A dormitory at a large university, built 50 years ago, has exterior walls constructed of L, conductivity of k, = 0.1 W/m-K. To reduce heat losses in the winter, the university decides to encapsulate the entire dormitory by applying an L; = 25-mm-thick layer of extruded insulation characterized by k; = 0.029 W/m-K to the exterior of the original sheathing. The extruded insulation is, in turn, covered with an Lg = 5-mm-thick architectural glass with kg = 1.4 W/m-K. Determine the heat flux through the original and retrofitted walls when the interior and exterior air temperatures are T4 = 22°C and To O°C, respectively. The inner and outer convection heat transfer coefficients are h; = 5W/m?-Kand h, 25-mm-thick sheathing with a thermal 00,4 25 W/m2-K, respectively.

A dormitory at a large university, built 50 years ago, has exterior walls constructed of L, conductivity of k, = 0.1 W/m-K. To reduce heat losses in the winter, the university decides to encapsulate the entire dormitory by applying an L; = 25-mm-thick layer of extruded insulation characterized by k; = 0.029 W/m-K to the exterior of the original sheathing. The extruded insulation is, in turn, covered with an Lg = 5-mm-thick architectural glass with kg = 1.4 W/m-K. Determine the heat flux through the original and retrofitted walls when the interior and exterior air temperatures are T4 = 22°C and To O°C, respectively. The inner and outer convection heat transfer coefficients are h; = 5W/m?-Kand h, 25-mm-thick sheathing with a thermal 00,4 25 W/m2-K, respectively.

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

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Concept explainers

Conduction and Convection

When energy travels from one object to another it is said to have undergone heat transfer. Heat transfer is nothing but the transfer of thermal energy or internal energy from one thing to another, like e.g., when a vessel with water, kept on top of a burner, heats up because of the flame underneath it.

Question

X Your answer is incorrect.
A dormitory at a large university, built 50 years ago, has exterior walls constructed of L, = 25-mm-thick sheathing with a thermal
conductivity of k, = 0.1 W/m-K. To reduce heat losses in the winter, the university decides to encapsulate the entire dormitory by
applying an L; = 25-mm-thick layer of extruded insulation characterized by k; = 0.029 W/m-K to the exterior of the original
sheathing. The extruded insulation is, in turn, covered with an Lg = 5-mm-thick architectural glass with kg = 1.4 W/m-K. Determine
the heat flux through the original and retrofitted walls when the interior and exterior air temperatures are T = 22°C and To =
O°C, respectively. The inner and outer convection heat transfer coefficients are h; = 5 W/m?-Kand h,
00,
25 W/m2-K, respectively.
The heat flux through the original walls is 1.46
W/m?.
The heat flux through the retrofitted walls is
0.92
W/m?.

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