Transient CFD analysis of greenhouse microclimate under temperature-regulated heating

Effective thermal management in greenhouses requires modelling approaches that capture spatial and temporal variations in the indoor microclimate, particularly during winter when heat losses are significant. Maintaining suitable indoor conditions while limiting energy consumption remains a key challenge, making reliable heating regulation essential in greenhouse operation. Previous studies rely on steady‑state or simplified models, which do not represent the changing thermal behaviour observed under practical operating conditions. While computational fluid dynamics (CFD) is widely used to analyse airflow and heat transfer in greenhouses, most studies focus on ventilation or fixed heating inputs, with limited treatment of transient heating. This study develops a transient three‑dimensional CFD model of a single‑span tomato greenhouse with radiator‑based heating. A temperature-regulated on-off heating operation with hysteresis is implemented to represent a practical greenhouse heating mode and to examine its interaction with the indoor microclimate. The model is validated against experimental measurements and used to analyse the evolution of the indoor thermal field over a 4-h heating period, including temperature distribution, vertical stratification, and heating response. The results show that the temperature-regulated on-off heating operation maintains indoor conditions within the target range while capturing the transient behaviour of the greenhouse environment. Comparison with constant-output and conventional on-off heating cases shows that heating operation affects both energy demand and temperature stability. Continuous heating increases energy use, while the conventional on-off case lowers energy demand but maintains the target range less consistently. Spatial analysis shows vertical thermal stratification, with the most uniform conditions at mid-height and localised effects in the lower and upper regions. These results show that transient CFD modelling can capture greenhouse microclimate behaviour and help assess how heating operation affects energy use and indoor thermal conditions.