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• John Hosford Joshua Thornock

• Free ConvectionGeneral AssumptionsCooling without the pad will be considered free convection as opposed to an enclosureCooling without the pad does not include fans previously installed or air flow within the casingAir and surface temperature assumed 27C and 67CAIRFLOW

• Internal Flow Non-Circular TubesGeneral AssumptionsCooling with the pad will be considered internal flow in a non-circular tube closely representing a rectangleFlow begins at the center of the laptop and moves to the outside so the non-circular tube length will be half of the length of the laptop

HORIZONTAL PLATEFREE CONVECTION

• Determine Convection Coefficient for Forced ConvectionThree terms had to be estimated Cross sectional area (Ac)Perimeter (P)Mass flow (mdot)

Solve Hydrolic diameter (Dh)

Solve Reynolds number

=>FLOW IS TURBULENT

Laptop Surface4 inchesCooling pad surfaceSide ViewAir

• Determine Convection Coefficient for Forced ConvectionFor turbulent flow use Equation 8.61

• Comparing CoefficientsThe actual heat transfer will depend on the temperatures of the surroundings and the computer surface. Still these coefficients show a drastic difference between having and not having the cooling pad. This is where we need to remember our assumptions. We ignored the fact that the computer has fans and convection inside the case. These more difficult calculations may give a more accurate answer, however, the analysis performed may give us a good idea that the cooling pad will aid the heat transfer a significant amountincreasing the heat transfer by approximately 20 times!NN

• ConclusionIn addition to providing a cooler surface to contact your lap, laptop cooling pads greatly aid the transfer of heat away from a laptops surface. Although only the convection coefficient was determined in this study, the amount of heat wicked away from the laptop surface is only a linear function of this coefficient for a given temperature difference:Therefore, the increase in heat transfer is proportional to the increase in convection coefficientin this case, 20x.

• AppendixA Hewlett Packard laptop and a Belkin laptop cooling pad were the basis for this model.Properties:Air at laptop surface (Ts): 67C ( 152.6F)Ambient air (T): 27C (8o.6F)L=.1524m (6 inches, for a 14.1 laptop)

Properties of ambient air (27C)Properties of air at surface temperature (67C)