Minimal Heat Research Articles

Attenuated Natural Convection in Molten Salt Electrochemical Systems with Minimal Heat Dissipation.

The accurate understanding of mass transfer in molten salt contributes to revealing the reaction mechanism and advancing the technologies. The existence of notable natural convection effects has been demonstrated in our previous studies, even though the driving forces for such a high natural convection are still not clear. Herein, we showed that the intense natural convection in molten salts resulted from severe heat dissipation through the electrodes (or the system). With an adiabatic design, natural convection effects were significantly suppressed in molten LiCl-KCl. The derived value of the natural convection layer (δconv) ranged from 190 to 250 μm in molten LiCl-KCl containing a redox couple (e.g., SmCl3, EuCl3, and CrCl3), comparable to those in aqueous solutions. The values of δconv in LiCl-KCl-173 mM CrCl3 increased to ∼360 μm due to the change in salt viscosity. The density-driven convection became dominant under a high redox concentration, and the increasing working temperature had no apparent effect on the natural convection effects because of the adiabatic design.

Exploring the Potential of Tunnel Field-Effect Transistors in Biomedical Devices: A Comprehensive Survey

Implantable medical devices have revolutionized healthcare by providing continuous monitoring and therapeutic interventions within the human body. The overall performance of these devices is heavily dependent on the effectiveness and efficiency of integrated electronic components, such as transistors. This survey explores the growing utilization of Tunnel Field-Effect Transistors (TFETs) in implantable devices, shedding light on their advantages and challenges in this specific application domain. TFETs, characterized by their unique tunnelling mechanism, offer several advantages that make them well suited for implantable devices. Their low-power consumption, reduced leakage current, and improved subthreshold swing make them ideal for energy-efficient, long-lasting operation within the constrained power budgets of implantable devices. Furthermore, TFETs exhibit excellent performance at low supply voltages, ensuring minimal tissue damage and heat generation. This survey also addresses the challenges associated with TFETs in implantable devices, including fabrication complexities, variability, and compatibility with existing technologies. It highlights recent advancements in TFET technology that address these concerns, such as improved material choices and manufacturing techniques. As technology continues to advance, TFETs are poised to play a pivotal role in improving the overall efficiency and reliability of life-saving technologies and medical devices. Overall, this survey provides valuable insights into the current state and future prospects of TFETs in implantable devices, guiding researchers and engineers in harnessing their potential for the benefit of healthcare and patient well-being.

Optimization of Triply Periodic Minimal Surface Heat Exchanger to Achieve Compactness, High Efficiency, and Low-Pressure Drop

With advancements in additive manufacturing (AM) techniques, high-quality triply periodic minimal surface (TPMS) structures can now be produced. TPMS walled heat exchangers (HX) hold significant potential for industrial applications and are receiving increasing attention. This paper explores the impact of various TPMS design variables on flow and thermal performance to optimize TPMS heat exchangers for compactness, high efficiency, and low pressure drop. The design variables examined include the type of TPMS lattice, unit cell size, wall thickness, aspect ratio, TPMS orientation, and equivalent thickness. The study reveals that the flow and heat transfer performance of TPMS structures are significantly affected by these design variables. For the Gyroid, Diamond, and SplitP lattices, performance is nearly identical when the surface-to-volume ratio is kept constant. The average velocity of the fluid in the TPMS HX should be 0.3 m/s. The corresponding Re is between 300~800. Thin wall thickness, small equivalent thickness, and flat lattice configurations can significantly reduce pressure drop while maintaining the overall heat transfer coefficient. Additionally, the angle between the flow direction and TPMS orientation can increase pressure drop. Three aluminum heat exchangers were successfully printed using an AM machine, and testing results are comparable with theoretical prediction.

