Latent Heat Transfer Research Articles

Approximate Solution of Fuzzy Sedimentary Ocean Basin Boundary Value Problem Using Variational Iteration Method

The problem that is considered in this paper is developed from the migration of the coastline over time in sedimentary ocean basins that may be considered as a moving boundary problem with a variable latent heat transfer equation as a governing equation if one of the boundaries is unknown, with boundary and initial conditions are given. This model discusses the shoreline movement within sedimentary basins. The main objective of the paper is to use fuzzy logic to formulate this problem when modelling sand particles migration in saltwater by utilizing fuzzy numbers whenever replacing some of the problem's parameters. In reality, the proposed model is more general than the nonfuzzy or crisp models. By employing the variational iteration method, the approximate numerical solution of the proposed problem has been found, and computer software written in Mathematica 11 have been used to obtain the results.

Acoustics of wet porous media with evaporation/condensation

This paper investigates acoustic wave propagation in wet rigid-frame porous media accounting for evaporation and condensation. At equilibrium, the solid walls are covered by a thin water film, and water vapor in the air is at its temperature-dependent saturation pressure. Small acoustic perturbations cause water to vaporize or condense, which together with the reversibility of the phase change, lead to a linear problem where the usual local poro-acoustics physics is enriched with the (i) Clapeyron relation linking liquid-wall temperature, vapor pressure, and latent heat of vaporization, (ii) latent heat transfer in the solid frame, (iii) diffusion equation for water vapor in air, and (iv) water vapor's equation of state. The equilibrium temperature highly influences the vapor concentration and the physical parameters of saturated moist air. Using the two-scale asymptotic homogenization method, it is shown that the dynamic permeability is determined similarly to classical porous media, while the effective compressibility is modified by evaporation/condensation and the equilibrium temperature. This modification is influenced by vapor mass and heat flows associated with phase changes through a local fully coupled heat transfer and water vapor diffusion problem, with specific boundary conditions at the gas–water interface. The analysis identifies dimensionless parameters and characteristic frequencies defining the upscaled model's features. Depending on equilibrium temperature, the theory qualitatively and quantitatively determines the characteristics of acoustic waves propagating through the media. The results are illustrated and discussed with analytically developed models.

Pulsating Heat Pipe Performance Modeling with Liquid Metal Coolants Under Hypersonic Aerothermal Heating

Hypersonic heating loads concentrate at leading-edge compression areas to create excessively high local temperatures and thermally driven stresses. The fast and reliable thermal dispersion of heat pipes with significantly high thermal conductance can alleviate these localized thermal stiffness problems. The pulsating heat pipe (PHP) holds numerous advantages when compared to capillary, constant-conductance heat pipes for hypersonic thermal management applications, primarily because they lack a wicking structure. This paper numerically investigates thermal performances of a four-turn C103 niobium alloy PHP operating with lithium, potassium, sodium, and a eutectic sodium–potassium alloy (NaK-78) when exposed to heating conditions relevant to the hypersonic environment, investigating flight Mach numbers ranging from 6 to 8 and dynamic pressures ranging from 40 to 44 kPa. The robust thermofluidic properties of liquid metals, along with the powerful fluid pulsation induced in the PHP, can provide significant thermal transport from hot stagnant regions of the leading edge to the cooler trailing surfaces. Potassium showed superior thermal performance when compared to other liquid metal coolants under the presently tested conditions, with overall PHP thermal conductance as high as 34 W/K predicted for Mach 8 flight conditions. In contrast, sodium was associated with startup difficulties in the PHP; this paper attributes this to its significantly larger thermal conductivity, which can limit the vapor pressure difference over the liquid slug lengths. These predictions indicate an overall latent heat transfer dominance of around 70–95% in liquid metal PHPs.

