Experimentally Determining the Convection Coefficient over a Vehicle’s Surface

The goal of this project is to experimentally determine the convection coefficient from a car’s exterior surface to the outside air for a wide range of speed and wind conditions. Experimental measurements of the convection coefficient are required as the convection coefficient varies with air velocity. Proper sizing of vehicle cabin heaters and air conditioners (a contributing factor to fuel efficiency) depends on accurate measurements of the convection coefficient. The focus of this work is on designing, calibrating, testing, and analyzing the values from a thermocouple assembly to find the convection coefficient. The thermocouple assembly will include two thermocouples, separated by a styrofoam block that is mounted on an aluminum plate. A heater will be underneath the top thermocouple where the heating element in the assembly will be controlled by a variable voltage source. An energy balance equation for the heater was used to determine the convection coefficient through heat transfer rates for conduction, convection, and radiation of the rig. The expected results should consist of an experimentally determined convection coefficient for the vehicle’s exterior surface that satisfies the energy balance equation through the compilation of data gathered by the thermocouple assembly rig.