Performance comparison of different flow arrangements of 4-fluid internally-cooled liquid desiccant dehumidifiers

In this study, the performance of 10 different flow arrangements of 4-fluid internally-cooled liquid desiccant dehumidifiers were compared. The four fluids are supply air, exhaust air, liquid desiccant, and water. The comparison was performed using a two-dimensional heat and mass transfer model of the dehumidifier that was solved numerically. The model's predictions of supply air outlet humidity ratio matched experimental measurements within 6.7%. The two-dimensional variation of the air temperature and humidity ratio in the supply channel showed the importance of using a two-dimensional heat and mass transfer model when at least one of the fluids is in cross-flow with the other fluids. Moreover, a sensitivity analysis was performed to evaluate the effect of nine input parameters (supply air temperature and humidity ratio, exhaust air temperature and humidity ratio, liquid desiccant temperature, concentration, and flow rate, supply air mass flow rate, and exhaust to supply air mass flow rate ratio) on the performance of the dehumidifiers. The results showed that the best performance, in terms of the supply air humidity ratio and enthalpy decrease, was obtained when the supply air was in counter-flow with the exhaust air, liquid desiccant, and water. While the poorest performance was obtained when the supply air was in parallel-flow with the exhaust air and in counter-flow with the liquid desiccant and water. The approximate difference between the best and poorest performing flow arrangements in terms of the decrease in supply air humidity ratio and enthalpy is 4.3% and 10.5%, respectively. The results of the sensitivity analysis showed that for the 10 flow arrangements, the liquid desiccant inlet temperature, and flow rate have the least effects on the performance of the dehumidifier.This work was supported by the Qatar National Research Fund [Grant Number NPRP11S-0114-180295]. The contents of this work are solely the responsibility of the authors and do not necessarily represent the official views of the Qatar National Research Fund.Scopu

Erosion-corrosion behavior and failure analysis of offshore steel tubular joint

An extensive investigation into the erosion-corrosion behavior and failure analysis of an offshore steel tubular joint has been carried out by using various electrochemical techniques, visual inspection, optical microscope examination, mechanical testing, microstructure examination, chemical analyses, Scanning Electron Microscope (SEM) examination, Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD). The open circuit potential (OCP) was recorded for the T-joint material in 0.6 M NaCl without and with electrolyte erosion. Potentiodynamic polarization scans were used to study and compare the material resistance against synergistic impact of erosion-corrosion and corrosion. An optical microscope was used to compare the morphology of pitting corrosion in the absence and presence of erosion. The change in the pitting potential due to electrolyte impingement has been discussed. Pits are slightly stretched in the direction of erosion because of the impingement and disruption of the passive layer in that direction.Visual inspection resultsshowed that the T-joint is heavily eroded and corrosion products were noted. Hardness variation was noted along one of the inspected directions which indicated non-uniform heat treatment. Accordingly, a slow cooling process during heat treatment or manufacturing process is believed to have occurred based on the fine grains observed. Tensile test and microstructure examination indicated that the material of the T-joint is low carbon steel. Furthermore, the chemical analysis indicated that the material of the T-joint is AISI 1026.The results of the chemical analysis of the corrosion products indicated a sulfur-dominant type of corrosion attack. SEM examination revealed presence of cracks, aluminum and calcium inclusions and sea water is believed to be the working fluid. CFD simulation indicated that the fast flow issuing from the main small inlet created relatively high turbulentflow at the area where erosion took place. The fatigue cracks initiation and growth is linked to turbulence intensity and pressure fluctuations.ACKNOWLEDGEMENT This publication was made possible by NPRP grant No. 08-159-2-046 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu

Multiplicity counting using organic scintillators to distinguish neutron sources: An advanced teaching laboratory

In this advanced instructional laboratory, students explore complex detection systems and nondestructive assay techniques used in the field of nuclear physics. After setting up and calibrating a neutron detection system, students carry out timing and energy deposition analyses of radiation signals. Through the timing of prompt fission neutron signals, multiplicity counting is used to carry out a special nuclear material (SNM) nondestructive assay. Our experimental setup is comprised of eight trans-stilbene organic scintillation detectors in a well-counter configuration, and measurements are taken on a spontaneous fission source as well as two ({\alpha},n) sources. By comparing each source's measured multiplicity distribution, the resulting measurements of the ({\alpha},n) sources can be distinguished from that of the spontaneous fission source. Such comparisons prevent the spoofing, i.e., intentional imitation, of a fission source by an ({\alpha},n) neutron source. This instructional laboratory is designed for nuclear engineering and physics students interested in organic scintillators, neutron sources, and nonproliferation radiation measurement techniques.Comment: 29 pages, 17 figures, pre-proof accepted to AJP, AJP number AJP22-AR-01524R2 (DOI: 10.1119/5.0139531

