Evaluating the effect of number of spans on heat transfer in greenhouses

S. Kruger, L. Pretorius

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

Abstract

The present study concerns convective flows in the empty volume above the plant canopy in a confined greenhouse. The purpose of this paper is to numerically investigate the effect of the number of spans on the convective heat transfer in closed greenhouses. The initial greenhouse CFD model cavity is validated against experimental results found in the literature. Thermal convection is induced by heating the bottom of the cavity. The numerical model is then modified to represent two- l greenhouse cavities with different numbers of spans. The computational fluid dynamic (CFD) software is then used to analyze mainly the natural convective heat transfer, velocity and temperature distributions for the single span greenhouse, as well as multi-span greenhouses (containing two and three spans). The greenhouse CFD model floor is heated, and the walls are adiabatic, corresponding to Rayleigh-Bénard convection. A mesh sensitivity analysis was conducted to determine a suitable size for the mesh. Results show that adding additional spans to the initial single-span cavity has a pronounced effect on the Nusselt-number distribution on the floor of the cavity. The temperature and velocity distributions were also significantly influenced. The four-span cavity showed three convective cells instead of four as for the lowest Rayleigh number.

Original languageEnglish
Title of host publicationHeat Transfer and Thermal Engineering
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791859452
DOIs
Publication statusPublished - 2019
EventASME 2019 International Mechanical Engineering Congress and Exposition, IMECE 2019 - Salt Lake City, United States
Duration: 11 Nov 201914 Nov 2019

Publication series

NameASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)
Volume8

Conference

ConferenceASME 2019 International Mechanical Engineering Congress and Exposition, IMECE 2019
Country/TerritoryUnited States
CitySalt Lake City
Period11/11/1914/11/19

Keywords

  • Computational Fluid Dynamics
  • Greenhouses
  • Natural convection

ASJC Scopus subject areas

  • Mechanical Engineering

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