,.,,, ;,.,.,, [ 1 ]. [ 2 ],. [ 3-4 ] CFD (Computational Fluid Dynam ic),, :, 25%. [ 5 ],. [ 6 ] CFD,, CFD. CFD, CFD,,. 2 / 18 /mm 85 /mm 360

Size: px

Start display at page:

Download ",.,,, ;,.,.,, [ 1 ]. [ 2 ],. [ 3-4 ] CFD (Computational Fluid Dynam ic),, :, 25%. [ 5 ],. [ 6 ] CFD,, CFD. CFD, CFD,,. 2 / 18 /mm 85 /mm 360"

矮苍
5 years ago
Views:

1 Journal of Beijing University of Aeronautics and A stronautics October 2008 Vol. 34 No110 CFD (, ) (, ) (, ) :.,,,.,;, ;,,.,. : ; ; (CFD ) : TK 519 : A : (2008) C FD study of fluid flow in an a ll2g la ss evacua ted tube so la r w a te r hea te r A i N ing (College ofmechanical Engineering, Zhejiang University of Technology, Hangzhou , China) Fan J ianhua (Dep t. of Civil Engineering, Technical University of Denmark, Copenhagen) L i Yum in (College of Chem ical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou , China) Ab s tra c t: The all2glass evacuated tube solar water heater is one of the most w idely used solar therm al technologies. The aim of the paper is to investigate fluid flow in the solar water heater by means of the compu2 tational fluid dynam ics ( CFD). The investigation was carried out w ith a focus on the convective heat transfer in the tube. The buoyancy induced flow circulation in different parts of the tube was analyzed. It is shown that fluid flow becomes stochastic and turbulent if fluid temperature is high enough. The flow instability leads to m ixing of the warm up rising flow and the cold downward flow, which decreases efficiency of the heat exchange p rocess. A baffle in the tube can p revent the flow instability and secure the flow circulation in the tube. The results of the investigation p rovide a helpful guidance for further investigation of the mechanism of heat transfer p rocesses and a reference for future system op tim ization. Ke y wo rd s: all2glass evacuated tube solar water heater; flow field; computational fluid dynam ic (CFD),. : : ( ),,,, aining@ zjut. edu. cn.

2 ,.,,, ;,.,.,, [ 1 ]. [ 2 ],. [ 3-4 ] CFD (Computational Fluid Dynam ic),, :, 25%. [ 5 ],. [ 6 ] CFD,, CFD. CFD, CFD,,. 2 / 18 /mm 85 /mm 360 /mm /L 160 ( ) 1. 2 CFD /W (m K) - 1 /% /% /mm , 1., 45.,,., W /m 2, 80W.,,,, 650 W /m 2, 2 A. [ 3 ]., 0. 85W / (m 2 K), /mm 58 /mm 1. 7 /mm 47 /mm 1. 5 /mm % /mm ( 1. 5) (80 5 ) 1 CFD, W / (m K)., = T T 2 = T ,, kg/m 3 ;, kg/ (m s) ; T, K.,, 2.

10 : CFD 1197. CFD, 20,, 20 s. 3 CFD [ 3 ] P IV a A b B 2 39 40, P IV., CFD P IV., CFD. 2. 2, :,,, ;,. CFD, 4. 2 2. 1 CFD. 3.,,,., CFD [ 3 ] P IV ( Particle Image Velocimetry), 3.

3 10 : CFD CFD, 20,, 20 s. 3 CFD [ 3 ] P IV a A b B , P IV., CFD P IV., CFD. 2. 2, :,,, ;,. CFD, CFD. 3.,,,., CFD [ 3 ] P IV ( Particle Image Velocimetry), 3. 3, CFD, CFD m / s, P IV m / s. CFD P IV : [ 3 ] P IV 52 mm 1. 42m, CFD 44 mm 1. 8m; CFD 650W /m 2, 4 4, 1 2, m, 2, 1 2,. 2,,,. 3 CFD

1198 2008. 600 5.,,, ; 38 39,.,.,,. 5 600 2 400 6.

2m, 1 3. 7., 0. 3 0. 6m,. 0. 3 m, 0. 3 0. 6m,,,,.

