Phase Heat Research Articles

Preparation and physicochemical properties: a new extruded rice using cassava starch and broken rice flour

With the increasing demand for nutrition and health, many researchers are trying to develop a rice product with lower aging rate and convenient nutrient fortification. Being composed of high amylopectin content, cassava starch (CS) shows a lower retrogradation tendency compared to rice starch. So, it has a broad application prospect to partially replace rice starch with CS in rice by extrusion technology. In this study, a new extruded rice (ER) was prepared by broken rice flour and CS using single-screw extruder through “improved extrusion cooking technology,” and the maximum addition level of CS in ER was 30%. Color parameters and texture profile analysis showed that ER was a little darker in appearance with lower hardness, adhesiveness and chewiness. Rapid visco analysis demonstrated that the viscosity of ER paste appeared earlier during the initial heating phase and displayed a lower retrogradation trend than normal rice in the cooling process. The gelatinization temperature and gelatinization enthalpy decreased with the increasing CS in ER, while the degree of gelatinization increased to 76.36% when the content of CS was 30% after extrusion. The X-ray diffraction patterns of control was typical A-type structure, while ER changed to V-type structure with a lower degree of crystallinity. The microstructure observation showed that ER exhibited a looser and more porous structure with increasing the content of CS, which facilitated easier cooking and nutritional enhancement.

Solid–liquid phase transition simulated by the lattice Boltzmann model: from pore scale to representative elementary volume scale

Purpose This paper aims to establish a lattice Boltzmann (LB) method for solid-liquid phase transition (SLPT) from the pore scale to the representative elementary volume (REV) scale. By applying this method, detailed information about heat transfer and phase change processes within the pores can be obtained, while also enabling the calculation of larger-scale SLPT problems, such as shell-and-tube phase change heat storage systems. Design/methodology/approach Three-dimensional (3D) pore-scale enthalpy-based LB model is developed. The computational input parameters at the REV scale are derived from calculations at the pore scale, ensuring consistency between the two scales. The approaches to reconstruct the 3D porous structure and determine the REV of metal foam were discussed. The implementation of conjugate heat transfer between the solid matrix and the solid−liquid phase change material (SLPCM) for the proposed model is developed. A simple REV-scale LB model under the local thermal nonequilibrium condition is presented. The method of bridging the gap between the pore-scale and REV-scale enthalpy-based LB models by the REV is given. Findings This coupled method facilitates detailed simulations of flow, heat transfer and phase change within pores. The approach holds promise for multiscale calculations in latent heat storage devices with porous structures. The SLPT of the heat sinks for electronic device thermal control was simulated as a case, demonstrating the efficiency of the present models in designing and optimizing SLPT devices. Originality/value A coupled pore-scale and REV-scale LB method as a numerical tool for investigating phase change in porous materials was developed. This innovative approach allows for the capture of details within pores while addressing computations over a large domain. The LB method for simulating SLPT from the pore scale to the REV scale was given. The proposed method addresses the conjugate heat transfer between the SLPCM and the solid matrix in the enthalpy-based LB model.

A novel cement mortar comprising natural zeolite/dodecyl alcohol shape stable composite phase change material for energy effective buildings

