Research On Heat Transfer Characteristics Of The Organic Working Fliuds For Low Temperature Waste Heat Power Generation

Industry is the most important part of energy consumption in our country. Itconsumes more than70percent energy of all. But the energy efficiency is very low,and a lot of energy conversed into different carriers and different temperature ofindustrial waste heat. Consider the country’s sintering process, there is more than50percent energy couldn’t be use and taken away by sintering flue gas and exhaust gasof cooling machine. The sensible heat of sintering waste gas accounted for more than20percent of total energy consumption. So, efficient and comprehensive utilization ofindustrial waste heat is an important way to achieve the strategic goal of China’senergy-saving emission reduction. The low boiling point organic working fluids fororganic Rankine cycle power generation is an effective way of low temperature wasteheat utilization. Determination of the organic working fluid flow boiling heat transferis an important component of the Organic Rankine Cycle power generation system. Inthis paper, numerical simulation of flow boiling heat transfer characteristic inhorizontal smooth tubes of R123are made,bi-circulating organic working fluid flowboiling heat transfer experiment table are established, and make a base for furtherresearch on the heat transfer characteristic of the organic working fluid for lowtemperature waste heat power generation.Firstly, some basic parameters of gas-liquid two phase flow and flow boiling heattransfer characteristic inside a horizontal smooth tube have been analysis, includingcross-section gas rate and liquid rate; volumetric flow; volumetric fraction, real gasvelocity, gas superficial velocity, sliding ratio; sliding speed, basic flow patterns ofgas-liquid two-phase flow, different area of flow boiling heat transfer.Secondly, flow boiling heat transfer characteristic in horizontal smooth tubes ofR245fa and R123are numerical simulation using CFD software. The computingmodels of a tube heat exchanger were built using gambit software, and meshed. Theboundary conditions were set and turbulence model and the multiphase flow modelwere selected through the analysis of thermodynamics and fluid dynamics. Throughsimulation, the distribution and variation law of the temperature field, velocity andheat transfer coefficient on flow boiling heat transfer of R245fa and R123in tubeswere obtained. By changing the boundary conditions, simulated the influence lawsof the mass flow rate, evaporating temperature and dryness on the boiling heat transfer.The changeful rules of flow boiling heat transfer coefficient with the variety ofthe mass flux，evaporative temperature，and vapor quality are analyzed and discussed.The experiential results show that flow boiling heat transfer coefficients goes up withincrease of working fluid mass flow rate, but it is contrary to evaporation temperature,with the increased dryness, heat transfer coefficient firstly increases to a maximum,and then decrease quickly.On the basic of theoretical analysis, experiential platform is designed and builtabout flow boiling heat transfer characteristic in horizontal smooth tubes of organicworking fluids.