Theoretical modelling and experimental evaluation of thermal performance of a combined earth-to-air heat exchanger and return air hybrid system

To both alleviate thermal saturation in surrounding soil and avoid indoor air pollution caused by closed-loop earth-to-air heat exchanger (EAHE) systems, this study proposes a hybrid mode that combines EAHE and return air (RA), i.e., the EAHE-RA system. A theoretical model was proposed to predict the thermal performance of EAHE-RA systems considering both sensible and latent heat transfer inside the EAHE. Full-scale experiments on both open-loop EAHE system and EAHE-RA system were carried out. The results indicated that the average cooling capacity of EAHE in EAHE-RA system was decreased by 1202.8 W (43.82 %) in summer compared to open-loop EAHE system, while the average cooling capacity recovery of return air was 645.4 W. In winter, the average heating capacity of the EAHE of EAHE-RA system was decreased by 394.1 W (48.91 %), while the average heating capacity recovery of the return air was 1021.7 W. Theoretical predictions of EAHE outlet and indoor air temperature agree well with the measured ones in both summer and winter. Theoretical results indicated that the EAHE-RA system has lower/higher pipe wall temperatures in summer/winter than the open-loop EAHE does, indicating a lower thermal interference on surrounding soils and thus better durability.

Thermodynamic study of water/solvent, bitumen/solvent, water/bitumen, and water/bitumen/solvent systems: From CPA EoS parametrization towards phase diagram construction

Various fluid phase equilibria happen in solvent-aided steam-assisted gravity drainage (SA-SAGD). An appropriate fluid model is a prerequisite for reservoir simulation, SA-SAGD operation analysis, and the design of various phase behavior experiments. Computational thermodynamics is a powerful tool for phase behavior studies in this application. We used the Cubic Plus Association Equation of State (CPA EoS) to predict equilibrium properties due to the presence of molecules with highly directional attractive forces. Calibration of the thermodynamic model is performed by parametrizing its unknown parameters versus two-phase equilibrium data. The model’s prediction capability of three-phase experimental data is evaluated, and it is used to construct the phase diagram of water/multicomponent solvent and water/multicomponent solvent/bitumen systems. For the water/multicomponent solvent system, the Txy diagram is obtained at 25 bar, and various phase equilibria regions are specified. These phase regions are presented on ternary diagrams for water/multicomponent solvent/bitumen systems at 25 bar and 475 K, 480 K, and 485 K. The steam/solvent coinjection analysis shows that at the same pressure, temperature, and steam/solvent composition, the multicomponent solvent/steam coinjection yields more aqueous phase compared to pure solvent/steam. This results in the transfer of more latent heat to bitumen, significantly contributing to its viscosity reduction. Analysis of the SA-SAGD operating conditions shows that a multicomponent solvent outperforms pure solvents in promoting steam condensation. The results aids in designing experiments, reducing the risk of failure of experiments, and saving time and resources in phase behavior studies.

Thermal performance of energy piles in unsaturated soils: Experiment, simulation, and case study

The operation of energy piles in unsaturated soils involves coupled heat and moisture transfer, demanding further detailed investigation. In this paper, laboratory tests were conducted to validate a numerical model that incorporated vapor and liquid migration, convection, and latent heat transfer in unsaturated soils. Moreover, this model captured the dynamic variation in characteristic parameters of unsaturated soils. Building upon this observation, this study delved into the thermal performance of the energy pile under ten-year cooling and heating cycles, specifically focusing on the temperature, heat exchange rate, volumetric water content, and thermal conductivity. It is demonstrated that the imbalanced cooling and heating load adversely affects the long-term operation. In particular, the cooling power experiences a reduction of 15.1% after ten years of operation. The results indicate that higher soil temperatures positively impact the heat exchange rate in heating mode, while rainfall facilitates heat transfer in both seasons. Furthermore, a case study of an energy pile system was carried out, encompassing load calculation, pile group simulation, economic analysis, and design optimization. A comprehensive evaluation of the technical and economic feasibility demonstrates that the system exhibits excellent performance, particularly when the ratio of cooling and heating loads ranges from 1.1 to 1.3.

