Concept explainers
Videos
Show that the rate of heat conduction per unit length through a long, hollow cylinder of inner radius
where
Want to see the full answer?
Check out a sample textbook solution
Chapter 2 Solutions
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
- A plane wall, 7.5 cm thick, generates heat internally at the rate of 105 W/m3. One side of the wall is insulated, and the other side is exposed to an environment at 90C. The convection heat transfer coefficient between the wall and the environment is 500 W/m2 K. If the thermal conductivity of the wall is 12 W/m K, calculate the maximum temperature in the wall.arrow_forwardA spherical container, with an inner radius r1= 1.4 m and an outer radius r2 = 1.45 m has its inner surface subjected to a uniform heat flux of q1= 7 kW/m2. The outer surface of the container has a temperature T2 = 25°C, and the container wall thermal conductivity is k = 1.5 W/m∙K. Determine the inner surface temperature of the container. (Round your answer to the nearest whole number.) The inner surface temperature is ____°C.arrow_forwardQ 1.1: The inner and outer surfaces of a 5-m x 6-m brick wall of thickness 30 cm and thermal conductivity 0.69 W/m · °C are maintained at temperatures of 20°C and 5°C, respectively. Determine the rate of heat transfer through the wall, in W.arrow_forward
- The resistance of a copper wire used to make a motor is 0.5 Ω at 25 oC and 0.8 Ω at the motor’s operating temperature. Determine the operating temperature and the rise in temperature of the motor, given that copper has a temperature constant of 234.5 oC.arrow_forward3. A lumped system with a volume of 0.003 m³ and a surface area of 0.08 m² is made of a material with density of 3800 kg/m³, thermal conductivity of 300 W/m K, and specific heat of 200 J/kg K. If the system is exposed to a convection environment with h = 60 W/m2 K, what is the approximate time it will take for this system to reach equilibrium with the environment? Express your answer in minutes.arrow_forwardA 0.6-cm-diameter mild steel rod at 38°C is suddenly immersed in a liquid at 93°C with h=110 W/m2 K. Determine the time required for the rod to warm to 88°C. Thermal conductivity (k) = 43 W/(m K); Specific heat (c) = 473 J/(kg K); Density = 7801 kg/m3 Thermal diffusivity (α) = 1.172 *10–5 m2/s.arrow_forward
- 10 m long pipe is being used to deliver steam through a processing plant. The inner radius of the pipe is r1 = 6 cm and the thickness of the pipe is 2 cm. Thermal conductivity k = 8 W/m⋅K and the average temperature steam flowing through the pipe is 160°C, the average convection heat transfer coefficient on the inner surface is given to be h = 20 W/m2⋅K. If the average temperature on the outer surfaces of the pipe is T2 = 70°C, (a) express the differential equation and the boundary conditions for steady operating conditions, (b) determine a relation for the variation of temperature in the pipe, and (c) evaluate the rate of heat loss (heat of conduction) from the steam through the pipe.arrow_forwardIf H is the work output of a heat engine and Q is the total heat input of an engine, then determine its thermal efficiency.arrow_forwardTwo metal rods of equal length-one aluminum, the other stainless steel-are connected in parallel with a temperature of 18.0 ∘C at one end and 110 ∘C at the other end. Both rods have a circular cross section with a diameter of 6.00 cm Determine the length the rods must have if the combined rate of heat flow through them is to be 17.5 JJ per second. If the length of the rods is doubled, by what factor does the rate of heat flow change?arrow_forward
- Two surfaces of a 2-cm-thick plate are maintained at 0°C and 100°C, respectively. If it is determined that heat is transferred through the plate at a rate of 500 W/m2 , determine its thermal conductivity.arrow_forwardThe roof of an electrically heated house is 7 m long, 10 m wide, and 0.25 m thick. It is made of a flat layer of concrete whose thermal conductivity is 0.92 W/m·°C. During a certain winter night, the temperatures of the inner and outer surfaces of the roof were measured to be 15°C and 4°C, respectively. The average rate of heat loss through the roof that night was (a) 41 W (b) 177 W (c) 4894 W (d) 5567 W (e) 2834 Warrow_forwardWhat are the mechanisms of heat transfer?arrow_forward
Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning