All Matches

Solution Library

Expert Answer

Textbooks

Search Textbook questions, tutors and Books

Oops, something went wrong!

Change your search query and then try again

Result Not Found

Books FREE
Tutors
Study Help
Ask a Question

Search
Sign In
Register

study help
engineering
heat and mass transfer fundamentals and applications

Questions and Answers of Heat And Mass Transfer Fundamentals And Applications

The ___________ number is a significant dimensionless parameter for forced convection and the ___________ number is a significant dimensionless parameter for natural convection.(a) Reynolds,
The coefficient of friction Cf for a fluid flowing across a surface in terms of the surface shear stress, ts, is given by (a) 2pV²/Tw (d) 4Tw/pV² W (b) 2Tw/pV² (c) 2Tw/pV²AT (e) None of them
Most correlations for the convection heat transfer coefficient use the dimensionless Nusselt number, which is defined as(a) h/k(b) k/h(c) hLc /k(d) kLc/h(e) k/ρcp
For the same initial conditions, one can expect the laminar thermal and momentum boundary layers on a flat plate to have the same thickness when the Prandtl number of the flowing fluid is(a) Close to
One can expect the heat transfer coefficient for turbulent flow to be ___________ for laminar flow.(a) Less than(b) Same as(c) Greater than
An electrical water (k = 0.61 W/m· K) heater uses natural convection to transfer heat from a 1-cm-diameter by 0.65-m-long, 110 V electrical resistance heater to the water. During operation, the
In turbulent flow, one can estimate the Nusselt number using the analogy between heat and momentum transfer (Colburn analogy). This analogy relates the Nusselt number to the coefficient of friction,
A facility is equipped with a wind tunnel, and can measure the friction coefficient for flat surfaces and airfoils. Design an experiment to determine the mean heat transfer coefficient for a surface
Consider laminar flow over a flat plate. Will the friction coefficient change with distance from the leading edge? How about the heat transfer coefficient?
How are the average friction and heat transfer coefficients determined in flow over a flat plate?
Repeat Prob. 7–14 for water.Data from problem 14Air at 25°C and 1 atm is flowing over a long flat plate with a velocity of 8 m/s. Determine the distance from the leading edge of the plate where
The weight of a thin flat plate 40 cm 3 40 cm in size is balanced by a counterweight that has a mass of 2 kg, as shown in the figure. Now a fan is turned on, and air at 1 atm and 258C flows downward
Engine oil at 80ºC flows over a 10-m-long flat plate whose temperature is 30ºC with a velocity of 2.5 m/s. Determine the total drag force and the rate of heat transfer over the entire plate per
Air at 60ºF flows over a 10-ft-long flat plate at 7 ft/s. Determine the local friction and heat transfer coefficients at intervals of 1 ft, and plot the results against the distance from the leading
Consider laminar flow of a fluid over a flat plate maintained at a constant temperature. Now the free-stream velocity of the fluid is doubled. Determine the change in the drag force on the plate and
A transformer that is 10 cm long, 6.2 cm wide, and 5 cm high is to be cooled by attaching a 10-cm × 6.2-cm-wide polished aluminum heat sink (emissivity = 0.03) to its top surface. The heat sink has
Repeat Prob. 7–26 assuming the heat sink to be blackanodized and thus to have an effective emissivity of 0.90. Note that in radiation calculations the base area (10 cm × 6.2 cm) is to be used, not
Heat dissipated from a machine in operation can cause hot spots on its surface. Exposed hot spots that are a potential to cause thermal burns on human skin tissue are considered to be hazards in the
Air at 1 atm and 20°C is flowing over the top surface of a 0.5-m-long thin flat plate. The air stream velocity is 50 m/s and the plate is maintained at a constant surface temperature of 180°C.
A 5-m-long strip of sheet metal is being transported on a conveyor at a velocity of 5 m/s, while the coating on the upper surface is being cured by infrared lamps. The coating on the upper surface of
Reconsider Prob. 7–42. Using EES (or other) software, investigate the effects of wind velocity and outside air temperature on the rate of heat loss from the wall by convection. Let the wind
Reconsider Prob. 7–39. Using the EES (or other) software, evaluate the effect of the sheet metal velocity on its surface temperature. By varying the sheet metal velocity from 3 to 30 m/s, plot the
Reconsider Prob. 7–45. Using EES (or other) software, investigate the effects of the train velocity and the rate of absorption of solar radiation on the equilibrium temperature of the top surface
The outer surface of an engine is situated in a place where oil leakage can occur. When leaked oil comes in contact with a hot surface that has a temperature above its autoignition temperature, the
