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A mild steel plate that is 1.4 in. thick and cross section 2 ft. x 2...
A wall panel is insulated on the back and exposed to solar radiation on the front...
A wall panel is insulated on the back and exposed to solar radiation on the front surface. The exposed surface of the plate has an absorptivity α = 0.8 for radiation (i.e. 80% of radiant energy is absorbed). Solar radiation arrives to the panel at a rate of 1 kW⁄m2. The panel emissivity ϵ = 1 and the surrounding air temperature is 25°C. a. If we assume radiation is the only mechanism of heat transfer, in this scenario determine the...
A 50 mm thick steel plate (AISI347) has a uniform heat flux applied to its bottom...
A 50 mm thick steel plate (AISI347) has a uniform heat flux
applied to its bottom surface by a heater. The heater is in contact
with the steel plate, and the interface between the heater and
steel has a contact resistance of 2.0 x 10-4
m2*K/W. The top surface of the plate is exposed to
surrounding air (T = 20oC, h = 10 W/m2*K) and
exchanges radiation with surroundings at Tsur =
10oC. The emissivity of the plate is 0.85....
1. A ¾ inch (nominal), Schedule 40, mild steel pipe carries 40 psia steam through a...
1. A ¾ inch (nominal), Schedule 40, mild steel pipe carries 40 psia steam through a room having an air temperature of 80°F. The pipe is covered with a 0.125 ft thick layer of fiberglass insulation having a thermal conductivity of 0.037 Btu/(h ft ‘F). The hi value on the steam side of the pipe is 1000 Btu/h ft2 °F. The ho value on the outside of the insulation is 2.0 Btu/(h ft2 ’F). For the mild steel, k=26Btu/(ft H...
Q2 (a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is exposed...
Q2 (a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is exposed to cooling airflow at 27 "C resulting in the convective coefficient, h = 114 W/m' K. The relevant properties of mild steel are given as follows: Density p= 7850 kg/m . Specific heat c = 475 J/kg K and thermal diffusivity a = 0.043 m/hr Determine: (i) Time required to cool the sphere (lumped parameter system) from 540 °C to 95°C. [7 marks] (ii)...
2. A 6 in thick concrete wall, having thermal conductivity of 0.8Btu/h.ft.°F, is exposed to air...
2. A 6 in thick concrete wall, having thermal conductivity of 0.8Btu/h.ft.°F, is exposed to air at 70°F on one side and air at 20°F on the opposite side. The convective heat transfer coefficients are 2Btu/h.ft.F on the 70°F side and 10 Btu/h.ft'.°F on the 20°F side. Compute the following: 1. Total thermal resistance 2. Rate of heat transfer 3. The surface temperatures of the wall 4. Check the temp. of the wall is within the allowable limit of 50°F
Heat Transfer Problems 1. A window pane (1/8 inch thick) in an old house owned by...
Heat Transfer
Problems 1. A window pane (1/8 inch thick) in an old house owned by a professor is 3 ft. by 4 ft. He likes to be warm in the winter so the inside temperature is kept at 70 °F even when the outside temperature is 10 •F. For this problem assume the inside and outside temperatures are for the window surface. How much heat is transferred through the window (k=.54 BTU/hr ft ° F)? 2. A small heated...
PROBLEM 2.1. Determine the steady-state temperature of the surface of the wire of 0.25 in. diameter...
PROBLEM 2.1. Determine the steady-state temperature of the surface of the wire of 0.25 in. diameter and 2, 1 ft long, carrying a current of 50 A. The convective heat transfer coefficient is 4.0 BTUhr-ft-oF, temperature of the air surrounding the wire is 32°F, the electrical resistivity of the material of the wire is 1.5 μΩ-ft and its thermal conductivity is 11 BTU/hr-ft-up,
An aluminum plate with a thickness of L=5 mm is mounted in a horizontal position, and...
An aluminum plate with a thickness of L=5 mm is mounted in a horizontal position, and its bottom surface is well insulated. A special, thin coating (with emissivity and solar absorptivity of 0.25) is applied to the top surface. The density ρ and specific heat c of aluminum are known to be 2700 kg/m3 and 900 J/kg · K, respectively. Consider conditions for which the plate is initially at a temperature of ??????=25 °C and its top surface is suddenly...
