A 4-m-high and 6-m-wide wall consists of a long 18-cm x 30-cm cross section of horizontal bricks (k = 0.72 W/m-K) separated by 3-cm-thickplaster layers (k = 0.22 W/m-K). There are also 2-cm-thick plaster layers on each side of the wall, and a 2-cm thick rigid foam (k = 0.026W/m-K) on the inner side of the wall. The indoor and the outdoor temperatures are 38°C and -4°C, respectively, and the convection heattransfer coefficients on the inner and the outer sides are hy = 10 W/m2-K and h2 = 20 W/m2K, respectively. Assuming one-dimensional heat%3Dtransfer and disregarding radiation, determine the rate of heat transfer through the wall (in W).FoamPlasterBrick

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Answered: A 4-m-high and 6-m-wide wall consists…

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

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A total of 10 rectangular aluminum fins (k = 203 W/m:K) are placed on the outside flat surface of an electronic device. Each fin is 100 mm wide, 20 mm high, and 4 mm thick. The fins are located parallel to each other at a center-to-center distance of 8 mm. The temperature at the outside surface of the electronic device is 72°C. The air is at 20°C, and the heat transfer coefficient is 80 W/m?K. Determine (a) the rate of heat loss from the electronic device to the surrounding air and (b) the fin effectiveness.
Consider a large plane wall of thickness 2L=20mm. Both surfaces of the wall are convectively cooled by the surrounding coolant at To = 250°C with a heat transfer coefficient of h= 1100 W/m².K. A fuel element of a nuclear reactor is considered in the shape of this large plane wall with given constant thermal properties as thermal conductivity k = 30 W/m.K and a = 5 x 10-6m²/s. It is known that heat is generated uniformly within the element at a volumetric rate of q = 1x 107W /m³. A departure from the steady-state conditions associated with normal operation will occur if there is a change in the generation rate. Consider a sudden change to q2 = 2 x 107W/m³. Assuming steady one-dimensional heat transfer along the wall, use the explicit finite- difference method to show how to calculate temperature To at 1.2 sec and temperature Ts at 1.5 sec. (show which equation to use and the calculations in details)
The interior of a refrigerator whose dimensions are 0.05 x 0.05 dam base area and 1.25 m high, must be kept at 4 °C. The refrigerator walls are constructed of two steel sheets (k= 35 kcal/h.m.°C) 3 mm thick, with 65 mm of material insulation (k=0.213 kcal/h.m.°C) between them. The film coefficient of the inner surface is 10 kcal/h.m².°C, while on the external surface it varies from 8 to 12.5 kcal/h.m².°C. Calculate: a) The power (in HP) of the refrigerator motor so that the heat flux removed from the inside the refrigerator maintain the specified temperature, in a kitchen whose temperature can vary from 21 to 36 °C; b) The temperatures of the inner and outer surfaces of the wall. Given 1 HP = 641.2 Kcal/h
A cylindrical cold storage facility with an inner diameter of 4m and height of 2m is constructed. For the wall, the first layer is 6 cm of glass wool (0.1 W/m-C), followed by 30 cm of concrete. The temperature inside is maintained at -10C (hin = 55 W/m^2-C) while the outside temperature is 10°C (hout = 22 w/m^2-C). If the steady rate of heat transfer is at 60W, (a) what is the thermal conductivity of concrete? (b) At what radius is the temperature at 0°C? To prevent water condensation inside the concrete wall (which damages the structure), A 5 cm layer of insulation (k = 0.15 W/m-C) is added to the exterior of the facility. (c) What is the new rate of heat transfer? (d) What is the temperature at the interface of the concrete wall and new insulation? (e) is condensation within the core of the wall prevented?
A 4-m high and 6-m-wide wall consists of long 15-cm x 20 cm cross section horizontal bricks (k of 0.69 W/m K) separated by 2-cm thick plaster layers (k of 0.2 W/m K). There are also 2-cm-thck plaster layers on each side of the brick and a 3-cm-thick rigid foam (k of 0.025 W/m K) on the inner side of the wall. See figure below. The indoor and the outdoor air temperatures are 18 and -8oC, respectively. Convective heat transfer coefficient for inside and outer surfaces are 8 and 22 W/m2 K, respectively. Assume 1-D heat transfer. Neglect radiation assume any plane wall normal to the x-direction is isothermal, draw the thermal circuit and calculate the heat transfer rate through the wall
