You've experienced convection cooling if you've ever extended your hand out the window of a moving vehicle or into a flowing water stream. With the surface of your hand at a temperature of 30°C, consider the two following conditions. Condition A: a vehicle speed of 35 km/h in air at -5°C with a convection coefficient of 40 W/m2-K. Condition B: a velocity of 0.2 m/s in a water stream at 10°C with a convection coefficient of 700 W/m2-K. What is the convection heat flux for the following? Condition A: i W/m? air Condition B: W/m? wate

You've experienced convection cooling if you've ever extended your hand out the window of a moving vehicle or into a flowing water stream. With the surface of your hand at a temperature of 30°C, consider the two following conditions. Condition A: a vehicle speed of 35 km/h in air at -5°C with a convection coefficient of 40 W/m2-K. Condition B: a velocity of 0.2 m/s in a water stream at 10°C with a convection coefficient of 700 W/m2-K. What is the convection heat flux for the following? Condition A: i W/m? air Condition B: W/m? wate

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

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.
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.
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 ℃)
During a cold winter day, wind at 55 km/h is blowing parallel to a 4m high and 10m long wall of a house. If the air outside is at 5 degrees Celsius and the surface temperature of the wall is 12 degrees Celsius , determine the rate of heat loss from the wall by convection. What would your answer be if the wind velocity has doubled? From Table A-1:thermal conductivity, k = 0.0246 W/m degrees Celsiusviscosity, v = 1.4 x 10^-5 m^2/sPrandtl no. Pr = 0.717
You’ve experienced convection cooling if you’ve ever extended your hand out the window of a moving vehicle or into a flowing water stream. With the surface of your hand at a temperature of 30degC, determine the convection heat flux for (a) a vehicle speed of 47 km/h in air at 5degC with a convection coefficient of 40 W/m^2-K and (b) a velocity of 0.4 m/s in a water stream at10degC with a convection coefficient of 900 W/m^2-K. Which condition would feel colder? Add file
A 10 cm * 10 cm plate has a constant surface temperature of 150°C. Determine the Grashof number if the chip is placed in the following fluids: air (1 atm, 30°C), liquid water (30°C), and engine oil (10°C). Discuss how the Grashof number affects the natural convection flow.
The shooter holds a leather-covered baseball for a certain period of time, bringing the outer surface temperature of the ball to 30 ℃. Then the shooter throws the ball at 80 km/h to another athlete standing 18.5 meters away. It is known that the diameter of the ball is 7 cm and the air temperature is 20 ℃. Calculate the total heat transfer from the ball to the ambient air during flight, in Joules, assuming that the outer surface temperature of the ball remains constant throughout the shot. (When finding the properties, find the real values by interpolating. Ignore the air resistance.)
Write the comparison between forced and free convection in a non-isothermal system?
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).
Air at 25 ° C blows over the hot steel plate whose surface temperature is maintained at 150 ° C. The plates are 50 cm x 40 cm in dimensions and 2.5 cm thick. The convection heat transfer coefficient on the upper surface is 40 W / (m² ° C). The thermal conductivity of steel is 45 W / (m ° C). Calculate the hourly heat loss from the plate surface. a. heat loss per hour = Answer kJ. b. If the reverse side surface temperature is maintained, determine the hourly heat loss occurring = Answer kJ. Air at 25 ° C blows over the hot steel plate whose surface temperature is maintained at 150 ° C. The plates are 50 cm x 40 cm in dimensions and 2.5 cm thick. The convection heat transfer coefficient on the upper surface is 40 W / (m² ° C). The thermal conductivity of steel is 45 W / (m ° C). Calculate the hourly heat loss from the plate surface. a. heat loss per hour = Answer kJ. b. If the reverse side surface temperature is maintained, determine the hourly heat loss occurring = Answer kJ.
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?
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 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 0.5 m/s and 10°C respectively. The properties of air at Tf = 30°C are k = 0.02588 W/m∙K, ν = 1.608 × 10−5 m2/s, and Pr = 0.7282. Determine the local convection heat transfer coefficients at 1 m and 3 m from the leading edge.