A leading manufacturer of household appliances is proposing a self-cleaning oven design that involves use of a composite window separating the oven cavity from the room air (Figure 2a). The composite is to consist of two high-temperature plastics (A and B) of thicknesses LA = 2LB and thermal conductivities ka = 0.15 W/m·K and kB = 0.08 W/m K. During the self-cleaning process, the oven wall and air temperatures, Tw and Ta, are 400°C, while the room air temperature T is 25°C. The inside convection and radiation heat transfer coefficients h; and hr, as well as the outside convection coefficient ho, are each approximately 25 W/m2.K. What is the minimum window thickness, L = La + LB, needed to ensure a temperature that is 50°C or less at the outer surface of the window? This temperature must not be exceeded for safety reasons.

A leading manufacturer of household appliances is proposing a self-cleaning oven design that involves use of a composite window separating the oven cavity from the room air (Figure 2a). The composite is to consist of two high-temperature plastics (A and B) of thicknesses LA = 2LB and thermal conductivities ka = 0.15 W/m·K and kB = 0.08 W/m K. During the self-cleaning process, the oven wall and air temperatures, Tw and Ta, are 400°C, while the room air temperature T is 25°C. The inside convection and radiation heat transfer coefficients h; and hr, as well as the outside convection coefficient ho, are each approximately 25 W/m2.K. What is the minimum window thickness, L = La + LB, needed to ensure a temperature that is 50°C or less at the outer surface of the window? This temperature must not be exceeded for safety reasons.

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

See similar textbooks

Similar questions

(A) The front window of an truck is defogged by passing warm air over its inner surface. If the warm air is at Toi=50°C and the corresponding convection coefficient is h;= 35 W/m².K, what are the inner and outer surface temperatures of 7 mm-thick window glass, if the outside ambient air temperature is T,0=10°C and the associated convection coefficient is h, = 65 W/m².K? (Assume k for glass =1.4 W/m•K)
14- A south wall group D at (32 oN, Kw = 0.65). The room temperature is (24 oC). The maximum outside temperature is (42 oC). The daily range is (12 oC). Its heat transfer coefficient is (1.2 W/m2.oC) and dimensions are (5 x 3 m) with door of dimensions of (1.5 x 2 m). At (17 PM) in August, its Cooling load is Select one: a. 361.7 W b. None of these c. 261.7 W d. 303 W
Determine the optimum thickness of enamel paint.
two parts to a question
Calculate the critical radius of insulation for asbestos (k=0.17 W/m.C) surrounding a pipe and exposed to room air at 17 C with h= 3 W/m².C. Calculate the heat loss from a 180 C, 3.5 cm diameter pipe when covered with the critical radius of insulation and without insulation.
Please show all step, not Ai generated.
The Golden Gate Bridge in San Francisco has a main span of length 1.28 km, one of the longest in the world. Imagine that a steel wire with this length and a cross-sectional area of 4.10 x 106 m2 is laid in a straight line on the bridge deck with its ends attached to the towers of the bridge. On a summer day the temperature of the wire is 22.0°C. (a) When winter arrives, the towers stay the same distance apart and the bridge deck keeps the same shape as its expansion joints open. When the temperature drops to -10°C, what is the tension in the wire? (Take Young's modulus for steel to be 2.00 x 1011 N/m2, and the average linear expansion coefficient for steel to be 1.1 x 10-Soc-1.) (b) Permanent deformation occurs if the stress in the steel exceeds its elastic limit of 3.00 x 10° N/m2. At what temperature would the wire reach its elastic limit? (c) Explain how your answers to parts (a) and (b) would change if the Golden Gate Bridge were twice as long.
"You did calculations using the simplified HAZ time-temperature formulas, assuming 3D heat flow, and are presenting your final internship conclusions to management. You realize with horror, in the middle of your presentation, that you forgot to label your calculated curves (below). Which curve is which? Pick the best answer A: "Plot 1 is HYPERFILL® and Plot 2 is p-GMAW. Since HYPERFILL® has the higher heat input, it cools more slowly." B: "Plot 2 is HYPERFILL® and Plot 1 is p-GMAW. Since HYPERFILL® has the faster travel speed of the two processes, it cools faster." C: "Plot 1 is p-GMAW and Plot 2 is HYPERFILL®. Since p-GMAW has the slower travel speed, it cools more slowly." D: "Plot 2 is p-GMAW and Plot 1 is HYPERFILL®. Since p-GMAW has the lower heat input, it cools faster" Both (A) and (D)
brick and 1. An outside wall for a building consists of a 10-cm (k=0.69 W/m-C) layer of common a 2.5 cm layer of fiber glass (k= 0.05 W/m-C). Calculate the heat flow through the wall for 25 C temperature differential.. 10 cm 2.5cm
Problem 1 A hot water pipe is used for domestic applications is insulated with a layer of calcium silicate. If the insulation is 25 mm thick and its inner and outer surfaces are maintained at Ts,1 = 800 K and Ts,2 = 400 K, respectively. The outside diameter is 0.12 m. Given the thermal conductivity calcium silicate insulation equals to 0.09 W/m.K. A. Define the difference between lagged and unlagged pipes. B. Calculate the heat loss per unit length for this pipe.
For the 21.5-cm thick multilayer assembly as listed below, please estimate the temperature on the interface between material layers 3 and 4 Material layers - counted from the interior side: (1) 1.5 - cm gypsum board; (2) 4.0-cm - concrete of density - 2400-kg/m3; (3) 10-cm of XPS foam; (4) 6.0-cm - concrete of density - 2400-kg/m3 Interior film resistance is Ri = 0.121 m2K/W Exterior film resistance is Re - 0.029 m2K/W Internal temperature +20 degC External Temperature - 20 degC All necessary material properties can be found in the ASHRAE Handbook of Fundamentals, or other sources