题目内容

A heat exchanger had an overall heat transfer coefficient of 70W/m2K when it was firstly used, and the heat transfer coefficient decreased to 50W/m2K after 1 year of use. What is the thermal resistance of fouling ?

A. 6m2K/W
B. 0.6m2K/W
C. 0.06m2K/W
D. 0.006m2K/W

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Which of the shell and tube heat exchanger is easier to scale, helical baffles or segmental baffles?

A. Helical baffles
B. Segmental baffles
C. Same
D. Can not be determined

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Which of the following methods cannot be used to reduce the thermal resistance of fouling inside the tube

A. Decrease water velocity
B. Increase water velocity
C. Add chemical cleaning substances to the fluid
D. Use ultrasonic sound field to treat the fluid

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In the steady-state heat transfer, the temperature difference is constant. In order to increase the heat transfer, which of the following methods cannot be used?

A. Increase heat transfer area
B. Increase heat transfer thermal resistance
C. Increase the heat transfer coefficient
D. Increase convective heat transfer

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To enhance the single-phase forced convection heat transfer on the air side, the commonly used methods generally do not include:

Additional fins
B. Increase the roughness of heat transfer surface
C. Use longitudinal vortex generator
D. Use high-fin tubes

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A heat exchanger had an overall heat transfer coefficient of 70W/m2K when it was firstly used, and the heat transfer coefficient decreased to 50W/m2K after 1 year of use. What is the thermal resistance of fouling ?

A. 6m2K/W B. 0.6m2K/W C. 0.06m2K/W D. 0.006m2K/W

Which of the shell and tube heat exchanger is easier to scale, helical baffles or segmental baffles?

Which of the following methods cannot be used to reduce the thermal resistance of fouling inside the tube

In the steady-state heat transfer, the temperature difference is constant. In order to increase the heat transfer, which of the following methods cannot be used?

To enhance the single-phase forced convection heat transfer on the air side, the commonly used methods generally do not include:

A. 6m2K/W
B. 0.6m2K/W
C. 0.06m2K/W
D. 0.006m2K/W