Reconsider Example 7–2. Another method that could be explored to keep the engine outer surface temperature below the fire hazard limit of 180°C is to increase the insulation thickness. Increase
Metal plates (k = 180 W/m · K, ρ = 2800 kg/m3, and cp = 880 J/kg · K) with a length of 1 m and a thickness of 2 cm exiting an oven are then conveyed through a 10-m-long cooling chamber at a speed
Air is flowing in parallel over the upper surface of a flat plate with a length of 4 m. The first half of the plate length, from the leading edge, has a constant surface temperature of 50°C. The
Mercury at 25°C flows over a 3-m-long and 2-m-wide flat plate maintained at 75°C with a velocity of 0.8 m/s. Determine the rate of heat transfer from the entire plate. Mercury V = 0.8 m/s T =
Reconsider Prob. 7–55. Using the EES (or other) software, evaluate the local convection heat transfer coefficient, the local surface temperature, and the local film temperature along the plate. By
Liquid mercury at 2508C is flowing in parallel over a flat plate at a velocity of 0.3 m/s. Surface temperature of the 0.1-m-long flat plate is constant at 508C. Determine(a) The local convection heat
Reconsider Prob. 7–57. Using the EES (or other) software, evaluate the local convection heat transfer coefficient, the local surface temperature, and the local film temperature along the plate. By
In flow over blunt bodies such as a cylinder, how does the pressure drag differ from the friction drag?
Why is flow separation in flow over cylinders delayed in turbulent flow?
Reconsider Prob. 7–67E. Using EES (or other) software, investigate the effects of air temperature and wind velocity on the rate of heat loss from the arm. Let the air temperature vary from 20°F to
Consider the flow of a fluid across a cylinder maintained at a constant temperature. Now the free-stream velocity of the fluid is doubled. Determine the change in the drag force on the cylinder and
Consider a person who is trying to keep cool on a hot summer day by turning a fan on and exposing his entire body to air flow. The air temperature is 85°F and the fan is blowing air at a velocity of
Reconsider Prob. 7–70. Using EES (or other) software, investigate the effect of the wind velocity on the surface temperature of the wire. Let the wind velocity vary from 10 km/h to 80 km/h. Plot
Reconsider Prob. 7–76. Using EES (or other) software, plot the temperature of the tank as a function of the cooling time as the time varies from 30 min to 5 h, and discuss the results.Data from
Exhaust gases from a manufacturing plant are being discharged through a 10-m-tall exhaust stack with outer diameter of 1 m. The exhaust gases are discharged at a rate of 1.2 kg/s, while temperature
Repeat Prob. 7–32 for a location at an elevation of 1610 m where the atmospheric pressure is 83.4 kPa.Data from problem 32An array of power transistors, dissipating 6 W of power each, are to be
A stainless steel ball (ρ = 8055 kg/m3, cp = 480 J/kg.K) of diameter D = 15 cm is removed from the oven at a uniform temperature of 350°C. The ball is then subjected to the flow of air at 1 atm
Air at 20°C (1 atm) is flowing over a 5-cm diameter sphere with a velocity of 3.5 m/s. If the surface temperature of the sphere is constant at 80°C, determine(a) The average drag coefficient on the
Ice slurry is being transported in a pipe (k = 15 W/m · K, Di = 2.5 cm, Do = 3 cm, and L = 5 m) with an inner surface temperature of 0°C. The ambient condition surrounding the pipe has a
A 0.2-m-long and 25-mm-thick vertical plate (k = 1.5 W/m ∙ K) separates the hot water from the cold air at 2°C. The plate surface exposed to the hot water has a temperature of 100°C, and the
Reconsider Prob. 9-18. Using the EES (or other) software, investigate the effect of the plate thermal conductivity on the surface temperature exposed to the cold water. By varying the plate thermal
In a food processing plant, hot liquid water is being transported in a pipe (k = 15 W/m ∙ K, Di = 2.5 cm, Do = 3 cm, and L = 10 m). The hot water flowing with a mass flow rate of 0.15 kg/s enters
A 15-cm × 20-cm printed circuit board whose components are not allowed to come into direct contact with air for reliability reasons is to be cooled by passing cool air through a 20-cm-long channel
A tube bank consists of 300 tubes at a distance of 6 cm between the centerlines of any two adjacent tubes. Air approaches the tube bank in the normal direction at 20°C and 1 atm with a mean velocity
Reconsider Prob. 7–85. Using EES (or other) software, investigate the effect of air velocity on the average convection heat transfer coefficient and the cooling time. Let the air velocity vary from
Consider a fluid whose volume does not change with temperature at constant pressure. What can you say about natural convection heat transfer in this medium?
