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 1.5P
Consider Figure 1.3. The heat flux in the x-direction is
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4. Which of the following expresses thermal diffusivity of a substance in terms of thermal
conductivity(k), density (p) and specific heat (Cp)
A. p.k.Cp
C. 1/ p.k.Cp
В. К/р.Ср
D. p.Cp /k
5. The boundary condition of the end insulated fin are:
dT
В.
- kA) = 0 and T=To at x=0
dT
- kA -0
dx
A.
= 0 and T=Too at x-L
dx
C. T=0 at x=0 and q=0 at x=L
D. None of them
An electric heater producing 260 W of heat is used to warm up a room containing 7 m3 of air. If we assume the room is perfectly sealed and there is no heat loss through the room boundaries, such that all of the heater output goes into increasing the air temperature, how long will it take to heat up the air in the room from 5.0 °C to 24.1 °C?
Give your answer to the nearest minute and assume that the specific volume (v = 0.85 m3/kg) and specific heat capacity at constant volume (cv = 1.005 kJ/(kg K)) remain constant throughout the heating process.
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
Chapter 1 Solutions
Fundamentals of Heat and Mass Transfer
Ch. 1 - The thermal conductivity of a sheet of rigid,...Ch. 1 - The heat flux that is applied to the left face of...Ch. 1 - A concrete wall, which has a surface area of 20m2...Ch. 1 - The concrete slab of a basement is 11 in long. 8...Ch. 1 - Consider Figure 1.3. The heat flux in the...Ch. 1 - The heal flux through a wood slab 50 mm thick,...Ch. 1 - The inner and outer surface temperatures of a...Ch. 1 - A thermodynamic analysis of a proposed Brayton...Ch. 1 - A glass window of width W=1m and height H=2m is 5...Ch. 1 - A freezer compartment consists of a cubical cavity...
Ch. 1 - The heat flux that is applied to one face of a...Ch. 1 - An inexpensive food and beverage container is...Ch. 1 - What is the thickness required of a masonry wall...Ch. 1 - A wall is made from an inhomogeneous...Ch. 1 - The 5-mm-thick bottom of a 200-mm-diameter panmay...Ch. 1 - A square silicon chip (k=150W/mK) is of width...Ch. 1 - For a boiling process such as shown in Figure 1.5...Ch. 1 - You’ve experienced convection cooling if you’ve...Ch. 1 - Air at 40°C flows over a long, 25-mm-diameter...Ch. 1 - A wall has inner and outer surface temperatures of...Ch. 1 - An electric resistance heater is embedded in a...Ch. 1 - The free convection heat transfer coefficient on a...Ch. 1 - A transmission case measures W=0.30m on a sideand...Ch. 1 - A cartridge electrical heater is shaped as a...Ch. 1 - A common procedure for measuring the velocity of...Ch. 1 - A square isothermal chip is of width w=5mm on...Ch. 1 - The temperature controller for a clothes dryer...Ch. 1 - An overhead 25-m-long, uninsulated industrial...Ch. 1 - Under conditions for which the same room...Ch. 1 - A spherical interplanetary probe of 0.5-m diameter...Ch. 1 - An instrumentation package has a spherical outer...Ch. 1 - Consider the conditions of Problem 1.22. However,...Ch. 1 - If TsTsur in Equation 1.9, the radiation heat...Ch. 1 - A vacuum system, as used ¡n sputtering...Ch. 1 - An electrical resistor is connected to a battery,...Ch. 1 - Pressurized water (pin=10bar,Tin=110C) enters...Ch. 1 - Consider the tube and inlet conditions of Problem...Ch. 1 - An internally reversible refrigerator has a...Ch. 1 - A household refrigerator operates with cold-...Ch. 1 - Chips of width L=15mm on a side are mounted to...Ch. 1 - Consider the transmission case of Problem 1...Ch. 1 - One method for growing thin silicon sheets for...Ch. 1 - Heat is transferred by radiation and convection...Ch. 1 - Radioactive wastes are packed in a long,...Ch. 1 - An aluminum plate 4 mm thick is mounted in a...Ch. 1 - A blood warmer is to be used during the...Ch. 1 - Consider a carton of milk that is refrigerated at...Ch. 1 - Prob. 1.48PCh. 1 - Liquid oxygen, which has a boiling into of 90 K...Ch. 1 - The emissivity of galvanized steel sheet, a...Ch. 1 - Three electric resistance heaters of length...Ch. 1 - A hair dryer may be idealized as a circular duct...Ch. 1 - In one stage of an annealing process, 304...Ch. 1 - Convection ovens operate on the principle of...Ch. 1 - Annealing, an important step ¡n semiconductor...Ch. 1 - In the thermal processing of semiconductor...Ch. 1 - A furnace tor processing semiconductor materials...Ch. 1 - Prob. 1.58PCh. 1 - Consider the wind turbine of Example 1.3. To...Ch. 1 - Consider the conducting rod of Example 1.4...Ch. 1 - A long bus bar (cylindrical rod used for making...Ch. 1 - A 50mm45mm20mm cell phone chargerhas a surface...Ch. 1 - A spherical, stainless steel (AISI 302) canister...Ch. 1 - A freezer compartment is covered with a...Ch. 1 - A vertical slab of Wood’s metal is joined to a...Ch. 1 - A photovoltaic panel of dimension 2m4m isinstalled...Ch. 1 - Following the hot vacuum forming of a...Ch. 1 - Prob. 1.69PCh. 1 - A computer consists of an array of five printed...Ch. 1 - Prob. 1.71PCh. 1 - The roof of a car in a parking lot absorbs a solar...Ch. 1 - Consider the conditions of Problem 1.22,but the...Ch. 1 - Most of the energy we consume as food ¡s converted...Ch. 1 - Prob. 1.75PCh. 1 - The wall of an oven used to cure plastic parts is...Ch. 1 - An experiment to determine the convection...Ch. 1 - A thin electrical heating element provides a...Ch. 1 - A rectangular forced air healing duct is suspended...Ch. 1 - Consider the steam pipe of Example 1.2. The...Ch. 1 - During its manufacture, plate glass at 600°C is...Ch. 1 - The curing press of Example 1.9 involves exposure...Ch. 1 - The diameter and surface emissivity of an...Ch. 1 - Prob. 1.84PCh. 1 - A solar flux of 700W/m2K is incident on a...Ch. 1 - In considering the following problems involving...
