An electrical resistor is connected to a battery, asshown schematically. After a brief transient, the resistorassumes a nearly uniform, steady-state temperature of95°C, while the battery and lead wires remain at theambient temperature of 25°C. Neglect the electrical resistance of the lead wires.
(a) Consider the resistor as a system abut whicha control surface ¡s placed and Equation 1,12c is applied. Determine the corresponding values of
(b) If electrical energy is dissipated uniformly within theresistor, which ¡s a cylinder of diameter
(e) Neglecting radiation from the resistor, what is theconvection coefficient?
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Fundamentals of Heat and Mass Transfer
- 1.4 To measure thermal conductivity, two similar 1-cm-thick specimens are placed in the apparatus shown in the accompanying sketch. Electric current is supplied to the guard heater, and a wattmeter shows that the power dissipation is 10 W. Thermocouples attached to the warmer and to the cooler surfaces show temperatures of 322 and 300 K, respectively. Calculate the thermal conductivity of the material at the mean temperature in W/m K. Problem 1.4arrow_forwardA 0.6-cm diameter mild steel rod at 38C is suddenly immersed in a liquid at 93C with hc=110W/m2K. Determine the time required for the rod to warm to 88C.arrow_forward(a) The heating power generated by the nuclear heating rod and the inner temperature of the metallic cylinder, T2. (b) The temperature liquid X, which is located between the nuclear heating rod and the meatllic cylinder, Tliquid. (c) The temperature at the surface of the heating rod, T1. (d) If the salt solution temperature is 300 degree Celcius, what is the value of convection heat transfer coefficient, h of the salt solution ? (e) If the heating rod is not covered by metallic cylinder and corresponds to the result of part (c) and (d), how much the rate of energy transfer to the salt solution ? (f) Compare and discuss the difference of heat transfer with and without the matallic cylinder.arrow_forward
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- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning