Investigation of Heat Transfer Processes in Multi-Sized Solar-Sintered Regolith for Lunar ISRU Program

Effective Thermal Conductivity (ETC) prediction of sintered lunar regolith plays a crucial role in developing extraterrestrial thermal processing and construction techniques for In-situ Resource Utilization (ISRU) projects on the moon. Most existing literature has been focused on the packed lunar regolith without considering the sintering mechanism. Herein, we presented a mechanistic model to estimate the ETC of sintered lunar regolith. The Monte-Carlo method was applied to simulate the thermal neck resistance between multi-scaled particles, while the irregular particle geometry was characterized by shape factors. The presented model was experimentally validated by measuring ETC and specific surface area of fabricated lunar simulant samples LMS-1 with various granularities sintered under air, argon gas and low vacuum (10-3 Pa). Furthermore, the heat transfer process within solar sintered LMS-1 bed was simulated coupled with the ETC model. Transient behaviors of microstructure, thermal conductivity and temperature profile during solar heating were simulated iteratively. The simulated temperature profiles concur well with measured data obtained from the solar sinter testing with an average Root Mean Squared Error (RMSE) of 5.5%, which performs better than the un-sintered ETC model (RMSE=12.7%). The measured sintered depth was improved by 45% with an optimized particle size distribution (PSD) arrangement.