High Flow Rates Research Articles

Evaluating the Thermal Performance of Shell-and-Tube Heat Exchangers: The Role of Flow Rate in Water-Based Systems

This research investigates the performance of water as a working fluid in the shell side of shell-and-tube heat exchangers (STHEs), explicitly analyzing how variations in flow rate influence the heat transfer coefficient, pressure drop, and friction factor characteristics. Experiments were conducted using an STHE with a SUS 201 stainless steel shell and a pure copper tube featuring an inner diameter of 10 mm and an outer diameter of 13 mm. The flow rates of the cold fluid varied at 9, 10, and 12 liters per minute (LPM), while the hot fluid flow was maintained at a constant rate of 6.67 LPM. A 600 W heater, regulated by a PID system, was utilized to evaluate thermal performance, with water serving as the hot fluid on the shell side and the cold fluid on the tube side. Results demonstrate a significant increase in both the heat transfer coefficient and the heat transfer rate with higher flow rates of the cold fluid, with the maximum heat transfer coefficient recorded at 12 LPM and the minimum at 9 LPM. The STHE exhibited high efficiency, with heat transfer rate differences between the shell and tube sides remaining below 5%. Although pressure fluctuations were observed with increasing flow rates, they did not substantially affect the friction factor, indicating a predominantly turbulent flow regime. These findings provide critical insights for optimizing heat transfer performance in STHEs, contributing to advancements in thermal management technologies and enhancing the design of efficient heat exchangers.

Comparative experimental and numerical study of mixing efficiency in 3D-printed microfluidic droplet generators: T junction, cross junction, and asymmetric junctions with varying angles

In droplet-based microfluidics, rapid mixing during droplet formation enhances reaction uniformity, eliminating the need for micromixers. In this research, we conducted a comprehensive study by first employing a series of two-dimensional (2D) numerical simulations, followed by experimental investigations using 3D-printed microfluidic chips. We compared the mixing efficiency, droplet diameter, and droplet eccentricity of three different types of droplet generators: T junction, cross junction, and asymmetric droplet generators with various angles. Regarding mixing efficiency, we observed that the asymmetric droplet generators outperformed the cross junction by 30 % but fell slightly short of the mixing efficiency achieved by the T junction (1 %). Additionally, while the mixing index in the asymmetric generators closely matched that of the T junction, these asymmetric generators produced smaller droplets by 72 %. Increasing the angle in asymmetric droplet generators resulted in enhanced mixing efficiencies and an increase in droplet diameters. The asymmetric junction with a 30° angle could achieve a mixing efficiency of up to 80 %. Additionally, an analysis of the dispersed phase flow rate revealed that higher flow rates lead to larger droplet sizes and reduced mixing efficiencies. The asymmetric droplet generators improve mixing efficiency facilitating rapid reagent mixing, all while maintaining a small droplet diameter.

Development of a superheated water chromatography method for the sustainable determination of preservatives in foods and cosmetics

The present research focused on the use of high temperatures to achieve fast separations in Liquid Chromatography (LC) and minimize the consumption of organic solvents. Particularly, superheated water was employed, by exploiting the decrease in dielectric constant of water when increasing the temperature. To realize this kind of application, the availability of LC columns resistant at high temperature is mandatory. Recently, porous graphitic carbon (PGC) columns have been proposed as stationary phases resistant up to 250 °C. Hardware modifications were also necessary to guarantee the efficient heating of the mobile phase prior of entering the column, as well as its rapid cooling before detection by photodiode array (PDA). Specifically, an LC system was interfaced to a GC oven, which hosted the LC column; to achieve a fast and efficient heating of the eluent coming from the autosampler prior to enter into the column, a pre-heating tube was interposed between the autosampler outlet and the column inlet. Instead, a cooling loop was connected between the column outlet and the PDA cell. A mixture of 1-nitroalkanes was used to evaluate the performance of the system in terms of dead volumes, band broadening and peak shape, as well as chromatographic efficiency and resolution. The use of higher temperatures allowed to perform analyses at higher flow rates in reduced analysis time and was also in terms of peak bandwidth resulting to increased efficiency for the most retained compound. Moreover, van't Hoff plots were obtained at different temperature, confirming that the most retained analyte greatly benefited of the temperature increase.The system was applied to the analysis of parabens in cosmetic and food products. The method combined eco-sustainable sample preparation with high-temperature LC separation on a PGC column and was fully validated in terms of linearity, precision, accuracy and detection and quantification limits. The developed method was critically evaluated by comparing the output of different metric tools implemented in the last decade for the quantitative assessment of the greenness.

