Heat transfer A dormitory at a large university, built 50 yearsago, has exterior walls constructed of L. = 25-mm-thick sheathing with a thermalk,conductivity of K₁= 0.1 W/m.K. To reduce heatlosses in the winter, the university decides toencapsulate the entire dormitory by applyingan L = 25-mm-thick layer of extruded insulationcharacterized by = 0.029 W/m.K to theexterior of the original sheathing. TheLgextruded insulation is, in turn, covered with anL₁= 5-mm-thick architectural glass with k, = 1.4W/m.K. Determine the heat flux through theoriginal and retrofitted walls when the interiorand exterior air temperatures are T = 22°C andTop = -20°C, respectively. The inner and outerconvection heat transfer coefficients are h, = 5W/m2.K and = 25 W/m2.K, respectively.h₂The heat flux through the original walls isW/m2.The heat flux through the retrofitted walls isW/m2.

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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 ,- 0.1 W/m.K. To reduce heat k, = losses in the winter the university decides to

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 ,- 0.1 W/m.K. To reduce heat k, = losses in the winter the university decides to

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 1.64P: The interior wall of a large, commercial walk-in type meat freezer is covered under normal operating...

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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

Heat transfer

A dormitory at a large university, built 50 years
ago, has exterior walls constructed of L. = 25-
mm-thick sheathing with a thermal
k,
conductivity of K₁= 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 = 0.029 W/m.K to the
exterior of the original sheathing. The
Lg
extruded insulation is, in turn, covered with an
L₁= 5-mm-thick architectural glass with k, = 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
Top = -20°C, respectively. The inner and outer
convection heat transfer coefficients are h, = 5
W/m2.K and = 25 W/m2.K, respectively.
h₂
The heat flux through the original walls is
W/m2.
The heat flux through the retrofitted walls is
W/m2.

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