NUMERICAL MODELING OF THERMAL PROCESSESIN VERTICAL GROUND HEAT EXCHANGERS

The article presents the results of numerical modeling of thermal processes in vertical ground heat exchangers of concentric and U-shaped types aimed at improving the energy efficiency of microclimate control systems in agro-industrial facilities. Analytical studies of pneumatic losses demonstrated that their magnitude is nearly identical for both configurations, while the capacity of the U-shaped heat exchanger exceeds that of the concentric design by 0.9–1.7 %, confirming the feasibility of its further application. Dependencies of the U-shaped exchanger’s capacity on its geometric parameters (length, diameter) and air flow rate were established, enabling optimization of its structural characteristics. Numerical simulations conducted in Simcenter Star-CCM+ provided spatial distributions of temperature fields under various operating conditions. It was shown that, in summer, the air flow temperature decreases by 7.2 °C in the concentric and by 8.5 °C in the U-shaped exchanger, whereas in winter, the corresponding increases amount to 8.1 °C and 9.3 °C, respectively. Characteristic zones of minimum and maximum temperature values were identified at a depth of 26.75–28.50 m, which substantiates the necessity of thermal insulation within the range of 1.50–3.25 m to maintain system efficiency. Further data processing in Wolfram Cloud enabled the derivation of second-order regression equations describing the relationships between the change in air flow temperature and effective thermal capacity with respect to inlet air temperature and air flow rate. This allowed the determination of optimal flow rates: 453.8 m³/h for the concentric and 455.2 m³/h for the U-shaped exchanger. Under these conditions, the thermal capacity of the concentric scheme ranges from 1052 to 1266 W depending on the season, while that of the U-shaped exchanger varies from 1235 to 1575 W. The obtained results indicate that the U-shaped heat exchanger demonstrates 17–24 % higher efficiency compared to the concentric one, making it a promising solution for use in energy-efficient microclimate systems and providing a foundation for the development of adaptive control algorithms.