Thermo-hydraulic performance of a parabolic trough solar collector filled with three different waste materials

This study presents the experimental investigation of the performance enhancement of a parabolic trough solar collcector (PTC) utilising air as the working fluid and various metallic waste materials as absorber fillers. The experiments have been carried out according to the ISO 9806:2017 norm under clear sky conditions for several days. The application of wire mesh, metal chips and bearing balls as the absorber filling has led to the increase in the performance of PTC and higher outlet temperatures compared to the smooth pipe as a receiver: 282 % (117.6 °C), 250 % (103.1 °C) and 335 % (128.3 °C) respectively. A decrease in PTC performance due to pressure drop was observed. The maximum drop for wire mesh, metal chips and bearing balls filling was: 9.7 %, 5.7 % and 5.7 % respectively. It has been shown that the use of metallic waste materials can significantly improve the thermal performance of PTC, but the rapidly increasing hydraulic resistance may limit their application for high flow rates.

Experimental comparison of aerosol transmission in displacement ventilation and mixing ventilation in a meeting scenario

The performance of displacement ventilation (DV) and mixing ventilation (MV) in aerosol contamination control was compared. The considered contamination was an aerosol emitted from a person in meeting scenarios of two and four persons. The experiments were carried out in a full-scale room measuring 4.4 m × 5.2 m × 2.9 m. Particle counting was carried out at 41 measurement points in the room to assess the concentration field of particles in the room and in the inhalation zone. The influence of the supply airflow rate and the number of activated thermal mannequins on the contaminant removal effectiveness were examined. The main conclusion is that the DV system was superior to the MV system in reducing contamination. An enhanced contaminant removal effectiveness of displacement ventilation was observed for all supply air flow rates and increased with higher airflow rates. At lower airflow rates, contamination in the inhalation zone was reduced by 40% compared to mixing ventilation, while at higher flow rates, the reduction surpassed 50%. This study highlights the advantages of displacement ventilation in terms of contamination control, infection prevention and energy efficiency, emphasising the importance of ventilation system selection for indoor environments, particularly those where airborne transmission risks are prevalent.

Axial Flow Fan Performance in a Forced Draught Air-Cooled Heat Exchanger for a Supercritical Carbon Dioxide Brayton Cycle

Abstract An axial flow cooling fan has been designed for use in a concentrated solar power plant. The plant is based on a supercritical carbon dioxide (sCO2) Brayton cycle, and uses a forced draft air-cooled heat exchanger (ACHE) for cooling. The fan performance has been investigated using both computational fluid dynamics (CFD) and scaled fan tests. This paper presents a CFD model that integrates the fan with the heat exchanger. The objective is to establish a foundation for similar models and to contribute to the development of efficient ACHE units designed for sCO2 power cycles. The finned-tube bundle is simplified, with a Porous Media Model representing the pressure drop through the bundle. Pressure inlet and -outlet boundary conditions are used, meaning the air flowrate is solved based on the fan and tube bundle interaction. The flowrate predicted by the CFD model is 0.5% higher than the analytical prediction, and 3.6% lower than the design value, demonstrating that the assumptions used in the design procedure are reasonable. The plenum height is also found to affect the flowrate, with shorter plenums resulting in higher flow rates and fan efficiencies, and longer plenums resulting in more uniform cooling air flow.

