The Effect of Concentration Change on Heat Transfer in Drag-Reducing Solutions
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Date
2018-05
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The Ohio State University
Abstract
Worm-like surfactant micelles are already being used to efficiently and inexpensively transport fluids by reducing the effect of pressure loss in turbulent flow. However, these solutions are not easily used in systems that require changes in temperature since these micelles also reduce the effect of heat transfer. It has been found that for a certain aqueous drag-reducing solution that combines zwitterionic and cationic surfactants, adding solvent to the solution can cause these micelles to precipitate. When these micelles have precipitated out of solution, they are no longer able to reduce drag and heat transfer. Therefore, for this research project, the concentration of drag-reducing solutions in a lab-scale piping system was changed in order to test whether or not dilution and re-concentration are viable methods for turning drag and heat transfer reduction on and off. To do this, a zwittercationic solution at a concentration nearly low enough to exhibit dilution precipitation was tested for drag reduction and heat transfer reduction in a recirculating flow system. The solution was diluted and tested until drag and heat transfer reduction were no longer evident. The solution was brought back to its original concentration by using a reverse osmosis membrane to take out water. As the solution was re-concentrated, it was tested to see if drag and heat transfer reduction came back. Graphs showing the drag reduction and heat transfer reduction in comparison to water at varying Reynolds numbers were produced for the zwittercationic solution used in this experiment. These graphs were then analyzed to determine if concentration change was a feasible method for reducing drag with little to no heat transfer reduction. The graphs showed that concentration change is a legitimate method for improving heat transfer in this drag-reducing solution. However, any success with this concentration change method was largely dependent on time between dilution and re-concentration stages and ignoring potential membrane fouling that would occur during long-term use, making this an unlikely method for improving heat transfer in re-circulating flow systems in the near future.
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Keywords
Drag Reduction, Heat Transfer Reduction, Surfactant, Fluid Dynamics, Reverse Osmosis, Concentration