Investigations into Phase Change Materials (PCMs) for heat storage in facilities have gained significance, contributing to indoor temperature regulation, decreased energy usage, and improved building efficiency, thereby supporting sustainability initiatives. However, the issue of PCM leakage during the heating phase has constrained its thermal energy storage (TES) prospective at large scaled-practices. Addressing this concern, the present study emphases on elimination of the leakage problem of dodecyl alcohol (DA) as a PCM with appropriate melting temperature for building TES request by its impregnating into the natural zeolite (NZ) as a low cost host matrix. In the second stage of the work, using the developed shape stable-NZ/DA (SS-NZ/DA) composite PCM in cement mortar instead of sand, novel cementitious mortars with enhanced thermal properties were created by incorporating different weight percentages (25 %, 50 %, 75 %, and 100 %) compared to the mortar comprising NZ. Experimental works were carried out to analyze the shape-stability, TES features, cycling TES stability and thermal endurance of the SS-NZ/DA composite as well the physical properties, mechanical strength, and solar temperature regulation performance of the SS-NZ/DA included mortars. The SS-NZ/DA demonstrated the melting enthalpy of 107.5 J/g at 19.47 °C and a freezing enthalpy of 106.1 J/g at 19.86 °C. The performance test results obtained under real weather conditions indicated that the integration of SS-NZ/DA into mortar presented maximum drop of 10 % and 9.26 % in peak indoor temperature at the SS-CPCM slab surface and the center of SS-CPCM slab-cabin, respectively, accompanied by an approximate 3-hour time delay. Mortars with SS-NZ/DA composite PCM exhibited a decreased dry unit weight (1189 kg/m3) and thermal conductivity (0.394 W/mK) while experiencing a moderate strength loss (4.5 MPa). These favorable physico-mechanical properties, TES characteristics and thermal management capability make the novel cementitious mortar containing composite PCM as an energy-efficient material for creating thermo-regulative building components. In this study, the natural, economical, and environmentally friendly nature of the NZ material used for PCM impregnation, its ability to contain a high percentage of PCM (up to 45 %) without any leakage issues, is the most fundamental and important characteristic of the composite used. The most unique feature of this composite mortar is the ability to achieve sufficient mechanical and thermal properties in cementitious mortars produced using this composite material without any leakage problems.

Disodium hydrogen phosphate dodecahydrate/fumed silica composites with high latent heat and suitable phase change temperature for use in building roof

Introducing phase change materials (PCM) with suitable phase change temperature and large latent heat into the application of building roofs is conducive to building energy efficiency, which can reduce indoor temperature fluctuation and improve thermal comfort. In this paper, the optimized disodium hydrogen phosphate dodecahydrate (DHPD) was combined with fumed silica (FS) to prepare a new type of DHPD/FS composites, with a phase change temperature of 41.5 °C, a latent heat of change of 103.46 J/g, and an optimal content of 22.5 % of FS. The leakage experiments proved that there was no leakage of the PCM at this ratio, and after 200 cycles of thermal cycling, the phase change temperature of DHPD/FS composites basically remains unchanged, with good thermal reliability, but the addition of FS will make the material decrease in thermal conductivity, and the thermal conductivity is reduced to 0.19 W·m−1·K−1. Furthermore, the study investigated the application of the encapsulated DHPD/FS composites as a phase change board on the roof. The results indicated that the inclusion of the phase change board improved indoor thermal comfort and demonstrated good thermal performance. When the phase change board was positioned in the top layer, the enhancement of thermal comfort was most optimal.

Validation of a Novel Noninvasive Technology to Estimate Blood Oxygen Saturation Using Green Light: Observational Study

Background Pulse oximeters work within the red-infrared wavelengths. Therefore, these oximeters produce erratic results in dark-skinned subjects and in subjects with cold extremities. Pulse oximetry is routinely performed in patients with fever; however, an elevation in body temperature decreases the affinity of hemoglobin for oxygen, causing a drop in oxygen saturation or oxyhemoglobin concentrations. Objective We aimed to determine whether our new investigational device, the Shani device or SH1 (US Patent 11191460), detects a drop in oxygen saturation or a decrease in oxyhemoglobin concentrations. Methods An observational study (phase 1) was performed in two separate groups to validate measurements of hemoglobin and oxygen concentrations, including 39 participants recruited among current university students and staff aged 20-40 years. All volunteers completed baseline readings using the SH1 device and the commercially available Food and Drug Administration–approved pulse oximeter Masimo. SH1 uses two light-emitting diodes in which the emitted wavelengths match with absorption peaks of oxyhemoglobin (hemoglobin combined with oxygen) and deoxyhemoglobin (hemoglobin without oxygen or reduced hemoglobin). Total hemoglobin was calculated as the sum of oxyhemoglobin and deoxyhemoglobin. Subsequently, 16 subjects completed the “heat jacket study” and the others completed the “blood donation study.” Masimo was consistently used on the finger for comparison. The melanin level was accounted for using the von Luschan skin color scale (VLS) and a specifically designed algorithm. We here focus on the results of the heat jacket study, in which the subject wore a double-layered heated jacket and pair of trousers including a network of polythene tubules along with an inlet and outlet. Warm water was circulated to increase the body temperature by 0.5-0.8 °C above the baseline body temperature. We expected a slight drop in oxyhemoglobin concentrations in the heating phase at the tissue level. Results The mean age of the participants was 24.1 (SD 0.8) years. The skin tone varied from 12 to 36 on the VLS, representing a uniform distribution with one-third of the participants having fair skin, brown skin, and dark skin, respectively. Using a specific algorithm and software, the reflection ratio for oxyhemoglobin was displayed on the screen of the device along with direct hemoglobin values. The SH1 device picked up more minor changes in oxyhemoglobin levels after a change in body temperature compared to the pulse oximeter, with a maximum drop in oxyhemoglobin concentration detected of 6.5% and 2.54%, respectively. Conclusions Our new investigational device SH1 measures oxygen saturation at the tissue level by reflectance spectroscopy using green wavelengths. This device fared well regardless of skin color. This device can thus eliminate racial disparity in these key biomarker assessments. Moreover, since the light is shone on the wrist, SH1 can be readily miniaturized into a wearable device.

