Concept explainers
Functionally graded materials are intentionally fabricated to establish a spatial distribution of properties in the final product. Consider an
- Determine the spatially averaged value of the thermal conductivity k. Use this value to estimate the heat rate per unit length for cases I and 2.
- Using a grid spacing of 2 mm. determine the heat rate per unit depth for case 1. Compare your result to the estimated value calculated in part (a).
- Using a grid spacing of 2 mm, determine the heat rate per unit depth for case 2. Compare your result to the estimated value calculated in part (a).
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Chapter 4 Solutions
Fundamentals of Heat and Mass Transfer
- The first part of the question has been worked on, where the heat transfer was calculated to be 6.770 kilowatt, but the problem also asks to calculate the temperature of the outer most surface. What is the temperature of the outer most surface?arrow_forwardA team of students tests a material for its thermal conductivity (k). After 20 minutes in a heat box, the temperature is 48° C inside the box and 28° C on top of the material. The following data is true about this test: Area of material = .0225 m2 Thickness of material = .0127 m Light bulb = 25 W What is the thermal conductivity constant for the material? Calculate the amount of energy transferred through the material. Determine the R-value of the material. Based on your calculations, would the material be a reasonable choice for home insulation? Yes of Noarrow_forwardX Your answer is incorrect. 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 k, = 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 = 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 To = O°C, respectively. The inner and outer convection heat transfer coefficients are h; = 5 W/m?-Kand h, 00, 25 W/m2-K, respectively. The heat flux through the original walls is 1.46 W/m?. The heat flux through the retrofitted walls is 0.92 W/m?.arrow_forward
- i need the answer quicklyarrow_forwardBoth ends of a 32 cm long rod are maintained a constant temperature of 100 °C. Dimensions and thermal parameters of the rod are as follows: Diameter D = 2 cm Convection coefficient h = 10 W/m2K Ambient temperature T¥ = 20 °C Thermal conductivity k = 10 W/mK What is the midpoint temperature of the rod?arrow_forwardThe composite wall of an oven consists of three materials, two of which are ofknown thermal conductivity, kA = 25 W/m ⋅ K and kC = 60 W/m ⋅ K, and knownthickness, LA = 0.40 m and LC = 0.20 m. The third material, B, which is sandwichedbetween materials A and C, is of known thickness, LB = 0.20 m, but unknownthermal conductivity kB. Under steady-state operating conditions, measurementsreveal an outer surface temperature of Ts,o = 20°C, an inner surface temperature ofTs,i = 600°C, and an oven air temperature of T∞ = 800°C. The inside convection coefficient h is known to be 25 W/m2 ⋅K. Neglecting convection transfer effect,what is the value of kB?arrow_forward
- 1. A beverage cooler is in the shape of a cube, 42 cm on each inside edge. Its 3.0-cm thick wall are made up of plastic (kr = 0.050 W/mK). When the outside temperature is 20°C, how much ice will melt each hour? Tice is 0°C. 2. One of the possible mechanisms of heat transfer in human body is conduction through body fat. Suppose that heat travels through 0.03 m of fat in reaching the skin, which has a total surface area of 1.7 m² and a temperature of 34°C. Find the amount of heat that reaches the skin in half an hour, if the temperature at the body, interior is maintained at the normal value 37°C ? Thermal conductivity of body fat is k = 0.2 J/sm°C. 3. The air in a room is at 25°C and outside temperature is 0°C. The window of the room has an area of 2m² and thickness 2mm. Calculate the rate of loss of heat by conduction through window ? Thermal conductivity for glass is 1 Wm¯'degree!.arrow_forward= Consider a large plane wall of thickness L=0.3 m, thermal conductivity k = 2.5 W/m.K, and surface area A = 12 m². The left side of the wall at x=0 is subjected to a net heat flux of ɖo = 700 W/m² while the temperature at that surface is measured to be T₁ = 80°C. Assuming constant thermal conductivity and no heat generation in the wall, (a) express the differential equation and the boundary equations for steady one- dimensional heat conduction through the wall, (b) obtain a relation for the variation of the temperature in the wall by solving the differential equation, and (c) evaluate the temperature of the right surface of the wall at x=L. Ti до L Xarrow_forwardGiven the illustration and data below. Determine the heat lost per day. T1 = 1000°C T2 T3 = 80°C A = 1 m²2 5 cm 10 сm W k = 0.09 т-к %3D W k = 1.64; т-кarrow_forward
- A square steel bar of side length w = 0.21 m has a thermal conductivity of k = 15.6 J/(s⋅m⋅°C) and is L = 2.7 m long. One end is placed near a blowtorch so that the temperature is T1 = 95° C while the other end rests on a block of ice so that the temperature is a constant T2. a. input an expression for the heat transferred to the cold end of the bar as a function of time using A=w^2 as the cross-sectional area of the bar. b. how much energy in joules was conducted in 1 hour, assuming t2=0*C c. input an expression for the mass of the water melted in one hour using Q1 from above and Lf in the latent heat of fusion. mw=arrow_forwardThree (3) bricks, specifically A, B, and C were arranged horizontally in such a way that it can be illustrated as a sandwich panel. Consider the system to be in series and in the order of Brick A, Brick B and Brick C. The outside surface temperature of Brick A is 1,500℃ and 150 ℃ for the outside surface of Brick C. The thermal conductivities for Brick A, Brick B and Brick C, are 2 ?/? °? , 0.50 ?/? °? , 60 ?/? °?. The thickness of Brick A and Brick C are 50 cm and 22 cm. The rate of heat transfer per unit area is 1,000 ?/?2 . Determine the following: The thickness of Brick B in the unit of mm. Assume that all the conditions were retain except that the thickness of Brick B was increased to 800 mm, what is the new value for the rate of heat transfer per unit area in ???/ℎ? . ??2 please explain the principles to solve thisarrow_forwardQ1/ A thick wall consists two layers of Gypsum, insulation and brick as shown in figure below. The ambient temperature is 20 °C and heat transfer coefficient is 5 W/m2. K in the left side. The surface temperature of right side is 45 °C. find the heat losses per meter length. What will happen if the insulation's thickness * .increases by 25% Gypsum k = 0.04W/m. K T = 45 °C h=5 W/m'. K T. = 20 °C 5 cm Insulation k = 0.04W/m. K Brick k = 0.69 W/m. Karrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning