ON the DESIGN of TRIPLE CONCENTRIC‐TUBE HEAT EXCHANGERS1

Abstract

ABSTRACTA set of analytical equations for a triple‐tube heat exchanger was developed. They allow for independent computations of bulk (cross‐sectional area averaged) fluid temperatures at any axial location along the heat exchanger and are valid for parallel and counter flow configurations. the equations account for heat losses to the surroundings and are useful for design purposes. Mass flow rates, inlet fluid temperatures and heat transfer coefficients are input parameters required for temperature calculations. A simplified approximate equation for total rate of heat transfer, in terms of logarithmic mean temperature differences, was derived for well‐insulated heat exchangers and tested with the analytical equations. A case study is presented and the computational procedure is discussed. Results obtained with the simplified total rate of heat transfer equation were in excellent agreement with those obtained with the analytical equations. Simulations show that the creation of an annular region within the inner pipe increases the overall heat transfer efficiency and reduces the heat exchanger length requirement by almost 25%.