Heat Transfer and Fluid Flow in Naturally Ventilated Greenhouses

M. Elashmawy, A. A. A. A. Al-Rashed, L. Kolsi, I. Badawy, N. B. Ali, S. S. Ali

Abstract


In this paper, heat transfer and fluid flow in naturally ventilated greenhouses are studied numerically for tow configuration according to the number and positions of the opening. The equations governing the phenomenon are developed using the stream function-vorticity formalism and solved using the finite volume method. The aim of the study is to investigate how buoyancy forces influence airflow and temperature patterns inside the greenhouse. Rayleigh number is the main parameter which changes from 103 to 106 and Prandtl number is fixed at Pr=0.71. Results are reported in terms of stream function, isotherms and average Nusselt number. It is found that the flow structure is sensitive to the value of Rayleigh number and the number of openings. Also, that using asymmetric opening positions improve the natural ventilation and facilitate the occurrence of buoyancy induced upward cross-airflow inside the greenhouse.


Keywords


natural ventilation; open greenhouse; heat transfer; fluid flow

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References


L. Okushima, S. Sase, M. Nara, “A support system for natural ventilation design of greenhouse based on computational aerodynamics”, Acta Horticulturae, Vol. 248, pp. 129–136, 1989

M. A. Lamrani, T. Boulard, J. C. Roy, A. Jaffrin, “Airflow and temperature patterns induced in a confined greenhouse”, Journal of Agricultural Engineering Research, Vol. 78, pp. 75–88, 2001

J. I. Montero, P. Munoz, A. Anton, N. Iglesias, “Computational fluid dynamic modelling of night-time energy fluxes in unheated greenhouses”, Acta Horticulturae, Vol. 693, pp. 403–410, 2005

P. E. Bournet, V. Winiarek, G. Chassériaux, “Coupled energy radiation balance in a closed partitioned glasshouse during night using computational fluid dynamics”, International Symposium on Greenhouse Cooling: Methods, Technologies and Plant Response, Alméria, Spain, 24–27 April, 2006

T. Boulard, R. Haxaire, M. A. Lamrani, J. C. Roy, A. Jaffrin, “Characterization and modelling of the air fluxes induced by natural ventilation in a greenhouse”, Journal of Agricultural Engineering Research, Vol. 74, pp. 135–144, 1999.

S. Sase, T. Takakura, M. Nara, “Wind tunnel testing on airflow and temperature distribution of a naturally ventilated greenhouse”, Acta Horticulturae, Vol. 148, pp. 329–336, 1984

A. Mistriotis, C. Arcidiacono, P. Picuno, G. P. A. Bot, G. Scarascia-Mugnozza, “Computational analysis of ventilation in greenhouses at zero and low-windspeed”, Agricultural and Forest Meteorology, Vol. 88, pp. 121–135, 1997

T. Bartzanas, C. Kittas, “Optimisation of greenhouses ventilation performance with computational fluid dynamics”, 2nd Southeastern Europe Fluent Users Group Meeting, Bucharest Romania, 2001

J. I. Montero, G. R. Hunt, R. Kamaruddin, A. Anton, B. J. Bailey, “Effect of ventilator configuration on wind driven ventilation in a crop protection structure for the tropics”, Journal of Agricultural Engineering Research, Vol. 80, No. 1, pp. 99–107, 2001

C. Kittas, B. Draoui, T. Boulard, “Quantification of the ventilation of a greenhouse with a roof opening”, Agricultural and Forest Meteorology, Vol. 77, No. 1, pp. 95–111, 1995

S. V. Patankar, Numerical Heat Transfer and Fluid Flow, Hemisphere, McGraw Hill, New York. 1980.

K. Khanafer, K. Vafai, M. Lightstone, “Buoyancy-driven heat transfer enhancement in a two-dimensional enclosure utilizing nanofluids”, International Journal of Heat and Mass Transfer, Vol. 46, pp. 3639–3653, 2003




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