https://www.mechanicaljournals.com/ijmte/rss Int. J. Mech. Therm. Eng. 2026 - 7(2) International Journal of Mechanical and Thermal Engineering AkiNik Publications 2707-8043 Kalp Agarwal Archit Dhingra Article International Journal of Mechanical and Thermal Engineering 2026 7(2):96-103 doi:10.22271/27078043.2026.v7.i2b.141 International Journal of Mechanical and Thermal Engineering 10.22271/27078043.2026.v7.i2b.141 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.141 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.141 7 2 96 103 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.141 Kalp Agarwal and Archit Dhingra

International Journal of Mechanical and Thermal Engineering 2026 7(2):96-103

The increasing interest in establishing permanent human settlements on the Moon and Mars has accelerated the development of habitat construction technologies based on In-Situ Resource Utilisation (ISRU). Among the available approaches, regolith-based composite materials have emerged as promising candidates due to their ability to utilise local resources, reduce transportation costs, and enhance mission sustainability. However, habitat hulls must provide high mechanical strength, thermal stability, radiation shielding, and long-term durability under harsh extraterrestrial environments. This review presents a comprehensive analysis of the thermo-mechanical performance of regolith-based composite hull structures, covering engineering requirements, material development, thermo-mechanical behaviour, additive manufacturing, comparative mechanical performance, research challenges, and future directions. Comparative analysis shows that Regolith Resin Composites (RRC) exhibit the highest compressive strength (107.7 Megapascals (MPa)). In contrast, Multi-Walled Carbon Nanotubes (MWCNT), Polyether Ether Ketone (PEEK), and fibre-reinforced composites offer improved thermal stability and lightweight performance for ISRU-based habitat construction. The review concludes that integrating advanced composite materials with autonomous additive manufacturing, artificial intelligence-assisted material optimisation, and next-generation ISRU technologies would enhance the safety, sustainability, and reliability of future lunar and Martian habitats. ]]> Wed,1 Jul 2026 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.141 Amjed Ahmed Jasim Article International Journal of Mechanical and Thermal Engineering 2026 7(2):104-109 doi:10.22271/27078043.2026.v7.i2b.142 International Journal of Mechanical and Thermal Engineering 10.22271/27078043.2026.v7.i2b.142 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.142 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.142 7 2 104 109 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.142 Amjed Ahmed Jasim

International Journal of Mechanical and Thermal Engineering 2026 7(2):104-109

This study proposes a computational framework to address the uncertainties and evaluates the reliability of the computational predictions of the thermal-hydraulic design, between different models, for perforated helical twisted-tape (P-HTT) inserts. The contribution is methodological – it is not a new insert geometry, CFD dataset or conventional deterministic optimization, but rather, an experimentally validated empirical model is treated as an engineering prediction model and model behavior on the domain boundaries, uncertainty-conditioned model performance, convergence of the model numerical solution, and model transferability are tested. The audited P-HTT model is evaluated over Re = 6000–20000, d/w = 0.2–0.6, and s/w = 1–2. The outcome of the boundary analysis indicates that the nominal maximum is found at ? ? 1.283, Re = 6000, d/w = 0.20 and s/w = 2.0 which is a domain constrained optimum. A discrete search and a continuous search are compared and it is found that there is no contradiction with the optimum value of interpolation. Moreover, the numerical stability of the Monte Carlo method, with a Monte Carlo sample size ranging from 103 to 2.5 × 105, is demonstrated, with the value of the reference uncertainty ?5% remaining at around 1.248 over the clearly defined reference uncertainty scenario. Logarithmic-elasticity analysis analysis showed that the models have approximately 3.84× and 7.38× different effect size when using an independent correlation with the perforated twisted-tape under Reynolds number and perforation diameter respectively conditions, while the direction of the effect of both these variables can be transferred from one model to the other. Additionally, the analysis can be separated into the trends which are common to both tested models and the sensitivities which are related to the model structure to allow a meaningful interpretation of the optimal values ??of the thermo-hydraulic performance under conditions of uncertainty. ]]> Wed,1 Jul 2026 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.142 Areej Sabr Mohammed Alaa Kadhim Mohammed Article International Journal of Mechanical and Thermal Engineering 2026 7(2):110-119 doi:10.22271/27078043.2026.v7.i2b.143 International Journal of Mechanical and Thermal Engineering 10.22271/27078043.2026.v7.i2b.143 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.143 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.143 7 2 110 119 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.143 Areej Sabr Mohammed, Alaa Kadhim Mohammed