Development of an Event Tracking Feature in OpenMC for Neutron Spectroscopy and Scatter Camera Systems

This paper presents the development and application of an event tracking feature within the OpenMC Monte Carlo code, designed for advanced neutron spectroscopy and scatter camera system simulations. The newly implemented feature enables the tracking of individual neutron collisions, with potential applications in nuclear non-proliferation, reactor physics, and nuclear security. Additionally, the feature holds potential for the calibration of neutron detectors, specifically in converting light output into energy deposited within the detectors. The implementation consists of a set of filters - such as reaction type, energy, cell, and material - that constrain the set of events that are tracked, a tie-in to the Python API to enable simple user input formats, and different file format saving options as OpenMC’s native HDF5-based format or Monte Carlo particle lists (MCPL). This feature is still in development and is not yet part of an OpenMC release; it remains subject to change. The verification of the new feature is performed using a model of an optically segmented scatter camera exposed to a 252Cf source. We apply the time-of-flight analysis technique to extract the neutron spectrum and infer the direction of the incoming source by the simple back-projection method

Original Article

Abstract Background: Mosquitoes transmit several diseases to human. There are several measures for control of larvae. As part of Integrated Vector Management (IVM) program, the utility of floating layers of polystyrene beads (EPS) is a potential alternative in habitats of mosquito larva. EPS beads prevent oviposition of mosquito as well as killing the immature stages by forming a tick layer on the water surface. They are cheap, environmentally safe and do not need frequent application and remain on the surface of water for long time. The objective of the current study was to asses the effectiveness of two types of polystyrene beads of (EPS) and (SWAP) for control of mosquito larvae under laboratory conditions. Methods: Anopheles stephensi and Culex quinquefasciatus were used for experimental purposes. In each tray 250 larvae of late 3 rd and early 4 th instars were introduced. The experiment was conducted on 4 replicates for An. stephensi, Cu. quinquefasciatus and combination of both. Emerging of adult mosquitoes were calculated every day until the end of experiments. Results: Mortality rate and Inhibition of Emerge (IE) for Cu. quinquefasciatus, An. stephensi and combination of both species was 97.8%, 100% and 99.07%, respectively using EPS. In average, EPS was able to kill 98.9% of larvae. The figures with SWAP were 63%, 91.05% and 72.65%, respectively. The average mortality for mosquitoes was 75.57% Conclusion: EPS and SWAP beads can be very effective and practical for elimination of An. stephensi and Cx. quinquefasciatus under the laboratory conditions

Call for emergency action to restore dietary diversity and protect global food systems in times of COVID-19 and beyond: Results from a cross-sectional study in 38 countries

