Influence of helix twisted tape on heat transfer and friction factor in forced circulation V-trough solar water heater

Abstract

The effect of helix twisted tape with several twist ratios (Y = 3, 4, 5 and 6) in a V-trough solar water heater for enhancing heat transfer, thermal performance and the friction factor has been examined experimentally in forced circulation with the Reynolds number ranging from 3000 to 23,000. The experimental results of plain V-trough solar collector (PVT) fitted with the standard equations and the variation in the Nusselt number are ±7.23% and the variation in friction factor is about ±5.91%. The PVT has been compared with plain flat plate (PFP) collector. The obtained result shows that the average Nusselt number of PVT performs better than PFP by 8.4%. This is owing to the additional reflectors, reflection of the solar incident rays to the receiver plate, which tend to rise in the temperature gradient of water inlet and outlet of the system. The thermal performance has been increased further by inserting the helix twisted tape with several twist ratios and the results are also presented. The minimum twist ratio 3 provides a higher heat transfer rate and friction factor owing to the increase in the hydraulic length and swirl flow. The experimental Nusselt number and friction factor are correlated and the deficiency falls ±6.44% and ±11.91%, respectively.

Keywords

• reflector
• swirl flow
• forced circulation
• heat transfer
• friction factor