A wall has inner and outer surface temperatures of 16 and 6 C, respectively. The interior andexterior air temperatures are 20 and 5 C, respectively. The inner and outer convection heattransfer coefficients are 5 and 20 W/m²K, respectively. Calculate the heat flux from the interiorair to the wall, from the wall to the exterior air, and from the wall to the interior air. Is the wallunder steady-state conditions?KNOWN: Inner and outer surface temperatures of a wall. Inner and outer air temperatures andconvection heat transfer coefficients.FIND: Heat flux from inner air to wall. Heat flux from wall to outer air. Heat flux from wall toinner air. Whether wall is under steady-state conditions.SCHEMATIC:Outer surfaceAirT=20°Ch, 5 W/m²-K9"x-wT=6°CdE/dtT=16°CAirT=5°Ch=20 W/m²-KInner surfaceASSUMPTIONS: (1) Negligible radiation, (2) No internal energy generation.

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Answered: A wall has inner and outer surface…

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

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6. A solid cylinder with a diameter of 3.0 cm and length of 3.2 cm, initially at a uniform temperature of 210°C, is suddenly exposed to a convection environment at 43°C with a convection coefficient of 380 W/m2 K. What is the minimum thermal conductivity of the cylinder material such that the lumped capacity method is applicable? Express your answer in W/m K.
Two different fluids are separated by an insulating barrier. The barrier consists of two different materials as shown in Fig. 2. The temperature of the fluids are maintained 80°C and To02 steady at Too1 30°C. The convection coefficients between the fluids and respective k2 barrier surfaces are hi 15 W/m2.K and h2 : 10 W/m².K. Too2 The thickness of the slabs are L1 0.1 m and L2 = = 0.15 m. The thermal conductivity of the slabs are A B X= 0 respectively k1 = 2 W/m-K and k2 out the temperature distribution within the slabs (i.e., = 1.5 W/m-K. Find Perfect interface temperature as a function of x). What is the difference Figure 2: Note the indicated positive x direction for reference. of temperature between the center of slab A and slab B (i.e., TA(L1/2) – TB(L1 + L2/2))? Fluid 2 Fluid 1 I
In an experiment to measure the thermal conductivity of a plate of unknown material with area 1 m2 and thickness 0.1m, one of its surfaces is maintained at 100 °C and the other at 20 °C and a heat at the rate of 100 kW was supplied across it. Determine the thermal conductivity of the hot plate. Is the material metallic, non-metallic, or gas/liquid?
Homework problem for unsteady-state heat transfer Consider a product to be sterilized if its coldest location during heating reaches 115°C. Consider sterilization of potatoes where potatoes (4 cm diameter) is heated in steam at 121°C. Assume symmetrical heating of potatoes and the heat transfer coefficient between the steam and the potatoes is 20 W/m² K. The thermal diffusivity for potatoes is 1.5 × 107m²/s and the thermal conductivity is 0.4 W/m K. The potatoes are initially at 30°C. 1) Calculate the heating time needed for sterilization. 2) Calculate the temperature at the center of the potato after heating 1000 s and 2000 s. Plot how the temperature at the center changes with time t. 3) Calculate the temperature at the surface of the potato at 2000 s. Qualitatively plot how the temperature changes across the apple at t = 2000 s.
A cylindrical resistor element on a circuit board dissipates 0.22 W of power in an environment at 28°C. The resistor is 1.2 cm long, and has a diameter of 3 mm. Assuming heat to be transferred uniformly from all surfaces. What is the surface temperature of the resistor for a combined convection and radiation heat transfer coefficient of 13 W/m . C?
Required information Consider a 5-m-high, 8-m-long, and 0.22-m-thick wall whose representative cross section is as given in the figure. The thermal conductivities of various materials used, in W/m-K, are kA=kF=2, kg-8. kc-20, kp=15, and ke-35. The left and right surfaces of the wall are maintained at uniform temperatures of 345°C and 100°C, respectively. Assume heat transfer through the wall to be one-dimensional. Disregard any contact resistances at the interfaces. 1 cm. A4 cm B 4 cm रेव 4 cm Sem 6 cm DI 4 E 6 cm F 10 cm 6 cm 100°C 8m Determine the rate of heat transfer through the wall (in W).
The thermal conductivities of human tissues vary greatly. “Fat” and “skin” have conductivities of approximately 0.200 W /m 0K and 0.0200 W /m 0K, respectively, while other “tissues” inside the body have conductivities of approximately 0.500 W /m 0 Assume that between the core region of the body and the skin surface lies a “skin” layer of 1.00mm, a “fat” layer of 0.500 cm., and 3.20 cm. layer of other “tissues”. A)Find the R-factor for each of these three layers, and the R-factor for all layers taken together
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Plate glass 5 mm thick at 200°C is to be cooled from both sides using air at 40°C. If surface cracks are to be avoided, determine the maximum value of convective heat transfer coefficient. Material properties are density = 2500 kg/m3, specific heat 670 J/kgK. Thermal conductivity 0.744 W/mk. Also determine the time required in this to cool the plate to 80°C.
Can you help me answer my sample problem for my review?
A furnace wall comprises three layers of thickness 250 mm, 100 mm, and 150 mm with thermal conductivities of 1.65, k and 9. W/m K respectively. The inside is exposed to gases at 1250 ˚C with convection of 25 W/m2K, and the inside surface is at 1100 ˚C, the outside surface air at 25 ˚C with convection of 12 W/m2K. Determine the temperatures of the mid-inner surface in 0C to 1 d.p.?

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