FLUID FLOW AND HEAT TRANSFER OF NATURAL CONVECTION AROUND MULTIPLE HEAT SOURCES PLACED IN THE SAME HORIZONTAL PLANE

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Interactions of natural convection plumes issued from multiple heat sources placed in the same horizontal plane have been investigated experimentaly in the present study. The special concerns were focused on the fluid flow and the heat transfer around the horizontal rows of vertical plates, horizontal cylinders and upward-facing horizontal plates, which were placed at the constant intervals and were heated with the constant heat fluxes. The test fluid is water at room temperature. The flow field around these heat sources were visualized with dye. The results demonstrate that the plumes departed from the heat sources interact with each other and gather to the symmetrical plane between the heat sources. These interactions occur even when the intervals between the heat sources are ten times larger than the dimensions of the heat sources. The influences of the plume interactions on the heat transfer characteristics of the heat sources were also investigated. The results for the vertical plates show no substantial change in the local heat transfer coefficients, while the local coefficients of the horizontal cylinders and of the horizontal plates are changed by the plume interaction. It is found from the visualization study that the separation points over the above two heat sources move toward the center of the heat sources when the interactions occur and this could cause the variations in the local coefficients. On the basis of the above discussions, the heat transfer characteristics of the upward-facing horizontal plates were investigated. It was revealed that the local heat transfer coefficients are affected seriously when the plates are placed at small intervals. However, the effect of the plume interaction on the heat transfer coefficients becomes smaller with increasing the intervals, and the over-all coefficients of the plates become the same as those of the single plate when the plate intervals exceed 50mm.