A 5 cm thick steel pipe, 1.0 m long, with an internal diameter of 8 cm is covered with 4 cm thick insulation. The inside wall temperature of the steel pipe is 100°C. The ambient temperature around the insulated pipe is 24°C. The convective heat-transfer coeffi cient on the outer insulated surface is 50 W/(m² K). Calculate the temperature at the steel insulation interface. The thermal conductivity of steel is 54 W/(m K), and the thermal conductivity of insulation is 0.04 W/(m K).

A glass window of width W = 1 m and height H = 2 m is 5 mm thick and has a thermal conductivity of k 1.4 W/m K. If the inner and outer surface temperatures of the glass are 15°C and -20°C, respectively, on a cold winter day, what is the rate of heat loss through the glass? To reduce heat loss through windows, it is cus- tomary to use a double pane construction in which adjoining panes are separated by an air space. If the spacing is 10 mm and the glass surfaces in contact with the air have temperatures of 10°C and -15°C, what is the rate of heat loss from a 1 m x 2 m window? The thermal conductivity of air is k, = 0.024 W/m.K.

Air at 25 ° C blows over the hot steel plate whose surface temperature is maintained at 200 ° C. The plates have dimensions of 50 cm x 50 cm and a thickness of 2.5 cm. The convection heat transfer coefficient on the upper surface is 25 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 = AnswerkJ. b. If the reverse side surface temperature is maintained, specify hourly heat loss = AnswerkJ.

Homework 2 The possible existence of an optimum insulation thickness for radial systems is suggested by the presence of competing effects associated with an increase in this thickness. In particular, although the conduction resistance increases with the addition of insulation, the convection resistance decreases due to increasing outer surface area. Hence there may exist an insulation thickness that minimizes heat loss by maximizing the total resistance to heat transfer. Resolve this issue by considering the following system. 1. A thin-walled copper tube of radius r, is used to transport a low-temperature refrigerant and is at a temperature Ti that is less than that of the ambient air at Ta around the tube. Is there an optimum thickness associated with application of insulation to the tube? 2. Confirm the above result by computing the total thermal resistance per unit length of tube for a 10-mm-diameter tube having the following insulation thicknesses: 0, 2, 5, 10, 20, and 40 mm. The…

An experiment to measure the thermal conductivity of food formulations was carried out by measuring the surface temperature of the food formulations which were formed into flat plates with a thickness of 10 mm. It is found that at steady-state conditions, there is a temperature difference of 40 ° C between the two surfaces, the heat transfer rate per unit area of 4700 W / m2 is measured near the center of the two surfaces. Calculate: the thermal conductivity of the product, = AnswerW / m ° C

An industrial cold room has four 200 mm thick walls made of concrete. The walls are insulated on the outside with a layer of foam 60 mm thick. Cladding with a thickness of 15 mm protects the foam on the outside from the elements. The composite wall surface temperatures are –3 °C on the inside and 18 °C on the outside of the room respectively. The thermal conductivities of concrete, foam and cladding are 0.75, 0.35 and 0.5 W/m K respectively. a) Assuming perfect thermal contact between the layers of the composite walls, draw the typical temperature distribution across the layers and determine the heat energy gained per hour through all 4 walls of the room with a total surface area of 20 m2 . What does this heat energy represent in terms of the refrigeration system of the cold room?

In a multi-layered square wall, the thermal resistance of the first layer is 0.005 ° C / W, the resistance of the second layer is 0.4 ° C / W, and the third layer is 0.1 ° C / W. The overall temperature gradient in the wall is multilayered from one side. to the other side is 60 ° C. a. Determine the heat flux through the walls. = Answerwatts / m2. b. If the thermal resistance of the second layer is changed to 0.2 ° C / W, what is the effect in% on heat flux, assuming the temperature gradient remains the same? = %. Answer

In a multi-layered square wall, the thermal resistance of the first layer is 0.005 ° C / W, the resistance of the second layer is 0.4 ° C / W, and the third layer is 0.1 ° C / W. The overall temperature gradient in the wall is multilayered from one side. to the other side is 60 ° C. a. Determine the heat flux through the walls. = Answerwatt / m2. b. If the thermal resistance of the second layer is changed to 0.2 ° C / W, what is the effect in% on heat flux, assuming the temperature gradient remains the same? = AnswerAnswer%.

Thermal Conductivity of G10 fiberglass is 0.3 silcone is 0.2 aluminum is 200

If the thickness of a plane wall is doubled from x to 2x while maintaining the same temperatures on each side of the wall, the conductive heat transfer rate (q) 2x increases decreases stays the same none of the above