Equilibrium vapor pressure of aqueous sodium acetate and potassium acetate solutions used as working fluids in frost-free air–source heat pumps at 263–328 K

Aqueous solutions of sodium acetate (CH3COONa) and potassium acetate (CH3COOK) are considered effective alternative heat exchange media for frost-free air–source heat pumps (FFASHPs) owing to the low corrosiveness, low viscosity, and low cost. Equilibrium vapor pressure is the most crucial property that characterizes freezing point and latent heat transfer. However, studies on this property, especially in subzero temperature ranges are scarce. This study was conducted to experimentally investigate the equilibrium vapor pressure of CH3COONa and CH3COOK solutions. The developed apparatus and procedures were based on the static method, and validated by evaluating the vapor pressure of distilled water, n-heptane, and calcium chloride (CaCl2) aqueous solution. Their average absolute deviations were within 1.94%. As the temperature increased from 263 to 328 K and solute concentration increased from 9.27 to 33.81 wt%, 124 data points of the vapor pressure of the CH3COONa and CH3COOK solutions were obtained, ranging from 0.2759 to 13.2608 kPa. Modified Antoine equation and ion interaction (Pitzer) model were established for correlation of the experimental data. The average absolute deviations of the CH3COONa and CH3COOK solutions produced by Antoine equation were 2.08 and 2.48%, respectively. Those produced by Pitzer model further decreased to 1.36 and 1.45% due to the import of osmotic coefficient and the accuracy improvement. Furthermore, according to the experimental and calculation results, the vapor pressure of the CH3COONa solution was lower than that of the CH3COOK solution. Therefore, under the same antifreezing conditions, the CH3COONa solution facilitates latent heat absorption from ambient air, while the CH3COOK solution is conducive to achieve regeneration. The results of this study provide foundational data for the vapor pressure of the two solutions and can promote their application in FFASHPs.

Improvement of Latent Heat Thermal Energy Storage Rate for Domestic Solar Water Heater Systems Using Anisotropic Layers of Metal Foam

Latent Heat Transfer Thermal Energy Storage (LHTES) units are crucial in managing the variability of solar energy in solar thermal storage systems. This study explores the effectiveness of strategically placing layers of anisotropic and uniform metal foam (MF) within an LHTES to optimize the melting times of phase-change materials (PCMs) in three different setups. Using the enthalpy–porosity approach and finite element method simulations for fluid dynamics in MF, this research evaluates the impact of the metal foam’s anisotropy parameter (Kn) and orientation angle (ω) on thermal performance. The results indicate that the configuration placing the anisotropic MF layer to channel heat towards the lower right corner shortens the phase transition time by 2.72% compared to other setups. Conversely, the middle setup experiences extended melting periods, particularly when ω is at 90°—an increase in Kn from 0.1 to 0.2 cuts the melting time by 4.14%, although it remains the least efficient option. The findings highlight the critical influence of MF anisotropy and the pivotal role of ω = 45°. Angles greater than this significantly increase the liquefaction time, especially at higher Kn values, due to altered thermal conductivity directions. Furthermore, the tactical placement of the anisotropic MF layer significantly boosts thermal efficiency, as evidenced by a 13.12% reduction in the PCM liquefaction time, most notably in configurations with a lower angle orientation.

Uptake and Transfer of Heat Within the Firn Layer of Greenland Ice Sheet's Percolation Zone

AbstractThe thermal field within the firn layer on the Greenland Ice Sheet (GrIS) governs meltwater retention processes, firn densification with surface elevation change, and heat transfer from the surface boundary to deep ice. However, there are few observational data to constrain these processes with only sparse in situ temperature time series that does not extend through the full firn depth. Here, we quantify the thermal structure of Western Greenland’s firn column using instrumentation installed in an elevation transect of boreholes extending to 30 and 96 m depth. During the high‐melt summer of 2019, heat gain in the firn layer showed strong elevation dependency, with greater uptake and deeper penetration of heat at lower elevations. The bulk thermal conductivity increased by 15% per 100 m elevation loss due to higher density related to ice layers. Nevertheless, the conductive heat gain remained relatively constant along the transect due to stronger temperature gradients in the near surface firn at higher elevations. The primary driver of heat gain during this high melt summer was latent heat transfer, which increased up to ten‐fold over the transect, growing by 34 MJ m−2 per 100 m elevation loss. The deep‐firn temperature gradient beneath the seasonally active layer doubled over a 270‐m elevation drop across the study transect, increasing heat flux from the firn layer into deep ice at lower elevations. Our in situ firn temperature time series offers observational constraints for modeling studies and insights into the future evolution of the percolation zone in a warmer climate.

