Fundamentals of Heat and Mass Transfer

7th Edition

ISBN: 9780470501979

Author: Frank P. Incropera, David P. DeWitt, Theodore L. Bergman, Adrienne S. Lavine

Publisher: Wiley, John & Sons, Incorporated

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Textbook Question

Chapter 1, Problem 1.2P

The heat flux that is applied to the left face of a planewall is

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1. Temperatures are measured at the left-hand face and at a point 4 cm from the left-hand
face of the planar wall shown in the figure below. These temperatures are T₁ = 45.3 °C
and T* = 21.2 °C. The heat flow through the planar wall is steady and one dimensional.
What is the value of T2 at the right-hand surface of the wall?
TI
T*
4 cm
10 cm
T2

Consider a plate whose thickness is 2L=20 cm and thermal conductivity is 44 W/mK. Heat generation
inside the plate (5x105 W/m³) is uniform. The surface of the plate is maintained at Ts=10°C. Find the
temperature at the center of plate.
T
Ts
-L
L X
O a. 45 °C
ОБ.75 °С
О с. 67 оС
O d. 90 °C
O e. 85 °C

The heat flux that is applied to the left face of a plane wall is q
conductivity k = 12 W/m-K.
= 50 W/m². The wall is of thickness L = 12 mm and of thermal
If the surface temperatures of the wall are measured to be 50°C on the left side and 30°C on the right side,
then steady-state conditions have been reached.
then steady-state conditions have not been reached.

# Chapter 1 Solutions

Fundamentals of Heat and Mass Transfer

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- A section of a composite wall with the dimensions shown below has uniformtemperatures of 200°C and 50°C over the left and right surfaces, respectively. If the thermal conductivities of the wall materials are: kA = 70 W/(m K), kB = 60 W/(m K), kc = 40 W/(m K) and kD = 20 W/(m K), determine the rate of heat transfer through this section of the wall and the temperatures at the interfaces.
*arrow_forward*Consider a composite wall of overall height H = 30 mm and thickness L = 40 mm. Section A hasthickness LA = 15 mm and thermal conductivity of 3 W/(m·K). Sections B and C each have heightHB = 15 mm and thickness LB = 25 mm. The thermal conductivity is 1 W/(m·K) in section B and 2W/(m·K) in section C. The temperatures of the left and right faces of the composite wall are T1 =60°C and T2 = 30°C, respectively. The top and bottom of the wall are insulated. A) Draw a thermal circuit based on heat flux for the composite wall shown above.Assume that the temperature is uniform “vertically” in material A. Indicate thetemperatures, thermal resistances, and heat flux in the circuit diagram. Show theequations for the thermal resistances in the circuits. Do NOT need to perform anycalculations in this part.B. Draw a thermal circuit based on heat flux for the composite wall shown above.Assume that the temperature is NOT uniform “vertically” in material A and heat onlyflows along horizontal direction.…*arrow_forward*A gas filled tube has 2 mm inside diameter and 25 cm length. The gas is heated by an electrical wire of diameter 50 microns (o.05 mm) located along the axis of the tube. Current and voltage drop across the heating element are 0.5A and 4 volts, respectively. If the measured wire and inside tube wall temps are 175C and 150C respectively, find the thermal conductivity of the gas filling the tube.*arrow_forward* - 2. A refrigerated cold room wall has a thickness of 100mm and a thermal conductivity 0.14 W/m-K. The room wall has a 60mm thick internal lining of cork having a thermal conductivity of 0.05 W/m.K. The thermal conductance between the exposed faces and the respective atmosphere is 12 W/m²-K. If the room is maintained at 0°C and the external atmospheric temperature is 20°C, Calculate the heat loss rate through 1m² of the wall.
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