Combination of hot/cold wire technique for instantaneous velocity and temperature measurements

A combination of a hot/cold wire technique was used for the simultaneous measurements of instantaneous velocity and temperature in a vertical pipe. The detailed study of the effects of buoyancy on flow characteristics and heat transfer of opposing mixed convection had been carried out experimentally. The performance of cold wire for temperature compensating the velocity reading of a hot-wire probe due to varying fluid temperature was assessed. Heat transfer results for opposing mixed convection have been presented in non-dimensional equations using the buoyancy parameter Ω (Ω = Grd/Red2), in which Red from 900 to 18000, ω from 0.004899 to 0.5047. It is found that the heat transfer is enhanced due to buoyancy effect. With the increasing of Grd (Grashof number), the temperature fluctuation, streamwise Reynolds normal stress and streamwise heat flux are increased, especially in the near wall region. The combination of hot/cold wire enables the study of iso-thermal flow characteristics, thus it is helpful to look inside of buoyancy effects on heat transfer in the mixed convection flows.