Heat transfer characteristics of a baffled U-tube working with MEPCM slurry in a geothermal heat pump

To improve the thermal efficiency of Geothermal heat pumps (GHPs) and reduce the depth, utilizing a geothermal heat exchanger (GHE) with new structures is a promising method. Working fluid also has a pivotal role in enhancing the thermal performance of the GHEs. While assessing the impacts of coil configurations on the GHEs has been performed previously, the influence on the coil surfaces and alternative fluids has not been investigated extensively. The study aims to enhance the thermal performance of the GHPs by utilizing 3-D baffled U-tubes working with a micro-encapsulated phase change material (MEPCM) slurry, thereby supporting a building load of 80 W in a CFD-based analysis. The configurations influence of a 2-m deep baffled U-tube and MEPCM slurry are evaluated by analyzing different thermal parameters. The results indicated that due to the contact surface improvement and better baffles distribution, the quarter-circular baffled U-tube has the best impact on GHE's efficiency. Employing MEPCM slurry as a fluid enhances the thermal performance of the fluid, causing superior effectiveness compared to water. The maximum thermal improvement of 18.5 % is obtained in the quarter-circular baffled U-tube, and the GHE operating by MEPCM slurry shows maximum effectiveness enhancement of 69 % in the best case. • Evaluation of the thermal performance of the different baffled U-tubes. • Influence of MEPCM slurry on thermal efficiency of the ground heat exchanger. • The maximum heat transfer rate achieved in quarter-circular baffled U-tube. • Superior effectiveness in the ground heat exchanger working with MEPCM.