Consider a 3-m-high rectangular enclosure consisting of two surfaces separated by an air gap (L)-0.5-m at 1 atm. The surface temperatures across the air gap are 12.5°C and 7.5°C. The properties of air at Ty= (T, + T-y2 = 10°C are k = 0.02439 W/m-K, v = 1.426 x 10-5 m2/s, Pr = 0.7336, and B = 1/T, = 3.534 × 10-3 K-1. 7.5°C 12.5°C Air 7.5°C 3 m Lm L m Air 12.5°C 3 m The Nusselt numbers for vertical orientation is

Consider a 3-m-high rectangular enclosure consisting of two surfaces separated by an air gap (L)-0.5-m at 1 atm. The surface temperatures across the air gap are 12.5°C and 7.5°C. The properties of air at Ty= (T, + T-y2 = 10°C are k = 0.02439 W/m-K, v = 1.426 x 10-5 m2/s, Pr = 0.7336, and B = 1/T, = 3.534 × 10-3 K-1. 7.5°C 12.5°C Air 7.5°C 3 m Lm L m Air 12.5°C 3 m The Nusselt numbers for vertical orientation is

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

See similar textbooks

Similar questions

Consider a 150 W incandescent lamp in a room at 25 °C. The filament of the lamp is 5 cm long and has a diameter of 0.5 mm. The emissivity of the filament is 0.90. The diameter of the glass bulb of the lamp is 8 cm. The inside surface temperature of the glass bulb is 150 °C. Determine: (a) the heat flux, in W∙m-2, on the surface of the filament, (b) the heat flux, in W∙m-2, on the surface of the glass bulb, and (c) the surface temperature of the filament. The surface area of a sphere is ? = 4??2, and the volume of a sphere is ? = (4?/3)?3.
Troom = 25°C Problem-4: An 8-m-internal-diameter spherical tank made of 1.5-cm-thick stainless steel (k = 15 W/m-K) is used to store iced water at 0°C. The tank is located in a room whose temperature is 25°C. The walls of the room are also at 25°C. The outer surface of the tank is black (emissivity = 1), and heat transfer between the outer surface of the tank and the surroundings is by natural convection and radiation. The convection heat transfer coefficients at the inner and the outer surfaces of the tank are 80 W/m²-K and 10 W/m².K, respectively. Determine (a) the rate of heat transfer to the iced water in the tank and (b) the amount of ice at 0°C that melts during a 24-h period. The heat of the fusion of water at atmospheric pressure is hf5 333.7 kJ/kg. Iced water D D₁= 8 m Tin = 0°C 1.5 cm
1. The upper surface of a 50-cm-thick solid brass plate (k=109 W/m·K) is being cooled by water with temperature of 10°C. The upper and lower surfaces of the solid plate maintained at constant temperatures of 60°C and 190°C, respectively. Determine the water convection heat transfer coefficient and the water temperature gradient at the upper plate surface. Water 1111 Ts,2
A 21.5-cm-wide and 31 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 31-cm- long in the vertical direction. Given: Consider the characteristic length to be the height of the surface. The properties of air at T₁ = 52.5°C: k = 0.02753 W/m °C, v= 1.823 × 10–5 m²/s, Pr = 0.7222 a. Determine the optimum fin spacing of the heat sink if the base temperature is 85°C. b. Determine the rate of heat transfer by natural convection from the heat sink if the base temperature is 85°C.
In the arctic sea, the ice sheets are melting. Let's calculate the temperautre distribution in one such ice sheet. The sheet is 2 m thick. Under the sheet there is ice-water mixture and it can be assumed that the temperature of the bottom surface of the ice sheet is approximately 0°C. Air at -20°C is blowing above the sheet. The convection coefficient of air is 15 W/m².K. The thermal conductivity of ice is 2.2 W/m.K. What is the temperautre of icesheet at its center (i.e., at 1 m from the surface)?
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 250C. The emissivity of the outer surface of the pipe is 0.8, and the effective sky temperature is-300C. 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+To)/2 = (25+0)/2 = 12.5°C are: k = 0.02458 W/m.oC, v = 1.448x10-5 m2/s, Pr = 0.7330 D=m
Fruit is impeded from ripening when it reaches high temperatures (>32°C). Farmer Joe isworried that Deleware's summer heat wave will affect the ripening of his ground cherries.The spherical fruit (1 cm in diameter) is surrounded by a spherical papery husk (λhusk = 0.3W/m K) with an inner diameter of 2 cm and an outer diameter of 2.1 cm. The air in betweenthe fruit and the husk is stagnant (λair = 0.03 W/m K). On a calm day in July, the delewareair (outside of the husk) is very warm, with a temperature of ~38°C and a heat transfercoefficient of h deleware,calm = 10 W/m 2K. (a) Sketch the system, labeling all temperatures, dimensions, and proportionality constants. (b) sketch the electrical analogy tothis system, labeling all temperatures, resistances, and heat flows (c) what is the overall resistance to heat transfer from the air in Deleware to the fruit?
Consider a hot automotive engine, which can be ap- proximated as a 0.5-m-high, 0.40-m-wide, and 0.8-m-long rec- tangular block. The bottom surface of the block is at a temperature of 80°C and has an emissivity of 0.95. The ambi- ent 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 veloc- ity of 80 km/h. Assume the flow to be turbulent over the entire surface because of the constant agitation of the engine block.