Analysis of natural convection in a mono-span naturally ventilated greenhouse

Sunita Kruger, Leon Pretorius

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

4 Citations (Scopus)

Abstract

Natural convection in a two-dimensional enclosure as an approximation to a greenhouse is numerically investigated using Computational Fluid Dynamics. The cavity consisted of two adiabatic vertical walls, an isothermal horizontal wall located at the bottom at Th and the top wall isothermal at Tc. The configuration was investigated for Ra = 9.1 x 107 to Ra = 1.9 x 109 (turbulent) and corresponds to the classic Rayleigh- Benard convection. Simulations are performed firstly for a square enclosure to compare to experimental values found in the literature. The geometry is then modified to represent a mono-span closed greenhouse as well as a greenhouse containing a roof vent. The results are presented using isotherm and vector plots. The convective heat transfer at the hot wall was investigated by calculating the local and average Nusselt numbers. Results from the initial simulations for the square cavity correlated well with the experimental data found in the literature when the low-Reynolds number k-epsilon turbulence model was applied. The influence of the roof angle was found to have a relatively small effect for small roof angles compared to the initial 0 degree roof angle case, and increases significantly if the roof angle is increased to 60 Degrees. A roof angle of 30 degrees exhibits completely different behavior compared to the other roof angles investigated. If a roll-up vent is added to the leeward side of the cavity the local Nusselt numbers on the hot wall are influenced. A slight decrease is visible for Ra = 4.27 x 108 when compared to the closed greenhouse, while a small increase can be seen for Ra = 1.35 x 109 and Ra = 1.9 x 109.

Original languageEnglish
Title of host publication8th South African Conference on Computational and Applied Mechanics, SACAM 2012 - Conference Proceedings
EditorsAndre Leon Nel, Nickey Janse van Rensburg, Daniel M. Madyira
PublisherSouth African Association for Theoretical and Applied Mechanics (SAAM)
Pages234-243
Number of pages10
ISBN (Electronic)9780869707289
Publication statusPublished - 2012
Event8th South African Conference on Computational and Applied Mechanics, SACAM 2012 - Johannesburg, South Africa
Duration: 3 Sept 20125 Sept 2012

Publication series

Name8th South African Conference on Computational and Applied Mechanics, SACAM 2012 - Conference Proceedings

Conference

Conference8th South African Conference on Computational and Applied Mechanics, SACAM 2012
Country/TerritorySouth Africa
CityJohannesburg
Period3/09/125/09/12

Keywords

  • Compultational fluid dynamics
  • Greenhouse
  • Natural convection
  • Natural ventilation

ASJC Scopus subject areas

  • Computational Mechanics
  • Mechanical Engineering

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