Determine the resistance of an aluminium coil of 140 cm as diameter consists of 15800 turns and the mean length per turn is 4305 cm. Take the electrical conductivity of the aluminium coil as 0.24 MS/m. Solution: Area of Cross-section of the Coil (in m2) 1.53 Total Length (in m) 680190 The Resistance of the Coil (in 2) 1.849

Determine the resistance of an aluminium coil of 140 cm as diameter consists of 15800 turns and the mean length per turn is 4305 cm. Take the electrical conductivity of the aluminium coil as 0.24 MS/m. Solution: Area of Cross-section of the Coil (in m2) 1.53 Total Length (in m) 680190 The Resistance of the Coil (in 2) 1.849

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 1.37P: 1.37 Mild steel nails were driven through a solid wood wall consisting of two layers, each 2.5-cm...

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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.
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.
2.38 The addition of aluminum fins has been suggested to increase the rate of heat dissipation from one side of an electronic device 1 m wide and 1 m tall. The fins are to be rectangular in cross section, 2.5 cm long and 0.25 cm thick, as shown in the figure. There are to be 100 fins per meter. The convection heat transfer coefficient, both for the wall and the fins, is estimated to be K. With this information determine the percent increase in the rate of heat transfer of the finned wall compared to the bare wall.
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.
A 1.69 m wide by 1.06 m high metal plate must be insulated to prevent contact burn injuries. If the heat transfer rate is 131 W and the temperature across the insulation must be reduced from 87.9°C to 40.2°C, what is the minimum thickness (in cm) of insulation required [round your final answer to two decimal places]? {kins = 0.033 W/m∙K}
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Consider a house that has a 10-m × 20-m base and a 4-m-high wall. All four walls of the house have an R-value of 2.31 m2 · °C/W. The two 10-m × 4-m walls have no windows. The third wall has five windows made of 0.5-cm-thick glass (k = 0.78 W/m · °C), 1.2 m × 1.8 m in size. The fourth wall has the same size and number of windows, but they are double paned with a 1.5-cm-thick stagnant air space (k = 0.026 W/m · °C) enclosed between two 0.5-cm-thick glass layers. The thermostat in the house is set at 22°C and the average temperature outside at that location is 8°C during the seven-month long heating season. Disregarding any direct radiation gain or loss through the windows and taking the heat transfer coefficients at the inner and outer surfaces of the house to be 7 and 15 W/m2 · °C, respectively, determine the average rate of heat transfer through each wall.
Determine the resistance (in F-h/BTU) of a hollow cylinder with an inside and outside radius of 2 in and 2.1 in, respectively. The length of the cylinder is 3 ft while the thermal conductivity is 24 BTU/hr-ft-F. Correct Answer: 1.0784994169E-4 ± 1%
To cool hot oil, an engineer has suggested that the oil be pumped through a pipe submerged in a nearby lake. The pipe (external diameter = 15 cm) will be placed in the horizontal direction. The temperature of the outer surface of the pipe averages 125 ° C. The surrounding water temperature is assumed to be constant at 15 ° C. Pipe length 100 m. If it is assumed that there is no water movement. a. Determine the convective heat transfer coefficient of the outer pipe surface to the water. = ..... Watt / (m² ° C) b. Determine the heat transfer rate from the pipe to the water. = ..... kW
A 3-meter - long steel pipe has its upper end leaning against a vertical wall and lower end on a level ground. The lower end moves away at a constant rate of 2 cm/s. How fast is the pipe rotating when the lower end is 2 meters from the wall in rad/sec?0.009840.008940.004890.00725
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