A retrospective characterization of pediatric facemasks marketed in the United States and implications for future designs

Background Device manufacturers who seek to market their pediatric facemasks in the United States (U.S.), as part of anthropometric data requirement, need to demonstrate their mask designs are expected to fit the intended user population. However, currently there are no well accepted test methodologies for pediatric facemasks. In addition, unlike N95 respirators, the expected maximum flow rate, and the pressure drop at that expected maximum flow rate for pediatric facemasks have not been established. Method The objective of this article is three-fold; use a literature survey to determine the worst-case flow rate, and an acceptable breathing resistance; and come up with a bench-test based protocol for assessing fit of pediatric facemasks. Results & discussion The worst-case breathing flow rate for mask testing in the pediatric population is 45–60 Liters/minute (LPM), and the acceptable pressure drop at the worst-case flow rate is 2.0 mmH2O. A retrospective assessment of all the four brands of legally marketed facemasks in the U.S. that could be purchased, revealed that majority of the brands have high filtration efficiency (>95%) at low flow rate 5 LPM which reduces to ~ 80% at 45 LPM. At 5 LPM, the pressure drop ranges from 0.3–0.6 mmH2O, remaining below the 2.0 mmH2O. However, at higher flow rates, (representing strenuous activities, or older children (> 12 years)), most masks exhibited a pressure drop within the range of 2.9 to 6.0 mmH2O. Furthermore, opening the pleats of the facemasks completely results in a notable reduction in pressure drop (a 6.6-fold decrease, p = 0.03). To assess fit of these same brands of facemasks, we then updated our previous validated adult manikin fit-test method and used it in manikins in the age group of 2 to 14 years. Either poor nose-clip adherence to the manikin, low filtration efficiency of the pediatric facemasks, or off-label use (i.e. when donned on manikins representing 2 years to 14 years) contributed to low fit. Conclusions A new bench-top tool to evaluate quantitative fit of pediatric facemasks was developed. In addition, based on the research reported here, we provide practical implications for the members of the community: users, academia and medical device manufacturers.

Successful Microsurgical Clipping under Extracorporeal Membrane Oxygenation Treatment for a Poor-Grade Subarachnoid Hemorrhage Patient with Severe Pulmonary Neurogenic Lung

AbstractHemorrhagic strokes are considered as contraindications of extracorporeal membrane oxygenation (ECMO) therapy because of anticoagulant administration and ECMO-associated coagulopathy. We present a rare case of successful microsurgical clipping under ECMO for a poor-grade subarachnoid hemorrhage (SAH) patient with severe neurogenic pulmonary edema (NPE). A 50-year-old man presenting with the sudden loss of consciousness was diagnosed with poor-grade SAH with severe NPE, and was intubated. Because of severe hypoxemia refractory to conventional treatment, venovenous ECMO was used 6 hours after admission. To avoid thrombosis inside the ECMO circuit despite no anticoagulants, a heparin-bonded ECMO was maintained at a comparatively high blood flow rate. Subsequently, the patient underwent a microsurgical clipping under ECMO. Intraoperatively we had difficulty in bleeding control, and therefore the multiple transfusions were necessary to correct anemia and ECMO-associated coagulopathy. The aneurysmal clipping was accomplished without hemorrhagic intracranial complications. After 2 years from onset, his activities of daily life were independent. To our knowledge, this is the first report of successful microsurgical clipping for poor-grade SAH under ECMO without any anticoagulants. The use of a heparin-bonded ECMO tubing, maintenance of a slightly higher ECMO pump speed, and multiple transfusions to correct ECMO-associated coagulopathy could make the micro-neurosurgical procedures under ECMO possible. This report demonstrated the possibility to extend the range of application of microsurgical clipping for poor-grade SAH patients requiring ECMO treatment.

Study on the Water Use at the Tailwater of Nam Theun 2 Hydropower Station through the Canal of the 3rd Water Gate (Case study: Nongping and Boungbao villages) Nhommalath District, Khammounce Province