4 ,,, ; 38 39,.,.,, ,,.,,..,,,. R e 9 400,,.,,,. 4,.,,. 0. 3, m, , m, m, m,,,,.,,,, 3, 17% 254%., CFD,. : m, ;,, ; 91 95,

5 10 : CFD 1199 ;,., 1. 2m,.,,. ( References) [ 1 ],,. CFD2P IV [ J ]., 2007, 26 ( 4) : A i N ing, Fan Jianhua, Ji Jianbing. Overview of CFD and PIV app lication in investigation of solar thermal system s[ J ]. Chem i2 cal Industry and Engineering Process, 2007, 26 ( 4) : ( in Chinese) [ 2 ] Harding G L, Yin Z. Thermosyphon circulation in solar water heaters incorporating evacuated tubular collectors and a novel water in glass manifold[ J ]. Solar Energy, 1985, 34 (1) : [ 3 ] Morrison G L, Budihardjo I, BehniaM. Measurement and simu2 lation of flow rate in a water2in glass evacuated tube solar water heater[ J ]. Solar Energy, 2005, 78 (3) : [ 4 ] Morrison G L, Budihardjo I, Behnia M. W ater in glass evacua2 ted tube solar water heaters[ J ]. Solar Energy, 2004, 76 ( 1-3) : [ 5 ] Hollands K G, L ightsone M F. A review of low2flow, stratified2 tank solar water2heating system s [ J ]. Solar Energy, 1989, 43 (2) : [ 6 ] Consul R, Rodriguez I, Perez Segarra C D, et al. V irtual p roto2 typing of storage tanks by means of three dimensional CFD and heat transfer numerical simulations[ J ]. Solar Energy, 2004, 77 (2) : ( : ) ( 1194 ) 4,,.,,., < ( References) [ 1 ] Chen Y, Heister S D. A numerical treatment for attached cavita2 tion flows[ J ]. Journal of Fluids Engineering, 1994, 116: [ 2 ] Deshpande M, Feng J, Merkle C L. Numerical modeling of the thermodynamic effects of cavitation[ J ]. Journal of Fluids Engi2 neering, 1997, 119: [ 3 ] Delannoy Y, Kueny J L. Cavity flow p redictions based on the Euler equations [ J ]. ASME Cavitation and Multi2Ohase Flow Forum, 1990, 109: [ 4 ] Chen Y, Heister SD. Modeling hydrodynam ic nonequilibrium in cavitating flows[ J ]. Journal of Fluids Engineering, 1996, 118: [ 5 ] Kubota A, Kato H, Yamaguchi H. A new modeling of cavitating flows: a numerical study of unsteady cavitation on a hydrofoil section[ J ]. J Fluidsmech, 1992, 240: [ 6 ] Merkle C L, Feng J, Buelow P E O. Computational modeling of the dynamics of sheet cavitation[ C ] / / 3 rd International Sympo2 sium on Cavitations. Grenoble, France: [ s. n. ], 1998 [ 7 ] Kunz F R, Boger A D, Stinebring R D, et al. A preconditioned Navier2Stokesmethod for two2phase flowswith application to cav2 itation prediction[ R ]. A IAA , 1999 [ 8 ] Buelow P E O, Venkateswaran S, Merkle C L. Grid aspect ratio effects on the convergence of upwind schemes[ R ]. A IAA , 1995 [ 9 ] Rouse H, McNown J S. Cavitation and pressure distribution, head form s at zero angle of yaw[d ]. City of Ames: Engineering, Bulletin 32, State University of Iowa, 1948 ( :)

1, : FLUENT 81 CA4113Z,,,,.,,. [ ] : :, 9 9t (<) + div (u<) = div ( < grad<) + S < (1) t, u, <, <, < S <,, 1., u i i, E,. k - RNG, () (3) [ 3-4 ],. 5

1, : FLUENT 81 CA4113Z,,,,.,,. [ ] : :, 9 9t (<) + div (u<) = div ( < grad<) + S < (1) t, u, <, <, < S <,, 1., u i i, E,. k - RNG, () (3) [ 3-4 ],. 5 38 1 010 () Journal of Fuzhou University(Natural Science) Vol. 38 No. 1 Feb. 010 : 1000-43 (010) 01-0080 - 06 FLUENT,, (, 350108) : (CFD), Fluent,,.,,,.,,,., CFD,,,. : FLUENT; ; ; ; : TK4 : A Num er ica