CONVECTION HEAT TRANSFER OF CO<,2> AT SUPERCRITICAL PRESSURES IN SMALL TUBES
Convection heat transfer of CO<,2> at supercritical pressures in vertical and horizontal small tubes with diameter of 1 mm and 2 mm was investigated experimentally and numerically. The tests investigated the effects of inlet temperature, pressure, mass flow rate, heat flux, buoyancy, flow acceleration and flow direction on the convection heat transfer. The experimental data indicates that the buoyancy significantly affected the convection heat transfer of supercritical pressure CO<,2> in the vertical small tubes, even if the magnitude order of Gr<,v>/Re<2> is 10<-3>. With the increase of the ratios of the heat flux to the mass flow rate, the heat transfer deterioration occurred for upward flow, but not for downward flow. It was shown that the buoyancy reduced the turbulent kinetic energy of the upward flow, which deteriorated the convection heat transfer. Numerical simulations were investigated in this paper. Numerical simulations were investigated in this paper. The numerical results corresponded well with the experimental data when inlet Reynolds number exceeds 4000 using the Realizable k-ε turbulent model. When inlet Reynolds number is less than 4000, different turbulent models were selected, but no one can correspond well with the experimental data.
convection heat transfer supercritical pressures buoyancy flow acceleration upward flow downward flow horizontal flow
Pei-Xue Jiang Zhi-Hui Li Run-Fu Shi Yu Zhang
Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Thermal Engineering, Tsinghua University, Beijing 100084, CHINA
国际会议
上海
英文
392
2007-03-12（万方平台首次上网日期，不代表论文的发表时间）