Foam Plaster A 4-m-high and 6-m-wide wall consists of a long 18-cm x 30-cm cross section of horizontal bricks (k=0.72W/m-°C) separated by 3-cm-thick plaster layers (k=0.22 W/m-°C). There are also 2-cm-thick plaster layers on each side of the wall, and a 2-cm-thick rigid foam (k=0.026W/m-°C) on the inner side of the wall. The indoor and the outdoor temperatures (1.5 cm Brick 30 cm are 22°C and -4°C, and the convection heat transfer coefficients on the inner and outer sides are hi=10W/m²-°C and h2=20 W/m²-°C, Į 1.5 cm respectively. Assuming one-dimensional heat transfer and disregarding radiation, determine the rate of heat transfer through the walI. 18 cm 2' 2 2
It is designed in such a way that the internal temperature of a commercial heat treatment furnace can reach up to 165 oC. All surfaces of the furnace consist of firebrick (10 cm), insulation material and sheet metal (3mm) from the inside out. Given that the outdoor temperature is 22 oC, the outer sheet will be allowed to go up to 35 oC, which is a temperature that will not disturb in contact with hands. In this case, determine the insulation material thickness to be used. The thermal conductivity coefficient of the insulation material is insulation 0.066 W / m oC, 60 W / m oC for sheet metal and 115 W / m oC for firebrick. Indoor heat transfer coefficient will be accepted as 25 W / m2 oC and 12 W / m2 oC for outdoor environment.
Answer this ASAP,thx An empty sphere is made of aluminum (k = 202 W/m. °C) with an inner diameter of 4 cm and an outer diameter of 8 cm. The inside temperature is 100°C and If the ball above is coated with an insulating material having k = 50 mW/m. °C 1 cm thick. The outside of this insulation is in contact with an environment having h = 20 W/m.°C and Ts = 10°C, calculate the heat transfer under these conditions.
You are designing a 3m x 3m floor with radiant heating. The floor has 12 parallel pex pipes (k = 40 W/mK) of L = 3m, OD = 25mm and ID = 20mm. Hot water (TInfintiy 1 = 90oC, h = 200 W/m2K) runs through the pipes continuously. The surface below the pipes is perfectly insulated. Above the pipes, there is a 3mm layer of bonding material (? = 12 W/mK) and a 9mm layer of tile (k = 2 W/mK). Above the tile, there is air (TInfinity 2 = 25oC, h = 20 W/m2K). Properties of Air: k = 0.025 W/mK, Pr = 0.72, v = 1.847 x 10−5, u = 16.84 x 10−6, p = 1.2 kg/m3, B = 1/Tf (ideal gas), Hint: Assume that the “layer” of pipe starts at the center point (e.g. for conduction purposes, the pipe is OD divided by 2 thick). For convection, consider the entire pipe surface. a) What is the total heat rate entering the room above the floor? b) What is the temperature of the top of the tile?
3-28E A wall is constructed of two layers of 0.6-in-thick sheetrock (k = 0.10 Btu/h-ft-°F), which is a plasterboard made of two layers of heavy paper separated by a layer of gypsum, placed 7 in apart. The space between the sheetrocks is filled with fiberglass insulation (k = 0.020 Btu/h-ft F). Determine (a) the thermal resistance of the wall and (b) its R-value of insulation in English units. FIGURE P3-28E Fiberglass insulation Sheetrock 0.6 in 7 in I 0.6 in
A 10 cm thick wall is to be constructed with 2.5 m long wood studs (k = 0.11 W/m.K), that has a cross section of 10 cm × 10 cm. At some point the builder has run out of those stud and started using pairs of 2.5 m long wood stud with cross section of 5 cm × 10 cm nailed to each other instead. The manganese steel nails (k = 50 W/m.K) are 10 cm long and have dia of 0.4 cm. A total 50 nails are used to connect the two studs. The temperature difference between inner and outer wall is 15°C. Assuming negligible thermal contact resistance between two layers. Calculate heat transfer rate (i) through a solid stud, (ii) through stud pair with equal length and width nailed to each other, (iii) also, determine the effective thermal conductivity of the nailed stud pair.
Radioactive material is stored in a spherical vessel with a diameter of 3.7 m, and the center of the vessel is 11 m below the ground. The vessel is surrounded by a 10.2 cm thick layer of rigid foam insulation (k = 0.026 W/m-K). The radioactive material releases heat at a rate of 1000 W/m³. The surface of the soil it's buried in (k = 2 W/m- K) is exposed to wind with a temperature of 20°C and a convection coefficient of 17 W/m²-K. What is the temperature of the surface of the tank?

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