A 3 m internal diameter spherical tank made of 1 cm thick stainless steel (k = 15 W/mK) is used to store water at 4°C, as shown in Figure 2.2. Inner surface of the tank is 4°C, while the outer surface of the tank is painted with black colour paints with emissivity, ɛ = 0.88 measured at temperature 5°C. It is located outdoor at 40°C and is subjected to wind at 25 km/h. Determine the total heat transfer rate to the ice water. To = 40°C %3D 25 km/h Iced T = 5°C water 1 cm D =3 m T= 4°C Figure 2.2

A 3 m internal diameter spherical tank made of 1 cm thick stainless steel (k = 15 W/mK) is used to store water at 4°C, as shown in Figure 2.2. Inner surface of the tank is 4°C, while the outer surface of the tank is painted with black colour paints with emissivity, ɛ = 0.88 measured at temperature 5°C. It is located outdoor at 40°C and is subjected to wind at 25 km/h. Determine the total heat transfer rate to the ice water. To = 40°C %3D 25 km/h Iced T = 5°C water 1 cm D =3 m T= 4°C Figure 2.2

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.

Chapter6: Forced Convection Over Exterior Surfaces

Section: Chapter Questions

Problem 6.4P: An electrical transmission line of 1.2-cm diameter carries a current of 200 amps and has a...

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A 3 m internal diameter spherical tank made of 1 cm thick stainless steel (k =15 W/mK) is used to store water at 4℃, as shown in Figure 2.2. Inner surfaceof the tank is 4℃, while the outer surface of the tank is painted with blackcolour paints with emissivity, ? = 0.88 measured at temperature 5℃. It islocated outdoor at 40℃ and is subjected to wind at 25 km/h. Determine the total heat transfer rate to the ice water.
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.
Space is considered a perfect black body with T= - 70 celsius AirDoes not absorb heat radiation from the water in the bowl.Air temperature is considered constant TAir = 15 celsiusHeat transfer coefficient from water to air: hc = 2.6 W/(m2∙celsius) cabbage with waterDepth to the water in the bowl: H = 0.020 mBase area to water layer: A= 0.020 m2Starting temperature: T0 = 15 celsiusEmissivity to water: = 0.98 a) Calculate heat transport by radiation from the water in the bowl to space at initial conditions. b) Calculate net heat transport from the water in the bowl at water temperature T= 0 celsius (beginning of freezing).
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
Q6: A large vertical plate 6.1 m high and 1.22 m wide is maintained at a constant temperature of 57+C and exposed to atmospheric air at 4°C. Calculate the heat lost by the plate. Answers: Q=1907 W
Four power transistors, each dissipating 12 W, are mounted on a thin vertical aluminum plate 22 cm * 22 cm in size. The heat generated by the transistors is to be dissipated by both surfaces of the plate to the surrounding air at 25°C, which is blown over the plate by a fan. The entire plate can be assumed to be nearly isothermal, and the exposed surface area of the transistor can be taken to be equal to its base area. If the average convection heat transfer coefficient is 25 W/m2·K, determine the temperature of the aluminum plate. Disregard any radiation effects.
The temperature of a tank in the form of 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, e= 1.
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 ℃)
Question No. 3: During a cold winter day, wind at 55 km/h is blowing parallel to a 4-m-high and 10-m-long wall of a house. If the air outside is at 5°C and the surface temperature of the wall is12°C, determine the rate of heat loss from that wall by convection. What would your answer be if the wind velocity was doubled
The vertical 0.8-m-high, 2-m-wide double-pane window consists of two sheets of glass separated by a 2-cm air gap at atmospheric pressure. If the glass surface temperatures across the air gap are measured to be 12°C and 2°C, determine the rate of heat transfer through the window.
Explain, motorcycle engine is either considered as free or forced convection. Justify your answer
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.