show schematic drawings, conversions, units and box in your final answers A furnace wall is made up of three layer of thickness 200 mm, 100 mm, and 125 mm with thermal conductivity of 1.65 W/m-K, k2, and 9.2 W/m-K respectively. The inside is exposed to gases at 1200°C with a convection coefficient of 25 W/m²-K and the inside surface temperature is at 1000°C, the outside air temperature is at 30°C with convection coefficient of 12 W/m²-K. Calculate: a. the unknown thermal conductivity; b. the outside surface temperature and mid-plane temperatures in °F.

show schematic drawings, conversions, units and box in your final answers A furnace wall is made up of three layer of thickness 200 mm, 100 mm, and 125 mm with thermal conductivity of 1.65 W/m-K, k2, and 9.2 W/m-K respectively. The inside is exposed to gases at 1200°C with a convection coefficient of 25 W/m²-K and the inside surface temperature is at 1000°C, the outside air temperature is at 30°C with convection coefficient of 12 W/m²-K. Calculate: a. the unknown thermal conductivity; b. the outside surface temperature and mid-plane temperatures in °F.

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 1.40P: As a designer working for a major electric appliance manufacturer, you are required to estimate the...

See similar textbooks

Similar questions

1.3 A furnace wall is to be constructed of brick having standard dimensions of Two kinds of material are available. One has a maximum usable temperature of 1040°C and a thermal conductivity of 1.7 W/(m K), and the other has a maximum temperature limit of 870°C and a thermal conductivity of 0.85 W/(m K). The bricks have the same cost and are laid in any manner, but we wish to design the most economical wall for a furnace with a temperature of 1040°C on the hot side and 200°C on the cold side. If the maximum amount of heat transfer permissible is 950 , determine the most economical arrangement using the available bricks.
1.77 Explain each in your own words. (a) What is the mode of heat transfer through a large steel plate that has its surfaces at specified temperatures? (b) What are the modes when the temperature on one surface of the steel plate is not specified, but the surface is exposed to a fluid at a specified temperature?
The compartment below is used as a freezer of refrigerator compartment. Inner wall is at -15 C and outer wall is at 25 C. Insulator with a thermal conductivity of 0.035 W/(mK) is used to prevent the heat losses from the compartment. The shape is in square form with a side of 1.2 m and unit width into the page. Determine the thickness of the insulator if the compartment heat load is 700 W? * inner wall outer wall insulating material
The compartment below is used as a freezer of refrigerator compartment. Inner wall is at -15 C and outer wall is at 25 C. Insulator with a thermal conductivity of 0.035 W/(mK) is used to prevent the heat losses from the compartment. The shape is in square form with a side of 1.2 m and unit width into the page. Determine the thickness of the insulator if the compartment heat load is 700 W? * inner wall outer wall insulating material 5 cm O 9.6 mm 4.2 cm none
The compartment below is used as a freezer of refrigerator compartment. Inner wall is at -10 C and outer wall is at 20 C. Insulator with a thermal conductivity of 0.040 W/(mK) is used to prevent the heat losses from the compartment. The shape is in square form with a side of 1.3 m and unit width into the page. Determine the amount of the heat load if the thickness of the insulator is 2 cm? *
2. In determining the thermal conductivity of a plateflat insulator, the temperature was measured on both sides of the 25 mm thick plate and gave the results of 318.4 K and 303.2 K. FluxThe measured heat is 35.1 W.m-2. Illustrate the problem in a simple schematic/drawing, then calculate the thermal conductivity inbtu/h.ft.oF and in W/m.K! (0.033 ; 0.058) 3. A coil-shaped cooling pipe is made of SS-304 material. This pipe is 1 ft long, 0.4 inch outside diameter, and inch inside diameter. This coil cooling pipe is used to cool the water in the bath. The temperature of the inner coil pipe is 40oF while the outer coil in contact with water is 80oF. The thermal conductivity of SS-304 is a function of temperature where k(T) = 7.75 + (7.78 x 10-3).T where k is in Btu/h.ft.oF and T is in oF. Calculate the rate of heat dissipation in watts! (1287.7)
