A plastic panel area A= 1 ft2 and thickness X=0.252 inches was found to conduct heat at a rate of 3.0 W at steady state with temperatures To = 24.00oC and T1 = 26.00oC imposed on the two main surfaces. What is the thermal conductivity of the plastic in
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A plastic panel area A= 1 ft2 and thickness X=0.252 inches was found to conduct heat at a rate of 3.0 W at steady state with temperatures To = 24.00oC and T1 = 26.00oC imposed on the two main surfaces. What is the thermal conductivity of the plastic in cal/cm-s-K at 25oC.
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- A plane wall, 7.5 cm thick, generates heat internally at the rate of 105 W/m3. One side of the wall is insulated, and the other side is exposed to an environment at 90C. The convection heat transfer coefficient between the wall and the environment is 500 W/m2 K. If the thermal conductivity of the wall is 12 W/m K, calculate the maximum temperature in the wall.2.2 A small dam, which is idealized by a large slab 1.2 m thick, is to be completely poured in a short Period of time. The hydration of the concrete results in the equivalent of a distributed source of constant strength of 100 W/m3. If both dam surfaces are at 16°C, determine the maximum temperature to which the concrete will be subjected, assuming steady-state conditions. The thermal conductivity of the wet concrete can be taken as 0.84 W/m K.A plane wall 15 cm thick has a thermal conductivity given by the relation k=2.0+0.0005T[W/mK] where T is in kelvin. If one surface of this wall is maintained at 150C and the other at 50C, determine the rate of heat transfer per square meter. Sketch the temperature distribution through the wall.
- 2.44 To determine the thermal conductivity of a long, solid 2.5-cm-diameter rod, one half of the rod was inserted into a furnace while the other half was projecting into air at . After steady state had been reached, the temperatures at two points 7.6 cm apart were measured and found to be and , respectively. The heat transfer coefficient over the surface of the rod exposed to the air was estimated to be 22.7 . What is thermal conductivity of the rod?54. As shown in the figure, to dissipate heat from an electrical appliance, thin plates of metal with a thermal conductivity of 10 Btu/h·ft·F are used. Find the number of the plates to dissipate 10.55 W at steady state operation. Data: Tbase = 85 F, Tf = 65 F, h = 1 Btu/h·ft2·F, L = 10 in, b = 1 in, δ = 0.03 in. [Ans.: 15].The front door of an oven is made up of walls made up of materials A, B and C, juxtaposed. The walls that make up the door have thermal conductivities, kA= 20 W/(m.K), kB= 0.027 W/(m.K) and kC= 50 W/(m.K) and known thicknesses LA=0.30 m and LC=0.15 m. At steady state operation, measurements indicate that the air temperatures inside the oven and its inner walls are equal to 600 oC (the temperature of the inner surface of the door is not known). The convective coefficient of air (inside and outside the oven) is 25 W/(m2.K) and the radiation coefficient is hr=25 W/m2K. outside the air is at 25oC. Based on this information:(a) schematic the thermal circuit for the system;(b) estimate the minimum thickness of wall B to ensure that thetemperature of the outer surface of the door (exposed to ambient air)is ≤40oC in order to ensure the safety of operators;(c) estimate the temperature of the surface of the oven's inner wall Answer: (b) 40 mm; (c) 592.5oC
- 4) In an experiment to find the thermal conductivity, a metallic rod of diameter 25 mm is placed in a furnace such that its one half is inserted into the furnace and other half is projected out in a room at 300 K. Once the steady state reached, the temperatures measured between two points 76 mm apart were 399 K and 364 K, respectively. Taking a convection coefficient of 22.7 W/m 2 – K, find the thermal conductivity of the metal.A heat conducting rod, 0.30 m long, is made of an aluminum section that is 0.10 m long, and a copper section that is 0.20 m long. Both sections have cross-sectional areas of 0.00040 m2. The aluminum end is maintained at a temperature of 10°C and the copper end is at 170°C. The thermal conductivity of aluminum is 205 W/m • K and of copper is 385 W/m • K. Steady state has been reached, and no heat is lost through the well-insulated sides of the rod. The temperature of the aluminum-copper junction in the rod is closest toIn an experiment to determine the thermal conductivity of a new metal alloy, a bar of the metal is completely surrounded by insulation and exposed to 705 W of constant heat energy at one end. The bar has a radius of 0.069 m and a length of 0.365 m. The entire set-up is place in a cold room and once the system has reached steady state conditions, the temperature at the hot end is measured to be 67.3°C and the temperature at the cold end is measured to be 10.5°C. What is the thermal conductivity (in W/m∙K) of the metal alloy [round your final answer to zero decimal places]?
- Two volumes of air are separated by a thin rectangular heater (0.2 cm x 15 cm x 2 cm). The volumetric heat generation associated with the heater is 350 kW/m3. What is the temperature of the heater at steady state?The air in the bottom chamber is at (TB= 20 °C, hB= 15 W/m2.K) while the air in the top chamber is at (TT= 55 °C, hT= 9 W/m2K). hint: for such thin application, we shall assume the same surface temperature on both sides of the heater.The initial temperature of a 50 cm long silver wire is 50 °C. The circumference of the wire in question is completely insulated, but both ends are kept at a temperature of 0 °C (zero degrees Celsius). Obtain the heat conduction along the wire as a function of time and position and, taking a single term in the solution, determine how many degrees Celsius the temperature in the middle of the rod will be after 7 minutes. (For silver wire, α=1.70 cm2/s.)- A 40 x 40 cm copper slab # mm thick at a uniform temperature of 250 °C suddenly has its surface temperature lowered 30 °C. Find the time at which the slab temperature becomes 90°C ; p=9000 ke/m’, c=0.38 KJ/kgK, k=370 W/mK and h=00 W/m’K. 2