Review of heat pipes for power batteries of new energy vehicles

With the global energy crisis becoming one of the most concerned topics, the application of new energy systems has become the most popular research at present. In addition, with the emerging new energy vehicles, problems such as high calorific value and insufficient heat dissipation performance of lithium batteries for new energy vehicles have not been solved, so the research on thermal management technology of lithium batteries is essential. Based on the analysis of heat pipe research, this paper summarizes heat pipe from three aspects, including structure and arrangement of the heat pipe, wall materials of the heat pipe and phase change materials of the heat pipe. This paper puts forward new insights and provides a reference for the research on the thermal management of lithium batteries for new energy vehicles.

Changes in the molecular and structural of wheat gluten in the presence of zein during heating: Comparative studies on gluten, glutenin and gliadin

This study comparatively investigated the heat-triggered molecular and structural changes of wheat gluten in the presence of zein to clarify the gluten and zein interaction mechanism from the perspective of gluten, glutenin, and gliadin polymerization behavior during heating. Scanning electron microscopy (SEM) images showed that zein induced more uniform dispersion of the gluten network during heating. Size exclusion-high performance liquid chromatography (SE-HPLC) results demonstrated that zein addition increased the SDS-soluble protein content in the gluten, glutenin, and gliadin during heating. After heating at 95 °C, zein increased the free sulfhydryl content in gluten and glutenin by 23.15% and 38.97%, respectively. Zein primarily enhanced the non-covalent interaction with gliadin more than with gluten and glutenin. The addition of zein led to a significant decrease in β-sheets content in gluten, glutenin, and gliadin during heating. Zein improved the thermal stability of gluten and gliadin after heating, resulting in higher degradation temperatures and lower weight loss. The improvement in rheological properties of gluten, glutenin, and gliadin during the 95 °C heating phase could be mainly attributed to the prevention of excessive protein aggregation and the promotion of non-covalent interactions by zein.

Effects of different heating strategies on the joint properties during infrared welding of glass fiber reinforced polyamide 6

In infrared welding, the heating phase is the phase offering the highest flexibility of choice regarding the process parameters. In this phase, the process parameters such as the heating time, emitter power, and emitter-component distance can be individually selected and combined with each other. The defined heating phases have a different influence on the joining components. In this work, the effects of four heating strategies and their influence on the resulting temperature distribution over the joining surface, the possible thermal material degradation, the morphology of the joining zone, and the short-term tensile strength of the welded samples are investigated. In order to investigate the morphology, microsections are prepared which enable transmitted light microscopy of the black PA6 GF50 used. In summary, it can be concluded that different heating strategies have a different influence on the material even if the generated melt layer thickness is kept the same. Three of the four strategies result in material degradation on the joining surface. However, this has almost no effect on the resulting short-term strength of the weld. The results allow the interpretation that a high joining pressure compensates for the influence of the material damage by pressing the damaged material into the bead.

