Greenhouse: Thermal and Humidity Analysis

Greenhouse Thermal and Humidity Analysis Using ANSYS Fluent

Description

This project presents a numerical simulation of greenhouse airflow, heat transfer, solar radiation, and moisture behavior using ANSYS Fluent. The goal was to investigate how environmental factors and boundary conditions influence internal temperature distribution, heat transfer from the floor through embedded pipes, air velocity, and moisture content — together characterizing the greenhouse's overall thermal performance. The simulation was run under steady-state conditions to capture the system's long-term behavior, accounting for solar radiation through ray tracing and the specific thermal properties of the structure's materials.

The 3D geometry was built in SpaceClaim, consisting of a computational domain, the greenhouse room region, and 9 floor-embedded pipes representing the fluid domain, alongside a ground region modeled as a solid body. The computational domain measured 30 m wide, 10 m high, and 40 m long, with the greenhouse itself measuring 4 m wide, 3.8 m high, and 10 m long. The greenhouse floor, positioned 3.3 m high, contained 9 pipes each with a cross-sectional area of 0.017671 m² and a length of 10 m. The domain was meshed in ANSYS Meshing, generating approximately 4,800,000 cells to balance simulation accuracy with computational cost.

Methodology

The simulation used a pressure-based solver, appropriate given the steady-state nature of the problem, with gravitational acceleration set to -9.81 m/s² in the Y-direction. The energy equation was activated to capture heat transfer throughout the domain, with turbulence modeled using the Realizable k-epsilon model and standard wall functions for near-wall treatment.

Radiation effects were captured using the Discrete Ordinates (DO) model with solar ray tracing enabled to account for solar heating. Humidity behavior was captured using the Species Transport model, with density defined as an incompressible ideal gas mixture of air and water vapor.

Boundary conditions included a mass flow rate inlet of 0.032 kg/s, nine pressure outlet surfaces each at 0 Pa gauge pressure, and no-slip conditions applied to all walls. Pressure-velocity coupling used the Coupled algorithm to ensure strong convergence, with the solution initialized using Fluent's standard initialization method.

Conclusion

Results include detailed distributions of temperature, velocity, radiation heat flux, and water vapor mass fraction throughout the greenhouse, presented through contour plots and vector fields alongside quantitative data at key interior locations. This output enables evaluation of temperature uniformity, ventilation effectiveness, solar radiation absorption, and moisture distribution — together offering a comprehensive picture of the greenhouse's thermal and humidity performance under the simulated conditions.