TY  - MANSCPT
AU  - Muhammad Aizzuddin Abdullah,
TI  - Characterization and optimum performance of sand-bentonite hybrid soil in ground heat exchanger
SN  - THE0010069 (Local)
PY  - 2024///
CY  - Kuantan, Pahang
PB  - UMPSA
KW  - Faculty of Mechanical and Automotive Engineering Technology
KW  - Dissertations
KW  - Universities and colleges
N1  - Faculty of Mechanical and Automotive Engineering Technology; Thesis (Doctor of Philosophy) -- Universiti Malaysia Pahang – 2025; Includes bibliographical references
N2  - Ground Heat Exchanger (GHE) is an essential system in utilizing geothermal energy  because of the system is able to provide environmentally friendly and sustainable heating or cooling options. Improving the thermal performance of the ground around the buried  pipes is one of the main obstacles to optimizing the efficiency of GHE systems. The  efficiency of this system is primarily determined by the thermal characteristics of the soil  near the GHE infrastructure. Thus, the main objective of the study is to create and analyse  sand-bentonite hybrid soil (SBHS) on the thermal performance of the GHE system with  the optimum working conditions. The key to enhance soil thermal properties involves the  strategic use of thermally enhanced backfilling materials (BFM) coupled with the  introduction of moisture. In this context, the investigation of SBHS emerges as a  promising avenue for the GHE’s performance. Bentonite, known for its thermal  enhancement properties, is introduced into the soil to improve its thermal properties.  Additionally, moisture content is manipulated to further enhance the overall thermal  performance of the soil. This study started with an in-depth analysis of the ground thermal  properties of SBHS. This initial phase is followed by evaluating the thermal performance  of the GHE system employing the SBHS and ends with optimising operating parameters  for enhancing efficiency. One Factor at a Time (OFAT) method is used to unravel the  complexities of SBHS. This method examines the impact of changing three critical  parameters: sand grain size, bentonite percentage, and moisture percentage. The grain  sizes that are considered are 0.154-0.355 mm, 0.355-0.6 mm, 0.6-1.0 mm, 1.0-1.6 mm,  and 1.6-2.0 mm. The bentonite percentage is investigated from 0 to 100%, while the  moisture content is investigated from 0 to 25%. Experimental analysis involves the  utilization of a GHE simulator to assess the system's performance under diverse  conditions of ground temperature, input temperature, and flow rate. The subsequent  optimization of operating parameters employs Response Surface Methodology (RSM),  accompanied by the formulation of regression models. The research outcomes shed light  on the consistent thermal properties across all grain sizes of sand, with the 1.6-2.0 mm  range exhibiting the highest thermal performance when combined with 8% bentonite and  20% moisture. The SBHS configuration consistently outperforms native soil in terms of  air temperature variation, heat transfer rate, and effectiveness across different conditions. As ground temperatures decrease from 27°C to 23°C and input temperatures drop from  35°C to 31°C, SBHS consistently achieves lower air temperatures, higher heat transfer  rates, and greater effectiveness than native soil along the GHE pipe. Similarly, with flow  rates increasing from 0.01 to 0.03 kg/s, SBHS maintains superior performance in all  aspects compared to native soil. This indicates that SBHS has superior heat retention or  heat dissipation capabilities compared to native soil, allowing it to maintain cooler air  temperatures and potentially enhance the performance of ground heat exchange systems. The optimized parameters for SBHS demonstrate a refined balance, yielding an air  temperature variation, heat transfer rate, and effectiveness of 26.49 °C, 79.65 W, and  0.58, respectively, with the highest desirability index of 0.531. The results highlight the  significance of soil-thermal dynamics in GHE performance and have implications for the  sustainable use of geothermal energy in heating and cooling applications
ER  -