Documents disponibles écrits par cet auteur

Air-side heat-transfer enhancement by a new winglet-type vortex generator array in a plain-fin round-tube heat exchanger / J. He in Journal of heat transfer, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 7 (Juillet 2010) . - pp. [071801-1/9] Titre : Air-side heat-transfer enhancement by a new winglet-type vortex generator array in a plain-fin round-tube heat exchanger Type de document : texte imprimé Auteurs : J. He, Auteur ; L. Liu, Auteur ; A. M. Jacobi, Auteur Article en page(s) : pp. [071801-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Heat  exchanger  Fin-and-tube  V  formation  Vortex  generator  Winglet  array Index. décimale : 536 Chaleur. Thermodynamique Résumé : The impact of a vortex-generation technique for air-side heat-transfer improvement is experimentally investigated through full-scale wind-tunnel testing of a plain-fin round-tube heat exchanger under dry-surface conditions. Inspired by the formation locomotion of animals in nature, a new vortex generator (VG) array deployed in a “V” is proposed in the present work, aiming to create constructive interference between vortices. The array is composed of two delta-winglet pairs and placed at an attack angle of 10 deg or 30 deg. Its effectiveness is compared with a baseline configuration and two conventional single-pair designs placed at 30 deg, a small pair with half the area of the array and a large pair with the same area as the array. The frontal air velocity considered ranges from 2.3 m/s to 5.5 m/s, corresponding to a Reynolds number range based on the hydraulic diameter of 1400–3400. The experimental results show little impact of the 10 deg array and a moderate heat-transfer improvement of up to 32% for the small pair, both introducing additional pressure loss of approximately 20–40%. For the 30 deg array and the large pair, similar augmentation of 25–55% in air-side heat-transfer coefficient is obtained accompanied by average pressure drop penalties of 90% and 140%, respectively. Performance evaluation using the criteria of the modified area goodness factor and the volume goodness factor indicates the superiority of the heat exchanger enhanced by the 30 deg array among all the investigated VGs. The VG array is found more effective at comparatively low Reynolds numbers, representative of many heating, ventilation, air-conditioning, and refrigeration applications and compact heat-exchanger designs. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Air-side heat-transfer enhancement by a new winglet-type vortex generator array in a plain-fin round-tube heat exchanger [texte imprimé] / J. He, Auteur ; L. Liu, Auteur ; A. M. Jacobi, Auteur . - pp. [071801-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 7 (Juillet 2010) . - pp. [071801-1/9] Mots-clés : Heat  exchanger  Fin-and-tube  V  formation  Vortex  generator  Winglet  array Index. décimale : 536 Chaleur. Thermodynamique Résumé : The impact of a vortex-generation technique for air-side heat-transfer improvement is experimentally investigated through full-scale wind-tunnel testing of a plain-fin round-tube heat exchanger under dry-surface conditions. Inspired by the formation locomotion of animals in nature, a new vortex generator (VG) array deployed in a “V” is proposed in the present work, aiming to create constructive interference between vortices. The array is composed of two delta-winglet pairs and placed at an attack angle of 10 deg or 30 deg. Its effectiveness is compared with a baseline configuration and two conventional single-pair designs placed at 30 deg, a small pair with half the area of the array and a large pair with the same area as the array. The frontal air velocity considered ranges from 2.3 m/s to 5.5 m/s, corresponding to a Reynolds number range based on the hydraulic diameter of 1400–3400. The experimental results show little impact of the 10 deg array and a moderate heat-transfer improvement of up to 32% for the small pair, both introducing additional pressure loss of approximately 20–40%. For the 30 deg array and the large pair, similar augmentation of 25–55% in air-side heat-transfer coefficient is obtained accompanied by average pressure drop penalties of 90% and 140%, respectively. Performance evaluation using the criteria of the modified area goodness factor and the volume goodness factor indicates the superiority of the heat exchanger enhanced by the 30 deg array among all the investigated VGs. The VG array is found more effective at comparatively low Reynolds numbers, representative of many heating, ventilation, air-conditioning, and refrigeration applications and compact heat-exchanger designs. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Load transfer behaviour of a tapered rigid pile / J. Liu in Géotechnique, Vol. 62 N° 7 (Juillet 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 7 (Juillet 2012) . - pp. 649 –652 Titre : Load transfer behaviour of a tapered rigid pile Type de document : texte imprimé Auteurs : J. Liu, Auteur ; J. He, Auteur ; Y.-P. Wu, Auteur Année de publication : 2012 Article en page(s) : pp. 649 –652 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Numerical  modelling  Settlement  Piles  Bearing  capacity  Model  tests Résumé : Based on Mohr–Coulomb theory and the load transfer method, a new method of analysing the load–settlement relation and the axial force distribution model in a tapered pile is suggested. The method proposed in the paper considers the influence of the pile–soil radial interaction on the bearing capacity and settlement behaviour. The calculation results show that the pile–soil radial interaction is strengthened and the bearing capacity of a single pile is increased when the taper angle of a rigid pile is increased. The reliability was verified by two model tests. Calculated results obtained by the proposed method were compared with the test data. The close agreement between the calculated and measured values confirmed that the method is reasonably accurate for analysing the behaviour of tapered rigid piles. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.T.001 [article] Load transfer behaviour of a tapered rigid pile [texte imprimé] / J. Liu, Auteur ; J. He, Auteur ; Y.-P. Wu, Auteur . - 2012 . - pp. 649 –652. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 7 (Juillet 2012) . - pp. 649 –652 Mots-clés : Numerical  modelling  Settlement  Piles  Bearing  capacity  Model  tests Résumé : Based on Mohr–Coulomb theory and the load transfer method, a new method of analysing the load–settlement relation and the axial force distribution model in a tapered pile is suggested. The method proposed in the paper considers the influence of the pile–soil radial interaction on the bearing capacity and settlement behaviour. The calculation results show that the pile–soil radial interaction is strengthened and the bearing capacity of a single pile is increased when the taper angle of a rigid pile is increased. The reliability was verified by two model tests. Calculated results obtained by the proposed method were compared with the test data. The close agreement between the calculated and measured values confirmed that the method is reasonably accurate for analysing the behaviour of tapered rigid piles. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.T.001