Applying isovolumic steam capsule as new thermal energy storage unit

In order to make up the inefficiencies of liquid–solid phase change material (PCM) such as low latent heat and low heat transfer rate, the possibility of adopting water steam as the phase change material is explored. Although great volume change occurs during the gas–liquid phase-changing, the specific latent heat is at least one order of magnitude larger than that of liquid–solid phase-changing. To minimize the adverse effect of the great volume change during vaporization or condensation, the steam can be accommodated inside sealed vessel with sturdy shell. In this study, an isovolumic steam capsule (ISC) was made by filling a cylinder with a small amount of liquid water and then heated and boiled to extinguish the non-condensable gas (NCG) before sealing it. Thermodynamic analysis shows the thermal energy contained in the isovolumic steam capsule per unit volume increases in approximately an exponential manner with the increase of temperature due to the evaporation of liquid, and can reach several times that of liquid–solid phase change material, demonstrating great potential as energy storage material. The heat transfer experiments show that the energy charging and discharging rates increase with the temperature difference. There exists thermodynamic non-equilibrium during heat transfer and the deviation from saturation enlarges with increasing temperature difference and non-condensable gas concentration. For both charging (vaporization) and discharging (condensation), a higher non-condensable gas concentration in the steam exhibits larger heat transfer rate in the beginning, but smaller heat transfer rate in the later stage. The mechanism of vaporization and condensation in the isovolumic steam capsule awaits to be further clarified.

Thermomechanics of phase transformation induced localization in NiTi tubes. Part I experiments

This two-Part study aims to illustrate and elucidate the effects of thermomechanical interactions in pseudoelastic NiTi structures that arise in the course of the reversible transformations between the austenitic and martensitic phases. Transformation leads to inhomogeneous deformation with the two phases coexisting and to latent heat-induced local heating/cooling. Part I first presents the results of displacement-controlled isothermal tension and compression experiments on NiTi tubes covering the pseudoelastic temperature regime. The experiments are conducted in a constant temperature circulating bath which suppresses thermomechanical interactions so the transformation front velocity is governed strictly by the applied displacement rate. The load/unload hystereses traced, quantify the transformation stresses and strains and will be used to calibrate the constitutive model of Part II. A set of isobaric experiments in which NiTi tubes are taken through a cool/heat cycle under constant stresses of different levels follow. The experiments are conducted in a custom small-scale environmental chamber with a circulating air stream run by a feedback temperature controller, coupled to load-controlled mechanical loading. The evolution of helical bands of the alternate phase is captured using digital image correlation. The results demonstrate that under such loading histories a strong interaction develops between the evolving inhomogeneous deformation, the latent heat and the surrounding environment. The speed of propagation of the helical fronts slows down or accelerates so as to match the rate at which heat is removed/added to the specimen by the airflow. Thus, here the evolution of localized deformation is strongly coupled to the interaction between the latent heats and heat transfer from the environment. The effect of the stress level on these events is examined through eight isobaric experiments, which provide a rich data set for evaluating constitutive models and structural analyses of these experiments such as those in Part II.