Lattice Boltzmann modeling of convective heat and solute transfer in additive manufacturing of multi-component alloys

Additive manufacturing (AM) is a remarkable breakthrough technology, allowing for the direct fabrication of three-dimensional components through the layer-by-layer stacking of materials. A novel free Surface lattice Boltzmann (LB) model is developed to simulate the heat and solute transfer in AM of multi-component alloys. The behavior liquid phase is described by using the free surface LB model, and the phase transitions between solid and liquid are modeled by using the LB-enthalpy method. A LB equation is directly constructed, which accounts for solute transfer in a certain multi-component alloys system. The thermodynamic information used in the calculation of phase transitions are determined by an extensive thermodynamic database. The model is validated via several benchmark examples of fluid flow and heat transfer. The characteristics of convective heat and solute transfer within various AM are investigated. Finally, the non-equilibrium convective heat transfer, phase transitions, and macroscopic segregation are discussed within the AM melt pools. The melt pool expands and convective heat transfer is enhanced by the Marangoni effect. Thus there is a consistent decrease in solute segregation. The solute segregation is more severe near the surface of the deposit layer. Additionally, the thermal convection experiences cyclic intensification attributed to the successive impact of multiple droplets in wire feeding and melting AM. This continuous impact serves to diminish the solute segregation. The results underscore the significant potential and advantages of LB method in accurately simulating the AM, which provides valuable insights for understanding the underlying mechanism of heat and solute transfer in materials and manufacturing.

The effect of graphene nanoparticleson the thermal conductivity enhancementof organic phase change material and its energystorage properties

Organic phase change materials (PCMs), which are typically used as the accumulating material in latent heat thermal energy storage, provide chemical and thermal stability, but have low thermal conductivity. This limits heat transfer rates and prolongs storage charging/discharging time. A method to improve the thermal conductivity of organic PCMs is to add nanomaterials with high thermal conductivity. The paper presents the research on the effect of the addition of graphene nanoparticles (GNPs) on the thermal conductivity of organic PCM (RT28 HC), and its energy storage properties. The transient hot wire and the pipe Poensgen apparatus methods were used to measure thermal conductivity, and the differential scanning calorimetry method was used to determine the heat capacity and phase change temperature. The achieved characteristics of thermal conductivity depending on the amount of added graphene nanoparticles (and stabilizer) indicate that GNPs allow to increase the thermal conductivity on average by 26–87% in the solid state and by 7–28% in the liquid, but this reduces the PCM heat capacity. Therefore, the paper indicates what mass fraction of dopants is optimal to achieve the greatest improvement in thermal conductivity of RT28 HC and its smallest reduction in heat capacity, to use this nano-enhanced PCM in practice.

Long-term thermal performance investigation of phase change plates (PCPs) employing tunnel lining ground heat exchangers for cool storage

Combining tunnel lining ground heat exchangers (GHEs) and phase change plates (PCPs) to extract and store the geothermal energy is a novel and environment-friendly energy utilization method, and then PCPs can be used for space cooling. However, existing investigations have not focused on the long-term thermal performances of PCPs employing tunnel lining GHEs for cool storage. In the present work, a coupled finite element model of tunnel lining GHEs and PCPs was built to study long-term operation performances of PCPs during the cold energy charging operation period. Numerical modeling and programming (i.e., co-simulation) were employed to realize the continuous cold energy charging operation mode of PCPs employing tunnel lining GHEs for cool storage. The results indicate that the solidification efficiency (i.e., cold energy charging efficiency) of PCPs and phase interface evolution within the PCPs under the long-term cold energy charging mode are affected by the number of times for cool storage (N) and thermal conductivity of the surrounding rock (ksr) compared with the short-term mode. The drop rate of the liquid fraction and solidification efficiency of PCPs decrease with an increase in the number of times for cool storage. At N = 1, there is no obvious difference for the solidification efficiency of PCPs with increasing ksr. The solidification efficiency of PCPs under N = 10 improves by approximately 35.3% as ksr rises by 3 W/(m K). Additionally, the solidification time of PCPs increases linearly with N under ksr = 1.22 W/(m K). However, the solidification time is related parabolically to N under ksr = 2.22, 3.22, and 4.22 W/(m K). Finally, the long-term thermal response of the surrounding rock is analyzed, which also verifies the heat transfer characteristics of PCPs under the long-term cold energy charging mode.

