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Heat Transfer - Engineering

Q1:

Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient for the cooling water, whether on shell side or tube side is the same. The best arrangement is

A vertical heat exchanger with steam on tube side.

B vertical heat exchanger with steam on shell side.

C horizontal heat exchanger with steam on tube side.

D horizontal heat exchanger with steam on shell side.

ANS:B - vertical heat exchanger with steam on shell side.

To determine the best arrangement for the heat exchanger, we need to consider factors such as natural convection, gravitational effects, and ease of maintenance.

  1. Vertical Heat Exchanger with Steam on Tube Side: In this arrangement, steam flows through the tubes while cooling water surrounds the tubes in the shell. The vertical orientation might lead to better natural convection flow in the shell side, enhancing heat transfer. Additionally, having steam on the tube side might allow for easier maintenance and inspection of the tubes. This arrangement seems reasonable.
  2. Vertical Heat Exchanger with Steam on Shell Side: In this case, steam flows through the shell while cooling water flows through the tubes. The vertical orientation may not be as favorable for natural convection on the shell side, potentially reducing heat transfer efficiency.
  3. Horizontal Heat Exchanger with Steam on Tube Side: This arrangement could lead to gravitational effects causing steam condensate to pool at the bottom of the tubes, potentially impeding heat transfer. Additionally, maintenance of tubes might be more challenging in a horizontal arrangement.
  4. Horizontal Heat Exchanger with Steam on Shell Side: Having steam on the shell side in a horizontal arrangement could lead to gravitational effects causing condensate to collect at the bottom, potentially reducing heat transfer efficiency.
Considering these factors, the best arrangement appears to be the vertical heat exchanger with steam on the tube side. This arrangement allows for potentially better natural convection on the shell side and facilitates easier maintenance of the tubes.