3. A 3-m-long steel rod (k = 43 W/m K. α = 1.17×10-5 m²/s) is initially at 20°C and is

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Answered: 3. A 3-m-long steel rod (k = 43 W/m K.…

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.

Chapter3: Transient Heat Conduction

Section: Chapter Questions

Problem 3.32P

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Solve (c) please.
Conduction 1. A thermodynamic analysis of a proposed Brayton cycle gas turbine yields P= 5 MW of net power production. The compressor, at an average temperature of T. = 400°C, is driven by the turbine at an average temperature of T₁ = 1000°C by way of an L = 1m-long, d= 70mm - diameter shaft of thermal conductivity k = 40 W/m K. Compressor min T Combustion chamber Shaft L Turbine Th out (a) Compare the steady-state conduction rate through the shaft connecting the hot turbine to the warm compressor to the net power predicted by the thermodynamics- based analysis. (b) A research team proposes to scale down the gas turbine of part (a), keeping all dimensions in the same proportions. The team assumes that the same hot and cold temperatures exist as in part (a) and that the net power output of the gas turbine is proportional to the overall volume of the device. Plot the ratio of the conduction through the shaft to the net power output of the turbine over the range 0.005 m s Ls 1 m. Is a…
O 4-Two identical metal plates (mass m, specific heat = 20°C, and the other is at 90 °C. They are placed in good thermal contact. What is their final temperature? c) have different temperatures; onc is
answer should be k = 4316 N/m
A solid hemisphere of radius 5 cm to be cooled in air (at 20 o C, h=10 W/m 2 .K) from 200 oC to center of 150 oC, assume following sphere properties ρ=8500kg/m3, k=20W/m.K , C=400 J/kg.Ka. List assumptions and justify selected method of solution b. How long does it take to cool the hemisphere? c. What is the temperature of the surface at end of cooling?
An insulated vertical cylindrical vessel of cross- sectional area A = 0.12 m² contains 20 mol of He gas at To = 300 K and Po= 0.5 bar. It is capped by a movable piston of mass m = 150 kg supported from the ceiling by a wire. The top of the vessel is open to the atmosphere (Patm= 1 bar, Tatm= 300K). The wire is cut and the weight falls and com- presses the gas. Patm 160 E Wir og SLOWA He gas 1019 (a) Obtain the pressure and temperature of the gas a short time after the wire has been cut, when a negligible amount of heat transfer has taken place. Comment on whether your solution takes into account the inevitable oscillations of the piston around its equilibrium position before it comes to rest. mut Ispl (b) After a long time, the He gas thermally equilibrates with the environ- ment by heat transfer through the piston. How much heat is exchanged with the environment during this process? Helium can be considered an ideal gas at all conditions of interest, with C₁=3R/2. INST
How long should it take to boil an egg? Model the egg as a sphere with radius of 2.3 cm that has properties similar to water with a density of = 1000 kg/m3 and thermal conductivity of k = 0.606 Watts/(mC) and specific heat of c = 4182 J/(kg C). Suppose that an egg is fully cooked when the temperature at the center reaches 70 C. Initially the egg is taken out of the fridge at 4 C and placed in the boiling water at 100 C. Since the egg shell is very thin assume that it quickly reaches a temperature of 100 C. The protein in the egg effectively immobilizes the water so the heat conduction is purely conduction (no convection). Plot the temperature of the egg over time and use the data tooltip in MATLAB to make your conclusion on the time it takes to cook the egg in minutes.
H2
3.112 A metal rod of length 21, diameter D. and thermal conductivity is inserted into a perfectly insulating wall, exposing one-half of its length to an air stream that is of temperature and provides a convection co- efficient h at the surface of the rod. An electro- magnetic field induces volumetric energy generation at a uniform rate q within the embedded portion of the rod. T=20°C h=100 W/m²K Rod, D. & T L 50 mm D-5 mm 25 W/m-K q=1 x 100 W/m² (a) Derive an expression for the steady-state tempera- ture 7, at the base of the exposed half of the rod. The exposed region may be approximated as a very long fin. (b) Derive an expression for the steady-state tempera- ture T at the end of the embedded half of the rod. (c) Using numerical values provided in the schematic plot the temperature distribution in the rod and de- scribe key features of the distribution. Does the rod behave as a very long fin?
Sipho’s mother is making a fire in the stove inside a shack using coal. A fan is used to extract the flue gasfrom the fire via a chimney made of zinc material. The wall thickness of Chimney is L=4mm and the walltemperature of the chimney on the flue gas side is T_si=60˚C. Sipho, playing outside next to the chimneyexperiences an ambient temperature of 20˚C. The surrounding temperature is T_sur=35˚C and the emissivityis ε=0.95. Assume the convection coefficient is 20W/m2K and the chimney is grey material.Under these conditions determine the outer surface (air side) temperature T_so=? of the chimney.
Two flat infinite slabs, each 5 m thick, are each initially uniform in temperature, with one being at 0° and the other at 20°. At t=0, the two slabs are stacked together (the warmer one at larger y) and both the top and bottom surfaces of the stack are kept at 0°. Find the temperature in the stacked slabs as a function of y and t for t > 0. Write out the heat flow equation, find the general solution, and the specific solution for this arrangement.
Solve please. Should correct

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