Heat (mass) transfer on effusion plate in impingement/effusion cooling systems

The local heat/mass transfer characteristics on an inner surface of the effusion plate in an impingement/effusion cooling system have been investigated. Two perforated plates are installed in parallel position to simulate the impingement/effusion cooling system. The experiments have been conducted for three different hole arrangements, staggered, square, and hexagonal, with various gap distances of 1, 2, 4, and 6 times the effusion hole diameter. The Reynolds number based on the effusion hole diameter is fixed at 1 × 10⁴. A naphthalene sublimation method is used to determine the local heat/mass transfer coefficients on the effusion plate. For all of the tested cases, high transfer regions are formed near the stagnation points and at the midline region of the adjacent impinging jets due to secondary vortices and flow acceleration to the effusion holes. The heat/mass transfer coefficient in the whole region increases with decreasing gap distance. The staggered hole arrangement shows the highest average heat transfer coefficient due to the largest area ratio of the effusion to the injection hole; however, the heat/mass transfer on the effusion plate is more uniform for the square and hexagonal hole arrangements because the number of injection holes is increased.