Evaluation of pressure drop characteristics around axial cooling fans with electrical components

Abstract

This paper describes the details of pressure drop characteristics around axial cooling fans mounted in high-density packaging electronic equipment in order to improve prediction accuracy of supply flow rate of the fans in thermal design. Forced air convection cooling driven by cooling fans is the commonest strategy for dissipating heat from electrical devices. Cooling performance of the fans is mainly decided by supply airflow rate. The supply flow rate is strongly affected by pressure drop characteristics in electronic equipment. Especially in the case of high-density packaging electronic equipment, the airflow around the fan generally becomes complex and an accurate prediction of pressure drop characteristics around the fans become significantly difficult. In addition, due to the change of the airflow pattern around the fans by the electrical components mounted near the fans, a deterioration of fan performance itself is sometimes caused. Hence the accurate prediction of supply flow rate of the fans in high-density packaging electronic equipment is generally difficult. However, in order to shorten the period of thermal design, more detailed investigation about airflow characteristics around the fans mounted in high-density packing electronic equipment should be done in order to achieve the accurate prediction of fan's supply flow rate easily. We are trying to develop a prediction model of accurate supply flow rate of the fans mounted in high-density packaging electronic equipment. In this report, the pressure drop characteristic near the axial fan when an obstruction, which simulates electrical components mounted near the fans, is mounted in front of the fan was evaluated while changing the type of the obstruction. The pressure drop around the fan with the obstruction is mainly composed of three factors; the pressure drop around the obstruction, the inlet pressure drop at the fan and the outlet pressure drop from the fan. A level of these pressure drop factors were evaluated quantitatively by comparing experimental results with the conventional pressure drop database. In order to evaluate the accurate supply flow rate of the fan in high-density packaging electronic equipment, an important factor was clarified from the viewpoint of the pressure drop characteristics around the fans.