A square aluminum plate 5 mm thick and 240 mm on a side is heated while vertically suspended in quiescent air at 40°C. Determine the average heat transfer coefficient for the plate when its temperature is 20°C by two methods: (a) using results from the similarity solution to the boundary layer equations, and (b) using results from an empirical correlation. Evaluate properties of air at the film temperature. (a) Determine the average heat transfer coefficient for the plate when its temperature is 20°C using the similarity solution, in W/m2-K. ! W/m2-K %3D (b) Determine the average heat transfer coefficient for the plate when its temperature is 20°C using an emperical correlation, in W/m2-K. i ! W/m2-K

A square aluminum plate 5 mm thick and 240 mm on a side is heated while vertically suspended in quiescent air at 40°C. Determine the average heat transfer coefficient for the plate when its temperature is 20°C by two methods: (a) using results from the similarity solution to the boundary layer equations, and (b) using results from an empirical correlation. Evaluate properties of air at the film temperature. (a) Determine the average heat transfer coefficient for the plate when its temperature is 20°C using the similarity solution, in W/m2-K. ! W/m2-K %3D (b) Determine the average heat transfer coefficient for the plate when its temperature is 20°C using an emperical correlation, in W/m2-K. i ! W/m2-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.

Chapter5: Analysis Of Convection Heat Transfer

Section: Chapter Questions

Problem 5.7P: 5.7 The average Reynolds number for air passing in turbulent flow over a 2-m-long, flat plate is ....

See similar textbooks

Similar questions

Write the comparison between forced and free convection in a non-isothermal system?
How can we use the transient temperature charts when the surface temperature of the geometry is specified instead of the temperature of the surrounding medium and the convection heat transfer coefficient?
Consider a 50-cm-diameter and 95-cm-long hot water tank. The tank is placed on the roof of a house. The water inside the tank is heated to 80°C by a flat-plate solar collector during the day. The tank is then exposed to windy air at 18°C with an average velocity of 40 km/h during the night. Estimate the temperature of the tank after a 45-min period. Assume the tank surface to be at the same temperature as the water inside, and the heat transfer coefficient on the top and bottom surfaces to be the same as that on the side surface. Evaluate the air properties at 50°C.
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 0.1 m, plot the plate surface temperature on the cold air side as a function of the plate thickness. Prob 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 surface exposed to the cold air has an emissivity of 0.73. Determine the temperature of the plate surface exposed to the cold air (Ts,c).
Partially-frozen ice cream is being placed in a package before completion of the freezing process. The package has dimensions of 8 cm by 10 cm by 20 cm and is placed in air- blast freezing with convective heat coefficient of 50 W/(m2 K) for freezing. The product temperature is -5°C when placed in the package, and the air temperature is -25°C. The product density is 700 kg/m3, the thermal conductivity (frozen) is 1.2 W/(m K), and the specific heat of the frozen product is 1.9 kJ/(kg K). If the latent heat to be removed during blast freezing is 100 kJ/kg, estimate the freezing time.
. Castor oil at 36 °C flows over a 6 m long and 1 m wide heated plate at 0.06 m/s. For a surfacetemperature of 96 °C, determine (i) the thermal boundary layer thickness at the end of the plate,(ii) the local heat transfer coefficient at the end of the plate, and (iii) the rate of heat transfer fromthe entire plate
Illustrate the concept of convection in heat transfer operation and also differentiate forced convection and natural convection with suitable examples. Why thermal conductivity of liquid decreases whereas that of gas increases by increasing temperature?
Consider a person who is trying to keep cool on a hot summer day by turning a fan on and exposing his body to air flow. The air temperature is 32°C, and the fan is blowing air at a velocity of 5 m/s. The surrounding surfaces are at 40°C, and the emissivity of the person can be taken to be 0.9. If the person is doing light work and generating sensible heat at a rate of 90 W, determine the average temperature of the outer surface (skin or clothing) of the person. The average human body can be treated as a 30-cmdiameter cylinder with an exposed surface area of 1.7 m2. Evaluate the air properties at film temperature of 35°C and 1 atm.
Thick fluids such as asphalt and waxes and the pipes in which they flow are often heated in order to reduce the viscosity of the fluids and thus to reduce the pumping costs. Consider the flow of such a fluid through a 100-m-long pipe of outer diameter 30 cm in calm ambient air at 0oC. The pipe is heated electrically, and a thermostat keeps the outer surface temperature of the pipe constant at 25oC. The emissivity of the outer surface of the pipe is 0.8, and the effective sky temperature is −30oC. Determine the power rating of the electric resistance heater, in kW, that needs to be used. Also, determine the cost of electricity associated with heating the pipe during a 10-h period under the above conditions if the price of electricity is $0.09/kWh. Properties The properties of air at 1 atm and the film temperature of (Ts+T∞)/2 = (25+0)/2 = 12.5°C are: k = 0.02458 W/m.oC, ν = 1.448x10-5 m2/s, Pr = 0.7330
Define Nusselt (Nu), Prandtl (Pr), Reynolds (Re) and Grashof (Gr) dimensionless numbers. State which numbers are used in free and forced convection to determine the heat transfer coefficient.
For the Convective Heat Transfer experiment, describe the difference in the procedures: Natural or FreeConvection and Forced convection. What makes the FORCED convection experiment as FORCED? Explain which, in your consideration should give the higher heat transfer rate? And REASON why? Did your results support your consideration?
Air is flowing in parallel over the upper surface of a flat plate with a length of 4m. The first half of the plate length, from the leading edge, has a constant surface temperature of 50 degrees Celsius. The second half of the plate length is subjected to a uniform heat flux of 86 W/m2. The air has a free stream velocity and temperature of 2 m/s and 10 degrees Celsius, respectively. Determine the local convection heat transfer coefficients at 1 m and 3 m from the leading edge. Evaluate the air properties at a film temperature of 30 degrees Celsius. Is the film temperature Tf=30 degrees Celsius applicable at x = 3 m?