Development and Characterization of Mesoporous Silica-MgSO4-MgCl2 Binary Salt Composites for Low-Grade Heat Storage in Fluidized Bed Systems

Achieving nearly zero-energy buildings requires efficient utilization and storage of renewable energy. Salt-hydrate-based thermochemical energy storage (TCES) systems are promising due to their high heat storage capacity and minimal seasonal heat loss. However, challenges remain for their commercialization and large-scale application. For example, TCES systems using magnesium sulfate (MgSO4) provide low temperature lifts due to slow reaction kinetics. Incorporating deliquescent salts like magnesium chloride (MgCl2) can enhance sorption performance but may introduce stability issues such as agglomeration and decomposition. This study proposes a novel binary-salt composite that combines MgSO4 and MgCl2 within commercial mesoporous silica (CMS) to address these challenges and enhance overall performance. The binary-salt composite powder, with a particle size range of 150 to 300 μm, is suitable for use in fluidized-bed reactors, where fast mass and heat transfer promote efficient moisture adsorption, prevent uneven temperature distribution, and reduce agglomeration. Measured using thermogravimetric analysis (TGA), the MgCl2-MgSO4@CMS binary-salt composites, with a total salt content of 50 wt% and salt mixing ratios of 3:1, 1:1, and 1:3, exhibited water sorption capacities of 0.95, 0.68, and 0.57 g/g, respectively. In comparison, the MgSO4@CMS single-salt composite showed a lower water adsorption capacity of 0.47 g/g and required higher temperatures above 150 °C for complete regeneration. Reactor-scale experiments demonstrated that the MgCl2-MgSO4(1:1)@CMS composite can be fluidized at low gas velocities on the order of 10-2 m/s, providing a maximum temperature lift of 24.7 °C and an energy density of 1018 kJ/kg during hydration at 80% relative humidity and 30 °C. The binary-salt composite also showed good cyclic stability with less particle agglomeration compared to the MgCl2@CMS single-salt composite.

The effect of pyrolysis heating rate on the mesoporosity of Pluronic F-127 templated carbon xerogels

This study explored the impact of pyrolysis heating rates ranging from 1 to 20 K min−1 (final temperature 500 °C) on the porosity of resorcinol-formaldehyde based carbonaceous xerogels soft-templated with Pluronic F-127. We primarily utilized thermoporometry (differential scanning calorimetry technique) and, to a lesser extent, conventional nitrogen adsorption at −196 °C to analyze the porosity of the resulting carbons. Additionally, we examined the effects of particle size and the scale of the pyrolysis experiment, comparing a laboratory furnace with a thermal analyzer. At lower heating rates, particularly in a thermal analyzer, mesopores approximately 7–8 nm in size were observed. An increase in the heating rate resulted in larger mesopores, from 7 to 17 nm, widened pore size distribution (PSD), and a rise in mesopore volume from 0.21 to 0.53 cm3g−1. Higher heating rates (> 5 K min-1) also accelerated the decomposition of the Pluronic F-127, leading to fast gas release, which subsequently caused cracking of the carbon skeleton and widening of the pores. Pyrolysis heating rate had no significant effect on the degree of graphitization in the pyrolyzed samples. Particle size showed minimal influence on porosity when xerogels were pyrolyzed at either the minimal or maximal heating rates in the thermal analyzer. However, experiments conducted in a laboratory furnace at the lowest heating rate demonstrated that imprecise temperature control and fluctuations can lead to the formation of larger mesopores.

Effect of fast frequency double pulse current on microstructural characteristics and mechanical properties of wire arc additively manufactured Ti-6Al-4V alloy