Water management is managed through the Nam Theun 2 hydroelectric project. The project has released water in two parts: 1) Water gates and channels release water into natural streams about 30 km long and can drain 1,200 m3/s; and 2) Releasing through the newly constructed regulating dam to the Xe Bang Fai River directly, with a length of about 27 km, can drain 330 m3/s. According to the length of the channel, there is a built water gate for 5 irrigations. Currently, only 3 water gates have been opened to supply water for production in 9 villages that depend on Nhommalath district, Khammouane province. In order to make the use of water through the channel to the maximum benefit, it can operate together between electricity generation and the actual use of water by the community. In this chapter, we have studied the amount of water flow according to the season through Regulating Dam during the past 11 years. Since 2012 to 2022, we have studied the participation of farmers in the management and use of water within the scope of agricultural land. Through comparing the amount of water flow during the past 11 years, from 2012 to 2022, The amount of water flow through the channel with the lowest flow in December 2022 is equal to 0.0 cubic meters per second caused by the stoppage of the company's electricity production to do various repairs, and the highest flow rate in November 2016 was 318.18 cubic meters per second. The reason is that the project has full production capacity to respond to the electricity buyers. Among them, the annual average flow volume with the lowest value in 2022 is equal to 153.06 cubic meters per second, and the annual average flow volume with the highest value in 2017 is equal to 239.11 cubic meters per second. At the time the company stopped production, it used a backup pump with a suction power equal to 0.083 m3/s, which was installed at 2 points to pump water into the irrigation channel for the people. The company is responsible for all costs, such as fuel for the pump, maintenance of the pump, and the water system from the pump to the channel. Assessment of farmers' participation in water management with topics such as survey participation and data collection, participation in the implementation of four seasonal plans, participation in monitoring and evaluation, and participation in the review of all outputs is at a very satisfactory level ( = 3-3.8), except for the topic of participation in determining water use regulations within the channel, and the flood problems are evaluated at a moderate level ( = 2.4). Because of management, the municipality has appointed a committee and has specific management rules. There has never been a natural disaster in the area in the past, such as a drought or flood.

Research on factors affecting bubble and particle behavior in a three-phase flotation system based on COMSOL

ABSTRACT To investigate the impact of various parameters on bubble and particle dynamics in a flotation system, COMSOL software was utilized. The “two-phase flow – Level Set” module coupled with the “fluid particle interaction” module was used to explore the behavior of single bubbles and particle groups. The bubbles were set as a discrete phase to represent a group of floating bubbles. By combining the “Single-phase flow” module with dual “fluid-particle interaction” modules, we examined the interactions between bubble populations and particles within the system. The research results show that as the bubble diameter increases, the carrying effect of the bubbles on the particles becomes stronger. When the bubble radii are 1, 1.25, 1.5, 1.75, and 2 mm respectively, the maximum movement speed of the particles in the area increases by 3.0%, 2.3%, 5.1%, and 2.7%. The average speed of the particles increases by 7.9%, 7.3%, 9.0%, and 10.0%. Increasing the mass flow rate can increase the collision probability between particles and bubbles, thus increasing the flotation rate. However, a too high mass flow rate will make the state of bubbles unstable. When the mass flow rate is less than 1.5 kg/s, the bubbles remain stable. When the mass flow rate exceeds 1.5 kg/s, the severity of bubble splitting increases. In the study area, the irregularity of the bubble clusters results in a more chaotic flow field, leading to greater speed and displacement of the particles. Increasing the number of bubbles entering at one time and their initial speed enhances the impact of the bubble clusters on the solid particles. When the number of bubbles entering at one time is 5, 10, 15, and 20 respectively, the maximum movement speed of the particles increases by 6.9%, 8.1%, and 9.0%. When the initial speed of the bubble entering is 0, 0.1, 0.2, and 0.3 m/s respectively, the maximum movement speed of the particles increases by 6.4%, 3.0%, and 8.8%.

Logistic regression model for predicting risk factors and contribution of cerebral microbleeds using renal function indicators.

