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Heat Transfer - Engineering

Q1:

Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2 .°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the

A higher condensing film co-efficient is desired.

B condensate is corrosive in nature.

C lower pressure drop through the exchanger is desired.

D temperature of the incoming vapor is very high.

ANS:B - condensate is corrosive in nature.

The statement "higher condensing film coefficient is desired" is true. Here's why: The condensing film coefficient represents the rate of heat transfer from the condensing vapor to the tube wall. A higher condensing film coefficient indicates more efficient heat transfer, meaning that heat is transferred more rapidly from the vapor to the tube wall, resulting in faster condensation. In a shell and tube heat exchanger where condensation of vapor occurs inside the tube, a higher condensing film coefficient is desired for several reasons:

  1. Increased Heat Transfer: A higher condensing film coefficient allows for more efficient heat transfer, leading to faster condensation of the vapor. This can result in higher overall heat transfer rates in the heat exchanger.
  2. Improved Performance: Higher heat transfer rates can lead to improved performance of the heat exchanger, allowing for better control of process temperatures and potentially reducing the size and cost of the heat exchanger.
  3. Reduced Surface Area: With a higher condensing film coefficient, less surface area is required to achieve the desired heat transfer rate. This can lead to a more compact and cost-effective heat exchanger design.
Therefore, in a shell and tube heat exchanger where condensation of vapor occurs inside the tube, a higher condensing film coefficient is desired to optimize heat transfer efficiency and overall performance of the heat exchanger.