04_thermal

# 04_thermal - Thermal Design Thermal Design Heat Transfer...

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Unformatted text preview: Thermal Design Thermal Design Heat Transfer Heat Transfer Temperature Measurement Temperature Measurement The prevalence of the number 5.7 The prevalence of the number 5.7 Winter 2011 UCSD: Physics 121; 2011 2 Why Care about Thermal? Why Care about Thermal? Scientific equipment often needs temperature control Scientific equipment often needs temperature control especially in precision measurement Want to calculate thermal energy requirements Want to calculate thermal energy requirements how much energy to change temperature? how much power to maintain temperature? Want to calculate thermal time constants Want to calculate thermal time constants how long will it take to change the temperature? Want to understand relative importance of radiation, Want to understand relative importance of radiation, convection, conduction convection, conduction which dominates? how much can we limit/exaggerate a particular process? Winter 2011 UCSD: Physics 121; 2011 3 Chief Thermal Properties Chief Thermal Properties Thermal Conductivity Thermal Conductivity measured in W/m/K heat flow (in W) is P = TA/t note that heat flow increases with increasing T , increasing surface area, and decreasing thickness (very intuitive) Specific Heat Capacity Specific Heat Capacity c p measured in J/kg/K energy locked up in heat is: E = c p Tm energy stored proportional to T , and mass (intuitive) Emisivity, Emisivity, power radiated is P = A T 4 Winter 2011 UCSD: Physics 121; 2011 4 Thermal Conductivity of Materials Thermal Conductivity of Materials (copied from materials lecture) (copied from materials lecture) Material (W m-1 K-1 ) comments Silver 422 room T metals feel cold Copper 391 great for pulling away heat Gold 295 Aluminum 205 Stainless Steel 1025 why cookware uses S.S. Glass, Concrete,Wood 0.53 buildings Many Plastics ~0.4 room T plastics feel warm G-10 fiberglass 0.29 strongest insulator choice Stagnant Air 0.024 but usually moving Styrofoam 0.010.03 can be better than air!...
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## This note was uploaded on 02/12/2012 for the course PHYSICS 104 taught by Professor Staff during the Fall '10 term at Rutgers.

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04_thermal - Thermal Design Thermal Design Heat Transfer...

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