Thermal Design of a Protruding Heater in Laminar Channel Flow

Abstract

The conjugate heat transfer from a single block heater mounted on a conductive wall of a parallel plates channel was investigated under conditions of laminar airflow. The heater cooling was attained by direct forced convection to the airflow and by conduction through its contact with the channel wall. The investigation was performed for a two-dimensional configuration with fixed channel geometry and variable heater height, where the heater upstream edge was centered on the channel wall. At the channel entrance the flow velocity and temperature were uniform. The channel wall thickness was constant and its thermal conductivity was varied in the range from 0 to 80 that of the air, while the heater block thermal conductivity was equal to 500 that of the air. The conservation equations were solved numerically by the control volumes method with the SIMPLE algorithm. The results were expressed in dimensionless form, considering three distinct constraints: fixed flow rate, fixed channel flow pressure drop and fixed pumping power. The last two constraints present an optimum heater height, but care was taken to avoid that the flow recirculation downstream the heater extended beyond the channel length. The heat transfer enhancement promoted by wall conduction was clearly indicated.