Abstract:
Heat and fluid flow characteristics for sinusoidal smooth pipes with different wavelength and amplitude have been investigated experimentally. The effects of the dimensionless wavelength (a/d(i)) and the amplitude (b/d(i)) on the thermal performance of a sinusoidal pipe inside a straight pipe heat exchanger are investigated. The experiments employed one straight smooth pipe, five sinusoidal smooth pipes at different a/d(i) and three sinusoidal smooth pipes at different b/d(i). The Reynolds number ranged from 8.8 x 10(3) to 2.8 x 10(4), and the Prandtl number ranged from 4.53 to 5.85. The range of the dimensionless wavelength (b/d(i)) is from 18.52 to 55.55, and the dimensionless amplitude (a/d(i)) range is from 4 to 13.6. The results showed that the heat transfers in sinusoidal pipes are increased in all cases of a/d(i) and b/d(i) above those of the straight pipe. Also, the friction factor(f) in the sinusoidal pipes is increased in all cases of a/d(i) and b/d(i) above that of the straight pipe. The dimensionless exergy loss (e) decreases with the increase of b/d(i), but in the case of a/d(i), the maximum of e is attained at a/d(i) = 6.22 and the minimum is attained at a/d(i) = 13.6. Correlations of Nu and f as a function of Re, b/d(i) and a/d(i) are presented. Also, a correlation of e as a function of Re, b/d(i) and a/d(i) is given. (c) 2007 Elsevier Ltd. All rights reserved.