Problemswithin the wall is T(x) = a(L- ) +b wherea = 10°C/m2 and b 30°C, what is the thermal con-ductivity of the wall? What is the value of the convec-tion heat transfer coefficient, h?2.11 Consider steady-state conditions for one-dimensionalconduction in a plane wall having a thermal conductiv-ity k 50 W/m K and a thickness L = 0.25 m, with nointernal heat generation.2.T2T1LDetermine the heat flux and the unknown quantity foreach case and sketch the temperature distribution, indi-cating the direction of the heat flux.2CaseTC)dTldx (K/m)T2(°C)150-202-30- 10370160440-80530200

Given data as per questionAssumptionsSteady state condition.One dimensional conductionNo internal…

Answered: Problems within the wall is T(x) = a(L-…

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.

Chapter2: Steady Heat Conduction

Section: Chapter Questions

Problem 2.47P

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3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer coefficient on one side is and on the other side is . If the temperature of both streams is suddenly changed from 38°C to 93°C, determine how long it takes for the copper plate to reach a temperature of 82°C.
1.10 A heat flux meter at the outer (cold) wall of a concrete building indicates that the heat loss through a wall of 10-cm thickness is . If a thermocouple at the inner surface of the wall indicates a temperature of 22°C while another at the outer surface shows 6°C, calculate the thermal conductivity of the concrete and compare your result with the value in Appendix 2, Table 11.
3.17 A 1.4-kg aluminum household iron has a 500-W heating element. The surface area is . The ambient temperature is 21°C, and the surface heat transfer coefficient is . How long after the iron is plugged in does its temperature reach 104°C?
2.55 A long, 1-cm-diameter electric copper cable is embedded in the center of a 25-cm-square concrete block. If the outside temperature of the concrete is 25oC and the rate of electrical energy dissipation in the cable is 150 W per meter length, determine temperatures at the outer surface and at the center of the cable.
1.60 Two electric resistance heaters with a 20 cm length and a 2 cm diameter are inserted into a well-insulated 40-L tank of water that is initially at 300 K. If each heater dissipates 500 W, what is the time required for bringing the water temperature in the tank to 340 K? State your assumption for your analysis.
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.)
2.9 In a large chemical factory, hot gases at 2273 K are cooled by a liquid at 373 K with gas-side and liquid-side convection heat transfer coefficients of 50 and , respectively. The wall that separates the gas and liquid streams is composed of a 2-cm thick oxide layer on the gas side and a 4-cm thick slab of stainless steel on the liquid side. There is a contact resistance between the oxide layer and the steel of . Determine the rate of heat loss from hot gases through the composite wall to the liquid.
A 10-cm diameter pipe is covered by 2 layers of lagging. The insidelayer is 4 cm thick and has a coefficient of thermal conductivity of 0.08W/m-K. The outside layer is 3cm thick and has a coefficient of thermalconductivity of 0.15 W/m-K. The steam main conveys steam apressure of 1.7 MPa with 25 C superheat. The outside temperature ofthe lagging is 27 C. If the steam main is 30 m long, determine theinterface temperature of the lagging and overall coefficient of heattransfer based on outside area.
HEAT TRANSFER A 2-in steel pipe has an inside diameter of 5.25cm and anoutside diameter of 6.03cm. The pipe has a thermal conductivity of k= 36 W/m*Kthat is insulated with a 2-cm-thick-layer of insulation(k=0.02 W/m*K). The inside surface of the pipe ismaintained at a temperature of 60°C, and the outside surfaceof the insulation is maintained at a temperature at 20°C.Find the heat transfer from the pipe per meter of length. SHOW COMPLETE SOLUTION IN A PAPER.
On a multi-layered square wall, the thermal resistance of the first layer is 0.005 ° C / W, the resistance of the second layer is 0.2 ° C / W, and the third layer is 0.1 ° C / W. The overall temperature gradient in the wall is multilayered from one side. to the other side is 70 ° C. a. Determine the heat flux through the walls. = Answerwatts / m2. b. If the thermal resistance of the second layer is changed to 0.4 ° C / W, what is the effect in% on heat flux, assuming the temperature gradient remains the same? = AnswerAnswer%.
A 1-in Sch 40 stainless steel pipe with a thermal conductivity of 45 W/m-K can move 1,000 kg of saturated steam per hour at 150 °C. Refractory material 0.25 inches thick with a thermal conductivity of 0.025 W/m-K insulates the pipe. At a temperature of 25 °C, the pipe is exposed to the outside air. There is a 1135 W/m2 internal heat transfer coefficient.40 W/m2-K is the outside heat transfer coefficient, whereas -K. Suppose that only the radial direction is involved in steady-state heat transfer and that radiation effects are negligible. ✓ Determine how much heat is being lost through these pipes to the environment.a. 399.1 W/mb. 1525.0 W/mc. 618.4 W/md. 1128.7 W/me. none of the above √ How about the insulated pipe's surface temperature?a. 118.5 °Cb. None of the abovec. 101.5 °Cd. 216.3 °Ce. 292.2 °C
The outer facing of a room is constructed from 25 cm thick brick, 2.5 cm of mortar, 10 cm of limestone (k = 0.186 W/m-K) and 1.2 cm of plaster (k = 0.096 W/m-K). Thermal conductivities of mortar and brick are both 0.52 W/m-K. Assume that the heat transfer coefficients on the inside (plaster side) and the outside (brick side) surfaces of the wall to be 6 and 12 W/sq. m, respectively. Calculate the rate of heat transfer per 10 sq. m of the wall surface from the room at 18 C to the outside air at 36 C.

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