Numerical Investigation of Natural Convection With Heated Tubes in Tunnel Greenhouse

Abstract

In this research, a numerical study was carried out on heat transfer by natural convection, in a closed tunnel greenhouse, in the range of the Rayleigh number (10 3 ≤Ra≤10 6 ). Were considered in the study, the number of heating tubes used (1≤Nt≤7), which were equidistant inside the greenhouse volume, when the bottom at an average temperature and cold Roof. The governing equations written in a bicylindrical coordinates were discretized using the finite volume method and vorticity-stream function formulation; the resulting algebraic equations were solved using successive over relaxation method (S.O.R). First, the effect of the Rayleigh number on heat transfer was examined for a fixed number of tubes as reference (Nt = 3) and the number of tubes was varied to investigate the influence on heat transfer in the greenhouse. Finally, the results obtained were summarized in the form of isotherms and streamlines, and for the average Nusselt number profile; in addition to the horizontal and vertical velocities and temperatures. However, in the reference case, for low Rayleigh numbers, the heat transfer is dominated by pure conduction.With the increase of the Rayleigh number and the number of tubes Nt, the natural convection becomes more dominant and the heat transfer increases, and in general the heat transfer increase with the increasing number of tubes.

Modeling heat transfer and air circulation by convection in bottom‐heated agricultural greenhouses

“…The average Nusselt number, representing overall heat transfer (convective to conductive), showed significant enhancement, especially for higher Rayleigh numbers (buoyant force to viscous force ratio). Slatni et al 6 studied natural convection heat transfer in a closed tunnel greenhouse, examining the impact of the Rayleigh number and heating tube quantity. Their findings showed a positive influence from both factors, and they calculated the average Nusselt number, providing a correlation.…”

“…In summary, studying airflow and convective heat transfer in agricultural greenhouses is crucial for maintaining optimum growing conditions and minimizing production losses 3–21 . Factors influencing these processes include plant layout, outside temperature, wall and cover surfaces, convection mode, temperature, humidity, and ventilation 4–17 .…”

“…In summary, studying airflow and convective heat transfer in agricultural greenhouses is crucial for maintaining optimum growing conditions and minimizing production losses 3–21 . Factors influencing these processes include plant layout, outside temperature, wall and cover surfaces, convection mode, temperature, humidity, and ventilation 4–17 . As indicated by the cited research, 3–21 numerical models play a vital role in accurately predicting the thermal and fluidic performance of agricultural greenhouses, enabling the optimization of their design and the control of environmental conditions.…”

“…In summary, studying airflow and convective heat transfer in agricultural greenhouses is crucial for maintaining optimum growing conditions and minimizing production losses. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Factors influencing these processes include plant layout, outside temperature, wall and cover surfaces, convection mode, temperature, humidity, and ventilation. [4][5][6][7][8][9][10][11][12][13][14][15][16][17] As indicated by the cited research, [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]<...…”

“…[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Factors influencing these processes include plant layout, outside temperature, wall and cover surfaces, convection mode, temperature, humidity, and ventilation. [4][5][6][7][8][9][10][11][12][13][14][15][16][17] As indicated by the cited research, [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] numerical models...…”