Numerical and experimental investigation of heat transfer augmentation potential of wire-loop structures

• Potential of wire-loop structures for heat transfer augmentation was investigated.
• Periodically fully-developed turbulent flow in a repeating module was analyzed.
• Turbulence was addressed by realizable k–ε model for a different Reynolds number.
• Effects of loop-density and loop-orientation were numerically studied.
• Loop-density has a stronger effect as compared to loop-orientation on performance.

The present paper explores the possibility of using wire-loop structures on the active plate of a parallel plate channel for efficient heat transfer augmentation. For this purpose, numerical simulations were carried out for periodically fully-developed turbulent flow in typical repeating modules using the realizable k–ε model. Experiments were also conducted in order to validate some of the results obtained from numerical simulations. For both studies, the Reynolds number was varied from 2000 to 20,000. The effect of three different loop-densities on fluid flow and heat transfer characteristics were investigated when wire-loops were placed perpendicular to the main flow direction, whereas the effect of loop-orientations on these parameters were studied for a fixed loop density of 2270 loops/m2. While for all investigated cases, substantial heat transfer augmentation was observed with wire-loop structures as compared to the empty parallel plate channel under the condition of identical pressure gradient, the thermal-hydraulic performance improved significantly with the increase in loop-density. The maximum attainable loop-density, however, was found to strongly depend on the loop-orientation owing mainly to the geometric as well as manufacturing constraints. It was also observed that loops, oriented diagonally to the main flow direction offer the best performance, although it is less sensitive to loop-orientation as compared to the loop-density.