How does the Rayleigh number differ from the Grashof number?
A 0.2-m-long and 25-mm-thick vertical plate (k = 15 W/m ∙ K) separates the hot water from the cold water. The plate surface exposed to the hot water has a temperature of 100°C, and the temperature
Reconsider Prob. 9–28E. Using EES (or other) software, plot the rate of natural convection heat transfer for different orientations of the plate as a function of the plate temperature as the
Repeat Prob. 9–31 assuming the circuit board to be positioned horizontally with(a) Chips facing up(b) Chips facing down.Data from problem 31A 50-cm × 50-cm circuit board that contains 121 square
Water is boiling in a 12-cm-deep pan with an outer diameter of 25 cm that is placed on top of a stove. The ambient air and thesurrounding surfaces are at a temperature of 25°C, and the emissivity of
Repeat Prob. 9–42 for a pan whose outer surface is polished and has an emissivity of 0.1.Data from problem 42Water is boiling in a 12-cm-deep pan with an outer diameter of 25 cm that is placed on
Reconsider Prob. 9–55. Using EES (or other) software, investigate the effect of the surface temperature of the steam pipe on the rate of heat loss from the pipe and the annual cost of this heat
Reconsider Prob. 9-60. Using the EES (or other) software, evaluate the effect of the insulation layer thickness on the outer surface temperature. By varying the insulation layer thickness from 5 to
A hot liquid (cp = 1000 J/kg ∙ K) flows at a flow rate of 0.028 kg/s inside a 5-m-long pipe with an inner diameter of 45 mm and a wall thickness of 5 mm. At the pipe exit, the liquid temperature
A stainless steel spherical tank, with an inner diameter of 3 m and a wall thickness of 10 mm, is used for containing a solution undergoing an exothermic reaction that generates 450 W/m3 of heat. The
A spherical tank (k = 15 W/m ∙ K) with an inner diameter of 3 m and a wall thickness of 10 mm is used for storing hot liquid. The hot liquid inside the tank causes the inner surface temperature to
Why are finned surfaces frequently used in practice? Why are the finned surfaces referred to as heat sinks in the electronics industry?
Why are heat sinks with closely packed fins not suitable for natural convection heat transfer, although they increase the heat transfer surface area more?
Consider a heat sink with optimum fin spacing. Explain how heat transfer from this heat sink will be affected by(a) Removing some of the fins on the heat sink(b) Doubling the number of fins on the
Aluminum heat sinks of rectangular profile are commonly used to cool electronic components. Consider a 7.62-cm-long and 9.68-cm-wide commercially available heat sink whose cross section and
Reconsider the heat sink in Prob. 9–75. In order to enhance heat transfer, a shroud (a thin rectangular metal plate) whose surface area is equal to the base area of the heat sink is placed very
A 15-cm-wide and 18-cm-high vertical hot surface in 20°C air is to be cooled by a heat sink with equally spaced fins of rectangular profile. The fins are 0.1 cm thick, 4 cm wide, and 18 cm long in
Reconsider Prob. 9–89E. Using EES (or other) software, investigate the effect of the air gap thickness on the rates of heat transfer by natural convection and radiation, and the R-value of
A 6-in-wide and 8-in-high vertical hot surface in 78°F air is to be cooled by a heat sink with equally spaced fins of rectangular profile. The fins are 0.08 in thick and 8 in long in the vertical
Reconsider Prob. 9–91. Using EES (or other) software, plot the rate of heat loss from the water by natural convection as a function of the ambient air temperature as the temperature varies from
Consider two concentric horizontal cylinders of diameters 55 cm and 65 cm, and length 125 cm. The surfaces of the inner and outer cylinders are maintained at 54°C and 106°C, respectively. Determine
A hot liquid (cp = 950 J/kg ∙ K) flows at a flow rate of 0.005 kg/s inside a tube with a diameter of 25 mm. At the tube exit, the liquid temperature decreases by 8°C from its temperature at the
Reconsider Prob. 9–96. Using EES (or other) software, plot the rate of natural convection heat transfer as a function of the hot surface temperature of the sphere as the temperature varies from 250
A spherical tank, with an inner diameter of 3 m, is filled with a solution undergoing an exothermic reaction that generates 233 W/m3 of heat and causes the surface temperature to be 120°C. To
When is natural convection negligible and when is it not negligible in forced convection heat transfer?
Under what conditions does natural convection enhance forced convection, and under what conditions does it hurt forced convection?
