题目内容

The temperature correction factor is determined by the dimensionless factors P and R, what is the physical meaning of R?

A. The ratio of the actual temperature rise of the fluid 1 and the maximum temperature rise that can be achieved theoretically
B. The ratio of the specific heat of fluid 1 and fluid 2
C. The ratio of the actual temperature rise of the fluid 2 and the maximum temperature rise that can be achieved theoretically
D. The ratio of the thermal capacity of fluid 1 and fluid 2

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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

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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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