Background: The COVID-19 pandemic has revealed the fragility of the global food system, sending shockwaves across countries\u27 societies and economy. This has presented formidable challenges to sustaining a healthy and resilient lifestyle. The objective of this study is to examine the food consumption patterns and assess diet diversity indicators, primarily focusing on the food consumption score (FCS), among households in 38 countries both before and during the first wave of the COVID-19 pandemic. Methods: A cross-sectional study with 37 207 participants (mean age: 36.70 ± 14.79, with 77 % women) was conducted in 38 countries through an online survey administered between April and June 2020. The study utilized a pre-tested food frequency questionnaire to explore food consumption patterns both before and during the COVID-19 periods. Additionally, the study computed Food Consumption Score (FCS) as a proxy indicator for assessing the dietary diversity of households. Findings: This quantification of global, regional and national dietary diversity across 38 countries showed an increment in the consumption of all food groups but a drop in the intake of vegetables and in the dietary diversity. The household\u27s food consumption scores indicating dietary diversity varied across regions. It decreased in the Middle East and North Africa (MENA) countries, including Lebanon (p \u3c 0.001) and increased in the Gulf Cooperation Council countries including Bahrain (p = 0.003), Egypt (p \u3c 0.001) and United Arab Emirates (p = 0.013). A decline in the household\u27s dietary diversity was observed in Australia (p \u3c 0.001), in South Africa including Uganda (p \u3c 0.001), in Europe including Belgium (p \u3c 0.001), Denmark (p = 0.002), Finland (p \u3c 0.001) and Netherland (p = 0.027) and in South America including Ecuador (p \u3c 0.001), Brazil (p \u3c 0.001), Mexico (p \u3c 0.0001) and Peru (p \u3c 0.001). Middle and older ages [OR = 1.2; 95 % CI = [1.125–1.426] [OR = 2.5; 95 % CI = [1.951–3.064], being a woman [OR = 1.2; 95 % CI = [1.117–1.367], having a high education (p \u3c 0.001), and showing amelioration in food-related behaviors [OR = 1.4; 95 % CI = [1.292–1.709] were all linked to having a higher dietary diversity. Conclusion: The minor to moderate changes in food consumption patterns observed across the 38 countries within relatively short time frames could become lasting, leading to a significant and prolonged reduction in dietary diversity, as demonstrated by our findings

Airflow assessment in a naturally ventilated greenhouse equipped with wind towers: numerical simulation and wind tunnel experiments

In this study, the air change rate and airflow distribution inside a greenhouse equipped with wind towers were analyzed using Computational Fluid Dynamics (CFD) simulations, considering different wind speeds (1–5 m/s) and incident angles (0–45°). The validation methods included smoke visualization, hot wire velocity point measurements, and Particle Image Velocimetry (PIV) measurements. The visualized and simulated flow regimes exhibited fair agreement. The average discrepancy between the hot wire velocity point measurements and simulated results was about 7.96%. The predicted vector fields in the inlet and outlet wind towers demonstrated good qualitative agreement with the corresponding PIV measurements. The discrepancy between the predicted and measured maximum air velocity in the inlet tower was 15%, while it was 3% in the outlet wind tower. At an external wind speed of 3 m/s and normal incidence angle, the average velocity of the airflow entering the greenhouse was 0.65 m/s (about one air change per minute), while the average air velocity in the greenhouse was 0.44 m/s. The average air velocity inside the greenhouse at a crop height (1 m) ranged from 0.3 to 1.8 m/s, which is within the optimum range of recommended air velocities for greenhouses.This work was supported by the Aspire Zone Foundation [award number: QUEX-CENG-ASPIRE-11/12-7].Scopu

Performance evaluation of a near-surface earth-to-air heat exchanger with short-grass ground cover: an experimental study

Given the negative environmental impact and high energy consumption of conventional air conditioning systems, the use of passive cooling systems has become particularly important. An earth-to-air heat exchanger, which utilizes the earth as a heat sink, is an efficient passive cooling system. Conventional earth-to-air heat exchangers are buried in the soil at a great depth, to ensure the soil temperature is relatively lower than the ambient air temperature during the hot season. Therefore, due to the great burial depth, their installation and maintenance are usually problematic. An alternative is a near-surface earth-to-air heat exchanger with short-grass ground cover. The grass cover reduces the near-surface soil temperature, eliminating the need to bury the earth-to-air heat exchanger at a great depth. In this study, the performance of a near-surface earth-to-air heat exchanger with short-grass ground cover was assessed experimentally. For an airflow rate of 607 m3/h, equivalent to 9.24 m/s, the inlet air temperature was reduced from 40.6 °C to about 34.1 °C, corresponding to a coefficient of performance of 13.4. The soil temperature 0.5 m away from the earth-to-air heat exchanger was not affected by its operation. On a typical summer day, compared to conventional air conditioning systems, about 76.5% less energy would be consumed by the earth-to-air heat exchanger to provide the same amount of cooling. Therefore, using this earth-to-air heat exchanger as a precooling system in combination with conventional air conditioning systems can both protect the environment and save energy.This work was supported by the Aspire Zone Foundation [award number QUEX-CENG-ASPIRE-11/12-7 ] and by a grant from the Qatar National Research Fund under its National Priorities Research Program [award number NPRP11S-0114-180295 ]. The contents of this work are solely the responsibility of the authors and do not necessarily represent the official views of the Qatar National Research Fund.Scopu