Large Area Spray Cooling

Abstract

A multi -nozzle plate with 48 miniature nozzles is designed to generate an array of 4×12 spray cones for the cooling of high power directed energy source components. A closed loop spray cooling test setup with a large cooling area of 19.3 cm 2 is established. The initial thermal performance test is carried out at a spray distance of 10 mm using FC-72 as the working fluid. Spray cooling tests are performed in two orientations of the spray target surface - (a) vertical and (b) horizontal facing downward. In both cases, the spray cone axis remains normal to the cooling surface. Critical heat flux (CHF) is investigated at various spray saturation temperatures and nozzle pressure drops. It is found that the thermal performance of the spray cooling is higher for the horizontal facing downward surface than for the vertical surface. Compared with the previous data for a small cooling surface area of 2.0 cm 2 , the maximum heat transfer coefficient and CHF of the large area (19.3 cm 2 ) spray cooling are lower by around 30% and 34% respectively.