International Journal of Mechanical and Thermal Engineering 2026 7(2):110-119

Fluid flow in porous channels is ubiquitous in engineering and environmental processes, such as filtration devices, geothermal energy, oil reservoirs, catalytic reactors, thermal management equipment, and porous heat exchangers. The permeability of the porous medium has a strong influence on the stability of such flows. Although many previous studies have focused on homogeneous porous media, real porous materials often have spatially variable permeability due to manufacturing defects, heterogeneity in pore distributions, degradation of materials or natural variations in geology. In the present work, the hydrodynamics and instability features of an incompressible flow through a porous channel with non-uniform permeability are studied numerically. The Darcy–Brinkman model is used to represent viscous diffusion and resistance due to the porous medium. The permeability is modeled as a spatially varying field, so that the influence of permeability gradients and intensity of heterogeneity can be systematically investigated. The governing equations are nondimensionalized using the Reynolds number and the Darcy number, and the heterogeneity of the permeability is measured by a permeability-variation parameter. A two-dimensional model is developed to study the velocity profile, pressure loss, streamline pattern, wall shear and onset of flow instability. It is shown that the variation of the permeability in space distorts the velocity profile of the base flow and leads to spatially localized regions of flow acceleration and deceleration. Increasing permeability heterogeneity leads to larger velocity gradients and rearrangement of pressure, thereby significantly affecting the stability characteristics as compared with that of the homogeneous porous channel. The results highlight that the permeability distribution, rather than only its spatially averaged value, is the key quantity for predicting the flow stability of porous-channel systems. The presented numerical framework can serve as a useful guide for designing porous-flow systems with tailored transport and stability features. ]]> Wed,1 Jul 2026 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.143 Mustafa Abdulhussein Lafta Article International Journal of Mechanical and Thermal Engineering 2026 7(2):120-131 doi:10.22271/27078043.2026.v7.i2b.144 International Journal of Mechanical and Thermal Engineering 10.22271/27078043.2026.v7.i2b.144 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.144 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.144 7 2 120 131 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.144 Mustafa Abdulhussein Lafta

International Journal of Mechanical and Thermal Engineering 2026 7(2):120-131

This study reports a combined experimental and numerical investigation of a hybrid solar thermal system in which a single-glazed flat-plate collector (aperture area 1.5 m²) supplies a plate heat exchanger that serves as the evaporator of a small organic Rankine cycle (ORC) driving a micro-expander, while the condenser delivers low-grade heat for domestic use. The system is therefore analysed as a combined heat-and-power (CHP) unit rather than as a pure power plant. A complete thermodynamic model is presented, comprising the Hottel–Whillier–Bliss collector equation with an explicitly evaluated heat-removal factor, an effectiveness–NTU description of the evaporator, a second-law formulation of the expander, a hydraulic model of the circulation loop, and a component-resolved exergy balance referred to the Petela radiation exergy. Experiments were conducted outdoors under steady-state conditions for mass flow rates of 0.01–0.05 kg s^?1 and irradiance levels of 600–1000 W m^?2, with a collector inlet temperature held at 60 °C. A three-dimensional conjugate heat-transfer model was solved in ANSYS Fluent using the k–? SST closure with y+ ? 1 and was verified by a formal grid-convergence study (apparent order p = 2.00, GCI = 1.19 %). Propagated measurement uncertainties, evaluated by the Kline–McClintock method, are ±2.0–2.3 % for useful heat gain, ±2.6–2.8 % for energy efficiency, ±2.8 % for exergy efficiency and ±3.1 % for net mechanical power. Predicted and measured outlet temperatures agree within an RMSE of 2.35 % and a maximum deviation of 2.97 %. The measured collector thermal efficiency rises from 59.1 % to 63.5 % as the flow rate increases from 0.01 to 0.05 kg s^?1, while the system energy efficiency rises from 56.1 % to 60.2 %. Net mechanical power and exergy efficiency, in contrast, exhibit a clear interior maximum at 0.03 kg s^?1, where 29.34 W and 3.11 % are obtained; beyond this point the cubic growth of pumping demand outweighs the marginal thermal gain. The exergy balance shows that 93.25 % of the incoming radiation exergy is destroyed in the collector through optical absorption and radiative degradation, whereas the expander (48.3 %) and the evaporator (41.6 %) dominate the component-level, technologically avoidable destruction. These findings identify the source temperature — not the collector thermal efficiency — as the binding constraint on thermo-mechanical conversion in flat-plate-driven solar CHP systems, and quantify the operating point at which the trade-off between heat collection and mechanical work extraction is optimal. ]]> Wed,1 Jul 2026 https://www.mechanicaljournals.com/ijmte/archives/2026.v7.i2.B.144