An experimental analyze of heat transfer enhancement in tubes by means of wire coil inserts

In this study, the use of wire coil in the pipe has been investigated experimentally in order to increase the heat transfer in the flow in the pipes. Firstly, 5 different pitch range and 3 different wire diameters were investigated in the use of wire coil to increase heat transfer in the pipes. Experiments were carried out with the Re number range of 500 to 14000. Secondly, in order to increase the heat transfer in flat plate solar collectors, the effect of wire coil configuration, which is found to be more suitable according to the experiment results in the first part of the study, to collector efficiency and pressure drop is investigated. In the experimental study, it was seen that the wire coils applied inside the pipe increased the heat transfer but also caused a significant pressure drop. The improvement rate in which the increase in heat transfer and pressure drop evaluated together was used as evaluation criteria. The best rates are observed at 10mm and 15mm pitch range for Ø0.8mm and Ø1.2mm wire coil, and for Ø1.34mm double spiral wire coil it is between at 5mm and 10mm pitch range. In the flat plate solar collector, effects of the implanted wire coils with diameters of Ø0.8 and Ø1.2 and with a pitch range of 10 mm and Ø1.34 mm double spiral wire coil with a pitch range of 10 mm on the collector efficiency were separately investigated. The experiments were carried out in a solar simulator in the indoor conditions. The effect of the mass flow rate of fluid on the collector efficiency was also investigated. For this purpose, the change in collector efficiency was observed for the standard fluid flow rate of 0.02 kg/sm2 and for the standard flow rate times 1.5 and 2.25. It was observed that the collector efficiency increased with the increase of fluid flow rate. It is thought that the results of the study will be useful for collector manufacturers.