In a production facility, thin square plates 2 m × 2 m in size coming out of the oven at 270°C are cooled by blowing ambient air at 18°C horizontally parallel to their surfaces. Determine the air
When neither natural nor forced convection is negligible, is it correct to calculate each independently and add them to determine the total convection heat transfer?
Consider a 5-m-long vertical plate at 60°C in water at 25°C. Determine the forced motion velocity above which natural convection heat transfer from this plate is negligible.
A 150-mm-diameter and 1-cm-long vertical rod has water flowing across its outer surface at a velocity of 0.5 m/s. The water temperature is uniform at 40°C, and the rod surface temperature is
A 150-mm-diameter and 1-m-long rod is positioned horizontally and has water flowing across its outer surface at a velocity of 0.2 m/s. The water temperature is uniform at 40°C and the rod surface
Consider a 5-m-long vertical plate at 85°C in air at 30°C. Determine the forced motion velocity above which natural convection heat transfer from this plate is negligible.
A 15-cm-diameter horizontal cylinder has a surface temperature that is maintained at 120°C. Water at 40°C is flowing across the cylinder with a velocity of 0.2 m/s. Determine the Nusselt number if
Reconsider Prob. 9–107. Using EES (or other) software, plot the forced motion velocity above which natural convection heat transfer is negligible as a function of the plate temperature as the
A 12-cm-high and 20-cm-wide circuit board houses 100 closely spaced logic chips on its surface, each dissipating 0.05W. The board is cooled by a fan that blows air over the hot surface of the board
Why are the windows considered in three regions when analyzing heat transfer through them? Name those regions and explain how the overall U-value of the window is determined when the heat transfer
Consider three similar double-pane windows with air gap widths of 5, 10, and 20 mm. For which case will the heat transfer through the window will be a minimum?
In an ordinary double-pane window, about half of the heat transfer is by radiation. Describe a practical way of reducing the radiation component of heat transfer.
Consider a double-pane window whose air space width is 20 mm. Now a thin polyester film is used to divide the air space into two 10-mm-wide layers. How will the film affect(a) Convection(b) Radiation
Consider a double-pane window whose air space is flashed and filled with argon gas. How will replacing the air in the gap by argon affect(a) Convection(b) Radiation heat transfer through the window?
Is the heat transfer rate through the glazing of a double-pane window higher at the center or edge section of the glass area? Explain.
How do the relative magnitudes of U-factors of windows with aluminum, wood, and vinyl frames compare? Assume the windows are identical except for the frames.
Determine the U-factor for the center-of-glass section of a double-pane window with a 13-mm air space for winter design conditions. The glazings are made of clear glass having an emissivity of 0.84.
The overall U-factor of a fixed wood-framed window with double glazing is given by the manufacturer to be U = 2.76 W/m2 . K under the conditions of still air inside and winds of 12 km/h outside.
The owner of an older house in Wichita, Kansas, is considering replacing the existing double-door type woodframed single-pane windows with vinyl-framed double-pane windows with an air space of 6.4
Consider a house in Atlanta, Georgia, that is maintained at 22°C and has a total of 14 m2 of window area. The windows are double-door-type with wood frames and metal spacers. The glazing consists of
Consider an ordinary house with R-13 walls (walls that have an R-value of 13 h · ft2 · °F/Btu). Compare this to the R-value of the common double-door windows that are double pane with 14 in of
A double-door wood-framed window with glass glazing and metal spacers is being considered for an opening that is 1.2 m high and 1.8 m wide in the wall of a house maintained at 20°C. Determine the
Reconsider Prob. 9-20. Using the EES (or other) software, evaluate the effect of the plate thickness on the surface temperature exposed to the cold air. By varying the plate thickness from 0.01 to
Reconsider Prob. 9-24. Using the EES (or other) software, evaluate the effect of the uniform surface heat flux on the plate midpoint temperature for(a) The highly polished surface(b) The black

Showing 1500 - 1600 of 2106

First
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22

Get In Touch

About Us
Contact Us
Career
Jobs
FAQ
Campus Ambassador

Company Info

Security
Copyrights
Privacy Policy
Terms & Condition
SolutionInn Fee
Scholarship

Services

Sitemap
Fun
Definitions
Become Tutor
Study Help Categories
Recent Questions
Expert Questions

Copyright © 2024 SolutionInn All Rights Reserved.

Get the SolutionInn - Study Help App