Optimization of a high-temperature recuperator equipped with corrugated helical heat exchanger for improvement of thermal-hydraulic performance

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The main aim of present study is to optimize a high-temperature recuperator equipped with corrugated helical heat exchanger numerically. This heat exchanger has inner corrugations and/or outer blades. Different geometrical parameters are analyzed according to thermal-hydraulic performance (THP) of the studied helical heat exchanger. The model with the maximum THP evaluation criteria index is introduced as the optimum model. Moreover, the effects of ash fouling characteristics on THP of recuperator are presented. The ash particles material is chosen K2SO4 with the density of 2665 kg/m3. As it is realized in this paper, in case of simulating the problem in steady-state condition, employing the two-phase model achieves to higher average Nusselt number (Nu) values versus all considered mass flow rates. However, it should be noted that in these two approaches the ash fouling characteristics are not determined. By transient solving, the ash fouling characteristics are applied on the outer wall of helical heat exchanger and therefore the convectional heat transfer coefficient is reduced. Hence, in case of employing two phase approach (with ash fouling characteristics) model, lower average Nu values are achieved and it is clear that these values are more validated than attained values from two other approaches. Usage of inner and/or outer corrugations has a substantial influence on THP of recuperator and increases the PEC index values versus all considered mass flow rates sharply. The recuperator equipped with finned helical heat exchanger with a = 3 mm, b = 7 mm, H = 8 mm, g = 2 mm and f = 3 mm is introduced as the optimum model in present work.