Two Phase Pressure Drop Performance of Refrigerant in a Small Horizontal Smooth Tube with 2.5 mm inside Diameter

Two-phase flow pressure drop measurements were made during the phase change heat transfer process of R22 in a small horizontal smooth tube with 2.5 mm inside diameter. Conclusions can be drawn that the quality corresponding to the pressure gradient peak value of small tubes became higher than that of large tubes. The effect of quality to pressure drop becomes weak as the mass flux increases. The experiment data were compared with the predicated values of the state-of-the-art correlations from the open literature. The comparisons between the data and the predictions indicate that most of the state-of-the-art correlations fails to predict the experimental data. Chisholm model shows a relatively better predictive ability than the other empirical correlations although it has a mean deviation of 26.7%. But the predicated values of Chisholm model are lower by 50% than the experimental data when the quality becomes larger.

Attention Deficit Hyperactivity Disorder in the General Adult Population in Benin (Parakou 2022)

Introduction: Attention deficit hyperactivity disorder (ADHD) is a little-studied psychiatric pathology in our countries, and particularly here in Benin. Objectives: To calculate the prevalence and identify the factors associated with attention deficit hyperactivity disorder among adults in the commune of Parakou in 2022. Methods: Cross-sectional, descriptive, analytical study including subjects aged 18 and over. ADHD was assessed with the Adult ADHD Self Report Scale (ARSR-v1.1) and consequences with the Weiss functional impairment rating scale (WFIRS-S). Results: A total of 456 people were included in the study. The mean age of those surveyed was 25.9 ± 11.6 years. The prevalence of ADHD symptoms among the adults surveyed was 6.8%. The clinical form of ADHD with a predominance of inattention had a prevalence of 3.3%. After multivariate analysis, the factor associated with the presence of ADHD symptoms in adults in the commune of Parakou was: a poor relationship with the subject’s partner (p = 0.031, ORa = 6.5 [1.18-35.68]). Conclusion: ADHD is present in the community of Parakou and needs further attention.

Correlations of Two-phase Friction of Refrigerant in Horizontal Smooth Tube with 2.5 mm inside Diameter

Two-phase flow pressure drop measurements are made during phase change heat transfer process of R-22 in small horizontal smooth tubes with 2.5 mm inside diameter. Conclusions are drawn that the quality corresponding to pressure gradient peak value of small tubes became higher than that of large tubes and that effects of quality on pressure drop become weak as the increase of mass flux. The experiment data are compared with predicted values of the state-of-the-art correlations from the open literature, which indicates that most of the state-of-the-art correlations fail to predict the present experimental data. Chisholm model shows a relatively better predictive ability than the other empirical correlations because it has the lowest mean deviation of 26.7%. But the predicted values of Chisholm model are 50% lower than experimental data when quality becomes higher. In this regard, an new empirical correlation based on Chisholm model is developed and this modified Chisholm correlation can describe 95% of the present data with ±20% mean deviations.

Impact of Number of Add/Drop Ports of OXCs on LSP Blocking Performance

This paper describes the connection establishment of label switched paths (LSP) in IP/MPLS over optical networks. Our investigations on two typical network topologies show that the number of add/drop ports of OXCs has a significant impact on the LSP blocking performance.

Thermal-Hydraulic Characteristics of Twisted Elliptical Tube Bundle in Staggered Arrangement

Based on experimental data,numerical simulations by turbulent air flowing across staggered tube bundle composed of twisted elliptical tube(TET)with constant tube wall temperature are conducted in present study.Parametric study on the thermal-hydraulic characteristics of air crossflow in TET bundles is investigated with physical parameters and Reynolds number(Re).The results show that spiral channels created by spiral deformation of TETs have a diversion effect on the air flow,which changes the flow direction of the air near the tube wall.The air in the near wall region is a three-dimensional flow,consisting of a flow perpendicular to the normal direction of the elliptical cross section and a spiral flow along the helicoid on the downstream side and the upstream side.And the interaction of the spiral channels makes the two flows and their mixing more complicated.The excellent heat transfer performance of staggered TET bundles is confirmed by the comparison of the comprehensive heat transfer performance with that of circular tube bundles.The average Nusselt number(Nu)increases with the increase of the aspect ratio(A/B)and with the increase of Re while decreases as the twist pitch(S)increases.The average Euler number(Eu)increases as A/B increases,while it decreases as Re increases and as S increases.Due to the fact that the suitable correlations for staggered TET bundles are not reported,correlations for Nu and Eu obtained from experimental data and numerical results are presented in the multiple forms.