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- 1.19 A square isothermal chip is of width w = front surface is exposed to the flow of a coolant at T = 15°C. From reliability considerations, the chip temperature must not exceed T = 85°C. 5 mm on a side and is mounted in a substrate such that its side and back surfaces are well insulated; the Coolant Chip If the coolant is air and the corresponding convection coefficient is h = 200 W/m² · K, what is the maximum allowable chip power? If the coolant is a dielectric liquid for which h = 3000 W/m² · K, what is the maximum allowable power?arrow_forwardFind the thermal resistance r (in hr - °F/BTU) and the equivalent R-value (in hr ft?. °F/BTU) of a typical frame 20' x 7.5" wall consisting of a 0.5" plaster board on the inside of the room, nominai 2 x 4 studs, and a 0.5" sheathing on the outside. The spaces between the studs are filled with an R-15 insulating foam. What is the heat loss (in BTU) through this wall in four hours if the inside temperature is 72°F and the outside temperature is 32°F? (Assume that the 15% of the wall's area are studs and the remaining 85% is filled with the insulating foam. Assume that the air is moving outside the wall.) r= 0.0805 x hr: OF/BTU R=0.09 x hr ft2. F/BTU AQ = BTUarrow_forwardIn a concentrated solar power plant, molten salt tank is used to store the thermal energy from the sun during the day. The tank wall thickness is 3cm containing molten salt at a temperature of 390 degree Celsius. There is atmospheric air outside the tank at a temperature of 30 degree Celsius. Suppose heat is lost as a result of heat transfer from the molten salt to the atmospheric air. What is the mode of heat transfer in this condition? conduction then convection convection then conduction convection then conduction then convection conduction then convection then conductionarrow_forward
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- 3. A cylindrical pipe of negligible thickness holding a hot fluid at 140°C and having an outer diameter of 0.4 m is insulated with three layers of each 50 mm thick insulation of k₁ = 0.02: k2 = 0.06 and k3 = 0.16 W/m-K (starting from inside). The outside surface temperature is 30°C. Solve for the value of T2 (°C). • show conversions, units, and box in your final answersarrow_forwardGive True or False for the following: 1.In liquids and gases, heat transmission is caused by conduction and convection 2.The surface geometry is the important factor in convection heat transfer 3. The heat transfer by conduction from heated surface to the adjacent layer of fluid, 4. The heat transfer is increased in the fin when &> 1 5.The unit of the thermal diffusivity is m²/s 6. Temperature change between the materials interfaces is attributed to the thermal contact resistance 7. A material that has a low heat capacity will have a large thermal diffusivity. 8. Heat conduction flowing from one side to other depends directly on thickness 9.Fin efficiency is the ratio of the fin heat dissipation with that of no fin 10.The critical radius is represented the ratio of the convicted heat transfer to the thermal conductivityarrow_forwardEXAMPLE 2.3 A = 10 m2 -q= 1000 Wm k= 40 W/mk p= 1600 kg/m The temperature distribution across a wall 1m thick at a certain instant of time is given as Tu) = a+ bx+ c- T(x) = a + bx + cr² where T is in degrees Celsius and x is in meters, while a = 900°C, b = -300°C/m, and c= -50°C/m². A uniform heat generation, ġ = 1000 W/m’, is present in the wall of area 10m² having the properties p = 1600 kg/m’, k = 40 W/m • K, and c, = 4 kJ/kg-K. %3D L=1m- %3D 1. Detemine the rate o heat cansler enterig the wall (x=0) and leaing he wl ( = Im). %3D %3D 2. Determine the rate of change of energy storage in the wall. 3. Detemine the lime rate of tmperature change at x = 0,025 ad 05m. AS 1x 56:43arrow_forward
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