer style of this system is counter current. Enhancement on heat transfer effective of the annular structure is proved in experiment of heat transfer with water as working fluid, improvement on mass transfer effective is proved in experiment of mass transfer with ammonia water as work fluid. The influences on heat and mass transfer have been investigated, for example, Reynolds of annular, temperature of falling and climbing fluid, annular gap. Correlation model with annular gap is obtained.In this study, the method of setting middle reboiler to reduce energy consume in absorption cycle was proposed. In fact, setting middle rebolier is an approach to multi-step utilizes column bottom fluid. Through structure of double film heat exchanger, inner falling film combines with annular climbing film. The structure is fit to setting middle reboiler. It can simplify system and reduce equipment size.