[2] An array of electronic chips is mounted within a sealed rectangular enclosure, and cooling is implemented byattaching an aluminum heat sink (k = 180 W/m K). The base of the heat sink has dimensions of w1 = W2 = 100 mm,while the 6 fins are of thickness t = 10 mm and pitch S = 18 mm. The fin length is Lr = 50 mm, and the base of the heatsink has a thickness of Lb = 10 mm.L-ChipsWater u TElectronicpackage,PelecIf cooling is implemented by water flow through the heat sink, with uo = 3 m/s and To =temperature Tb of the heat sink when power dissipation by the chips is Pelec = 1800 W? The average convectioncoefficient for surfaces of the fins and the exposed base may be estimated by assuming parallel flow over a flat plate.Properties of the water may be approximated as k = 0.62 W/m-K, p = 995 kg/m3, Cp = 4178 J/kg-K, v = 7.73 x 10-7 m2/s,and Pr = 5.2.17°C, what is the basea.) Base temperature.А. 37.8°CB. 43.9°CС. 31.4°СD. 46.2°C

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Answered: [2] An array of electronic chips is…

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter4: Numerical Analysis Of Heat Conduction

Section: Chapter Questions

Problem 4.15P

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2.30 An electrical heater capable of generating 10,000 W is to be designed. The heating element is to be a stainless steel wire having an electrical resistivity of ohm-centimeter. The operating temperature of the stainless steel is to be no more than 1260°C. The heat transfer coefficient at the outer surface is expected to be no less than in a medium whose maximum temperature is 93°C. A transformer capable of delivering current at 9 and 12 V is available. Determine a suitable size for the wire, the current required, and discuss what effect a reduction in the heat transfer coefficient would have. (Hint: Demonstrate first that the temperature drop between the center and the surface of the wire is independent of the wire diameter, and determine its value.)
Homework O H.W. 1: The walls of a refrigerator are typically constructed by sandwiching a layer of insulation between sheet metal panels. Consider a wall made from fiberglass insulation of thermal conductivity k; = 0.046 W/m.K and thickness L, = 50 mm and steel panels, each of thermal conductivity k, = 60 W/m.K and thickness L, = 3 mm. If the wall separates refrigerated air at T = 4 C from ambient air at T,. = 25 C, what is the heat gain per unit surface area? Coefficients associated with natural convection at the inner and outer surfaces may be approximated as h, = h, = 5 W/m?.K. %3D %3D L; = 0.050 m K K Lo = 0.003 m Refrigerated air Ambient air Too.i = 4°C hi = 5 W/m2-K To,o = 25°C ho = 5 W/m2-K %3D Panel (2) kp = 60 W/m-K Insulation k; = 0.046 W/m-K 22 Warith Alanbiyaa (Dr. ALI M) Heat Transfer Page 11 of
Below is a diagram of a pipe with 5 m radius, temperature of 5000 K, and k = 450 W/m-K. The pipe is covered by a steel that is 1.8 m thick with k = 17 W/m-K. The temperature inside is 5000 K while the temperature outside is 800 K. TB = 800 K TA = 5000 K k = 450 W/m-K K = 15 W/m-K Answer the following: 1. Calculate the system's heat loss per unit length (W/m²). 2. Calculate the temperature between the pipe and the steel (temperature in K). 5 m 1.8 m/
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HEAT TRANSFER: A thick-walled nuclear coolant pipe (k = 12.5 Btu/hr-ft-°F) with 10 in. inside diameter and 12 in. outside diameter is covered with a 3 in. layer of asbestos insulation (k 0.14 = Btu/hr-ft-°F). If the inside wall temperature of the pipe is maintained at 550°F, (a) calculate the heat loss per foot of length. The outside temperature is 100°F. (b) Find the interface temperature between the pipe and the insulation.
Problem-1: Superheated steam at an average temperature 200°C is transported through a steel pipe (k = 50 W/m-K, D₁ = 8.0 cm, D₁ = 6.0 cm, and L=20.0 m). The pipe is insulated with a 4-cm thick layer of gypsum plaster (k = 0.5 W/m K). The insulated pipe is placed horizontally inside a warehouse where the average air temperature is 10°C. The steam and the air heat transfer coefficients are estimated to be 800 and 200 W/m2.K, respectively. Calculate (a) the daily rate of heat transfer from the superheated steam and (b) the temperature on the outside surface of the gypsum plaster insulation.
A pipe covered with insulating material has inner diameter 0.1 m and outer diameter 0.11m. Assume k=1W/ mK, h=8W/mʼK, the temperature of fluid inside the pipe is 100°C and surroundings temperature is 20°C. The critical radius of insulation (in m) is
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Q. Steam in a heating system flows through tubes whose outer diameter is 5 cm and whose walls are maintained at a temperature of 130 °C. Circular aluminum alloy 2024-T6 fins k = 186 W/m.K of outer diameter 6 cm and constant thickness 1 mm are attached to the tube. The space between the fins is 3 mm, and thus there are 250 fins per length of the tube. Heat is transferred to the surrounding air at 25 °C, with a heat transfer coefficient of 40W/m².K. Determine: 1. The increase in heat transfer from the tube per meter of its length as result of adding fins. 2. The efficiency of the fins. 3. Temperature at mid-point of the fins. Note: Equations and any other data required can be taken from textbook/handbook. 130°C 25°C
Q. Steam in a heating system flows through tubes whose outer diameter is 5 cm and whose walls are maintained at a temperature of 130 °C. Circular aluminum alloy 2024-T6 fins k = 186 W/m.K of outer diameter 6 cm and constant thickness 1 mm are attached to the tube. The space between the fins is 3 mm, and thus there are 250 fins per length of the tube. Heat is transferred to the surrounding air at 25 °C, with a heat transfer coefficient of 40W/m2.K. Determine: 1. The increase in heat transfer from the tube per meter of its length as result of adding fins. 2. The efficiency of the fins. 3. Effectiveness of the fins 4. Temperature at mid-point of the fins. Note: Equations and any other data required can be taken from textbook/handbook. 130°C 25°C
Problem 3: The composite wall shown in the figure below is 200mm H x 100mm wide. What is the temperature at the surface between the G10 and the aluminum heatsink? Note: Answer should be to the nearest thousandth of a degree. Adiabatic Wall T. = 25°C W h = 45. m²K G10 Aluminum Fiberglass Heatsink 3mm 6mm W q" = 1200 m2
A steel duct whose internal diameter is 5.0 cm, and external diameter is 7.6 cm and thermal conductivity is: k = 15.0 (W/(m ºC)) is covered with an insulating material whose thickness is 2.0 cm and of thermal conductivity k = 0.2 (W/(m ºC)). A hot gas flows through the interior of the duct at a temperature of 330.0 ºC that generates a heat transfer coefficient by forced convection h=400.0 (W/(m^2 · ºC)). The outer surface of the insulating layer is exposed to air whose temperature is 30.0 ºC with forced convection heat transfer surface h = 60.0 (W/(m^2 · °C)). As a process engineer and in charge of company operations, you have been asked to: i. Determine the heat loss experienced by the pipe along 10.0 m.ii. The temperature drops that are generated in the different thermal resistances of the system. That is, on the air side, the duct wall and on the hot gas side.

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