抄録
In this study, we studied the heat transfer and fluid characteristics of vertical rectangular channel having grooved pattern; used as solar heat collection wall device, on conditions of natural and forced convection. A vertical rectangular channel (H=785mm, W=672mm) was used and the heat flux (100,200,300,400W/m^2) was given to the wall. Sheathed thermocouples were set at 8mm above on the inner wall, and at height from inlet z = 40, 372.5, 745mm to measure gas temperature, and they were also set under inlet to measure room temperature. On the condition of forced convection, the air was blown into only center channel and the average velocity was set to 0.18m/s at an inlet. On the condition of natural convection, the average velocity of air was measured using PIV system. On the forced convection, the velocity was estimated using the hot wire anemometer and the velocity profiles measured by PIV system. The heat transfer rate was calculated by the equation; Q=CpVp(T_<out>-T_<in>) {Q ; heat transfer rate [W], Cp; Specific heat at constant pressure [J/(kg・K)], V; Outlet volumetric flow [m^3/s], ρ; Density of air (293K) [kg/m^3], Tout; outlet gas temperature (z =745mm) [K], T_<in>; room Temperature [K]} As the result, when the heat flux was between 300 W/m^2 and 400W/m^2, heat transfer rate on forced convection was increased for 17% and 26% compared with natural convection. It was found that the heat transfer was significantly improved using forced convection.
