Baffles are provided in heat exchangers to increase the a. Fouling factor b. Heat transfer area c. Heat transfer coefficient d. Heat transfer rate

7. A dryer is shaped like a long semicylindrical duct of diameter 1.5 m. The base of the dryer is occupied with water-soaked materials to be dried. The base is maintained at a temperature of 370 K, while the dome of the dryer is maintained at 1000 K. If both surfaces behave as blackbodies, determine the drying rate per unit length experienced by the wet materials.

Explain the difference (in concept or definition) between boundary layer thickness and thermal boundary layer thickness?

Q2. (A) A wall consists of a 1-mm layer of copper, a 4-mm layer of 1 percent carbon steel, al-cm layer of asbestos sheet, and 10 cm of fiberglass blanket. Calculate the overall heat-transfer coefficient for this arrangement. If the two outside surfaces are at 10 and 150C°, calculate each of the interface temperatures. (B) Consider a layer of insulation might be installed around a circular pipe as shown in Figure.2, from basic equations that govern the heat transfer derive a relation for critical radius of insulation to prove that rc = k/h. Note:- adopt the assumptions in your solution.

A large slab of copper is initially at a uniform temperature of 90◦C. Its surfacetemperature is suddenly lowered to 30◦C. Calculate the heat-transfer rate through aplane 7.5 cm from the surface 10 s after the surface temperature is lowered.

Acomposite wall is formed of a 2.5-cm copper plate, a 3.2-mm layer of asbestos, anda 5-cm layer of fiberglass. The wall is subjected to an overall temperature differenceof 560◦C. Calculate the heat flow per unit area through the composite structure.

1. A layered wall consists of a copper plate with a thickness of 2.5 cm, the second layer is made of asbestos, the thickness is 3.2 mm, and the third layer is made of glass fiber with a thickness of 5 cm. The overall temperature difference of this wall is 560 ° C. a. Calculate the overall heat transfer rate on this layered wall. b. Calculate T2 and T3

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?

Define how a heat exchanger can be as simple as two concentric pipes.

One side of a copper block 4 cm thick is maintained at 175.C. The other side is covered with a layer of fiberglass 1.5 cm thick. The outside of the fiberglass is maintained at 80•C, and the total heat flow through the composite slab is 300 W. What is the area of the slab? 8:28 PM /