Preparation and Photothermal Properties of Accordion‐Like MXene/Sodium Acetate Trihydrate Composite Phase Change Materials

Phase change materials (PCMs) are promising options for thermal energy storage. Combining sodium acetate trihydrate (SAT) with MXene, the composite phase change materials (CPCMs) have been prepared. The surface morphology, thermal storage performance, and solar energy photothermal conversion efficiency of the CPCMs with various MXene contents are analyzed. According to the microstructure morphology analysis, MXene is accordion‐shaped, and tightly associated with SAT. Differential scanning calorimetry measurement results show that CPCMs possess high latent heat and suitable phase change temperature for the applications of solar heat storage. The absorption wavelength range of SAT/MXene is extended from 200–258 nm to 200–497.7 nm with a photothermal conversion efficiency of 81.3%. SAT/MXene‐2%, SAT/MXene‐8%, and SAT/MXene‐14% have thermal conductivities of 0.84, 1.14, and 1.47 W/ (m · K), respectively, which are higher by 44.9%, 96.6%, and 153.4% than 0.59 W/ (m · K) of pure SAT. CPCMs exhibit excellent thermal stability and reliable cycling stability after 50 cycles, which show that MXene can prevent leakage during the solid‐liquid phase transition process. The expansion of PCM's practical applicability and MXene/SAT composites with good photothermal characteristics create a theoretical foundation for the effective use of renewable energy sources.

Tensile Tests for Material Characterisation of High- and Ultra-High-Strength Steels S690QL and S960QL under Natural Fire Conditions

The mechanical material behavior of mild steels is reversible in the cooling phase of natural fires, which is proven by experimental evidence. For the material behavior of high-strength steels during cooling, no results are yet available. The paper provides the first comprehensive test program on the constitutive material behavior of high-strength steels S690QL and S960QL as well as mild steel S355 J2 + N in the case of natural fires. It is elaborated that the mechanical material behavior of high-strength steels in the cooling phase differs from the behavior in the heating phase and is not reversible due to phase changes of the microstructure. A constitutive material model for structural fire design purposes is developed on the basis of experimental data and the soundness and reliability of the model are proven by a statistical study that systematically evaluates the deviation of the model prediction from the test data.

High latent heat phase change materials composites based on MXene/biomass-derived cellulose nanocrystalline aerogel for solar-thermal energy conversion and storage

In this study, novel tetradecylamine/MXene/cellulose nanocrystal composite phase change materials (TDA/MXene/CNC CPCMs) were prepared using a vacuum impregnation method. For the first time, lightweight MXene/CNC composite aerogel was employed as a support material in energy storage, with TDA serving as the phase change material. The latent heat of TDA/MXene/CNC CPCMs reached 221.5 J/g. Furthermore, the density of the MXene/CNC-2 composite aerogel was 0.0614 g/cm3, and its loading rate for TDA was as high as 90.6 wt%. Additionally, the thermal conductivity of TDA/MXene/CNC CPCM-5 was 0.491 W/(m·K), 1.87 times higher than that of pure TDA. The TDA/MXene/CNC CPCMs exhibited exceptional thermal stability up to 120 °C and maintained excellent shape stability at 60 °C. The composites exhibit a superior solar-thermal conversion ability with the conversion efficiency as high as 94.1%, The incorporation of MXene significantly enhances the photothermal conversion capability, providing an important avenue for the high-efficiency utilisation of solar energy.

Enhancing heat transfer in thermosyphons: The role of self-rewetting nanofluids, and filling ratios for improved performance

This study investigates the complex dynamics of heat transfer and phase change within a flat-shaped thermosyphon, examining various parameters and working fluids. The research explores the effects of different working fluids, filling ratios, and heat inputs on the system's thermal performance. This study employs an axisymmetric model, to enhance the accuracy of the solution compared to a 2D model while maintaining a low computational cost. To validate our numerical model, we conducted comprehensive comparisons with experimental data, including the axisymmetric model, and capturing the nanofluid effects. Remarkably, our simulations consistently align with the experimental findings, demonstrating a high degree of accuracy and reliability in our model.The findings show that self-rewetting nanofluids exhibit superior heat transfer capabilities and a reduced risk of dry-out compared to traditional working fluids. Notably, self-rewetting fluids and self-rewetting nanofluids exhibit a unique behavior, reversed surface tension trends with rising temperatures, which effectively prevents dry-out by attracting liquid to hot regions. Additionally, the enhanced thermal conductivity of nanofluids during boiling enhances their performance furthermore. Also, the research studies the impact of filling ratios on temperature profiles and heat transfer rates, emphasizing the importance of higher filling ratios in lowering bottom plate temperatures. These insights offer valuable guidance for optimizing thermosyphons in applications like electronic cooling.

