The heat transfer characteristics of forced convection according to the geometric shapes with four rectangular blocks in a horizontal PCB channel was analyzed numerically using SST (Shear Stress Transport) turbulence model. As the boundary condition for CFD (Computational Fluid Dynamics) analysis, the inlet temperature and air velocity were respectively 300 K and 3.84 m/s and the heat flux of the block surface was 358 W/㎡. The shape factors of block were width, height, spacing and channel entrance height. As the results, the heat transfer rate was decreased as the width ratio (x/h) was increased, while it was increased as the height ratio (h/x) is increased. Also as the block spacing ratio (s/x) was increased, the heat transfer effects was not significantly affected. And as the channel entrance height ratio (H/x) was increased, the heat transfer performance was decreased.

In this study, the heat flow characteristics of natural convection was theoretically analyzed with time by changing various locations of heat trace with tube surface about enclosed circular tube by applying nominal tube diameter 90 mm of KS D 3507. Before carrying out CFD (Computational Fluid Dynamics) analysis, it is presumed that the boundary condition is the tube’s inside and outside fluid temperature of 273 °K, the tube surface heat flux according to the heat trace location of 16 W/m. The result confirmed that water of inside tube is occurred natural convection caused by density difference depending on temperature profile. Additionally, in case of heat trace location, the heat transfer and flow characteristics showed clearly that two-heat trace location =135° and 180° was more favorable distribution than one-heat trace appropriate location =135°.