The thermal efficiency of cabinets cooled by natural convection

The latest development in natural convection theory has made it possible to predict the heat transfer coefficient for cases where an air channel, a `chimney´, is located above parallel warm plates. If this theory is applied to a cabinet filled with printed circuit boards (PCBs), it is possible to define three thermal quantities: the thermal efficiency, the heat area ratio, and the surface heat load ratio. If cabinets with different approaches in the thermal design, such as serial and parallel cooling, are compared, it is found that the thermal efficiency is about the same. The surface heat load ratio is, however, superior for the parallel cooling approach, making it suitable for PCBs with high heat loads