Effects of location of nano-enhanced PCM-packed bed on the process of heat transfer and phase transition in a nonuniform magnetic field

The phase change and thermal process intensification under nonuniform magnetic field (MGF) effects during hybrid nanofluid (NF) convection are investigated in this study using various arrangements of phase change material (PCM)-packed bed (PB) in a vented cavity. The PCM-PB is is considered as a triangular shape. The numerical research is done using the finite element method for different Reynolds numbers (Re between 200 and 600), inlet port sizes (between 0.5 and 2.5), Hartmann numbers (Ha between 0 and 60), nonuniform MGF component amplitudes (between 0 and 1), and different locations of the triangle PCM-PB zone. The process of phase change is accelerated by increasing the Re and port size, and the entire transition time (tf ) is reduced by 63% and 76%, respectively, when mix/max Re and min/max port sizes are considered. By using NF, the phase change is improved even further, and tf is further reduced by 17.6%–31.5%. When MGF strength and amplitude of the nonuniform component are increased, tf is reduced by about 13% and 6%. At the highest Ha, the average heat transfer (HT) drops by about 59%. The flow patterns, phase transition, and thermal performance are all significantly impacted by the placement of the PCM-PB zone. In terms of phase change process, configuration C2 by using NF at Ha = 60 is the best case while case at Ha = 0 by using only water is the worst case. The tf value is reduced by about 82.6% at the best case. When phase change and HT processes are considered, the optimal design of triangular PCM-PB zones alters.

Mesozoic and Cenozoic Tectono-Thermal Reconstruction of the Southern Ordos Basin: Revealed by Apatite Fission Track and (U-Th)/He Dating

The Ordos Basin is rich in oil and gas resources in the Paleozoic strata. The southern part of the basin boasts a thick Paleozoic sedimentary sequence, enriched organic matter, favorable sedimentary facies, and hydrocarbon source rocks with an over-mature thermal evolution stage. However, the lack of in-depth study of the tectono-thermal evolution in the southern basin limits regional oil and gas exploration. In this study, drill core and outcrop samples were collected from the Shanbei Slope and the Weibei Uplift, respectively. These samples were subjected to apatite fission track (AFT) and (U-Th)/He dating (AHe). The results were used to reconstruct the thermal history of the southern basin, calculate exhumation rates, and analyze the tectonic evolution of the basin. The seven annealed AFT data values from the Shanbei Slope range from 21.4 to 52.8 Ma, with mean track lengths of 13.24 μm, and the twelve unannealed AFT data values from the Weibei Uplift range from 111.9 to 204.6 Ma. The seven AHe data values from the Shanbei Slope range from 17.0 to 31.8 Ma, and the eight AHe data values from the Weibei Uplift range from 31.7 to 47.5 Ma. The thermal history is characterized by a prolonged phase of burial and heating from the Triassic to the Late Early Cretaceous, followed by a phase of uplift and cooling that continued into the Cenozoic. This cooling phase exhibits three distinct stages with varying rates of uplift and cooling. According to the dating results, the cooling timing of the southern basin was earlier than that of the central part, and the southern basin experienced higher uplift rates during the Paleogene than in other periods of the Cenozoic. This may be attributed to the far-field effects of the collision between the Indian Plate and the Eurasian Plate during the Paleogene.

The Influence of Angle of Attack on the Icing Distribution Characteristics of DU97 Blade Airfoil Surface for Wind Turbines

This study explores the influence of angle of attack (AOA) on the icing distribution characteristics of asymmetric blade airfoil (DU97) surfaces for wind turbines under icing conditions by numerical simulation. The findings demonstrate a consistence between the simulated ice shapes and experimental data. The ice thickness distribution on the lower surface of the leading edge exhibits a trend of first rising and then declining along the chord direction while showing a gradually decreasing trend on the upper surface. The ice distribution range on the upper surface of the trailing edge is broader than that on the lower surface. The peak ice thickness at the trailing edge rises significantly as AOA increases from 5° to 10°, and at the leading edge raises dramatically at droplet sizes of 30–40 μm and wind speeds of 5–10 m/s. The peak ice thickness is more significantly influenced by AOA than by ambient temperature due to the combined effect of airflow characteristics induced by AOA and latent heat (phase change) and sensible heat (thermal convection and thermal radiation) caused by ambient temperature. The findings offer valuable insights into the flow and heat transfer physics, and can operate as references for wind turbine anti/de-icing technology.

