Effects of coolant flow and freeze pipe parameters on artificial ground freezing performance

This study examines the influence of freeze pipe design parameters on the thermal and hydraulic performance of artificial ground freezing (AGF) systems. A parametric analysis is conducted to evaluate the effects of geometric variables (inner and outer pipe diameters, wall thickness, and pipe length), material properties, and the heat transfer fluid’s flow regime. An analytical model is developed for steady-state heat transfer between the soil and circulating fluid, accounting for flow regime transitions and internal heat generation due to hydraulic resistance. Results demonstrate that thermal efficiency is highly sensitive to both geometry and operational conditions. The optimum inner pipe diameter generally ranges between 0.6 and 0.8 of the outer diameter, depending on the flow rate and fluid characteristics. While the material and thickness of the outer pipe have a strong effect on heat transfer, the properties of the inner pipe material exert only a minor influence. Additionally, extended pipe lengths and elevated flow rates may reduce performance due to self-heating of the circulating fluid, highlighting the need for integrated design optimization. The proposed framework offers practical guidance for enhancing freeze pipe configurations in AGF applications. • An analytical model for steady-state heat transfer in an ice wall, considering the coolant flow regime, is developed. • It is demonstrated that freeze pipe thermal efficiency is highly sensitive to its size, materials, and the coolant flow parameters. • It is shown that self-heating of coolant at high flow rates and long pipe lengths is a limiting factor for system performance. • A practical framework is provided to optimize freeze pipe design in artificial ground freezing systems.