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

Step 1: Step 2: please give helpful rating Thank you Step 3: Step 4:

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.

Chapter2: Steady Heat Conduction

Section: Chapter Questions

Problem 2.56P

See similar textbooks

Similar questions

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
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.
Solve it
Find the heat flow rate through the composite wall as shown in the following figure. Assume one dimensional flow and take k 1 = 150 W/m degree, k 2 = 30 W/m degree, k 3 = 65 W/m degree, k 4 = 50 W/m degree. AB = 3 cm, BC = 8 cm and CD = 5 cm. The distance between middle horizontal line from the top is 3 cm and from the bottom is 7 cm.
5. Consider a carton of milk that is refrigerated at a temperature of Tm = 5 °C. The kitchen temperature on a hot summer day is T- -30 °C. If the four sides of the carton are of height and width L = 200 mm and w= 100 mm, respectively, determine the heat transferred to the milk carton as it sits on the kitchen counter for durations of t=10 s, 60 s, and 300 s before it is returned to the refrigerator. The convection coefficient associated with natural convection on the sides of the carton is h = 10 W/m²K. The surface emissivity is 0.90. Assume the milk carton temperature remains at 5 °C during the process. Your parents have taught you the importance of refrigerating certain foods from the food safety perspective. Comment on the importance of quickly returning the milk carton to the refrigerator from an energy conservation point of view.
A heat sink is supported by three posts made of A-36 steel and brass, as shown in the figure. The sink is subject to a uniform loading of 50 kN/m along its 800 mm length. The circular posts have a length of 400 mm when no load is applied to the bar, and the temperature is 20 degrees Celsius. Complete the following tasks: 1) Determine the force supported by each post if the bar is subjected to a distributed load and the temperature is raised to 100 degrees. The heat expansion coefficient of brass is 18 x 10 m/mC and of A-36 steel is 12 x 10-6 m/mc. The modulus of elasticity for A-36 steel is 200 GPa and for brass is 110 GPa. 2) Determine whether the posts will enter the plastic region or not. The yield strength of A-36 steel is 250 MPa and for brass is 95 MPa. Justify your answer with calculated values. 30 mm Steel 800 mm 50 kN/m 50 mm Brass 400 mm Steel
3-78 Circular aluminum disk fins of constant rectangular profile are attached to a tube having D - 25 cm outside diamcter with a spacing of 8 mm (that is, 125 fins per l-m tube length). Fins have a thickness t-I mm, beight L- 15 mm, and thermal conductivity k- 200 W/(m- °C). The tube wall is main- tained at a temperature T, = 190°C, and the fins dissipate hcat by convection into ambient air at T. = 40°C with a heat transfer cocfficient h = 80 W/(m.°C). (a) Determine the fin efficiency. (b) Determine the area-weighted fin efficiency. (c) Determine the net heat loss per t-m length of tube. (d) What would be the heat loss per 1-m length of tube if no fins were attached?
n electric generator at a power plant produces energy by passing superheated steam from a high temperature container (reservoir), through a pipe connected to a series of fans, and then into a low temperature reservoir. As the steam passes across the blades of the fans some of the heat energy of the steam is transformed into mechanical energy, which turns the fans which in turn are connected to a generator, which in turn converts the mechanical energy into electrical energy. If the high temperature steam has a temperature of 412.1 K and the low temperature reservoir has a temperature of 105.4 K, what is the Carnot efficiency of this process?
3
2-1. Temperature Response in Cooling a Wire. A small copper wire with a diameter of 0.792 mm and initially at 366.5 K is suddenly immersed in a liquid held constant at 311 K. The convection coefficient h 85.2 W/m K. The physical properties can be assumed constant and are k =374 W/m K, c, = 0.389 kJ/kg K, and p = 8890 kg/m2. (a) Determine the time in seconds for the average temperature of the wire to drop to 338.8 K (one-half the initial temperature difference). (b) Do the same but for h 11.36 W/m2 K (c) For part (b), calculate the total amount of heat removed for a wire 1.0 m р u (A long. (a) t 5.66 s Ans. the Smou hire is lons asbume Nhere rraolius , here radlius yinder hitu x Chapter 14 Principles of Unsteady-State Heat Transfer

SEE MORE QUESTIONS

Recommended textbooks for you

Principles of Heat Transfer (Activate Learning wi…

Mechanical Engineering

ISBN:

9781305387102

Author:

Kreith, Frank; Manglik, Raj M.

Publisher:

Cengage Learning