heat_THINGY_REPORTbodyfinal1

heat_THINGY_REPORTbodyfinal1 - NANYANG TECHNOLOGICAL...

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Figure 1: Temperature gradient of conduction through a wall Figure 2: Picture showing the movements of the regions Figure 3: Diagram showing the boundary layers of forced flow over a cylinder. Figure 4: Surface-radiating heat to the surroundings 1 3 2 4 e ating Element with matte black finish placed in the duct. (3)Heat transfer service unit H110 used to show the various data. (4) Thermocouple that can be adjusted. T 9 Anemometer T 10 Heating Element Throttle Plate y turning thermocouple, we are able to determine the local heat transfer around the duct. diation H110. Air flows upwards through the duct and eventually across the heating element. Its temperature recorded at T 9 and T 10 . Table 1: Data collated for free convection Table 2: Data collated for forced convection at medium flow Figure 8: Comparisons between the three correlations (Q conv vsQ total ) Table 3: Data collated for free convection ure 9: Graph showing how h varies with angle for natural convection Table 4: Data collated for forced convection at medium flow re 10: Graph showing how h varies with angle for forced convection NANYANG TECHNOLOGICAL UNIVERSITY COMBINED HEAT TRANSFER BY FREE CONVECTION AND RADIATION 1. OBJECTIVES The objectives of this laboratory project are to: Determine the combined (radiation and convection) heat transfer (Q rad + Q conv ) from a horizontal cylinder, under natural and forced convection conditions, over a wide range of power input and corresponding surface temperatures. Explore the effects of locations of measurement in determining the local heat transfer around the duct. P3.22 COMBINED HEAT TRANSFER BY FREE CONVECTION AND RADIATION NANYANG TECHNOLOGICAL UNIVERSITY
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NANYANG TECHNOLOGICAL UNIVERSITY COMBINED HEAT TRANSFER BY FREE CONVECTION AND RADIATION 2. INTRODUCTION There are three fundamental modes to heat transfer, namely conduction, convection and radiation. Each of the modes of transfer has its own unique way of transferring thermal energy. Each of them also has their own equations that characterize the flow of heat and also their respective heat transport coefficient terms. All three modes of heat transfer are generally present in varying degrees in almost physical problems concerning heat transfer. The next three sub-chapters will briefly explain some of the concepts in heat transfer. 2.1 CONDUCTION Conduction deals with the transfer of thermal energy through a material without itself moving. It is described as the flow of heat due to interactions between molecules in a material. When this happens, there is a transfer of energy between more energetic molecules (due to being in a region of higher temperature) and molecules possessing higher energy (due to being in a region of lower temperature). This phenomenon is fundamentally a diffusion process that occurs at a microscopic level. Whenever a temperature gradient exists in a medium, heat conduction will almost definitely occur. At a more macroscopic level, the heat transfer per unit area normal to the direction of
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This note was uploaded on 10/22/2009 for the course PHY PHY taught by Professor Loh during the Spring '09 term at Nassau CC.

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heat_THINGY_REPORTbodyfinal1 - NANYANG TECHNOLOGICAL...

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