熱サイフォン作用による空気の循環速度

抄録

Natural circulation of air in a loop cylinder induced by heating a part of one of the vertical arms was investigated.
The method of analysis was the same used previously for the natural convection of air in vertical cylinders. From the energy equation of fluid flow combined with the continuity equation, the temperature distribution in the loop was obtained as Eqs.(5) and (6). These functions were applied to the momentum equation and were integrated over the total volume of the loop. The result is given by Eq.(13) or, after a few approximations, by Eq.(16), by which the rate of the circulation, or the Reynolds number, can be estimated from the wall temperature and the geometric conditions of the loop.
Fig. 1 illustrates the structure of the loops and Table 1 gives the conditions and the main results of experiments. In Fig. 2, the mean reduced temperature of air at the upstream end of the heating section is given as a fuction of a for the conditions of L/r₀=191 and l/r_o=10.4. Thus, under the conditions shown in Table 1, the temperature of air at the inlet of the heating section can be assumed to be very close to the room temperature.
Fig. 3 illustrates the relations of aα vs. T_w-T_oo, Figs. 4 and 5 illustrate the wall temperature of the heating section required to get a given value of a when the length of the horizontal arms is varied, and Fig. 6 illustrates the effect of the height of the heating section on the values of Good coincidences were observed between the experimental and the estimated values.
The effect of the curvature of the bends on the natural circulation was discussed under the view of White.