The brain and kidneys share similar low-resistance microvascular structures, receiving blood at consistently high flow rates and thus, are vulnerable to blood pressure fluctuations. This study investigates the causative factors of cerebral microbleeds (CMBs), aiming to quantify the contribution of each risk factor by constructing a multivariate model via stepwise regression. A total of 164 hospitalized patients were enrolled from January 2022 to March 2023 in this study, employing magnetic susceptibility-weighted imaging (SWI) to assess the presence of CMBs. The presence of CMBs in patients was determined by SWI, and history, renal function related to CMBs were analyzed. Out of 164 participants in the safety analysis, 36 (21.96%) exhibited CMBs and 128 (78.04%) did not exhibit CMBs, and the median age of the patients was 66 years (range: 49-86 years). Multivariate logistic regression identified hypertension (OR = 13.95%, 95% CI: 4.52, 50.07%), blood urea nitrogen (BUN) (OR = 1.57, 95% CI: 1.06-2.40), cystatin C (CyC) (OR = 4.90, 95% CI: 1.20-22.16), and urinary β-2 microglobulin, (OR = 2.11, 95% CI: 1.45-3.49) as significant risk factors for CMBs. The marginal R-square ( ) was 0.25. Among all determinants, hypertension (47.81%) had the highest weight, followed by UN (11.42%). Quasi-curves plotted using the bootstrap method (999 times) showed good agreement between the predictive model and actual observations. Hypertension, BUN, urinary β-2 microglobulin, CyC were risk factors for CMBs morbidity, and controlling the above indicators within a reasonable range will help to reduce the incidence of CMBs.

Experimental Investigation on collection efficiency of Deep-Sea hydraulic collection parameters

Hydraulic suction collection has been extensively utilized in deep-sea mining due to its high flow rate and efficiency. This paper introduces a novel hydraulic collection model to investigate the impact of various collection parameters on collection efficiency. We analyze the effect of different ore collection parameters on collection efficiency using a radial basis function network and make predictions. The optimal parameter range was obtained by performing combined parameter experiments. The two-parameter combination give better results compared to a single parameter. A theoretical model of collection efficiency is established based on experimental observations and principles of water jet theory. The accuracy of the model is confirmed through experimental validation, and the research findings can provide valuable insights for the ore collection process in deep-sea mining.

Experimental assessment of a multilayered packed-sphere La–Fe–Si active magnetic regenerator

This study investigates the performance of a multilayered packed-bed active magnetic regenerator (AMR) using spheroidal particles with first-order magnetocaloric properties. The hydraulic performance is assessed via the interstitial friction factor, showing significant underestimation by the Ergun Equation at high mass flow rates. Coefficient adjustments are made to accurately represent the AMR pressure drop, considering particle nonuniformity and structural components, such as layer mesh dividers. This facilitates the pressure drop modeling and provides a means to check the AMR integrity on a routine basis, without requiring AMR disassembly. The thermal performance, evaluated in terms of the regenerator effectiveness, shows a satisfactory cooling potential for practical applications but emphasizes the need for flow control to prevent effectiveness imbalance between hot and cold flows, crucial for optimal operation. The cooling capacity and maximum temperature span are also evaluated, demonstrating that higher mass flow rates yield higher cooling capacities with lower temperature spans, while lower rates achieve higher spans. Varying the blow fraction shows that regenerators at 50% blow fraction achieve 10% higher cooling capacities than at 37.5%. Increasing operational frequency improves cooling by increasing the number of cycles and reducing losses, resulting in a 15% capacity increase between 0.25 and 0.50 Hz. However, this trend may reverse at higher frequencies beyond the experimental limits. While this study improves the understanding of the hydraulic and thermal performance of packed-bed AMRs, its findings underscore the importance of flow balance and frequency in achieving optimal performance, thus providing insights for future system improvements.

Automated, Transferable, and Ethanol-Free Radiosynthesis of [11C]Butanol.

Cerebral blood flow and blood-brain barrier permeability assessment are crucial hemodynamic parameters to measure under neurological conditions. In conjunction with positron emission tomography (PET), oxygen-15-labeled water has emerged as a gold standard for measuring cerebral perfusion; however, at higher flow rates, [15O]water extraction becomes nonlinear. In such a scenario, freely diffusible [11C]butanol can provide a truer estimate. Radiosyntheses of [11C]butanol reported to date are protracted, are not automated, or require ethanol in the final formulation. By using a flow-based, captive solvent approach on a commercially available radiosynthesizer, we automated and reduced the synthesis time to 28 min. Forgoing cartridge-based purification for an aqueous high-performance liquid chromatography method, we obtained high purity [11C]butanol in ethanol-free phosphate buffered saline in sufficient yields for clinical PET studies. We here report our expedited, automated, and ethanol-free radiosynthesis of [11C]butanol along with preliminary imaging of a porcine subject.

