A steel bar 7 cm long is welded end to end to a copper bar 21 cm long. Both bars are insulated perfectly on their sides. Each bar has a square cross-section 2.0 cm on a side. The free end of the steel bar is maintained at 100 deg C by placing it in contact with steam, and the free end of the copper bar is maintained at 0 deg C by placing it in contact with ice. Find the temperature (in deg C) at the junction of the two bars. kst = 50.2 W/m.K; kcu = 385 W/m.K Round your answer to 2 decimal places. (Topic: Heat Transfer, Waves, and Oscillations)

A steel bar 7 cm long is welded end to end to a copper bar 21 cm long. Both bars are insulated perfectly on their sides. Each bar has a square cross-section 2.0 cm on a side. The free end of the steel bar is maintained at 100 deg C by placing it in contact with steam, and the free end of the copper bar is maintained at 0 deg C by placing it in contact with ice. Find the temperature (in deg C) at the junction of the two bars. kst = 50.2 W/m.K; kcu = 385 W/m.K Round your answer to 2 decimal places. (Topic: Heat Transfer, Waves, and Oscillations)

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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2.55 A long, 1-cm-diameter electric copper cable is embedded in the center of a 25-cm-square concrete block. If the outside temperature of the concrete is 25oC and the rate of electrical energy dissipation in the cable is 150 W per meter length, determine temperatures at the outer surface and at the center of the cable.
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.
2.2 A small dam, which is idealized by a large slab 1.2 m thick, is to be completely poured in a short Period of time. The hydration of the concrete results in the equivalent of a distributed source of constant strength of 100 W/m3. If both dam surfaces are at 16°C, determine the maximum temperature to which the concrete will be subjected, assuming steady-state conditions. The thermal conductivity of the wet concrete can be taken as 0.84 W/m K.
2.44 To determine the thermal conductivity of a long, solid 2.5-cm-diameter rod, one half of the rod was inserted into a furnace while the other half was projecting into air at . After steady state had been reached, the temperatures at two points 7.6 cm apart were measured and found to be and , respectively. The heat transfer coefficient over the surface of the rod exposed to the air was estimated to be 22.7 . What is thermal conductivity of the rod?
A window panel that measures 20.0 cm by 15.0 cm is set into the front door of a house. The glass is 0.32 cm thick. The temperature outdoors is −15°C and inside is 22°C. The single-paned window is replaced by a double-paned window with an argon gas gap of 12mm between the two panes. The inner surface of the inner pane is at 22°C, and the outer surface of the outer pane is at −15°C. ( C glass=0.63 W/mK)Specific heat of Argon is 0.52 J/g K. Latent Heat of Fusion of Argon is 1.188 kJ/mol .calculat and compare the heat transfers
a pipe with an outside diameter of 2.5 inches is insulated with 2 inches layer of asbestos ( K= 0.396(btu-in)/(hr-ft-F) followed by a layer of cork 1.5 inches thick ( K= 0.30 (btu-in)/ft (hr-ft-F). if the temperature of the outer surface of the cork and pipe is 90 F and 290 F RESPECTIVELY, calculate the heat loss per 100 ft of insulated pipe in btu/hr
In an experiment to determine the thermal conductivity of a new metal alloy, a bar of the metal is completely surrounded by insulation and exposed to 705 W of constant heat energy at one end. The bar has a radius of 0.069 m and a length of 0.365 m. The entire set-up is place in a cold room and once the system has reached steady state conditions, the temperature at the hot end is measured to be 67.3°C and the temperature at the cold end is measured to be 10.5°C. What is the thermal conductivity (in W/m∙K) of the metal alloy [round your final answer to zero decimal places]?
Q4. Two long rods of the same diameter, one of brass(k= 85 W/mK) and the other of copper (k=375 W/mK) have one of their ends inserted in a furnace and the other ends exposed to the same atmosphere. At a distance of 105mm away from the furnace, the temperature of the brass rod is 120' C. Find the distance from the furnace in which the copper rod have the same temperature.
A small sphere (emissivity = 0.745, radius = r1) is located at the center of a spherical asbestos shell (thickness = 1.72 cm, outer radius = r2; thermal conductivity of asbestos is 0.090 J/(s m Co)). The thickness of the shell is small compared to the inner and outer radii of the shell. The temperature of the small sphere is 727 °C, while the temperature of the inner surface of the shell is 406 °C, both temperatures remaining constant. Assuming that r2/r1 = 6.54 and ignoring any air inside the shell, find the temperature in degrees Celsius of the outer surface of the shell.
8.9 One end of a 9-in long × 7-in diameter copper bar is heated to 59.4°F, the far end of the bar is held at 23°C. If the sides of the bar are covered with thermal insulation, what is the rate of heat transfer? 8.11 When the far end of the copper bar in Prob. 8.9 has a 30-ft2 cooling fin attached to the end of the bar and is cooled by air convection, the temperature of the fin rises to t °F. If the temperature of the air is 23°F and the coefficient of heat transfer of the surface is 0.22 BTU/h, what is the value of t?
A pipe with an outside diameter of 3.5 in. is insulated with a 3 in. layer of asbestos (ka=0.396 BTU-in/hr- ft2 - 0 F), followed by a layer of cork 1.5 in. thick (kc=0.30 BTU-in/hr-ft2 - 0 F). If the temperature of the outer surface of the cork and pipe is 1000 F and 3000 F, respectively, calculate the heat lost per 100ft or insulated pipe.
One wall of a refrigerated warehouse is 10.0-m-high and 5.0-m-wide. The wall is made of three layers: 1.0-cm-thick aluminum (k = 200 W/m·K), 8.0-cm-thick fibreglass (k =0.038 W/m·K), and 3.0-cm thick gypsum board (k = 0.48 W/m·K). The warehouse inside and outside temperatures are 210°C and 20°C, respectively, and the average value of both inside and outside heat transfer coefficients is 40 W/m2·K. (a) Calculate the rate of heat transfer across the warehouse wall in steady operation. (b) Suppose that 400 metal bolts (k = 43 W/m·K), each 2.0 cm in diameter and 12.0 cm long, are used to fasten (i.e., hold together) the three wall layers. Calculate the rate of heat transfer for the “bolted” wall. (c) What is the percent change in the rate of heat transfer across the wall due to metal bolts?