This study introduces an innovative technique known as fast-frequency double pulse wire arc metal additive manufacturing (FFDP-WAAM). This method employs periodic fluctuations in arc plasma and force to enhance the stirring effect within the molten pool, resulting in the fragmentation of β grains and the formation of finer prior-β grains. The microstructure primarily comprises α', attributed to the high cooling rates and minimal heat accumulation. Compared to the conventional gas tungsten arc welding-based WAAM (CGT-WAAM) process, FFDP-WAAM significantly reduces α-variant selection, thereby achieving a more uniform α phase orientation distribution. Additionally, ultrasonic vibration in the FFDP-WAAM process facilitates recrystallization and mitigates residual strain. The tensile strength and elongation of the FFDP-WAAM specimens reached 939.2 MPa and 9.0 %, respectively, whereas the CGT-WAAM specimens showed a lower tensile strength of 830 MPa and elongation of 9.2 %. The enhanced strength, fatigue life and microhardness of Ti-6Al-4V produced by FFDP-WAAM is ascribed to the refined grain-size distribution. Furthermore, the low Schmid factor (SF) distribution and the stable triangular structure of Category I α-clusters are anticipated to contribute to the increased strength of the FFDP-WAAM-fabricated wall.

Topography of textured surfaces using an abrasive-water jet technology

Surface texturing is a technique that allows for the shaping of surface topography to meet various mechanical and tribological requirements. Abrasive-water jet (AWJ) technology is a promising approach to surface texturing, offering minimal heat impact, flexibility, and compatibility with complex surface geometries. High-pressure abrasive-water jet (AWJ) technology, as an innovative and versatile approach, significantly expands the possibilities of surface texturing for materials. Its advantages, such as precision, minimal thermal impact, sustainability, and a wide range of industrial applications, make it an attractive solution across various sectors. With continuous development and integration with modern digital technologies, AWJ is becoming an increasingly practical and cutting-edge tool in surface processing. The abrasive-water jet texturing process also affects surface geometry during the mating of components, which may be significant in reducing wear. The aim of the research was to determine the feasibility of obtaining specific structures on the surface of 304/1.4301 steel using abrasive-water jet technology. Results show that the highest load-bearing ratio of Smrk1 peaks, approximately 25%, was achieved at a texturing speed of 0.803 m/min. Conversely, the lowest load-bearing ratio of Smrk1 peaks, below 10%, was achieved at a texturing speed of 1.948 m/min. Grinding the surface after texturing increases its load-bearing capacity, leading to a twofold increase in the ability to maintain an oil layer. The obtained results may find application in various fields where controlling surface geometry is essential for improving material functionality and efficiency.

Optical trapping-induced crystallization promoted by gold and silicon nanoparticles.

This study investigates the promotion of sodium chlorate (NaClO3) crystallization through optical trapping, enhanced by the addition of gold nanoparticles (AuNPs) and silicon nanoparticles (SiNPs). Using a focused laser beam at the air-solution interface of a saturated NaClO3 solution with AuNPs or SiNPs, the aggregates of these particles were formed at the laser focus, the nucleation and growth of metastable NaClO3 (m-NaClO3) crystals were induced. Continued laser irradiation caused these m-NaClO3 crystals to undergo repeated cycles of growth and dissolution, eventually transitioning to a stable crystal form. Our comparative analysis showed that AuNPs, due to their significant heating due to higher photon absorption efficiency, caused more pronounced size fluctuations in m-NaClO3 crystals compared to the stable behavior observed with SiNPs. Interestingly, the maximum diameter of the m-NaClO3 crystals that appeared during the size fluctuation step was consistent, regardless of nanoparticle type, concentration, or size. The crystallization process was also promoted by using polystyrene nanoparticles, which have minimal heating and electric field enhancement, suggesting that the reduction in activation energy for nucleation at the particle surface is a key factor. These findings provide critical insights into the mechanisms of laser-induced crystallization, emphasizing the roles of plasmonic heating, particle surfaces, and optical forces.

A NOVEL DOUBLE-SIDE LASER WELDED THICK PLATE: MICROSTRUCTURE AND NUMERICAL PREDICTION OF TENSILE TEST

The study aims to provide firsthand knowledge on finite element simulation (FES) of double-side laser welded (LW) stainless steel 304 (SS-304) thick plates used for automobile application. Double-side welding technique is an idea of achieving complete penetration with minimal heat input. The microstructural evaluation revealed the presence of dendritic growth that results in the enhancement of tensile strength (TS) for the welded sample. There is a slight increase in the delta ferrite content in weldment. The change in microstructure is due to thermal history during solidification. The TS of base metal (BM) was [Formula: see text][Formula: see text]MPa whereas the welded sample exhibited strength of [Formula: see text][Formula: see text]MPa. FES was successfully employed to simulate TS with error percentage less than 1.

