Abstract
This study performed evaluations of the shell and helically-coiled tube heat exchangers with various dimple arrangements, that is, flat, inline, staggered, and bulged, at different Dean numbers (De) and inlet temperatures of a hot channel. Conjugated heat transfer was analyzed to evaluate the heat transfer performance of the exchangers through temperature difference between the inlet and outlet, Nusselt number inside the coiled tube, and pressure drop of the coiled tube by using 3-D Reynolds-averaged Navier–Stokes (RANS) equations with shear stress transport turbulence closure. A grid dependency test was performed to determine the optimal number of the grid system. The numerical results were validated using the experimental data, and showed good agreement. The inline and staggered arrangements show the highest temperature differences through all De. The staggered arrangement shows the best heat transfer performance, whereas the inline arrangement shows the second highest performance with all ranges of De and the hot channel’s inlet temperature. The inline and staggered arrangements show the highest pressure drop among all inlet temperatures of the hot channel.
Highlights
Pyrolysis is defined as one of the most effective and efficient processes of thermal decomposition to obtain energy in the form of char from resources in an anoxic condition
Fesanghary et al [15] explored the use of global sensitivity analysis (GSA) and a harmony search algorithm (HSA) for design optimization of shell and tube heat exchanger (STHX) from the economic viewpoint; total cost of STHXs are identified using GSA
The results show that, based on the same shell-side flow rate, the heat transfer coefficient of the heat exchanger with helical baffles is lower than that of the heat exchanger with segmental baffles, while the shell-side pressure drop of the exchanger with helical baffles is even lower
Summary
Pyrolysis is defined as one of the most effective and efficient processes of thermal decomposition to obtain energy in the form of char from resources in an anoxic condition. Fesanghary et al [15] explored the use of global sensitivity analysis (GSA) and a harmony search algorithm (HSA) for design optimization of STHXs from the economic viewpoint; total cost of STHXs are identified using GSA They compared the HSA results with those obtained using GA, and revealed that the HSA can converge to an optimum solution with higher accuracy. Many researchers have focused on the STHX systems to enhance the heat transfer performance during condensation of odorized materials. There has been no attempt to develop a new combined system with the dimpled helical tube that enhances the heat transfer performance of the STHX systems. The present study suggests several arrangements of the dimples on the helical tube; the heat transfer performance was evaluated in terms of the Nusselt number.
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