## THERMAL SCIENCE

International Scientific Journal

### Thermal Science - Online First

online first only
### Three dimensional CFD analysis of buoyancy-driven natural ventilation and entropy generation in a prismatic greenhouse

**ABSTRACT**

A computational analysis of the natural ventilation process and entropy generation in three-dimensional (3-D) prismatic greenhouse was performed using computational fluid dynamics (CFD). The aim of the study is to investigate how buoyancy forces influence airflow and temperature patterns inside the greenhouse having lower level opening in its right heated facade and also upper level opening near the roof top in the opposite cooled facade. The bottom and all other walls are assumed to be perfect thermal insulators. 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 particles trajectories, iso-surfaces of temperature, mean Nusselt number, and entropy generation. It has been found that the flow structure is sensitive to the value of Rayleigh number and that heat transfer increases with increasing this parameter. Also, it have been noticed that, using asymmetric opening positions improve the natural ventilation and facilitate the occurrence of buoyancy induced upward cross-airflow (low-level supply and upper-level extraction) inside the greenhouse.

**KEYWORDS**

PAPER SUBMITTED: 2015-10-15

PAPER REVISED: 2016-02-22

PAPER ACCEPTED: 2016-03-02

PUBLISHED ONLINE: 2016-03-12

- Okushima, L., Sase, S., Nara, M., A support system for natural ventilation design of greenhouse based on computational aerodynamics. Acta Horticulturae, 248 (1989), pp. 129-136.
- Lamrani, M.A., Boulard, T., Roy, J.C., Jaffrin, A., Airflow and temperature patterns induced in a confined greenhouse. Journal of Agricultural Engineering Research 78 (2001), pp. 75-88.
- Montero, J.I., Munoz, P., Anton, A., Iglesias, N., Computational fluid dynamic modelling of nighttime energy fluxes in unheated greenhouses. Acta Horticulturae 693 (2005), pp. 403-410.
- Boulard, T., Haxaire, R., Lamrani, M.A., Roy, J.C., Jaffrin, A., Characterization and modelling of the air fluxes induced by natural ventilation in a greenhouse. Journal of Agricultural Engineering Research 74 (1999a), pp. 135-144.
- Sase, S., Takakura, T., Nara, M., Wind tunnel testing on airflow and temperature distribution of a naturally ventilated greenhouse. Acta Horticulturae 148 (1984), pp. 329-336.
- Mistriotis, A., Arcidiacono, C., Picuno, P., Bot, G.P.A., Scarascia-Mugnozza, G., Computational analysis of ventilation in greenhouses at zero and low-windspeed. Agricultural and Forest Meteorology 88 (1997a), pp. 121-135.
- Montero, J.I., Hunt, G.R., Kamaruddin, R., Anton, A., Bailey, B.J., Effect of ventilator configuration on wind driven ventilation in a crop protection structure for the tropics. Journal of Agricultural Engineering Research 80 (2001), 1, pp. 99-107.
- Kittas, C., Draoui, B., Boulard, T., Quantification of the ventilation of a greenhouse with a roof opening. Agricultural and Forest Meteorology 77 (1995), 2, pp. 95-111.
- Ould Khaoua, S.A., Bournet, P.E., Migeon, C., Chassériaux, G., Boulard, T., Analysis of greenhouse ventilation efficiency with CFD. Biosystems Engineering 95 (2006), 1, pp. 83-98.
- Bournet, P.E., Ould Khaoua, S.A., Boulard, T., Numerical prediction of the effect of vents arrangements on the ventilation and energy transfers in a multispan glasshouse using a bi-band radiation model. Biosystems Engineering 98 (2007a), pp. 224-234.
- Bournet, P.E., Ould Khaoua, S.A., Boulard, T., Migeon, C., Chassériaux, G., Effect of roof and side opening combinations on the ventilation of a glasshouse using computer simulations. Transactions of the ASABE, American Society of Agricultural and Biological Engineers 50 (2007b), 1, pp. 201-212.
- Lee, I.B., Short, T.H., Sase, S., Okushima, L., Qiu, G.Y., Evaluation of structural characteristics of naturally ventilated multi-span greenhouse using computer simulation. Japan Agricultural Research Quarterly 34 (2000b), pp. 247-256.
- Kacira, M., Short, T.H., Stowell, R., A CFD evaluation of naturally ventilated multi-span, sawtooth greenhouses. Transaction of the ASAE 41 (1998), 3, pp. 833-836.
- Kacira, M., Sase, S., Ikeguchi, A., Ishii, M., Giacomelli, G., Sabeh, N., Effect of vent configuration and wind speed on three-dimensional temperature distributions in a naturally ventilated multi-span greenhouse by wind tunnel experiments. Acta Horticulturae 801 (2008), pp. 393-400.
- Lo LJ, Novoselac A. Cross ventilation with small openings: measurements in a multi-zone test building. Build Environ 57 (2012), pp. 377-386.
- Aich, W., Omri. A., Numerical Analysis of natural convection in a prismatic cavity. Thermal Science. 15 (2011), 2, pp. 437-446.
- Oztop, H. F., Kolsi, L., Borjini, M. N., Al-Salem, K., Numerical study of three-dimensional combined buoyancy and thermocapillary convection and evaluation of entropy generation. International Journal of Numerical Methods for Heat & Fluid Flow. 24 (2014), 1, pp. 148-168.
- Kolsi, L., Oztop, H. F., Borjini, M. N., Al-Salem, K., Second law analysis in a three dimensional lid-driven cavity. International Communications in Heat and Mass Transfer. 38 (2011), pp 1376-1383.
- Blocken B. 50 years of computational wind engineering: past, present and future. J Wind Eng Ind Aerodyn 129 (2014), pp. 69-102.
- Blocken B, Stathopoulos T, Carmeliet J, Hensen JLM. Application of computational fluid dynamics in building performance simulation for the outdoor environment: an overview. J Build Perform Simul 4 (2011), pp. 157-184.
- Kolsi, L., Abidi, A., Borjini, M.N., Daous, N. Ben Aïssia, H., Effect of an external magnetic field on the 3-D un steady natural convection in a cubical enclosure, Numerical Heat Transfer Part A 51 (2007), pp. 1003-1021.
- Patankar SV. Numerical Heat Transfer and Fluid Flow. PA: Taylor & Francis, Philadelphia, USA, 1981.
- Wakashima, S., Saitoh, T. S., Benchmark solutions for natural convection in a cubic cavity using the high-order time-space method. Int. J. Heat Mass Transfer 47 (2004), pp. 853-864.