Inducing hydrophobicity in stainless steel 304 by mechanical texturing and chemical functionalization

This study investigates the impact of combined texturing by micromachining and chemical functionalization on the wetting behavior and water condensation on stainless steel 304. The transition from Wenzel to Cassie-Baxter or impregnated Cassie-Baxter regimes is investigated. Understanding this transition is critical for advancing surface engineering, as it enables precise control over wetting behavior for various applications. Herein, we report on the wire EDM (wEDM) machining on stainless steel 304 to produce two distinct microstructure patterns with directional canals or pyramidal structure, and their performance in water condensation. These patterns significantly impact water condensation performance. wEDM is employed to create surface roughness, followed by phosphoric acid treatment and chemical functionalization with trichloro-1H,1H,2H,2H-perfluorooctyl silane. Contact angle measurements reveal a synergistic effect between groove direction and silane coating, leading to hydrophobic surfaces and dropwise water condensation. Specimens with directional canals exhibit a contact angle of 150°, while specimens with pyramidal structures exhibit 151o. Roll-off angle experiments showcased distinct behavior among specimens featuring canals or pyramidal structures. Specimens with canals exhibit notably lower roll-off angles compared to both flat surfaces and those with pyramidal patterns, leading to a dependence of roll-off angles on the orientation of canals. In humid environments, micromachined specimens exhibit superior water condensation capability compared to untreated SS304 surfaces. Chemically functionalized grooved specimens present larger condensate droplet diameters than flat surfaces. An enhancement in water condensation and a sevenfold higher latent heat transfer coefficient is reported. Specimens with chemical functionalization achieve corrosion protection with an efficiency reaching 82.9%.

Techniques for Enhancing Thermal Conductivity and Heat Transfer in Phase Change Materials in Hybrid Phase Change Material–Water Storage Tanks

In recent years, extensive research has been dedicated to enhancing energy efficiency and promoting environmental sustainability in heating and cooling systems. Among the promising solutions, phase change materials (PCM) technology stands out as a key area of exploration. This study focuses on improving the thermal performance of PCM–water hybrid tanks by investigating methods to enhance thermal conductivity and heat transfer. Through experimental testing using techniques such as copper matrices, steel twisted matrices, and copper spirals, this study demonstrates significant improvements in thermal conductivity, particularly with the use of copper matrices. The integration of a copper matrix placed in the PCM reservoir increased the heat transfer coefficient and thermal conductivity of the PCM, and thus, the total phase transformation time for solidification was reduced by 79.19% and for melting by 54.7%. Our experimental results demonstrate that the integration of a copper matrix can increase latent heat transfer from 55,677.6 J up to 125,274.6 J, marking a 125% enhancement over the experiment with pure PCM. Additionally, comparisons of the energy storage potentials for different PCMs underscore the benefits of integrating PCMs into hybrid storage tanks. These findings highlight the immense potential of PCM technology to increase energy storage efficiency in heating and cooling applications.

A Numerical Investigation of the Influence of Humid Environments on the Thermal Performance of a Phase Change Thermal Storage Cooling System in Buildings

Phase change thermal energy storage (PCTES) technology has garnered significant attention in addressing thermal management challenges in building HVAC systems. However, the cooling performance of PCTES systems in humid scenarios remains unexplored, which is crucial in subtropical regions, high-humidity underground areas, and densely populated spaces. Taking the mine refuge chamber (MRC) as an example, this study focuses on a passive temperature and humidity control system by employing cold storage phase change plates (PCPs) for 96 h. First, an improved and simplified full-scale numerical model including PCPs and MRC parts is established. Then, the model is validated through the experimental results and solved using a numerical method. Finally, the influence of various factors within the system is investigated and an optimization method involving batch operation is proposed. The results indicate that (1) within 40 h, the use of cold storage PCPs leads to an indoor temperature reduction of 4.8 °C and a 7% decrease in relative humidity; (2) the PCPs show asynchronous states in sensible and latent heat transfer rates; (3) for every 50 additional PCPs, the average indoor temperature increases by 0.6 °C and the relative humidity decreases by 1.5%; (4) implementing batch operation of PCPs ensures that the indoor Heat Index drops by 10 °C, which is vital for human survival. The findings will play a crucial role in the global expansion and application (including geographical and functional aspects) of phase change thermal storage technology.

