"Laboratory/Demonstration Experiments in Heat Transfer: Forced Convection"

Laboratory exercises or demonstrations which are designed to compare experimental data with data or correlations from the literature are excellent methods for reinforcing course content.As part of the requirements for CHEG 3143, Heat Transport, and CHEG 3232, Laboratory II, junior level chemical engineering students were required to perform simple heat transfer experiments using inexpensive materials that are readily available in most engineering departments.The design, implementation and analysis of three of these experiments are described.Experimental forced convection heat transfer coefficients were determined by flowing air over an upward facing horizontal plate, past the bulb of a mercury/glass thermometer and through an annulus.In each case, the apparatus (the plate, cylinder or inner cylinder) was allowed to cool or heat in the flowing air, while recording temperature as a function of time.The experimental heat transfer coefficients were then determined from a heat balance over the heat transfer surface.Finally, the experimental coefficients were compared to those obtained from appropriate literature correlations.The experimental forced convection heat transfer coefficients for parallel flow over flat plate were 2.2-3.5 times higher than literature correlation coefficients, most likely resulting from the high turbulence generated by the fan.The experimental forced convection heat transfer coefficient for two different sizes of mercury/glass thermometer bulbs, were within 20% of the literature correlation coefficients.The experimental forced convection coefficients from flow of hot air over a brass rod centered in an annulus were 1.6-2.2times higher than literature correlation coefficients, most likely resulting from the the hair dryer jet velocity being 3.6 times higher than the annulus velocity.