Explain how you would estimate the time to cool a sheet of Cornings Willow Glass that...
Explain how you would estimate the time to cool a sheet of Cornings Willow Glass that is 100 microns thick. Assume that the initial melt temperature is 1000C and the final temperature required is 50C. The heat transfer coefficient is 20 W/(m2*K)
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Explain how you would estimate the time to cool a sheet of
Cornings Willow Glass that...
Estimate the time required to kook a hot dog in boiling water. Assume that the hot...
Estimate the time required to kook a hot dog in boiling water. Assume that the hot dog is initially at 6°C, that the convection heat transfer coefficient is 100 W/m2 k, and that the final temperature is 80°C at the centerline. Treat the hot dog as a long cylinder of 20 mm diameter having the properties: ρ 880 kgm, C,-3.350 kJ/kg·k, and k 0.52 W/mk 52.
A freezer compartment is covered with a 3-mm-thick layer of frost at the time it malfunctions....
A freezer compartment is covered with a 3-mm-thick layer of frost at the time it malfunctions. If the compartment is in ambient air at 20°C and a coefficient of h 2 W/m2 、K characterizes heat transfer by natural convection from the exposed surface oi the layer, estimate the time required to completely melt the frost. The frost may be assumed to have a mass density of 700 kg/m3 and a latent heat of fusion of 334 kJ/kg
Problem 2: A 25 mm thick glass sheet needs to be rapidly quenched by air jets...
Problem 2: A 25 mm thick glass sheet needs to be rapidly quenched by air jets (h-800 W/m2-K, T-25°C) on both sides to "temper" it. The glass starts at an initial temperature of 800°C, and its surface must be cooled to less than 150°C. (a) What type of transient analysis is appropriate for this problem? You must justify your answer. (b) How long would this process take? (c) What is the glass centerline temperature at that time?
The temperature distribution across a wall 0.2 m thick at a certain instant of time is...
The temperature distribution across a wall 0.2 m thick at a certain instant of time is T(x) = a + bx + cxº, where T is in degrees Celsius and x is in meters, a = 200°C, b = -190°c/m, and c = 30°C/m2. The wall has a thermal conductivity of 1 W/m.k. (a) On a unit surface area basis, determine the rate of heat transfer into and out of the wall and the rate of change of energy stored...
Heat Transfer Problem: A sphere of pure aluminum weighing 6 kg and initially at a temperature...
Heat Transfer Problem:
A sphere of pure aluminum weighing 6 kg and initially at a temperature of 300°C is cooled by an air stream at 20°C with a convection coefficient of 24 W/m2 C. Calculate the time required to cool the sphere center to 100°C.
I figured out the first question but im not sure how to answer question 2 and 3?
i
figured out the first question but im not sure how to answer
question 2 and 3?
i
have figured out question 2. Question #3 is what is diffcult to
grasp because i have to guess my Fo #. Fo=time
1. To reduce building heating costs, modern building codes in many parts of the country require the use of double-pane windows (sometimes, called "double-glazed" or "thermopane" windows). Some of In one design of a double-pane window, each glass layer is...
A bare copper cable 2.5 cm in diameter is situated in still air at 15°C. A...
A bare copper cable 2.5 cm in diameter is situated in still air at 15°C. A current of 800 Amps is passed along the cable. Heat is transferred from the cable to its surroundings by natural convection for which the heat transfer coefficient may be expressed as 2.95025 W/m2 K. Determine whether or not it may be assumed that the temperature across the copper cross section is uniform and what the equilibrium temperature of the cable surface will be. If...
PROBLEM 4 (20 pts) Water at 25 °C is used to cool oil from 120 °C...
PROBLEM 4 (20 pts) Water at 25 °C is used to cool oil from 120 °C to 80 °C. Oil flows at a rate of 1 kg/s in a tube of inside diameter 1.6 cm and outside diameter 1.9 cm. The tube makes 18 passes in a shell. Water flows through the shell at a rate of 1.5 kg/s. The water side heat transfer coefficient is 12,000 W/m2°C. Oil properties at 100 °C are: Cp = 2219J/(kg.), k = 0.137...
Problem 1 (20 marks): A 1-m x 1-m surface at 100 °C is to be cooled...
Problem 1 (20 marks): A 1-m x 1-m surface at 100 °C is to be cooled by attaching to it 5-cm long, 0.25- cm-thick square aluminum fins (k = 237 W/m- K), with an edge-to-edge distance between the fins of 0.25 cm. The temperature of the fin tip is the same as surrounding medium at 30°C, und the heat transfer coefficient on the surfaces is 35 W/m2 K. Determine: temperature at distance of 2 cm away from the base the...