Cooling performance and optimization of a thermal management system based on CO2 heat pump for electric vehicles

Efficient integrated thermal management scheme is crucial for improving the driving range, thermal comfort, and safety of electric vehicles. Compared with the synthetic refrigerant heat pump indirect cooling/heating on the vehicle electrical system, the natural refrigerant CO2 heat pump direct thermal controlling integrated into the thermal management system has advantages in the thermal cycle performance and environmental friendliness. The present study proposed a thermal management system based on CO2 heat hump with multiple working modes for enhancing vehicle energy utilization coefficient. The system thermal performance under the World Light Vehicle Test Cycle was investigated via energy and exergy analyses. The operational control strategies of the thermal management system were optimized for the thermal controls of the cabin, battery and motor. The results show that the minimum exergy destruction of the thermal system occurs at the optimal discharge pressure corresponding to the highest coefficient of performance. Ensuring two-phase latent heat transfer for battery cooling is the most effective measure to maintain battery temperature uniformity via dynamic collaborative regulation of expansion valves’ openings and compressor speed. Compared with constant expansion valve’s opening, the coefficient of performance of the system can be improved by a maximum of 10% with the saturated CO2 vapor at the outlet of battery cooling plate. Due to the low thermal capacitance and minimal thermal inertia of driving motor, its cooling performance is significantly influenced by the heat generation rate and refrigerant flow. Optimal motor cooling efficiency is achieved when controlling the refrigerant quality to 0.85 at the cooling passage outlet. Under the World Light Vehicle Test Cycle, the thermal management system effectively regulated the temperatures across different operating modes while operating at optimal discharge pressures.

Feedforward decoupling control of indoor temperature and humidity using a single direct expansion air conditioning unit

Achieving simultaneous control over temperature and humidity through a single direct expansion air conditioner would be advantageous, especially considering its widespread use in residential buildings. Traditional control strategies fail to achieve satisfactory control performance due to the nature of complexity and cross-decoupling of the system. Therefore, this research paper presents the advancement of a feedforward decoupling control scheme designed for a direct expansion air conditioning unit to effectively control both temperature and humidity. To facilitate the controller design, a dynamic model considering both sensible and latent heat transfers was developed and verified. The thermal responses of the coupled system were analyzed and their correlation coefficients also examined. Through identifying the transfer function model of the coupled system, a feedforward decoupling controller with two compensators was designed. The proposed decoupling control scheme was tested using the developed model as the plant to be controlled. Test results showed that, in comparison to the transitional PID based dual single-input and single-output controller, the proposed decoupling control scheme was capable of eliminating the interactions between indoor air temperature and humidity under variable speed operation, and realizing the simultaneous control over indoor air temperature and humidity with a desirable control performance.

Experimental study and performance evaluation of an air source heat pump (ASHP) system with a frost-free evaporator

The air source heat pump (ASHP) is operated in a low temperature and high humidity working environment. There is always a lot of frost forming on the outdoor heat exchanger, which hinders the heat transfer rate of the heat exchange surface, leading to the decrease of performance of the ASHP system. This paper presents a new type of frost-free evaporator for ASHP system. The heat transfer zone of the evaporator is composed of three parts: non-packing zone, plain finned-tube falling film zone and horizontal smooth tube bundle falling film zone. The experimental system of the frost-free evaporator is established, and the reliability of the experimental data is verified. The effects of refrigerant flow rate, inlet air temperature, fan frequency and solution spray mode on energy efficiency ratio, heat transfer expansion coefficient, air side pressure drop and exergy loss of the evaporator are studied. The performance of the evaporator is evaluated. The results show that with the increase of inlet air flow and temperature, the energy efficiency ratio of frost-free evaporator increases by about 8%–12%, and the air side pressure drop also increases. As the inlet air temperature increases from −10 to 15 °C, the heat transfer expansion coefficient of evaporator decreases by about 3%–6%, indicating that the increase of inlet air temperature will lead to an increase of sensible heat transfer ratio and a decrease of latent heat transfer ratio. The results also show that compared with no spray mode and continuous spray mode, the intermittent spray mode is more recommended as a feasible operation scheme to realize the continuous, efficient and stable operation of the new evaporator.

