题目内容

Divided by the working type, heat exchangers can be classified into which of the following type?

A. Recuperative type, mixing type, regenerative type
B. Recuperative type and non-recuperative type
C. Double-pipe, shell and tube, plate
D. Compact and non-compact

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For the process of heat transfer through a flat wall, which is the key factor that determins the heat transfer coeifficient?

A. The covective heat transfer coeifficient in the cold side
B. The covective heat transfer coeifficient in the hot side
C. The thickness and conductivity of the wall
D. All of the three above

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A wall is made of three layers: Fiberglass plate with the thicknees of 2.4 cm and the conductivity of 0.038W/(m.K), loose asbestos with the thicknees of 8.0 cm and the conductivity of 0.154W/(m.K), common brick with the thicknees of 10.0 cm and the conductivity of 0.69W/(m.K). Assumed that the convective heat transfer coeifficient around the wall is 15W/(m2.K), then the overall heat transfer coeifficient is ?

A. 0.7 W/(m2.K)
B. 1.4 W/(m2.K)
C. 4.0 W/(m2.K)
D. 15 W/(m2.K)

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A copper tube with the outer diameter of 24 mm, wall thickness of 1.5 mm and conductivity of 101 W/(m.K) is used inside a condenser. Cold water flows inside the tube and vaper condenses outside the tube. The convective heat transfer cofficients outside and inside the tube are 9500 W/(m2.K) and 6050 W/(m2.K), which of the following is overall the heat transfer cofficient based on the outer surface?

A. 8050 W/(m2.K)
B. 7300 W/(m2.K)
C. 3225 W/(m2.K)
D. 125 W/(m2.K)

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A thermal insulating layer is attached to a hot plate. The side near the hot plate is at 230℃, and the other side is at 40℃. the thickness of the layer is 30 mm and the conductivity is 0.2W/(m.K). The ambient temperature is 20℃, and the convective heat transfer cofficient should be?

A. 105 W/(m2.K)
B. 63 W/(m2.K)
C. 12 W/(m2.K)
D. 51 W/(m2.K)

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Divided by the working type, heat exchangers can be classified into which of the following type?

A. Recuperative type, mixing type, regenerative type B. Recuperative type and non-recuperative type C. Double-pipe, shell and tube, plate D. Compact and non-compact

For the process of heat transfer through a flat wall, which is the key factor that determins the heat transfer coeifficient?

A thermal insulating layer is attached to a hot plate. The side near the hot plate is at 230℃, and the other side is at 40℃. the thickness of the layer is 30 mm and the conductivity is 0.2W/(m.K). The ambient temperature is 20℃, and the convective heat transfer cofficient should be?

A. Recuperative type, mixing type, regenerative type
B. Recuperative type and non-recuperative type
C. Double-pipe, shell and tube, plate
D. Compact and non-compact