Aerodynamic and thermal investigation into axial flow fan cooling of electronic systems, part I: measurement techniques and steady flow measurements

摘要

Measurements of surface temperature and air velocity are presented for the case of a printed circuit board with heated metal elements in a fan-induced flow. The aim is firstly to provide a physical explanation of the heat transfer process for the board situated in the inlet and exit air flow from the fan, and secondly to provide a set of data to test predictive methods. The paper is in two parts: the first addresses in some detail how Particle Image Velocimetry may be accurately used to measure the flows. Repeatability tests, performed by viewing the flow from different angles, were used as the basis of an error analysis. An infra red camera was used to measure the surface temperature of the metal elements, which simulate electronic components. For these measurements, the transmissivity of the tunnel wall was calibrated. Surface temperature distribution and velocity field data are presented for the case of the fan drawing air from the system. The flow was found to be parallel and uniform. There were symmetrical temperature gradients across the board that were readily explained in terms of board conduction and boundary layer growth. This data set is in strong contrast to that presented in the second part of the paper, which deals with the board mounted in the fan exit flow.