人工糙管中湍流传热与温度分布

Turbulent Heat Transfer and Temperature Profiles in Artificially Roughened Pipes

以横肋管为典型人工糙管,空气为试验介质,恒热流操作,进行湍流传热时径向温度分布和传热特性的测定,试验Re为20000～70000.所得湍流核心区温度分布可以对数分布律和温度亏损律表示,式中常数与粗糙几何参数有关.由测得的温度分布和速度分布计算了湍流粘度和湍流导温系数.此外,还进行了温度脉动特性的测定.传热系数测定结果表明,人工粗糙管比光滑管强化150%～300%,传热膜系数可用简单关联式估算Nu/Nu_s=1+26(k/d)^(0.49)(S/K)^(-0.46)式中Nu_s=0.022Re^(0.8)Pr^(0.5)

Radial temperature profiles and heat transfer coefficients were measured for the turbulent flow of air in a smooth pipe and repeated-rib pipes with 0.01<k/d<0.04 and 10<S/k<40 over a Reynolds number range between 20000 and 70000. The experimentally measured temperature profiles in the turbulent core region can be described with logarithmic distribution and temperature defect. The coefficient in the expression are related to the roughness geometry. Thermal and momentum diffusivities were calculated from the temperature and velocity profiles. The intensities of temperature fluctuations were also measured. The measurements of heat transfer showed that the enhancement in a repeated-rib pipe varied from a factor of more than 150% to a factor of around 300% within the range of this experiment. A simple correlation of heat transfer coefficients was given where Nu, = 0.022Re0.8Pr0.5