Optimization of Root-zone Thermal Regulation in PCM-integrated Soil Matrix Blocks through Pipe Configuration and PCM Content Management

Existing greenhouse root-zone heating systems often suffer from limited thermal storage capacity and poor temperature uniformity, while the combined effects of PCM content and heating pipe configuration on thermal regulation performance remain insufficiently understood. This study evaluates a stereoculture rack growing system (SRGS) integrating phase change material (PCM)-enhanced soil matrix blocks (SMBs) with a closed-loop hydronic heating network for root-zone soil temperature control. Computational fluid dynamics simulations were conducted using STAR-CCM+ and validated experimentally to investigate the effects of PCM content, flow velocity, and pipe configuration on root-zone and canopy thermal performance. The results showed that SMBs containing ۲۰% PCM with a dual-pipe configuration, circulating water supplied at ۴۵ °C, and a flow velocity of ۱ m/s achieved the best thermal performance. Under an ambient temperature of ۱۰ °C, the root-zone thermally optimal zone (TOZ) volume reached ۴.۷۸ × ۱۰⁻³ m³ after ۱۸۰۰ s, while the canopy thermally suitable volume reached ۰.۵۸۴۸۶ m³, corresponding to ۶۹.۶۲% of the total canopy air volume. Compared with conventional soil, the PCM-enhanced SMBs extended the heating and cooling durations within the ۲۰–۲۶ °C phase transition interval by ۳.۶۹ and ۴.۳۸ times, respectively, demonstrating a substantial thermal buffering effect. The dual-pipe configuration provided the best balance between heating intensity and temperature uniformity, whereas excessive heating in the triple-pipe configuration reduced the TOZ volume due to local overheating. These findings demonstrate that PCM-enhanced SMBs can effectively improve greenhouse thermal regulation and root-zone temperature stability. However, the present study focuses on thermal performance under controlled operating conditions, and future work should evaluate long-term crop responses and field-scale applications.

کلیدواژه ها:

Computational fluid dynamics ، Phase change material ، Soil temperature field ، Numerical simulation