734. 垂直円管内ガス流の加熱による層流化実験

抄録

The experimental results of laminarization phenomena of strongly heated He gas flow in a vertical circular tube are presented. The inlet Reynolds numbers Re_i range of 1, 340-40, 000 and the inlet dimensionless average heat flux parameter q⁺_i(=q_w/G·cp·T_i) up to 7.2×10^-3. Turbulent fluctuations are measured by a hot-wire anemometer in strongly heated gas flow. The intermittent flow similar to isothermal transitional flow appears even if the bulk Reynolds number is larger than the transitional Reynolds number. When more heat is added, the fluctuation typical of turbulent flow is suppressed almost completely. The criteria for the starting and ending of laminarization are found to be expressed as follows:
Starting of laminarization: q⁺_i=4.94×10^-3·Re_i^0.05{1-(Re_ir/Re_i)^0.75}, 4, 500≤Re_i≤40, 000
Ending of laminarization: q⁺_i=5.87×10^-3·Re_i^0.05{1-(Re_i/Re_i)^0.75}, 4, 500≤e_i≤11, 000 where Re_ir and Re_ir' are upper and lower Reynolds numbers in the isothermal transitional flow, 3, 140 and 2, 800, respectively.