ENHANCED HEAT-TRANSFER CHARACTERISTICS OF SINGLE-PHASE FLOWS IN A PLATE HEAT-EXCHANGERS WITH MIXED CHEVRON PLATES

The enhanced thermal-hydraulic performance of single-phase flows in a plate heat exchanger with mixed chevron plates is investigated experim entally. The mixed arrangement consists of plates with chevron angle b eta = 30 degrees and 60 degrees, alternatingly stacked in a single-pas s, U-type, counterflow configuration. Vegetable oil(130 < Pr < 220) an d water (2.4 < Pr < 4.5) are used as test fluids, with flow rates in t he laminar, transition, and turbulent flow regimes (2 < Re < 6000). Re sults for isothermal friction factor and heat transfer under cooling c onditions, along with respective correlations for laminar (2 < Re < 40 0) and fully developed turbulent (Re greater than or equal to 1000) fl ows are presented; transition is observed to set in when Re similar to 500. The heat transfer data are obtained from controlled experiments, employing an extension of the Wilson Plot technique. A comparison of the data with previously reported results and predictive equations for Nu and f highlights the latter's lack of general applicability, and t he need for a larger database. The relative impact of using mixed chev ron plate arrangement is discussed, and their enhanced performance, in comparison with parallel-plate channels, is evaluated.