Problem 3 (30): Steam at Too,1 340 °C flows in a cast iron pipe [k- 80 W/m.°C] whose inner and outer diameter are Di 6 cm and D2 -8 cm, respectively. The pipe is covered with a 4-cm thick glass wool...
Problem 3 (30): Steam at Too,1 340 °C flows in a cast iron pipe [k- 80 W/m.°C] whose inner and outer diameter are Di 6 cm and D2 -8 cm, respectively. The pipe is covered with a 4-cm thick glass wool insulation [k-0.05 W/ m°C]. Heat is lost to the surroundings at Too,2 - 21°C by natural convection and radiation, with a combined heat transfer coefficient of h- 18 W/m2 °C. Taking the heat transfer coefficient inside the pipe to...
Estimate the time required to kook a hot dog in boiling water. Assume that the hot dog is initially at 6°C, that the convection heat transfer coefficient is 100 W/m2 k, and that the final temperature is 80°C at the centerline. Treat the hot dog as a long cylinder of 20 mm diameter having the properties: ρ 880 kgm, C,-3.350 kJ/kg·k, and k 0.52 W/mk 52.
A freezer compartment is covered with a 3-mm-thick layer of frost at the time it malfunctions. If the compartment is in ambient air at 20°C and a coefficient of h 2 W/m2 、K characterizes heat transfer by natural convection from the exposed surface oi the layer, estimate the time required to completely melt the frost. The frost may be assumed to have a mass density of 700 kg/m3 and a latent heat of fusion of 334 kJ/kg
Problem 2: A 25 mm thick glass sheet needs to be rapidly quenched by air jets (h-800 W/m2-K, T-25°C) on both sides to "temper" it. The glass starts at an initial temperature of 800°C, and its surface must be cooled to less than 150°C. (a) What type of transient analysis is appropriate for this problem? You must justify your answer. (b) How long would this process take? (c) What is the glass centerline temperature at that time?
The temperature distribution across a wall 0.2 m thick at a certain instant of time is T(x) = a + bx + cxº, where T is in degrees Celsius and x is in meters, a = 200°C, b = -190°c/m, and c = 30°C/m2. The wall has a thermal conductivity of 1 W/m.k. (a) On a unit surface area basis, determine the rate of heat transfer into and out of the wall and the rate of change of energy stored...
Heat Transfer Problem:
A sphere of pure aluminum weighing 6 kg and initially at a temperature of 300°C is cooled by an air stream at 20°C with a convection coefficient of 24 W/m2 C. Calculate the time required to cool the sphere center to 100°C.
i
figured out the first question but im not sure how to answer
question 2 and 3?
i
have figured out question 2. Question #3 is what is diffcult to
grasp because i have to guess my Fo #. Fo=time
1. To reduce building heating costs, modern building codes in many parts of the country require the use of double-pane windows (sometimes, called "double-glazed" or "thermopane" windows). Some of In one design of a double-pane window, each glass layer is...
A bare copper cable 2.5 cm in diameter is situated in still air at 15°C. A current of 800 Amps is passed along the cable. Heat is transferred from the cable to its surroundings by natural convection for which the heat transfer coefficient may be expressed as 2.95025 W/m2 K. Determine whether or not it may be assumed that the temperature across the copper cross section is uniform and what the equilibrium temperature of the cable surface will be. If...
PROBLEM 4 (20 pts) Water at 25 °C is used to cool oil from 120 °C to 80 °C. Oil flows at a rate of 1 kg/s in a tube of inside diameter 1.6 cm and outside diameter 1.9 cm. The tube makes 18 passes in a shell. Water flows through the shell at a rate of 1.5 kg/s. The water side heat transfer coefficient is 12,000 W/m2°C. Oil properties at 100 °C are: Cp = 2219J/(kg.), k = 0.137...
Problem 1 (20 marks): A 1-m x 1-m surface at 100 °C is to be cooled by attaching to it 5-cm long, 0.25- cm-thick square aluminum fins (k = 237 W/m- K), with an edge-to-edge distance between the fins of 0.25 cm. The temperature of the fin tip is the same as surrounding medium at 30°C, und the heat transfer coefficient on the surfaces is 35 W/m2 K. Determine: temperature at distance of 2 cm away from the base the...
Problem 3 (30): Steam at Too,1 340 °C flows in a cast iron pipe [k- 80 W/m.°C] whose inner and outer diameter are Di 6 cm and D2 -8 cm, respectively. The pipe is covered with a 4-cm thick glass wool insulation [k-0.05 W/ m°C]. Heat is lost to the surroundings at Too,2 - 21°C by natural convection and radiation, with a combined heat transfer coefficient of h- 18 W/m2 °C. Taking the heat transfer coefficient inside the pipe to...
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