Design of Thermoresponsive Genetic Controls with Minimal Heat-Shock Response.

As temperature serves as a versatile input signal, thermoresponsive genetic controls have gained significant interest for recombinant protein production and metabolic engineering applications. The conventional thermoresponsive systems normally require the continuous exposure of heat stimuli to trigger the prolonged expression of targeted genes, and the accompanied heat-shock response is detrimental to the bioproduction process. In this study, we present the design of thermoresponsive quorum-sensing (ThermoQS) circuits to make Escherichia coli record transient heat stimuli. By conversion of the heat input into the accumulation of quorum-sensing molecules such as acyl-homoserine lactone derived from Pseudomonas aeruginosa, sustained gene expressions were achieved by a minimal heat stimulus. Moreover, we also demonstrated that we reprogrammed the E. coli Lac operon to make it respond to heat stimuli with an impressive signal-to-noise ratio (S/N) of 15.3. Taken together, we envision that the ThermoQS systems reported in this study are expected to remarkably diminish both design and experimental expenditures for future metabolic engineering applications.

Investigation on thermochemical heat charging and discharging behavior of Ca(OH)2/CaO in a fixed bed reactor

Thermochemical heat storage (TCHS) technology plays a crucial role in the energy system, essential for maintaining the balance between energy supply and demand. The Ca(OH)2/CaO system holds significant promise for TCHS thanks to its high energy storage density, cost-effectiveness, and minimal heat loss. However, further research is required to elucidate the coupling mechanisms of the various physicochemical processes involved and to optimize the overall system performance. This paper focuses on assessing and elucidating the multi-physics coupled transport rules during both the charging and discharging stages in a fixed-bed reactor based on the developed numerical model. Results manifest the bed temperature rapidly increases to around 950 K, then slows down as the endothermic reaction predominates, completing dehydration in 1,900 s. During discharging, hydration conversion advances in a “U”-shaped pattern from the vapor inlet and side wall to the outlet, driven by the high vapor content near the inlet and the lower temperature near the wall. Furthermore, a thorough sensitivity analysis of the main parameters such as thermal conductivity and porosity is conducted to determine how different operating conditions affect the charging and discharging processes. Finally, a new reactor structure is proposed, in which a gas-guide duct is added at the central axis of the reactor to improve mass transport and uniformly distributed finned heating tube bundles to enhance heat transfer. These two functions can shorten the charging period by 9 % and 16 % respectively. The results can aid in predicting thermochemical conversion behaviors and multi-physic coupling transport processes, while also providing a foundational reference for the design of TCHS systems.

Performance analysis and optimization of the Gyroid-type triply periodic minimal surface heat sink incorporated with fin structures

The Triply Periodic Minimal Surface (TPMS) structures demonstrate substantial value and development potential in applications and research concerning heat sinks and heat exchangers. To further enhance the convective heat transfer performance of TPMS, this study proposes a novel method of incorporating fin structures into TPMS. This method is applicable to various types of TPMS, and the new structure constructed using this method is termed “TPMS with Fin Structures (TFS).” Subsequently, a TFS-Gyroid heat sink based on the Gyroid-type TPMS was constructed. This study presents a calculation method for the fin height in TFS-Gyroid (HTFS-Gyroid). Numerical simulation methods were employed to investigate the influence and mechanism of HTFS-Gyroid on the convective heat transfer performance and flow resistance of the TFS-Gyroid heat sink model, with air as the working fluid and under constant wall temperature (100 °C) conditions. The results indicate that within the flow range of 24–120 L/min, as HTFS-Gyroid increases from 0 to 1.6 mm, the average surface convective heat transfer coefficient (h̅) of the TFS-Gyroid heat sink model increases by 27.4 %-34.6 %, and the inlet–outlet pressure drop (ΔP) increases by 42.5–632.8 Pa. As HTFS-Gyroid increases, the PEC of the TFS-Gyroid heat sink model gradually decreases, whereas j/f gradually increases. The primary mechanisms by which the fin structures enhance the convective heat transfer performance of the TFS-Gyroid heat sink are: 1) increased heat exchange area, 2) the fin structures induce a large number of longitudinal vortices and secondary flows within the flow channels, and 3) the formation of “Fins Occupying the Perforated Structure (FOPS)” within the flow channels.