A thermal calculation model for tubular condensing heat exchanger

The condensing heat exchanger is commonly applied in various heat exchange systems. It can efficiently recover moisture and heat from the flue gas that contains water vapor. However, the convective-condensation heat transfer process is so complicated that no mature thermal calculation model is available. This study develops a thermal calculation model for the widely employed tubular condensing heat exchanger in industry. To characterize the degree of the heat and mass transfer, this study introduces two parameters, namely the sensible and latent heat transfer efficiencies of fin. The thermal calculations are conducted for the condensing heat exchangers reported in the literature to verify the proposed model by comparing it with the experimental data. The results show that the absolute error of the calculated sensible and latent heat transfer efficiencies is 0.0365 and 0.0268, respectively. A maximum difference of 5.2 K has been acquired between the measured and calculated values of the outlet temperature. The relative error of the condensate water flowrate is mostly within ± 5.0 % and ± 10.0 % under the bare-tube and finned-tube conditions, respectively, with a maximum deviation of 0.7 and 1.4 kg h−1. This study provides a general model for designing and optimizing various tubular condensing heat exchangers accurately.

Enhancing heat transfer at low temperatures by laser functionalization of the inner surface of metal pipes

The latent heat transfer during vapour condensation in the condenser section of passive heat transport devices such as the two-phase closed thermosiphon is limited by film condensation. Dropwise condensation provides an increase of the heat transfer coefficient by up to one order of magnitude and can be achieved with a water-repellant surface. The inner surface of pipes made from stainless steel was functionalized by laser surface texturing with ultrashort laser pulses and subsequent storage in a liquid containing long-chained hydrocarbons. The pipes were separated into half-pipes by wire eroding to enable laser texturing of the inner surface, and were then joined by electron beam welding after laser texturing. As a result, superhydrophobic and water-repellent surfaces with a contact angle of 153° were obtained on the inner surface of the pipes with a length of up to 1 m. The functionalized pipes were used in the condenser section of a two-phase closed thermosiphon to demonstrate a heat transfer rate of 0.92 kW at 45 °C, which is approximately three times the heat transfer rate of 0.31 kW of a smooth reference pipe.

Particulate Matter in the American Southwest: Detection and Analysis of Dust Storms Using Surface Measurements and Ground-Based LIDAR

This research study focuses on the coupling between particulate matter and the planetary boundary layer. Particulate matter affects human health and it is a complex mixture of suspended substances. Various sources of particulate matter include volcanic eruptions, soil lofted by strong winds, wildfires, and particles formed from chemical reactions of gas-phase emissions. Strong winds are one source of dust pollution when they loft soil particles. Particulate matter and the planetary boundary layer are closely linked. The planetary boundary layer plays a critical role in meteorology and particulate matter concentrations due to its involvement in energy, latent heat, and mass transfer with the free troposphere. Currently, there has been no research on the impact of dust events on the planetary boundary layer in our region, El Paso, Texas, which is located on one of the biggest sources of dust in the Western Hemisphere, the Chihuahuan Desert. In this study, we used PM10 concentrations to detect dust events during the 2016–2022 period in the El Paso region. During the study period, we observed 74 dust events. The dust events were categorized as synoptic or convective cases. Synoptic cases are associated with cold fronts, while convective cases are associated with local convective systems such as thunderstorms. We observed that synoptic cases occurred most frequently during springtime, while convective cases were more frequent during summer monsoon months. Synoptic cases tend to occur earlier in the afternoon with lower temperatures, while convective cases tend to occur in the late evening with higher temperatures. We also found that the planetary boundary layer height collapsed after the maximum hourly PM10 concentration and then the boundary layer returned to its original height.