A dormitory at a large university, built 50 years ago, has exterior walls constructed of Ls = 25-mm-thick sheathing with a thermal conductivity of ks = 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 the heat flux through the original and retrofitted walls when the interior and exterior air temperatures are Ti = 22°C and T.o -2.5°C, respectively. The inner and outer convection heat transfer coefficients are h; = 5W/m2-K and ho = 1.4 W/m-K. Determine 25 W/m2.K, respectively. The heat flux through the original walls is i W/m?. The heat flux through the retrofitted walls is i W/m?.

A dormitory at a large university, built 50 years ago, has exterior walls constructed of Ls = 25-mm-thick sheathing with a thermal conductivity of ks = 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 the heat flux through the original and retrofitted walls when the interior and exterior air temperatures are Ti = 22°C and T.o -2.5°C, respectively. The inner and outer convection heat transfer coefficients are h; = 5W/m2-K and ho = 1.4 W/m-K. Determine 25 W/m2.K, respectively. The heat flux through the original walls is i W/m?. The heat flux through the retrofitted walls is i W/m?.

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

A dormitory at a large university, built 50 years ago, has exterior walls constructed of Ls = 25-mm-thick sheathing with a thermal
conductivity of ks = 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
the heat flux through the original and retrofitted walls when the interior and exterior air temperatures are Ti = 22°C and T.o
-2.5°C, respectively. The inner and outer convection heat transfer coefficients are h; = 5W/m2-K and ho
= 1.4 W/m-K. Determine
25 W/m2-K, respectively.
The heat flux through the original walls is i
W/m?.
The heat flux through the retrofitted walls is
i
W/m?.

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