FIll in the blanks: A slab 0.25 m thick with thermal conductivity of 45 W/m-K receives heat from a furnace at 500 K both by convection and radiation. The convection coefficient has a value of 50 W/m²- K. The surface temperature is 400 K on this side. The heat is transferred to surroundings at T, both by convection and radiation. The convection coefficient on this side is 60 W/m2-K. Determine the surrounding temperature. K.
Q2/ A metal plate of 4mm thickness (k = 95.5 W/m°C) is exposed to vapor at 100°C on one side and cooling water at 25°C on the opposite side. The heat transfer coefficients on vapor side and waterside are 14500 W/m^2°C and 2250 W/m^2 °C respectively. Determine the overall heat transfer coefficient *
GChoose the right answer 1. The temperature profile for steady hest conduction through a plane wall of constant thermal conductivity is a. logarithmic b. parabolic 2. A brick wall (k-0.75 W/mK ) transmits $02 of heat loss through another wall (k-0.25 W/mK, x-100 mm). If the temperature difference across both walls is the same, the thickness of the brick wall would be a.150 mm c. linear 6T b. 240 mm c. 300 mm d. 375 mm 3. The maximum temperature at the center of the solid sphere of radius R having heat generation q (W/m') is given by g'R +9R b. T, + 4k T+9R 6k d. T+9R 8k a. 2k C. 4. The internal thermal resistance of a solid can be ignored if the Biot number is less than a. 1 b. 0.5 c. 0.1 d. Fourier number 5. The ratio of heat transfer of a fin to the heat transfer without fin is referred to as a. fin resistance b. fin efficieney efin effectiveness d. fin conductance.
show schematic drawings, conversions, units and box in your final answer An industrial freezer is designed to operate with an internal air temperature of - 18°C when the external air temperature is 29°C, and the internal and external heat transfer coefficients are 8 W/m²-K and 12 W/m²-K, respectively. The walls of the freezer are composite construction, comprising an inner layer of plastic (k = 0.33 W/m-K, and thickness of 10 mm), and an outer layer of stainless steel (k = 15 W/m- K, and thickness of 3 mm). Sandwiched between these two layers is a layer of insulation material with k = 0.07 W/m-K. Find the width (mm) of the insulation that is required to reduce the convective heat loss to 35 W/m².
A brass plate has a circular hole whose diameter is slightly smaller than the diameter of an aluminum ball. Ifthe ball and the plate are always kept at the same temperature,(a) should the temperature of the system be increased or decreasedin order for the ball to fit through the hole? (b) Choose the bestexplanation from among the following:I. The aluminum ball changes its diameter more with temperature than the brass plate, and therefore the temperatureshould be decreased.II. Changing the temperature won’t change the fact that the ballis larger than the hole.III. Heating the brass plate makes its hole larger, and that willallow the ball to pass through.
Q1. Double glazed window is made of 2 glass panes of 6 mm thick each with an air gap of 6 mm between them. Assuming that the air layer is stagnant and only conduction is involved, determine the thermal resistance and overall heat transfer coefficient. The inside is exposed to convection with h - 15 W/m?. K and the outside to 9 W/m'. K. Compare the values with that of a single glass of 12 mm thickness. The conductivity of the glass - 1.4 W/m. K and that for air is 0.025 W/m. K. h, = 15 Wim'k Glass Air gap Giass 14 Wmk =0.025 WimK h Wim'k 6 mm Q2. A 2m long, 0.3cm diameter electrical wire extends across a room at 15°C. Heat is generated in the wire as a result of resistance heating, and the surface temperature of the wire is measured to be 152°C in steady operation. Also, the voltage drop and electric current through the wire are measured to be 60 V and 1.5 A, respectively. Disregarding any heat transfer by radiation, determine the convection heat transfer coefficient for heat transfer…