Turbulent flow and heat transfer measurements in helically grooved tube

Tubes with grooved inner surfaces are widely used in heat exchangers of refrigerators and air conditioners. Although great databases exist, the state-of-the-art correlations often fail in predicting pressure drop or heat transfer coefficient for new groove patterns or new refrigerant media. CFD can be useful in simulation of interesting phenomena in grooved tubes, but the accuracy of these calculations can be proven only by experimental validation. The goal of this paper is to provide CFD calculations with accurate measurements and investigate measurement difficulties. Pressure drop and heat transfer coefficient are measured in low Re range (4000 to 12000). A new method is established for visualizing flow inside helically grooved microfin tubes. Copper pipes are filled with silicone rubber mold; then the solid silicone rod is coated with epoxy resin. Visually determined flow patterns provide qualitative understanding of physical phenomena. This fact underlines the importance of development of transparent pipe measurements.