3. Consider a hot automotive engine, which can be approximated as a 0.6 m high, 0.3 m wide, and 0.9 m long rectangular block. The bottom surface of the block is at a temperature of 90°C and has an emissivity of 0.9. The ambient air is at 23°C, and the road surface is at 28°C. The fluid properties of air are determined at the film temperature and can be found in the tables at the end of the tutorial. a. Determine the rate of heat transfer from the bottom surface of the engine block by convection and radiation as the car travels at a velocity of 60 km/h.

3. Consider a hot automotive engine, which can be approximated as a 0.6 m high, 0.3 m wide, and 0.9 m long rectangular block. The bottom surface of the block is at a temperature of 90°C and has an emissivity of 0.9. The ambient air is at 23°C, and the road surface is at 28°C. The fluid properties of air are determined at the film temperature and can be found in the tables at the end of the tutorial. a. Determine the rate of heat transfer from the bottom surface of the engine block by convection and radiation as the car travels at a velocity of 60 km/h.

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 5.40P

See similar textbooks

Similar questions

An electrical transmission line of 1.2-cm diameter carries a current of 200 amps and has a resistance of 310-4 ohm per meter of length. If the air around this line is at v, determine the surface temperature on a windy day, assuming a wind blows across the line at 33 km/h.
Determine the rate of heat loss from the wall of a building resulting from a 16 km/h wind blowing parallel to its surface. The wall is 24 m long and 6 m high, its surface temperature is 27C, and the temperature of the ambient air is 4C.
A spherical communications satellite, 2 m in diameter, is placed in orbit around the earth. The satellite generates 1000 W of internal power from a small nuclear generator. If the surface of the satellite has an emittance of 0.3, and is shaded from solar radiation by the earth, estimate its surface temperature.
Consider a hot automotive engine, which can be approximated as a 0.5-m-high, 0.40-m-wide, and 0.8-m-long rectangular block. The bottom surface of the block is at a temperature of 100°C and has an emissivity of 0.95. The ambient air is at 20°C, and the road surface is at 25°C. Determine the rate of heat transfer from the bottom surface of the engine block by convection and radiation as the car travels at a velocity of 80 km/h. Assume the flow to be turbulent over the entire surface because of the constant agitation of the engine block.
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
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.
Consider a 50-cm-diameter and 95-cm-long hot water tank. The tank is placed on the roof ofa house. The water inside the tank is heated to 80℃ by a flat-plate solar collector during theday. The tank is then exposed to windy air at 18℃ with an average velocity of 40 km/h duringthe night. Estimate the temperature of the tank after a 45-min period. Assume the tank surfaceto be at the same temperature as the water inside, and the heat transfer coefficient on the topand bottom surfaces to be the same as that on the side surface. Evaluate the air properties at50℃. (Answer: 69.9 ℃)
Consider laminar flow of air across a hot circular cylinder. At what point on the cylinder will the heat transfer be highest? What would your answer be if the flow were turbulent?
. 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
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).
What is Constant Flow Method? Discuss some applications whereby the Constant Flow Method is used in real life. What is Convection in a liquid? Discuss some applications whereby Convection in a liquid is used in real life.
Why is heat transfer faster in forced convection compared to natural convection