摘要

This paper presents the results of an experimental study of a heat transfer enhancement device to evaluate its performance. The convective heat transfer coefficient was determined experimentally with an enhancement device, wire-coil inserts, placed within the inner tube of a concentric tube heat exchanger. The experimental study was conducted over a range of Re=13,500 to 112,000 in separate test series. Friction factor data is also reported together with Nu∼Re results. Results obtained with wire-coil inserts constructed with stainless steel wires 0.813 mm, 1.016 mm and 1.575 mm in diameter and with coil pitch of 8.47 mm, 5.08 mm, 3.63 mm and 2.82 mm are presented. These measurements were obtained with steady state method as well as transient-based technique developed by the co-authors. The maximum uncertainties in the experimental data for convective heat transfer coefficient as well as friction factor both are estimated to be less than ±10% and ±20% for steady-state and transient-based techniques respectively. Results indicate that the convective heat transfer coefficient increased by a factor of 1.6 to 2.4 accompanied by 10 to 25-fold increase in friction factor (f). The performance evaluation using exergy analysis is also presented. It is shown that the exergy analysis provides a method to evaluate the performance of these devices for selection and/or determination of the most effective device.