The lower surface of a horizontal aluminum plate 5 in. by 7 in. is heated by...
The lower surface of a horizontal aluminum plate 5 in. by 7 in. is heated by an electric resistance heater that supplies 10 W. The upper surface is cooled by free convection and radiation. The convective transfer coefficient is 1.2 Btu/hr ft2 °F and the air temperature is 70 °F. Surrounding room surfaces are also at 70 °F. Find the surface temperature of the aluminum if it is a) clean and shiny with ε=0.05 b) painted with ε=0.9
PROBLEM 2.1. Determine the steady-state temperature of the surface of the wire of 0.25 in. diamet...
(2.1 for reference, solving 2.2)
PROBLEM 2.1. Determine the steady-state temperature of the surface of the wire of 0.25 in. diameter and 2, 1 ft long, carrying a current of 50 A. The convective heat transfer coefficient is 4.0 BTUhr-ft-oF, temperature of the air surrounding the wire is 32°F, the electrical resistivity of the material of the wire is 1.5 μΩ-ft and its thermal conductivity is 11 BTU/hr-ft-up, PROBLEM 2.2. Considering the wire of Problem 2.1, perform the following parametıri...
A 50 mm thick steel plate (AISI347) has a uniform heat flux
applied to its bottom surface by a heater. The heater is in contact
with the steel plate, and the interface between the heater and
steel has a contact resistance of 2.0 x 10-4
m2*K/W. The top surface of the plate is exposed to
surrounding air (T = 20oC, h = 10 W/m2*K) and
exchanges radiation with surroundings at Tsur =
10oC. The emissivity of the plate is 0.85....
Q2 (a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is exposed to cooling airflow at 27 "C resulting in the convective coefficient, h = 114 W/m' K. The relevant properties of mild steel are given as follows: Density p= 7850 kg/m . Specific heat c = 475 J/kg K and thermal diffusivity a = 0.043 m/hr Determine: (i) Time required to cool the sphere (lumped parameter system) from 540 °C to 95°C. [7 marks] (ii)...
2. A 6 in thick concrete wall, having thermal conductivity of 0.8Btu/h.ft.°F, is exposed to air at 70°F on one side and air at 20°F on the opposite side. The convective heat transfer coefficients are 2Btu/h.ft.F on the 70°F side and 10 Btu/h.ft'.°F on the 20°F side. Compute the following: 1. Total thermal resistance 2. Rate of heat transfer 3. The surface temperatures of the wall 4. Check the temp. of the wall is within the allowable limit of 50°F
Heat Transfer
Problems 1. A window pane (1/8 inch thick) in an old house owned by a professor is 3 ft. by 4 ft. He likes to be warm in the winter so the inside temperature is kept at 70 °F even when the outside temperature is 10 •F. For this problem assume the inside and outside temperatures are for the window surface. How much heat is transferred through the window (k=.54 BTU/hr ft ° F)? 2. A small heated...
PROBLEM 2.1. Determine the steady-state temperature of the surface of the wire of 0.25 in. diameter and 2, 1 ft long, carrying a current of 50 A. The convective heat transfer coefficient is 4.0 BTUhr-ft-oF, temperature of the air surrounding the wire is 32°F, the electrical resistivity of the material of the wire is 1.5 μΩ-ft and its thermal conductivity is 11 BTU/hr-ft-up,
(2.1 for reference, solving 2.2)
PROBLEM 2.1. Determine the steady-state temperature of the surface of the wire of 0.25 in. diameter and 2, 1 ft long, carrying a current of 50 A. The convective heat transfer coefficient is 4.0 BTUhr-ft-oF, temperature of the air surrounding the wire is 32°F, the electrical resistivity of the material of the wire is 1.5 μΩ-ft and its thermal conductivity is 11 BTU/hr-ft-up, PROBLEM 2.2. Considering the wire of Problem 2.1, perform the following parametıri...
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