Light‐Guided Genetic Scissors Based on Phosphorene Quantum Dot

AbstractGenetic engineering faces persistent challenges in achieving precise Deoxyribonucleic acid (DNA) cleavage, especially with the limitations associated with current enzyme‐based methods, exemplified by issues in CRISPR technologies. This study introduces a groundbreaking approach: utilizing reactive oxygen species (ROS) generated by Multiphoton Absorption (MPA)‐excited Black Phosphorus Quantum Dots (BPQDs) under femto‐second laser irradiation. This innovative method not only allows excitation with lower energy but also enhances overall efficiency. The integration of complementary RNA sequences facilitates high‐efficiency, site‐selective DNA cleavage in the system, named “TADPOLE” (Targeted DNA Precision Oriented Laser Excision). Beyond its precision in targeting arbitrary DNA sequences using quantum dots, TADPOLE harnesses the unique multiphoton absorption property of BPQDs, enabling excitation with lower‐energy light sources suitable for in vivo applications in the future. Moreover, the approach integrates guiding RNA and ultrafast laser technology to provide precise control over local ROS generation and minimal heat production. This guarantees site‐specific DNA cleavage while mitigating the risk of damage to non‐targeted sequences. In summary, this study catalyzes advancements in enzyme‐free DNA cleavage technologies, with transformative implications for genetic engineering, biotechnology, and medicine. The holistic precision, versatility, and endurance presented by TADPOLE open new avenues for targeted gene therapies and transformative applications in related fields.

A new approach for heat transfer coefficient determination in triply periodic minimal surface-based heat exchangers

The development of additive manufacturing offers increasing opportunities in heat transfer. A wider range of materials is used in the 3D printing process of heat exchangers based on the Triply Periodic Minimal Surface. Due to the complexity of these structures, it is difficult to precisely determine the values describing the heat transfer process in these devices. One of the parameters describing the heat transfer process in heat exchangers is the heat transfer coefficient. This study describes a new method for determining the heat transfer coefficient in a heat exchanger based on a gyroidal lattice. The proposed new method allows for determining the heat transfer coefficient values without interfering with the internal space of the compact heat exchanger. The developed formula can be used in the indirect method of determining the value of the heat transfer coefficient in two-phase flow with boiling or condensation of the working medium. The thermal tests were carried out in the range of working flow rates 4–24 kg/h; the media temperature was 20 and 50 °C, the heat flux was from 0.1 to 0.4 kW. Tests were conducted for laminar flow in the 20 < Re < 200 range.

"Coir Raincoat"-Boosted Biomimetic Hydrogel for Efficient Solar Desalination and Wastewater Purification.

Solar-driven interfacial evaporation is an efficient method for purifying contaminated or saline water. Nonetheless, the suboptimal design of the structure and composition still necessitates a compromise between evaporation rate and service life. Therefore, achieving efficient production of clean water remains a key challenge. Here, a biomimetic dictyophora hydrogel based on loofah/carbonized sucrose@ZIF-8/polyvinyl alcohol is demonstrated, which can serve as an independent solar evaporator for clean water recovery. This special structural design achieves effective thermal positioning and minimal heat loss, while reducing the actual enthalpy of water evaporation. The evaporator achieves a pure water evaporation rate of 3.88kg m-2 h-1 and a solar-vapor conversion efficiency of 97.16% under 1 sun irradiation. In comparison, the wastewater evaporation rate of the evaporator with ZIF-8 remains at 3.85kg m-2 h-1 for 30 days, which is 16.3% higher than the light irradiation without ZIF-8. Equally important, the evaporator also showcases the capability to cleanse water from diverse sources of contaminants, including those with small molecules, oil, heavy metal ions, and bacteria, greatly improving the lifespan of the evaporator.

