An industrial freezer is designed to operate with an internal air temperature of -20 °C when...
III. Convective coefficient (40 pt). An electric wire having diameter of 6.0 mm and covered with a plastic insulation (thickness 2.0 mm; thermal conductivity: 0.4 W/m K) is exposed to air at 300 K. The heat loss per meter of wire generated is 200 W/m. Determine: ) Convective heat-transfer coefficient between the insulation and the surrounding air, h (25 pt) 2) Temperature of the insulation surface T2. (15 pt) HINT: T2 is a value between 320K and 400K To T2...
On a windy day, we can define the wind-chill temperature Twc as the air temperature that would give the same rate of heat loss if experienced on a calm day. Consider a day when the air temperature is 2°C and the wind speed is 12 m/s, giving a convective heat transfer coefficient of 45 W/m2⋅K (compared with 10 W/m2⋅K on a calm day). Assume a person has a 3 mm layer of skin (k = 0.37 W/m⋅K), a body surface...
Q1) Inner surface of a side wall is used for heating of ambient-room air as shown below. There is an electrical heater with 10 W/m2 heat flux generation between a layer of insulation and 2 cm thick marble exposed to ambient-room air at T-20 °C with h-20 W/m2K. k-0.04 W/mK Marble with a thickness of 2 cm Ts= 10 ℃ outside Ambient-room air at To Electrical heating layer (negligible thickness) of temperature T-? Insulation with a thickness of 5 cm...
1. A steel tube [k 15 W/(m.°C)] of outside diameter 7.6 cm and thickness 1.3 cm is covered with an insulation material [k 0.2 W/(m. C)] of thickness 2 cm. A hot gas at 320°C with a heat transfer coefficient of 200 W/(m2.C) flows inside the tube. The outer surface of the insulation is exposed to cooler air at 20°C with a heat transfer coefficient of 50 W/(m2·°C). Calculate a) The heat loss from the tube to the air for...
Consider the following composite wall of a building. It is made out of plaster board (Lp 0.85 W/mK), glass fibre insulation (Lb-160 mm, k = 0.050 W/mK) and plywood (1,-40 m m, k = 0.70 W/mK) as shown below. On a certain day, the convective heat transfer coefficients inside and outside of the building are 35 W/m2K and 65 W/m2 K respectively. The inside and outside temperatures are 24°C and 36°C respectively. The wall has a total surface area of...
Problem : A cryogenic flui d is flowing in a 304 SS pipe. The pipe is insulated on its outside surface with 6 - mm thick, evacuated, aluminum foil/glass mat insulation. (“Evacuated” means a partial vacuum is drawn on the insulation to remove air that would otherwise fill pores inside the insulation.) The pipe inside diameter is 127 mm; it’s outside diameter is 138 mm. The fluid temperature is - 173 o C . T he air temperature outside the...
NE Steel tubes (k =35 W/m2.K) of 400-mm inner diameter and 30-mm wall thickness are used to route superheated steam from the boller to the turbine in a power plant. Safety and economic concerns make it practical to add a 200-mm layer of Insulation (k =0.1 W/mK) to each tube, which is wrapped in a thin sheet of aluminum with an emissivity e =0.15. The air (with a convective coefficient h =5 W/m2K) and wail temperatures of the plant are...
The roof of a refrigerated truck compartment consists of a layer of foamed urethane insulation (t2 = 62 mm, ki = 0.026 W/m K) between aluminum alloy panels (t1 = 6 mm, kp = 180 W/m K). The length of the roof is L = 9 m. The net solar radiation into the roof is 131 W/m2. The temperature of the inner surface is Ts,i = -3 °C and the air temperature is T. = 30 °C. The convective heat...
heat and mass transfer (20 points) Air at 25°C cools a 2170 cylindrical battery (with a diameter of 21 mm and a length of 70 mm) with a cross flow velocity of 6 m/s. a) Determine the average convective heat transfer coefficient. (b) If the battery's internal heat generation is 5W and its thermal conductivity is 0.6 w/m-k, the determine the battery surface temperature and the maximum temperature in battery (20 points) Air at 25°C cools a 2170 cylindrical battery...
A composite wall is comprised of two large plates separated by sheets of refractory insulation, as shown in the schematic. In the installation process, the sheets of thickness L =50 mm and thermal conductivity k = 0.05 W/m.Kare separated at 1-m intervals by gaps of width w = 15 mm. The hot and cold plates have temperatures and emissivities of Ti = 550°C, EI =0.85 and T2 =35°C, E2 =0.5, respectively. Assume that the plates and insulation are diffuse-gray surfaces....