Geothermal resources of Hungary: a play-based review

In this paper we review the geothermal resources of Hungary using the geothermal play concept and its scale-dependent hierarchical categorization. The Pannonian Basin belongs to an extensional domain play type, with two main plays: the porous Neogene basin fill sediments and the fractured-karstified Palaeozoic and Mesozoic basement rocks. Both plays can be divided into hydrostatic and overpressured play segments. The most widely utilized play level in the hydrostatic segment of the porous Neogene sediment play comprises laterally extended highly permeable sandstone layers storing low salinity thermal water with average flow rate around 900 l/min and temperatures between 50 °C and 100 °C in the depth range of 1–2 km. The other prosperous play level is represented by the fractured-karstified Mesozoic carbonates in the hydrostatic segment of the basement play having elevated temperatures (90–120 °C) and several thousand l/min flow rates. The play level related to fractured Palaeozoic rocks is less important due to its limited extent. The overpressured segment of the basement play may have high flow rates, but still an untapped resource, where exploitation is limited by high overpressure, high temperature (170–200 °C), and highly saline hot waters.

Flow Performance Analysis of Non-Return Multi-Door Reflux Valve: Experimental Case Study

Non-return multi-door reflux valves are essential in fluid control systems to prevent reverse flow and maintain system integrity. This study experimentally analyzes the flow performance of multi-door check valves under different operating conditions, focusing on pressure testing and evaluating their effectiveness in preventing backflow. A wide-ranging experimental setup was designed and implemented to simulate real-world scenarios, facilitating accurate measurement of flow rates, pressure differences, and valve response times. The collected experimental data were analyzed to evaluate the valve’s performance in terms of flow capacity, pressure drop, and hydraulic efficiency. Additionally, the effects of factors such as valve size, valve configuration, and fluid properties (water) on performance were considered. It was found that the non-return multi-door reflux valve has been proven effective and reliable in preserving system integrity and maintaining unidirectional flow at the same time during pressure testing. It exhibits no backflow, remains stable and constant across varied flow conditions, and demonstrates a low pressure drop and high flow capacity, making it suitable for critical pressure testing applications. The response curve revealed that valve opening takes longer to reach higher flow rates than closing, indicating pressure instability during transition periods. This non-linear relationship indicates possible irregularities in pressure drop response to flow rate changes, highlighting potential areas for further investigation.

Experimental study of a novel guided sequential immersion cooling system for battery thermal management

Immersion cooling exhibits superior cooling performance compared to traditional battery thermal management systems (BTMS). However, a significant challenge of immersion cooling is the spatial variation of temperature within both the coolant and lithium-ion batteries (LIBs). This research proposes a guided sequential immersion cooling (GSIC) BTMS to address this issue. Experimental studies were conducted to evaluate the heat dissipation performance of the GSIC structure under various conditions, including extreme loads. The results indicate that under the static flow immersion cooling (SFIC) scheme, cooling the tabs significantly influences the overall performance. Immersing the tabs can reduce the maximum battery temperature by 10.403 °C, although the spatial variation of temperature persists. Under forced flow immersion cooling (FFIC) conditions, increasing the coolant flow rate dissipates the heat generated by LIBs more effectively. Even at an extreme discharge rate of 5C, the maximum temperature remains below 45 °C. The average temperature reduction at the tabs is greater than the battery body, and with increased flow rates, the temperature difference between the two can be maintained within 1 °C under all conditions. As the flow rate keeps increasing, the average temperature at the tabs gets even lower than the battery body at low loads. This demonstrates that the GSIC BTMS can suppress the temperature rise at the tabs, which is a critical heat risk. Moreover, the temperature uniformity of the LIBs module is improved. As the flow rate increases, the temperature difference within the LIBs module decreases when the discharge rates is between 1C and 5C. Theoretical analysis confirms that increasing flow rates for low loads can suppress temperature rise, albeit with increased power consumption and reduced cooling efficiency. High flow rates are more suitable for high load conditions of the LIBs. These results validate the feasibility of the GSIC BTMS and provide new insights for the development of immersion cooling BTMS.