Microstructural and mechanical characterization of electron beam welded low-nickel nitrogen-strengthened austenitic stainless steel

In this paper, the Electron Beam Welding (EBW) was used to join thin plates of low-nickel nitrogen-strengthened austenitic stainless steel (LNiASS), a material valued for its superior mechanical properties and cost-effectiveness. Traditional welding techniques often lead to issues such as hot cracking, reduced toughness, and undesirable microstructures. The objective was to address these challenges using EB·W., which offers precise control, minimal heat input, and deeper penetration.Methodology included joining LNiASS plates with E.B.W. and analyzing the resulting microstructures and mechanical properties through optical microscopy, tensile testing, microhardness testing, and scanning electron microscopy (SEM). The findings indicated the presence of various ferrite morphologies without significant precipitation of deleterious phases like carbides and sigma phase. The weldment strength was ∼90 % of the base alloy, with fractures occurring near the weld cord due to nitrogen loss and grain coarsening in the (HAZ). Microhardness increased by ∼12.9 %, attributed to microstructural evolution and a fine-grained structure. Impact testing in Charpy V-Notch (CVN) configuration showed the weld absorbed ∼50 % more impact energy than the base material, due to refined Microstructure and enhanced hardness. Longitudinal residual stress analysis indicated compressive nature below mid-thickness, resulting from thermal expansion and contraction during welding. These results demonstrated E.B·W.'s effectiveness in preserving mechanical properties and enhancing the performance of nitrogen-strengthened stainless steel welds.

Startup characteristics of a water loop heat pipe with dual heat sources for battery thermal management system in electric vehicle

Abstract The usage of electric vehicles has significantly reduced emissions of greenhouse gases and other pollutants. However, the high heat release generated by the electric vehicle batteries poses a challenge. To solve this problem, scientists have created a passive cooling thermal management system specifically for electric vehicle based on heat pipes, particularly loop heat pipes. A battery pack often consists of several battery modules, which results in multiple heat sources being dispersed according to their power capacity. Startup behavior of loop heat pipe has been investigated extensively in the literature. However, most of the studies use only one heat source. This paper aims to fill the research gap, particularly when the system is implemented in dual heat sources managed by only one evaporator. To achieve the research objectives, a custom loop heat pipe was constructed. This cooling system’s design is briefly described. The evaporator is made of copper, deionized water was selected as the working fluid because of its high merit number, which indicates strong performance as a heat pipe working fluid and the stainless-steel wire mesh serves as the porous wick. Battery simulator was built using aluminum material and a cartridge heater to mimic the heat produced by the battery. Two case studies were done. First, only one battery simulator was used. Second, two battery simulators were placed on both sides of the evaporator. A type-K thermocouple attached to the NI DAQ 9214 module was used to measure the temperature while the electric heat load varied between 10 W and 50 W. The study investigated the interaction between the heat load distribution and the startup behavior of the loop heat pipe. Startup behavior is crucial for the performance of the loop heat pipe. Based on the experimental results, the loop heat pipe demonstrates outstanding startup performance. It can effectively initiate operation even at a minimal heat load as low as 30 W for the first and second case study. The findings of the study indicate that the dual heat source arrangement effectively mitigates overshoot temperatures and enhances heat transfer performance by increasing the contact area.

