Experimental Evaluation of a Novel Tube Bundle Solar Driven Liquid Desiccant Regenerator

摘要

A novel design of an internally heated tube-bundle heat and mass exchanger is presented and experimentallyrnexamined in this paper. The main focus for the design of the regenerator was to avoid carryover of thernlithium chloride solution (LiCl-H_2O) to the regenerator air-stream. Furthermore, an important aim was tornrealize an improved heat and mass transfer coefficients, as well as higher chemical, physical, and thermalrnstability of the construction and to reach an even wettability and maximum uniform distribution of the liquidrndesiccant in the regenerator.rnThe presented regenerator is the core of a demonstration plant of a liquid desiccant system that will be usedrnfor drying hay bales. The system will be installed in an agricultural domain in North Hessen, Germany. Thernliquid desiccant regenerator is made of copper pipes, protected from the corrosive medium, the LiClsolution,rnwith a thin powder coating layer. The copper tubes are covered with textile sleeves. The totalrnexposed surface area of the regenerator is about 4 m~2. The air stream and the LiCl solution flow are arrangedrnin a cross flow configuration.rnThe regenerator is tested in the laboratory at Kassel University. Four test sequences each with threernexperiments were performed by varying one of the inlet parameters in each test sequence. The moisturernremoval rate is studied as a function of desiccant mass flow rate, desiccant inlet temperature, heating-waterrninlet temperature and air inlet temperature. It is found that the moisture removal rate increases withrnincreasing desiccant flow rate, desiccant inlet temperature and heating-water inlet temperature. Also,rnincreasing the air inlet temperature has only a small effect on the increment of the moisture removal rate; thisrnraises the question about the viability of preheating the regeneration air before coming in contact with dilutedrndesiccant solution especially if the regenerator is internally heated.rnThe diluted desiccant solution could be re-concentrated by using heating water with a temperature of 50℃.rnFurthermore, an increase in the concentration of the LiCl-solution by 4% is observed when the inlet heatingwaterrntemperature is 70 ℃.