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Exp 1 Heat Conduction

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heat transfer experiment
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    1 OBJECTIVES ã To investigate Fourier’s Law for the linear conduction of heat along a simple bar. ã To investigate the influence of thermal insulation upon the conduction of heat between adjacent metals. The mechanism of the heat transfer design principles would be subsequently treated according to the modes of heat transfer, conduction, convection, and radiation. In this experiment the principle of conduction heat transfer based on Fourier's law would be associated with the rate of heat transfer, thermal conductivity, and thermal resistance. The heat conduction topic would be treated according to some geometry such as plane or cylindrical wall or bar. In this experiment the heat conduction study  bench consists of two electrically heated modules mounted on a bench support frame. One module contains a cylindrical metal bar arrangement for a variety of linear conduction experiments while the other consists of a disc for radial conduction experiment. Both test modules are equipped with an array of temperature sensors. Cooling water, to be supplied from a standard laboratory tap is fed to one side of the test pieces in order to maintain a steady temperature gradient. 1. INTRODUCTION This experiment will study data from two type of heat conduction configuration i.e. linear and radial module. The heat conduction study bench consists of two electrically heated modules mounted on a bench support frame. One module contains a cylindrical metal bar arrangement for a variety of linear conduction experiments while the other consists of a disc for radial conduction experiment. Both test modules are equipped with an array of temperature sensors. Cooling water, to be supplied from a standard laboratory tap is fed to one side of the test pieces in order to maintain a steady temperature gradient. Computer will display the direct reading of the temperature sensors and power input to the heater for ease of monitoring and data acquisition. HEAT CONDUCTION  KEYWORDS Heat Conduction, Fourier's Law, Overall Heat Transfer Coefficient OVERVIEW EXPERIMENT 1    2 2. THEORY 2.1 Linear Conduction Heat Transfer   Figure 1: Linear temperature distribution   It is often necessary to evaluate the heat flow through a solid when the flow is not steady e.g. through the wall of a furnace that is being heated or cooled. To calculate the heat flow under these conditions it is necessary to find the temperature distribution through the solid and how the distribution  varies with. Using the equipment set-up already described, it is a simple matter to monitor the temperature profile variation during either a heating or cooling cycle thus facilitating the study of unsteady state conduction. dx dT    3 Figure 2: Linear temperature distribution of different materials Fourier's Law states that: dxkAdt Q     Hence :  where, Q = heat flow rate, [W] k = thermal conductivity of the material,  A = cross-sectional area of the conduction, [m 2 ] dT = changes of temperature between 2 points, [K] dx = changes of displacement between 2 points, [m] From continuity the heat flow rate (Q) is the same for each section of the conductor. Also the thermal conductivity (k) is constant (assuming no change with average temperature). X H X S X C T HS T HI T Cl K  H K  s K  c 1    4 )dx()dT( A )dx()dT( A )dx()dT( A CCSSHH   ……………………………….. (2) i.e. the temperature gradient is inversely proportional to the cross-sectional area. Figure 3:  Temperature distribution with various cross-sectional areas 2.2   Radial Conduction Heat Transfer (Cylindrical) Figure 4:    Radial temperature distribution   When the inner and outer surfaces of a thick walled cylinder are each at a uniform temperature, heat rows radially through the cylinder wall. From continuity X H X s X c Q  A c   A c  A H R i  Ro   Temperature Distribution R i  R o  T i  T o  
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