You are designing a PCB laid horizontally on the ground. The PCB surface temperature can’t exceed 85℃ and has a size of 96mm x 90mm. Tinfinity = 45oC. "p" is the perimeter of the plate a) Calculate the Rayleigh number. b) If the PCB is laid hot-side UP, what is the Nusselt number and heat transfer coefficient? c) If the PCB is laid hot-side DOWN, what is the Nusselt number and heat transfer coefficient? d) Given your results from b and c, which one has better heat transfer? In that case, what is the maximum power dissipation the board can put out? Properties of Air: k = 0.025 W/mk Pr = 0.72 v = 1.847 x 10−5 u = 16.84 x10−6 p = 1.2 kg/m3 B =1/ Tf (idwal gass)

You are designing a PCB laid horizontally on the ground. The PCB surface temperature can’t exceed 85℃ and has a size of 96mm x 90mm. Tinfinity = 45oC. "p" is the perimeter of the plate a) Calculate the Rayleigh number. b) If the PCB is laid hot-side UP, what is the Nusselt number and heat transfer coefficient? c) If the PCB is laid hot-side DOWN, what is the Nusselt number and heat transfer coefficient? d) Given your results from b and c, which one has better heat transfer? In that case, what is the maximum power dissipation the board can put out? Properties of Air: k = 0.025 W/mk Pr = 0.72 v = 1.847 x 10−5 u = 16.84 x10−6 p = 1.2 kg/m3 B =1/ Tf (idwal gass)

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 1.68P

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1.3 A furnace wall is to be constructed of brick having standard dimensions of Two kinds of material are available. One has a maximum usable temperature of 1040°C and a thermal conductivity of 1.7 W/(m K), and the other has a maximum temperature limit of 870°C and a thermal conductivity of 0.85 W/(m K). The bricks have the same cost and are laid in any manner, but we wish to design the most economical wall for a furnace with a temperature of 1040°C on the hot side and 200°C on the cold side. If the maximum amount of heat transfer permissible is 950 , determine the most economical arrangement using the available bricks.
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Solve this with diagram: An engine cover is made from 1 cm thick stainless steel plate (k = 14 W/m K). Air on the inside of the engine cover is heated to 340°C with a heat transfer coefficient of 7 W/m2K. Outside of the engine coverthe ambient air has a temperature of 70°C. If oil was spilled on the outside of the engine cover (ambient side), it could ignite if the surface temperature were to exceed 200°C. In this configuration, would spilled oil ignite? Use calculations to justify your answer. If a 4 mm thermal coating (k = 1.1 W/m K) was applied tothe outside of the engine, what would the outside temperature of the engine cover be reduced to? Solve it with resistors method
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Solve for this : An engine cover is made from 1 cm thick stainless steel plate (k = 14 W/m K). Air on the inside of the engine cover is heated to 340°C with a heat transfer coefficient of 7 W/m2K. Outside of the engine coverthe ambient air has a temperature of 70°C. If oil was spilled on the outside of the engine cover (ambient side), it could ignite if the surface temperature were to exceed 200°C. In this configuration, would spilled oil ignite? Use calculations to justify your answer. If a 4 mm thermal coating (k = 1.1 W/m K) was applied tothe outside of the engine, what would the outside temperature of the engine cover be reduced to?
(a) The temperature at the surface of the heating rod, T1. (b) If the salt solution temperature is 300 degree Celcius, what is the value of convection heat transfer coefficient, h of the salt solution ? (c) If the heating rod is not covered by metallic cylinder and corresponds to the result of part (a) and (b), how much the rate of energy transfer to the salt solution ? (d) Compare and discuss the difference of heat transfer with and without the matallic cylinder.
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What is the rate of heat transfer through a piece of Celotex 3 ft by 8 ft by 1 in. in thickness, if the temp of one surface is 80°F and of the other side is 60°F? thermal conductivity of Celotex in AES = 0.028. Pls determine the temperature gradient and the direction of the heat transfer as well.