Effect of process parameters on weld geometry and mechanical properties in friction stir welding of AA2024 and AA7075 alloys

FSW joints are promising because they have a minimal heat input in welding and can limit the amount of intermetallic compound formation in dissimilar metals. Solid-state welding processes, particularly friction stir welding (FSW), are preferred for welding aluminium alloys due to their low heat input and ability to minimize intermetallic compound formation. This study conducted FSW trials on AA7075 and AA2024 alloys, each 4 mm thick. Parameters such as axial force, rotational speed, and traverse feed were adjusted while keeping other factors constant. The study analyzed weld geometry characteristics, including bead width and penetration depth. Angle distortions during FSW of thin plates in a butt joint were investigated. Additionally, the study examined the effects of FSW parameters on mechanical properties such as tensile strength and hardness immediately after welding. Microstructures of the welds were observed using optical microscopy (OM). The optimal mechanical properties are achieved at a rotational speed of 1000 rpm, a traverse feed of 30 mm/min, and an axial force of 10 kN. This optimal condition facilitates material flow around the pin at an ideal speed, ensuring adequate material filling and preventing tunnel formation. The stir zone's microstructure under these parameters exhibits a finely recrystallized structure with a significantly smaller grain size than the base material. Consequently, this enhances the joint's microhardness and tensile strength.

Investigation on uneven flow distribution in triply periodic minimal surface heat exchangers

The development in manufacturing engineering has made it possible to adopt the unique porous structure known as the triply periodic minimal surface to increase energy efficiency in a variety of energy-related sectors. With the unique morphological characteristics, triply periodic minimal surface exhibits remarkable mechanical strength and thermal performance, which makes it a potential candidate for compact, high-performance heat exchanger constructions. In this study, a theoretical model based on triply periodic minimal surface porous media is developed. Based on the hypothesis that the triply periodic minimal surface is isotropic and the heat transfer intensity of fluid and solid is uniform throughout the core of the heat exchanger, the simulation of the full-size heat exchanger is simplified by using a porous media model. The flow distribution characteristics of triply periodic minimal surface heat exchangers, as well as the effect mechanism of key factors, including the channel porosity, header configuration, the type of triply periodic minimal surface, the core length and Reynolds number on the flow distribution performance, are investigated. A dual-header configuration is proposed to improve the flow uniformity of triply periodic minimal surface heat exchangers. The results indicate that the flow distribution performance of triply periodic minimal surface based heat exchangers can be enhanced by the reduction of channel porosity. When the cold-side porosity is 0.7, the flow rate deviates from the mean value by 220% at its maximum for a Primitive heat exchanger. A dual-header configuration eliminates the columnar extreme high velocity space in the core and greatly reduces the “weak zone” of flow distribution, which improves the flow non-uniformity by 45–90% over the single-inlet headers. This paper provides data and theoretical support for the optimal design and practical application of the complex, high-performance triply periodic minimal surface based heat exchangers.

Assessing water position through distributed temperature sensing using Rayleigh-based optical frequency-domain reflectometry: a laboratory feasibility study

This study demonstrates the ability of the Rayleigh-based phase-noise compensated optical frequency-domain reflectometry (PNC-OFDR) sensing method to monitor the distributed temperature field with an ultra-short data acquisition period of 2 ms, a spatial resolution of 2 cm, and a temperature resolution of 0.1 °C. A heating cable (H-cable) was embedded within a cylindrical concrete mortar specimen and subjected to various heating powers. A sensing optical cable (T-cable) was placed adjacent to the heating cable to monitor the temperature distribution continuously. Two water-holding boxes were installed along the specimen at two positions to retain water. The results of the study indicated that the PNC-OFDR technique demonstrated a high sensitivity to even small temperature changes, enabling it to accurately pinpoint the locations of water at two distinct points. The research determined the minimal heating power required for successfully locating the water positions. The magnitude of the heating power exerted a significant impact on the temperature change. Three distinct phases of temperature increment were observed for a given heating period: rapid, fast, and gentle increase. The insights gained from this study have the potential to be applied in natural fields, allowing for the detection of groundwater and seepage phenomena in vulnerable slopes.