8. Consider an iron bar, of diameter 4 cm and length 1m, with specific heat c = 0.437 J/(g K), density p = 7.88 g/cm³, and thermal conductivity k = 0.836 W/(cm K). Suppose that the bar is insulated except at the ends, is heated to a constant temperature of 5 degrees Celsius, and the ends are placed in an ice bath (0 degrees Celsius). Compute the temperature (accurate to 3 digits) at the midpoint of the bar after 20 minutes. (Warning: Be sure to use consistent units.) %3D

8. Consider an iron bar, of diameter 4 cm and length 1m, with specific heat c = 0.437 J/(g K), density p = 7.88 g/cm³, and thermal conductivity k = 0.836 W/(cm K). Suppose that the bar is insulated except at the ends, is heated to a constant temperature of 5 degrees Celsius, and the ends are placed in an ice bath (0 degrees Celsius). Compute the temperature (accurate to 3 digits) at the midpoint of the bar after 20 minutes. (Warning: Be sure to use consistent units.) %3D

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 1.3P: 1.3 A furnace wall is to be constructed of brick having standard dimensions of Two kinds of...

See similar textbooks

Similar questions

1.3 A furnace wall is to be constructed of brick having standard dimensions of Two kinds of material are available. One has a maximum usable temperature of 1040°C and a thermal conductivity of 1.7 W/(m K), and the other has a maximum temperature limit of 870°C and a thermal conductivity of 0.85 W/(m K). The bricks have the same cost and are laid in any manner, but we wish to design the most economical wall for a furnace with a temperature of 1040°C on the hot side and 200°C on the cold side. If the maximum amount of heat transfer permissible is 950 , determine the most economical arrangement using the available bricks.
8. Consider an iron bar, of diameter 4cm and length 1m, with specific heat c = 0.437J/(g K), density p= 7.88 g/cm³, and thermal conductivity K = 0.836 W/(cm K). Suppose that the bar is insulated except at the ends, it is heated to a constant tem- perature of 5 degrees Celsius, and the ends are placed in an ice bath (0 degrees Celsius). Compute the temperature (accurate to 3 digits) at the midpoint of the bar after 20 minutes. (Warning: Be sure to use consistent units.)
A large 100-mm thick steel plate is initially at uniform temperature T = 180°C at time t = 0. Both sides of the plate are exposed to 30°C oil with convection coefficient h = 1500 W/m².K. The thermal conductivity, heat capacity, and density of the steel are k = 38 W/m-K, cp = 485 J/kg-K, and p = 7800 kg/m³. a) Find the temperature at the center of the slab when t = 125 s. b) Find the temperature at the surface of the slab when t=125 s.
Q2: 0.2 m diameter, 4 mm thick, k-120 W/m.ºC disc is welded to 10 cm diameter hot bar at 120 °C (heater). The system is exposed to air at 20 °C, heat transfer coefficient is 12 W/m².°C. Calculate the rate of heat transfer through the disc.
As shown in the sketh below, a steam pipe of 0.12-m inside diameter is insulated with a layer of calcium silicate. "2. Ta2} 1. Ta,1} Steam Insulation (a) If the insulation is 10 mm thick and its inner and outer surfaces are maintained at T, = 800 K and Ta = 490 K. respectively,. what is the rate of heat loss per unit length (q) of the pipe, in W/m? (b) Determine the rate of heat loss per unit length (d), in W/m, and outer surface temperature T,2, in K, for the steam pipe with the Inner surface temperature fixed at T = 800 K, inner radius = 0.06 m, and outer radius n = 0.18 m. The outer surface is exposed to an airflow (T 25°C) that maintains a convection coefficient of h = 25 W/m2-K and to large surroundings for which Tur = T, = 25°C. The surface emissivity of calcium silicate is approximately 0.8.
(Q4) A 4m x 6m wall consists of 4 glass windows of 2m x 1.5m dimensions. The wall has thickness of 0.13m and a thermal conductivity of 0.5 W/m.K, while the glass windows are 6 mm thick with a thermal conductivity of 1.228 W/m.K. The values of intemal and external surface conductance for the wall (including glass) are 7.8 W/m? K and 34.4 W/m².K, respectively. The intemal and extemal temperatures are 22° C and 42°C, respectively. Calculate the total heat transfer rate through the wall. What percentage of this heat transfer is through the windows?
1. A beverage cooler is in the shape of a cube, 42 cm on each inside edge. Its 3.0-cm thick wall are made up of plastic (kr = 0.050 W/mK). When the outside temperature is 20°C, how much ice will melt each hour? Tice is 0°C. 2. One of the possible mechanisms of heat transfer in human body is conduction through body fat. Suppose that heat travels through 0.03 m of fat in reaching the skin, which has a total surface area of 1.7 m² and a temperature of 34°C. Find the amount of heat that reaches the skin in half an hour, if the temperature at the body, interior is maintained at the normal value 37°C ? Thermal conductivity of body fat is k = 0.2 J/sm°C. 3. The air in a room is at 25°C and outside temperature is 0°C. The window of the room has an area of 2m² and thickness 2mm. Calculate the rate of loss of heat by conduction through window ? Thermal conductivity for glass is 1 Wm¯'degree!.
A metal rod 1 sq. in. in cross section and 6 in. long is heated at one end and cooled at the other. If the rate of heat input is 3 BTu/hr and the difference in temperature of the two ends is 2 deg. F, what is the coefficient of thermal conductivity in BTU/(hr)(ft²)(⁰F/ft)?
2-88 A 1.5-mm-diameter stainless-steel rod [k = 19 W/m.°C] protrudes from a wall maintained at 45°C. The rod is 12 mm long, and the convection coefficient is 500 W/m² . °C. The environment temperature is 20°C. Calculate the temperature of the tip of the rod. Repeat the calculation for h = 200 and 1500 W/m² . °C.
C:An aluminum fin [k=200 W/m C] 3.0 mm thick Z is fin width-20 cm and 7.5 cm long protrudes from a wall, as in Figure. The base is maintained at 300°C, and the ambient temperature is 50 C with h=10 W/m2°C. Calculate the heat loss from the fin per unit depth of material. 4 deh Pax (I)
To ensure a tight fit, the aluminum rivet used in airplane construction are made slightly larger than the rivet holes and cooled by dry ice (solid CO2) before being driven. If the diameter of a hole is 0.500 cm, what should be the diameter of a rive at 20 degree Celsius if its diameter is equal that of a hole when the rivet is cooled to -78 degree Celsius, the temperature of dry ice? Assume the coefficient of expansion to remain constant. (Given and solutions)
A copper rod has an initial length 5.0 cm and a thermal expansion coefficient of 16 x 106 /K. It is heated from room temperature (22 °C) to a final temperature T, and its final length is 5.0064 cm. What is the final temperature in °C? In your answer, use the relation (L final – Linitial)/Linitial a(Tfinal – Tinitial) where Linitial is the initial length, L final is the final length, Tinitial is the initial temperature, Tfinal is the final temperature, and a is the thermal expansion coefficient. (This question has only one correct answer) a. 133 b. 102 c. 107 d. 141