An 8-m long square duct with thin metal walls is hanging in a room where the temperature is 10 °C. Air enters the duct at 75 °C. The air has a specific heat of 1000 J/kg K and is flowing at 0.015 kg/s. The internal convection coefficient is 25 W/m2 K, and the external convection coefficient is 15 W/m2 K. The perimeter length of the duct is 18 cm. Neglecting radiation, what is the temperature of the air at the duct exit? (a) 10.2°C (b) 16.2'C (c) 25.0°C (d) 36.4°C (e) 42.5°C (f) 61.1'C (g) 74.8°C

An 8-m long square duct with thin metal walls is hanging in a room where the temperature is 10 °C. Air enters the duct at 75 °C. The air has a specific heat of 1000 J/kg K and is flowing at 0.015 kg/s. The internal convection coefficient is 25 W/m2 K, and the external convection coefficient is 15 W/m2 K. The perimeter length of the duct is 18 cm. Neglecting radiation, what is the temperature of the air at the duct exit? (a) 10.2°C (b) 16.2'C (c) 25.0°C (d) 36.4°C (e) 42.5°C (f) 61.1'C (g) 74.8°C

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

See similar textbooks

Similar questions

H.W1 Consider a person standing in a room. Determine the total rate of heat transfer from this person if the exposed surface area and temperature are 1.6m² and 29°C, respectively. Assume that the convection heat transfer coefficient is 6W/m².K and the emissivity of a person is 0.95. The air temperature in the room is maintained at 22°C at all times of the year. In summer, the wall and ceiling temperatures are observed to be 25°C, while in winter, they are 10°C. Ans: Qrotal =104.4 W In Summer Qrotal =231.3 W In Winter
S Ab Hello brother, Theed a safe handwritten answer as soon as possible, please Quiz 6: An ordinary egg can be approximated as a 5.5cm diameter sphere whose properties are roughly k = 0.6 W/m °C and a = 0.14×106 m²/s. The egg is initially at a uniform temperature of 8 °C and is dropped into a boiling water at 97 °C. Taking the convection heat transfer coefficient to be h = 1400 W/m².°C. Determine by using the teat transient equations only: a) how long it will take for the center b) The surface temperature of the egg at the same time in (a)? of the egg to reach 70 °C? The total heat transfer rate into the egg during the heating process?
The convection coefficient for a hot a fluid flowing over a cool surface is 150 W/m^2. The fluid temperature is 410 K and the surface is held at 290 K. Determine the heat transfer per unit surface area from the fluid to the surface.
In a dairy operation, milk at a flow rate of 0.25m3/hr and a cow-body temperature of 38.6°C must be chilled to a safe-to- store temperature of 13°C. Cold water at 2.2°C is available at a flow rate of 0.94m3/hr. The density and specific heat of milk are 1030 kg/m3 and 3860 J/kg.K, respectively. The density and specific heat of water is 1000 kg/m3 and 4187 J/kg.K. The chilling process is done by a double pipe counter-flow exchanger with an overall heat transfer coefficient U=1000 W/m2.K. The pipe of the heat exchanger has a 50-mm diameter with negligible thickness. Determine the pipe length L required. Select one: O a. 2.28 m O b. 4.28 m O c. 3.28 m O d. 1.28 m
Steam at 280° C flows in a stainless steel pipe (k = 15 W/m⋅K) whose inner and outer diameters are 5 cm and 5.5 cm, respectively. The pipe is covered with 3-cm-thick glass wool insulation (k = 0.038 W/m⋅K). Heat is lost to the surroundings at 5° C by natural convection and radiation, with a combined natural convection and radiation heat transfer coefficient of 22 W/ m2⋅K.Taking the heat transfer coefficient inside the pipe to be 80 W/ m2⋅K.Determine the rate of heat loss from the steam per unit length of the pipe and Determine the temperature decrease between the inner pipe surface and the outer insulation surface.
Determine the convection heat transfer coefficient (in W/m2-K) for air flowing at a velocity of 3 m/s in a 10-cm diameter and 10-m long tube. Air enters the tube at 10°C and leaves at 20°C, i.e. air is heated. Take the property of air at 1 atm and assume flow to be fully developed. For air at 1 atm: Temperature k, W/m-K v, m?/s Pr 15°C 0.02476 1.470x10-5 0.7323 20°C 0.02514 1.516×10-5 0.7309 25°C 0.02551 1.562x105 0.7296
A mercury-in-glass thermometer having a diameter of 6 mm is placed in a verti- cal position to measure the air temperature in a metal warehouse in the summer. The walls of the warehouse are at 50°C. The convection coefficient is 7 W/m² - °C, and the emissivity of the thermometer may be taken as € = 0.9. Calculate the temperature indicated by the thermometer if the air temperature is 32°C.
The temperature of a cylindrical tank containing liquid nitrogen is -10 ° C. Tank diameter is 16 cm. The amount of heat lost by convection and radiation from the tank to the environment is 65.5 W / m. Calculate the temperature of the environment where the tank is located: h = 4.35 W / m2K, ∈ = 1.
The outside temperature on a particular winter's day is 0°C. Consider two identical houses, each of external surface area 200 m² and internal temperature 20°C. The walls of the first are constructed of a single layer of brick, of thermal conductivity 1 W m-1 °C-1 and thickness 20 cm. What is the heat flux Q out of this house? What is its rate of heat loss in Watts? The walls of the second house are constructed of two layers of brick, each 10 cm thick, and a layer of insulation, also 10 cm thick. The insulation is made mostly out of air, thermal conductivity 0.01 W m of heat loss from this house? How different would your answer be if you neglected the layers of brick in this calculation? -1 °C-1. what are the heat flux and the rate
A 0.5-ampere current is flowing through a long electrically conducting cylindrical rod. The diameter of the rod is 6 mm, the electrical resistance of the rod is R = 2000 /m, and k =0.9 W/m K for the rod. The rod is encased in a 2-mm thick Pyrex tube and a 20°C liquid is flowing over the outer surface of the Pyrex tube. The convection heat transfer coefficient for the liquid h= 800 W/m2 . K. The interfacial conductance (contact resistance) at the interface between the rod and the Pyrex tube is h = 1200 W/m² - K. a) Compute the rate of heat generation in the rod and use it compute the volumetric rate of heat generation. b) Find the temperature drop across the interface between the outer surface of the rod and the inner surface of the Pyrex tube. c) Find the temperature at the center of the rod.
A pipe in a manufacturing plant is transporting superheated vapor at a mass flow rate of 0.3 kg/s. The pipe is 10 m long, has an inner diameter of 5 cm and pipe wall thickness of 6 mm. The pipe has a thermal conductivity of 17 W/m.K, and the inner pipe surface is at a uniform temperature of 120 °C. The temperature drop between the inlet and the exit of the pipe is 7 °C, and the constant pressure specific heat of vapor is 2190 J/kg.°C. If the air temperature in the manufacturing plant is 25°C, determine the heat transfer coefficient as a result if convection between the outer pipe surface and the surrounding air. T(r) = 120°C Superheated Air, 25°C r2 vapor r1 0.3 kg/s L = 10 m Tin-Tout = 7°C
A horizontal pipe with a diameter of 18 cm and a length of 10 m, which contains hot oil and has a surface temperature of 383.8 ° C, has an atmospheric pressure of 760 mm Hg. It is located in an environment (open air) where the temperature is 25 °C. Determine the rate of heat transfer from the pipe to the air (the heat transferred by radiation will be neglected).