Completely solve and box the final answer. Write legibly. 10. An uninsulated steam pipe passes through a room in which the air and walls are at 25°C. The outside diameter of the pipe is 82 mm, and its surface temperature and emissivity are 200°C and 0.80 respectively. If the coefficient associated with free convection heat transfer from the surface to the air is 15W/m2-k, what is the rate of heat loss for a 5 meter pipe? Round the answer in 2 decimals.

Completely solve and box the final answer. Write legibly. 10. An uninsulated steam pipe passes through a room in which the air and walls are at 25°C. The outside diameter of the pipe is 82 mm, and its surface temperature and emissivity are 200°C and 0.80 respectively. If the coefficient associated with free convection heat transfer from the surface to the air is 15W/m2-k, what is the rate of heat loss for a 5 meter pipe? Round the answer in 2 decimals.

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 1.36P: Repeat Problem 1.35 but assume that instead of surface temperatures, the given temperatures are...

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1.77 Explain each in your own words. (a) What is the mode of heat transfer through a large steel plate that has its surfaces at specified temperatures? (b) What are the modes when the temperature on one surface of the steel plate is not specified, but the surface is exposed to a fluid at a specified temperature?
1.3 A furnace wall is to be constructed of brick having standard dimensions of Two kinds of material are available. One has a maximum usable temperature of 1040°C and a thermal conductivity of 1.7 W/(m K), and the other has a maximum temperature limit of 870°C and a thermal conductivity of 0.85 W/(m K). The bricks have the same cost and are laid in any manner, but we wish to design the most economical wall for a furnace with a temperature of 1040°C on the hot side and 200°C on the cold side. If the maximum amount of heat transfer permissible is 950 , determine the most economical arrangement using the available bricks.
Using the information in Problem 1.22, estimate the ambient air temperature that could cause frostbite on a calm day on the ski slopes. 1.22 In order to prevent frostbite to skiers on chair lifts, the weather report at most ski areas gives both an air temperature and the wind-chill temperature. The air temperature is measured with a thermometer that is not affected by the wind. However, the rate of heat loss from the skier increases with wind velocity, and the wind-chill temperature is the temperature that would result in the same rate of heat loss in still air as occurs at the measured air temperature with the existing wind. Suppose that the inner temperature of a 3-mm-thick layer of skin with a thermal conductivity of 0.35W/mKis35C and the air temperature is 20C. Under calm ambient conditions the heat transfer coefficient at the outer skin surface is about 20W/m2K (see Table 1.4), but in a 40-mph wind it increases to 75W/m2K. If frostbite occurs when the skin temperature drops to about 10C, do you advise the skier to wear a face mask? What is the skin temperature drop due to the wind?
Repeat Problem 1.35 but assume that instead of surface temperatures, the given temperatures are those of the air on the left and right sides of the wall and that the convection heat transfer coefficients on the left and right surfaces are 6 and 10W/m2K, respectively.
2.15 Suppose that a pipe carrying a hot fluid with an external temperature of and outer radius is to be insulated with an insulation material of thermal conductivity k and outer radius . Show that if the convection heat transfer coefficient on the outside of the insulation is and the environmental temperature is , the addition of insulation actually increases the rate of heat loss if , and the maximum heat loss occurs when . This radius, is often called the critical radius.
3.9 The heat transfer coefficients for the flow of 26.6°C air over a sphere of 1.25 cm in diameter are measured by observing the temperature-time history of a copper ball the same dimension. The temperature of the copper ball was measured by two thermocouples, one located in the center and the other near the surface. The two thermocouples registered, within the accuracy of the recording instruments, the same temperature at any given instant. In one test run, the initial temperature of the ball was 66°C, and the temperature decreased by 7°C in 1.15 min. Calculate the heat transfer coefficient for this case.
1.63 Liquid oxygen (LOX) for the space shuttle is stored at 90 K prior to launch in a spherical container 4 m in diameter. To reduce the loss of oxygen, the sphere is insulated with superinsulation developed at the U.S. National Institute of Standards and Technology's Cryogenic Division; the superinsulation has an effective thermal conductivity of 0.00012 W/m K. If the outside temperature is on the average and the LOX has a heat of vaporization of 213 J/g, calculate the thickness of insulation required to keep the LOX evaporation rate below 200 g/h.
Completely solve and box the final answer. Write legibly 3. Determine the heat loss in KW of a vertical furnace made up of inner wall of firebrick 28 cm thick followed by insulating brick 18 cm thick and an outer wall of steel 1.5 cm thick. Surface temperature of the wall adjacent to the combustion chamber is 895ºC while that of the outer surface of steel is 42ºC. Use a thermal conductivity of wall in W/m-ºK for firebrick, insulating brick and steel to be 14, 0.92, and 52 respectively. The cross section is 2.5 m x 7.5 m.
PARTS A and B ( Label Them ) SOLVE CAREFULLY!! Please Write Clearly and Box the final Answer for both Question : Chilled pharmaceutical is transported through a steel pipe ( k= 15.0 W/m.k) with an inner diameter of 36 mm and a wall thickness of 2 mm. The liquid and ambient air are at temperatures of 5 C and 25 C, while the inner and outer convection coefficients are 500 W/m2.K and 10 W/m2.K respectively. If a 10 mm thick layer of calcium silicate ( k= 0.05 W/m.K) is applied to the tube, answer the following questions: Part A : What is the heat gain per 1m of the tube? Part B : What is the outside temperature of the calcium silicate?
Let's say a 3.0 gram copper wafer is dropped from a height of 50.0 meters. If 60% of the potential energy lost in the drop could be converted to thermal energy used to heat the copper from an initial temperature of 25 degrees celsius, what would the final temperature of the copper wafer? Would the answer be different if the wafer has a mass greater than 3 grams? Note: the specific heat of copper is 387 J/(kg*K). The temperature is between 25.8 and 26.0 degrees celsius, yes the bigger the mass the greater the energy. O The temperature is between 25.6 and 25.8 celsius, answer does not depend on mass. O The temperature is between 25.0 and 25.2 celsius, answer does not depend on mass. O The temperature is 25.5 and of course the more mass something has the greater energy will be needed to raise the temperature. The temperature is 26.2 and if the mass is doubled so will be the change in temperature. O The temperature is 25.9 degrees celsius and the answer does not depend on mass. O The…
Completely solve and box the final answer. Write legibly. 3. An electrical wire with 0.4cm in diameter and 2.5m long extends across a room with 15deg C temperature. Heat is generated in the wire as a result of resistance heating, and the surface of the wire is measured to be 162degC. the voltage drop and electric current along the wire is 60V and 1.86 A, respectively. Determine the convection heat transfer coefficient for the heat transfer between the surface of the wire and the room air. Hint, electric power formula. Round your answer to 2 decimal places.
Completely solve and box the final answer. Write legibly 4. Compute the heat conducted in KW through a sheet of plate glass, k = 0.025 Cal/s-cm-ºC, which is 3.5 m x 4.8 m and 12.5mm thick. The temperature of the surfaces are 28ºC and negative 5.4ºC.