Showing 161 to 170 of 1972 Questions
  • A steam pipe of 0.12-m outside diameter is insulated with a layer of calcium silicate. (a) If the insulation is 20 mm thick and its inner and outer surfaces are maintained at Ts,1 = 800 K and Ts.2 = 490 K, respectively, what is the heat loss per unit length (q') of the pipe? function of the dimensionless radial coordinate, (r – r1) / (

  • Consider the water heater described in Problem 1.37. We now wish to determine the energy needed to compensate for heat losses incurred while the water is prescribed temperature of 55°C. The cylindrical storage tank (with flat ends) has a capacity of 100 gallons, and foamed urethane is used to insulate the side and end walls from ambient

  • A thin electrical heater is wrapped around the outer surface of a long cylindrical tube whose inner surface is maintained at a temperature of 5°C. The tube wall has inner and outer radii of 25 and 75 mm, respectively, and a thermal conductivity of 10 W/m. K. The thermal contact resistance between the heater and the outer surface of the t

  • 1n the previous problem, the electrical power required to maintain the heater at To = 25°C depends on the thermal conductivity of the wall material k, the thermal contact resistance Rt,c, and the convection coefficient h. Compute and plot the separate effect of changes in k (1 < k < 200 W/m ∙ K), Rt,c (0 < Rt,c < 0.1 m ∙ K/W)

  • A stainless steel (AISI 304) tube used to transport a chilled pharmaceutical has an inner diameter of 36 mm and a wall thickness of 2 mm. The pharmaceutical and ambient air are at temperatures of 6°C and 23°C, respectively, while the corresponding inner and outer convection coefficients are 400 W/m2 ∙ K and 6 W/m2 ∙ K respec

  • Superheated steam at 575°C is routed from a boiler to the turbine of an electric power plant through steel tubes (k = 35 W/m ∙ K) of 300 mm inner diameter and 30 mm wall thickness. To reduce heat loss to the surroundings and to maintain a safe-to-touch outer surface temperature, a layer of calcium silicate insulation (k = 0.10 W/m

  • A thin electrical heater is inserted between a long circular rod and a concentric tube with inner and outer radii of 20 and 40 mm. The rod (A) has a thermal conductivity of k A = 0.15 W/m. K, while the tube (B) has a thermal conductivity of k B = 1.5 W/m. K and its outer surface is subjected to convection with a fluid of temperature TW

  • A wire of diameter D = 2 mm and uniform temperature T has an electrical resistance of 0.01 n/m and a current flow of 20 A. (a) What is the rate at which heat is dissipated per unit length of wire? What is the heat dissipation per unit volume within the wire? (b) If the wire is not insulated and is in ambient air and large surrounding

  • A 2-mm-diameter electrical wire is insulated by a 2-mm-thick rubberized sheath (k = 0.13 W/m ∙ K), and the wire/sheath interface is characterized by a thermal contact resistance of R c = 3 X 10-4 m2 ∙ K/W. The convection heat transfer coefficient at the outer surface of the sheath is 10 W/m2 ∙ K, and the temperature of t

  • Electric current flows through a long rod generating thermal energy at a uniform volumetric rate of q = 2 X 106 W/m3. The rod is concentric with a hollow ceramic cylinder, creating an enclosure that is filled with air. The thermal resistance per unit length due to radiation between the enclosure surfaces is Rrad =0.30 m ∙