Comprehensive study of the cold-temperature directed energy deposition: Multi-physics modelling and experimental validation

Currently almost all the directed energy deposition (DED) processes are performed under ideal lab conditions with the room temperature close to 20 °C. By contrast, the cold-temperature DED has potentially onsite use in cold environments, such as the winter in the Northern Hemisphere, where the ambient temperatures are often near or below freezing point temperature (0 °C). However, there is a lack of study on the cold-temperature DED process due to its unique temperature conditions. To fill this gap, the authors employed both multi-physics modelling and experimental approaches to study the DED process at cold temperature (CT) −3 °C, and compare to the room temperature (RT) 20 °C DED process. Stainless Steel 316L (SS316L) was selected as powder material. The multiple physics in the DED process involving laser heat source, local melting, rapid cooling, solidification, phase change, evaporation, and fluid-gas interactions were modeled using the computational fluid dynamics (CFD) – volume of fluid (VOF) approach. To validate the model, the DED experiments were conducted using a cryogenic DED platform in which the DED process was chilled to customized low temperatures. This high-fidelity model predicted accurate thermal results and deposit geometries for both the CT and RT DED cases. The results show that under sub-freezing conditions, the deposit size of the CT-DED is ∼62.1 % bigger than the RT-DED in the mean area throughout the length of the single-track thin wall. Furthermore, the CT-DED results show a steeper thermal gradient and at the same time a lower heat flux near the substrate. This high-fidelity modelling framework can be effectively expanded to study more cold-temperature additive manufacturing cases, like the Arctic exploration and in-Space manufacturing.

Convection and phase change in a lid-driven trapezoidal vented cavity with encapsulated PCM under non-uniform magnetic field by using ternary nanofluid

In this study, a novel configuration of lid-driven vented cavity system equipped with encapsulated phase change materials is studied where applications are relevant in drying, material processing, and electronic cooling. For controlling the convective heat transfer and phase transition, combined utilization of non-uniform magnetic field with ternary nanofluid is offered. Upper wall is inclined and moving with constant speed while ternary nanofluid up to a loading of 0.03 is used. Galerkin weighted residual finite element method is considered as the solution technique. A range of parameters for Reynolds number (Re, 200–1000), wall velocity (Rep, 0–1500), Hartmann number (Ha, 0–30), inclination parameter (yd, 0–0.4H), non-uniform amplitude (Af, 0–0.3), and nanoparticle loading (ϕ, 0–0.03) are considered in the analysis. When Re is increased, transition time (tf) is generally reduced for moving wall case. Reduction of tf up to 65% is obtained at the highest Re when moving wall is used at Rep=1000. For stationary wall case, the behavior of tf with Re is non-monotonic while at the highest Re, tf is reduced. The phase transition process is strongly influenced by the moving wall velocity while first increment and decrement of tf with wall velocity is observed. Thermal performance rises by around 58% and 22%, respectively by using the highest Re for stationary and moving walls. There is a significant increase in heat transfer, of around 211%, as wall velocities rise from Rep=0 (stationary) to Rep=1500. The tf for the moving wall is decreased by around 43.7% at the highest Ha. According to the stationary scenario, tf rises by around 33% until Ha=15 and falls by roughly 39.2% between Ha=15 and Ha=30. Amplitude of non-uniform magnetic field results in variation of tf between 4.5% and 19%. When imposing magnetic field at maximum strength, thermal performance is improved by 44.75% with a moving wall while it is just 5% in a stationary scenario. While raising the value of upper wall’s inclination (yd) increases the thermal performance, it also influences the phase change process. More loading of nanoparticles in base fluid results in a faster transition; the corresponding decreases in tf are 24.5% and 12.7% for stationary and moving wall setups, respectively. The increases in thermal performance for stationary and moving wall cases are 36.3% and 33.7%, respectively.