There is a 1.20-cm-thick stagnant air pocket. A) What thickness of cork would have the same R-factor as the stagnant air pocket? The thermal conductivity of air is 0.0230 W/m·K and of cork is 0.0460 W/m·K. in cm B) What thickness of tin would be required for the same R-factor as a 1.20-cm-thick stagnant air pocket? The thermal conductivity of air is 0.0230 W/m·K and of tin is 66.8 W/m·K . in m

There is a 1.20-cm-thick stagnant air pocket. A) What thickness of cork would have the same R-factor as the stagnant air pocket? The thermal conductivity of air is 0.0230 W/m·K and of cork is 0.0460 W/m·K. in cm B) What thickness of tin would be required for the same R-factor as a 1.20-cm-thick stagnant air pocket? The thermal conductivity of air is 0.0230 W/m·K and of tin is 66.8 W/m·K . in m

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.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.10P: 1.10 A heat flux meter at the outer (cold) wall of a concrete building indicates that the heat loss...

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A high-speed computer is located in a temperature-controlled room at 26C. When the machine is operating, its internal heat generation rate is estimated to be 800 W. The external surface temperature of the computer is to be maintained below 85C. The heat transfer coefficient for the surface of the computer is estimated to be 10W/m2K. What surface area would be necessary to assure safe operation of this machine? Comment on ways to reduce this area.
1.1 On a cold winter day, the outer surface of a 0.2-m-thick concrete wall of a warehouse is exposed to temperature of –5°C, while the inner surface is kept at 20°C. The thermal conductivity of the concrete is 1.2 W/m K. Determine the heat loss through the wall, which is 10-m long and 3-m high. Problem 1.1
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.
3.16 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.
An electronic device that internally generates 600 mW of heat has a maximum permissible operating temperature of 70C. It is to be cooled in 25C air by attaching aluminum fins with a total surface area of 12cm2. The convection heat transfer coefficient between the fins and the air is 20W/m2K. Estimate the operating temperature when the fins are attached in such a way that (a) there is a contact resistance of approximately 50 K/W between the surface of the device and the fin array and (b) there is no contact resistance (in this case, the construction of the device is more expensive). Comment on the design options.
1.37 Mild steel nails were driven through a solid wood wall consisting of two layers, each 2.5-cm thick, for reinforcement. If the total cross-sectional area of the nails is 0.5% of the wall area, determine the unit thermal conductance of the composite wall and the percent of the total heat flow that passes through the nails when the temperature difference across the wall is 25°C. Neglect contact resistance between the wood layers.
There is a 1.20-cm-thick stagnant air pocket. A) What thickness of cork would have the same R-factor as the stagnant air pocket? The thermal conductivity of air is 0.0230 W/m·K and of cork is 0.0460 W/m·K.in cm B) What thickness of tin would be required for the same R-factor as a 1.20-cm-thick stagnant air pocket? The thermal conductivity of air is 0.0230 W/m·K and of tin is 66.8 W/m·K . in m i asked how to do this but got the wrong soloution
12. A 3.1 cm long straight rectangular fin has a thickness of 2.7 mm. The thermal conductivity is 52 W/m K. The fin is attached to a wall maintained at 190 °C and is exposed to a convection environment at 40 °C and h- 31 W/m2 K. What is the fin efficiency? Express your answer in percent.
1 mm thick copper plate (k=386 W/m-c) that are 15 cm x 20 cm in size if the thermal contact conductance on both sides of the copper plate is estimated to be 6,000 W/m-c, determine the % error involved in the total thermal resistance of the plate if the thermal contact conductance are ignored.
Consider a closed cylindrical reactor vessel of diameter D= 1 ft, and length L= 1.5 ft. The surface temperature of the vessel, T1, and the surrounding temperature, T2, are 390 deg. F and 50 deg. F, respectively. The convective heat transfer coefficient, h, between the vessel wall and surrounding fluid is 4.0 Btu/h . ft . ⁰F. Calculate the thermal resistance in ⁰F .h/Btu.
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
Question 3: A house has a composite wall of wood, fiberglass insulation, and plaster board, as indicated in the sketch. On a cold winter day the convection heat transfer coefficients are ho 60 W/m2 K and hi 30 W/m2 K. The total wall surface area is 350 m2. (a)Determine the total heat loss through the wall. (b) If the wind were blowing violently, raising ho to 300 W/m2 K, determine the percentage increase in the heat loss.