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Question

In regenerator type heat exchanger, heat transfer takes place by

The correct answer is
flow of hot and cold fluids alternately over a surface

Regenerator Heat Transfer Mechanism

A regenerator type heat exchanger operates by cyclically transferring heat stored in an intermediate medium (like a matrix or packing material) between the hot and cold fluids.

The process involves:

  • Hot fluid flows through the matrix, heating it up and storing thermal energy.
  • The flow is then switched. Cold fluid flows through the now hot matrix, absorbing the stored heat.
  • This cycle of alternating fluid flow allows heat transfer without direct contact or continuous separation.

This method corresponds directly to the definition provided in Option 3.

Why Other Options Are Incorrect

  • Option 1 (Direct Mixing): This describes direct contact heat exchangers where fluids mix, which is not how regenerators function.
  • Option 2 (Complete Separation): This describes recuperative heat exchangers, where fluids are continuously separated by a solid wall (e.g., shell-and-tube). Regenerators use a cyclic, intermittent process.
  • Option 4 (Generation of Heat): Regenerators facilitate heat transfer, not heat generation.

Therefore, the defining characteristic of heat transfer in a regenerator is the flow of hot and cold fluids alternately over a surface.

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Important Questions from Heat Exchanger

  1. Heat exchangers are used in

    A. Condensers and boilers in steam plants

    B. Radiators

    C. Intercoolers and preheaters

    D. Condensers and evaporators in refrigerators and air conditioners

  2. For a specified inlet and outlet temperatures, for which kind of heat exchange will the log mean temperature difference, ΔTlm will be highest?

  3. The fouling factor in case of heat exchangers is given by ________

  4. In heat transfe,r NTU is given by ________.

    (Where U = heat transfer co-efficient, A = surface area, C = Heat capacitance, min = Minimum, max = Maximum

  5. Which of the following heat exchangers gives parallel and linear temperature profile for both cold and hot fluid?

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