1. Consider an opaque horizontal plate that is well insulated on its backside. The irradiation on the plate is 3000 W/m², of which 600 W/m² is reflected. The plate is at 150°C and has an emissivity of 0.5. Air at 30°C flows over the plate with a heat transfer convection coefficient of 20 W/m²K. Answer questions 1.1 to 1.3: Question 1 1.1) Determine the absorptivity of the plate: 0.8 Correct Question 2 1.2) Determine the net radioactive flux from the plate, W/m². 1,507.64 Wrong Question 3 1.3) What is the net heat transfer rate per unit area, W/m²? 307.64 Wrong

1. Consider an opaque horizontal plate that is well insulated on its backside. The irradiation on the plate is 3000 W/m², of which 600 W/m² is reflected. The plate is at 150°C and has an emissivity of 0.5. Air at 30°C flows over the plate with a heat transfer convection coefficient of 20 W/m²K. Answer questions 1.1 to 1.3: Question 1 1.1) Determine the absorptivity of the plate: 0.8 Correct Question 2 1.2) Determine the net radioactive flux from the plate, W/m². 1,507.64 Wrong Question 3 1.3) What is the net heat transfer rate per unit area, W/m²? 307.64 Wrong

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.48P: A horizontal, 3-mm-thick flat-copper plate, 1-m long and 0.5-m wide, is exposed in air at 27C to...

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A horizontal, 3-mm-thick flat-copper plate, 1-m long and 0.5-m wide, is exposed in air at 27C to radiation from the sun. If the total rate of solar radiation absorbed is 300 W and the combined radiation and convection heat transfer coefficients on the upper and lower surfaces are 20 and 15W/m2K, respectively, determine the equilibrium temperature of the plate.
1.13 If the outer air temperature in Problem is –2°C, calculate the convection heat transfer coefficient between the outer surface of the window and the air, assuming radiation is negligible.
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The emissivity of galvanized steel sheet, a common roofing material, is ε = 0.13 at temperatures around 300 K, while its absorptivity for solar irradiation is αS = 0.65. Would the neighborhood cat be comfortable walking on a roof constructed of the material on a day when GS = 750 W/m2, T∞ = 16°C, and h = 7 W/m2 · K? Assume the bottom surface of the steel is insulated.
How can we use the transient temperature charts when the surface temperature of the geometry is specified instead of the temperature of the surrounding medium and the convection heat transfer coefficient?
pnts) Chips of width L _ 15 mm on a side are mounted to a substrate that is installed in an enclosure whose walls and air are maintained at a temperature of Tsur=T∞=25oC. The chips have an emissivity of ε=0.60 and a maximum allowable temperature of Ts=85oC. (a) If heat is rejected from the chips by radiation and natural convection, what is the maximum operating power of each chip? The convection coefficient may be approximated as h=11.7 W/m2K. (b) If a fan is used to maintain airflow through the enclosure and heat transfer is by only forced convection, with h=250 W/m2K, what is the maximum operating power?
Chips of width L _ 15 mm on a side are mounted to a substrate that is installed in an enclosurewhose walls and air are maintained at a temperature of Tsur=T∞=25oC. The chips have an emissivity ofε=0.60 and a maximum allowable temperature of Ts=85oC.(a) If heat is rejected from the chips by radiation and natural convection, what is the maximum operatingpower of each chip? The convection coefficient may be approximated as h=11.7 W/m2K.(b) If a fan is used to maintain airflow through the enclosure and heat transfer is by only forcedconvection, with h=250 W/m2K, what is the maximum operating power?
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Differentiate between free and forced convection with examples.
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