The convective heat transfer lab was conducted in order to observe and analyze the heat transfer rates and various other criteria of two different geometries of heat sinks. First a rectangular fin heat sink and then a cylindrical pin fin heat sink were subject to a flow of air in a wind tunnel. The front and back fin tip temperatures, the fan speed and the free stream temperatures before and after the sink were measured and recorded with the aid of a LabView program. The values were measured for two different frequencies of the fan speed, which were 15 Hz and 30 Hz, for both types of heat sinks.
As the experiment was carried out the measured values and the calculated values of the Heat transfer rates and the fin tip temperatures were thoroughly analyzed compared and discussed. The highest calculated and the measured heat transfer rates were obtained in the case of the cylindrical pin fin heat sink and they are 944.4700 (W) and 1174.02 (W). Both the values were obtained for the lower fan speed of the wind tunnel.
The pin fin heat sink also displayed the highest efficiency of 100% for the lower fan speed of 15 Hz. The number of fins in the rectangular sink was calculated to be 13 and that of the pin fin heat sink was 144. It was determined that the pin fin heat sink has a higher efficiency and is more appropriate to be used than a rectangular fin heat sink, in real life applications, for example; laptop fans and heat sinks that reject heat. It was inferred that the higher the number of fins, larger the surface area and larger the diameter the heat sink would result in a higher heat transfer rate.
[...] V µ Free stream air temperatures of 298.63 Kelvin and 298.619 Kelvin and an atmospheric pressure of 1 atm were used in order to determine the air properties for the rectangular fins and the cylindrical fins respectively. The air properties that were looked up in the thermodynamic tables include the density, kinematic viscosity, thermal conductivity and the Prandtl number of air which is explained below. The following two equations & were used depending on the nature of the flow (laminar or turbulent), to calculate the Nusselt number in the case of the rectangular fins. [...]
[...] Introduction This experiment was conducted in order to compare measured and calculated fin tip temperatures and heat transfer of a rectangular fin base and a cylindrical fin base. The experiment was carried out for two frequencies of 15Hz and 30Hz for both types of fins. The temperature distribution studied in this lab depends on a few factors. They are the temperature between the base and the fluid, fin geometry, number of fins through which the air flows and the local fluid velocity. [...]
[...] Then it was allowed to reach steady state and the fan speed was doubled to 30Hz and the corresponding values were measured as before. Figure 1 displays the overall set up of the experiment. Figure Heat Sink in the Wind Tunnel The same procedure mentioned above was repeated for the cylindrical fin block at the two same fan speeds of 15Hz and 30Hz. Then the geometrical parameters that depend on the heat flow of the two different geometries were analyzed. Heat transfer coefficients were determined according to the equations and the description that follows in the introduction. [...]
[...] Table: 4 Pin Fin Heat Sink Parameter values (Measured) Parameter Table 5 displays the Comparison of the calculated and the measured heat transfer values for the rectangular fin heat sink. Table: 5 Comparisons of Rectangular Fin Heat Transfer Rates Transfer Rate Table 6 displays the comparison of the pin fin heat sink heat transfer rates. From tables 5 and 6 it is evident that the lowest deviation of the measured value from the calculated value ( 19.6 is displayed by the pin fin heat sink at the lower fan speed of 15Hz. [...]
[...] From the experiment performed it is evident that the pin fins have a higher rate of heat transfer as opposed to the rectangular fins. Therefore laptop cooling sinks should be constructed of as many pin shaped (cylindrical) fins in a loosely packed manner just sufficient for the flow to pass through every surfaced area of the fins. From equations and a material with high thermal conductivity reduces the value of ‘m'which in turns increases the efficiency of the system. Therefore a material with a fairly high thermal conductivity should be selected in constructing a laptop cooling sink. [...]
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