Investigation of a tube in tube conically coil heat exchanger thermal and fluid flow performance characteristics
摘要
The thermal and fluid flow characteristics of a tube in tube conical coiled heat exchanger (TTCCHE) were experimentally conducted. This research tends to improve the thermal performance characteristics of a curved tube. The effects of different design parameters, including coil torsions, λ; inclination angles, α; the Dean number, Dn; and flow arrangements for both the inner and annulus fluid sides were examined. Three test samples with different torsions, λ, values of 0.0352, 0.0713, and 0.1115 were designed, manufactured, and tested in both parallel and counterflow arrangments. Three different inclination angles, α, values of 0°, 45°, and 90° were also examined. The experimental runs were carried out in at from 2000 ≤ Dni ≤ 10,833 (corresponding to 12,300 ≤ Rei ≤ 62,600) for the inner tube side and from 430 ≤ Dno ≤ 3200 (corresponding to 2500 ≤ Reo ≤ 18,500) for the annulus. The results revealed that the TTCCHE coil torsion of λ = 0.0352 results in a significant increase in the Nu for both the inner and the annulus sides by 40.9% and 32.2%, respectively. The coil inclination angle of 90° has a noticeable influence on increasing Nu for both the inner and annulus fluid sides by 23.7% and 21.6%, respectively, compared with that of 45°. The maximum thermohydraulic performance criteria reach 1.45 and 2.26 for the inner tube and annulus sides at α = 90° and λ of 0.0352, respectively. New correlations to predict the Nu and f for both the inner tube and the annulus were presented.