Aerodynamic Size-Dependent Collection and Inactivation of Virus-Laden Aerosol Particles in an Electrostatic Precipitator.

Electrostatic precipitators (ESPs) may enable high particle collection efficiency with minimal pressure drop in HVAC systems. However, studies of pathogen collection and inactivation in ESPs at medium to higher flow rates are limited. Here, a single-stage, wire-plate ESP operated at flow rates of 51 and 85 m3 h-1 was used to study the removal of virus-laden aerosol particles for three different airborne viruses: (1) bovine coronavirus (BCoV), (2) influenza A virus (IAV), and (3) porcine reproductive and respiratory virus (PRRSV). Size-resolved measurements of collection efficiency were obtained using Andersen cascade impactors (ACI) sampling upstream and downstream of the ESP. All measurements were analyzed based on three distinctive but complementary methods: (1) fluorimetry to assess physical collection, (2) RT-qPCR to assess viral RNA concentrations and (3) virus titration to assess virus viability. In general, log reductions by virus titration were highest followed by those from RT-qPCR, and last fluorimetry, suggesting that a portion of virus may be potentially inactivated in flight in the ESP. An effective migration (deposition) velocity ranging from 3.10 to 10.05 cm s-1 was also determined using the spatially resolved measurements of virus collection on the ESP plates.

Improved surface morphology and reduced V-pits density of lattice-matched AlInN films grown by atmospheric pressure metalorganic chemical vapor deposition

AlInN has emerged as a promising material for advanced optoelectronic and electronic devices due to its unique properties. However, achieving AlInN layers with excellent surface morphology remains challenging. Here, Al0.83In0.17N layers lattice-matched to GaN/sapphire were grown by atmospheric-pressure metalorganic chemical vapor deposition at 875 °C. The lowest surface roughness measured by atomic force microscopy was 0.37 nm after optimizing the growth temperature and flux of precursors. The roughness value was constant in the range of 15–72 nm film thickness. Introducing a TMI pre-flow period before AlInN growth, further reduced roughness to 0.28 nm, although a graded inclusion of Ga into the AlInN near the GaN/AlInN interface was observed. This improved surface morphology was interpreted by the In-surfactant effect enriched by the pre-flow in the early stage of AlInN. Additionally, the V-pits density was as low as 2×105 cm−2, primarily due to high growth pressure and also influenced by relatively high growth temperature. Analysis of Al incorporation using second-order reaction model suggests that the severe parasitic reactions between TMA and NH3 at atmospheric pressure can be effectively eliminated by a high total gas flow rate of 72 slm, ensuring in-plane uniformity in surface morphology and relatively good crystalline quality.

A Novel Direct-Expansion Radiant Floor System Utilizing Water (R-718) for Cooling and Heating

While forced-air convective systems remain the predominant method for heating and cooling worldwide, radiant cooling and heating systems are emerging as a more efficient alternative. Current radiant cooling systems primarily rely on hydronic chilled water systems. This study introduces direct-expansion radiant cooling as a novel technique that could enhance the efficiency of radiant cooling and reduce its environmental impact. Water (R-718) has been tested as a refrigerant due to its favorable thermodynamic properties and environmental advantages; however, to the author’s knowledge, it has yet to be tested in direct-expansion radiant cooling. This research investigated several refrigerants, including water (R-718), ammonia (R-717), R-410a, R-32, R-134a, and R-1234yf, for this application. The findings indicate that water demonstrates efficiency comparable to other non-natural refrigerants, making it a promising candidate, given its favorable thermodynamic properties and substantial environmental benefits. Despite challenges such as a high compression ratio necessitating multi-stage compression, a high compressor discharge temperature exceeding 300 °C and requiring specialized blade materials, and a high suction volume flow rate, direct-expansion radiant cooling operates within a different temperature range. Consequently, the compressor discharge temperature can be reduced to 176 °C, and the compression ratio can be lowered to approximately 3.5, making water a more viable refrigerant option for this application.