Experimental Investigation of Average Heat-Transfer and Friction Coefficients for Air Flowing in Circular Tubes Having Square-Thread-Type Roughness

An investigation of forced-convection heat transfer and associated pressure drops was conducted with air flowing through electrically heated Inconel tubes having various degrees of square-thread-type roughness, an inside diameter of 1/2 inch, and a length of 24 inches. were obtained for tubes having conventional roughness ratios (height of thread/radius of tube) of 0 (smooth tube), 0.016, 0.025, and 0.037 over ranges of bulk Reynolds numbers up to 350,000, average inside-tube-wall temperatures up to 1950deg R, and heat-flux densities up to 115,000 Btu per hour per square foot. Data The experimental data showed that both heat transfer and friction increased with increase in surface roughness, becoming more pronounced with increase in Reynolds number; for a given roughness, both heat transfer and friction were also influenced by the tube wall-to-bulk temperature ratio. Good correlation of the heat-transfer data for all the tubes investigated was obtained by use of a modification of the conventional Nusselt correlation parameters wherein the mass velocity in the Reynolds number was replaced by the product of air density evaluated at the average film temperature and the so-called friction velocity; in addition, the physical properties of air were evaluated at the average film temperature. The isothermal friction data for the rough tubes, when plotted in the conventional manner, resulted in curves similar to those obtained by other investigators; that is, the curve for a given roughness breaks away from the Blasius line (representing turbulent flow in smooth tubes) at some value of Reynolds number, which decreases with increase in surface roughness, and then becomes a horizontal line (friction coefficient independent of Reynolds number). A comparison of the friction data for the rough tubes used herein indicated that the conventional roughness ratio is not an adequate measure of relative roughness for tubes having a square-thread-type element. The present data, as well as those of other investigators, were used to isolate the influence of ratios of thread height to width, thread spacing to width, and the conventional roughness ratio on the friction coefficient. A fair correlation of the friction data was obtained for each tube with heat addition when the friction coefficient and Reynolds number were defined on the basis of film properties; however, the data for each tube retained the curve characteristic of that particular roughness. The friction data for all the rough tubes could be represented by a single line for the complete turbulence region by incorporating a roughness parameter in the film correlation. No correlation was obtained for the region of incomplete turbulence

Refan program. Phase 1: Summary report

The Refan Program is aimed at a large reduction in aircraft approach and takeoff noise in the vicinity of airports caused by the JT3D-powered 707's and DC-8's and the JT8D-powered 727's, 737's and DC-9's. These aircraft represent a major part of the existing commercial fleet. The noise reductions can be achieved by engine and nacelle modifications in the form of aircraft retrofit kits. Engine turbomachinery noise is reduced by replacing the current two-stage fan with a larger single-stage fan and by nacelle acoustic treatment. Jet noise is reduced by the reduction on jet velocity caused by additional turbine work extraction to drive the larger bypass fan. The predicted net effect of these modifications on installed performance is large noise reductions on both approach and takeoff, increased takeoff thrust, decreased takeoff field length, and maintained or improved aircraft range depending on the amount of acoustic treatment included. The Refan Program is being conducted in two phases under contracts with one engine and two airframe companies. Results of the Phase I work are summarized in this report which describes the refan nacelle configurations studied, the airplane modifications required to install the nacelles, and the resulting airplane performance and noise reductions predicted for all five aircraft

Human Hypersensitivity Angiitis, An Immune Complex Disease

Human hypersensitivity angiitis is an immune complex disease in which patients present with palpable purpuric lesions of the skin and may often have multiple organ involvement. The antigen may be derived from an infectious organism such as the hepatitis virus, streptococcus, or a drug, and complexes with antibody. Under circumstances of vascular turbulence or vessel wall dilatation this complex may become fixed, activating the complement sequence with elaboration of chemotactic factors for neutrophils. These cells release lysosomal enzymes resulting in vessel wall destruction. Red blood cells leak into the tissue producing purpura and the inflammatory infiltrate accounts for the palpability. Although many patients have skin lesions only, others may have involvement of joints, gastrointestinal tract, kidneys, and even the lungs.The central question in the pathogenesis of this disease is why the immune complex is so selective in its site of deposition. Part of the reason must be related to the lattice formation of a particular complex, while other reasons are related to host factors of altered vascular permeability, integrity of clearance mechanisms or even a genetically determined defect of the phagocytic system

Association between School-Based Mentoring Intervention Programs and Drug Abuse Among African American Aged 10-24 Years

Drug abuse remains a significant global public health problem having socioeconomic consequences wrought by cognitive and physiological phenomena, as well as a cluster of behavioral, physical, serious social, and emotional problems. Worldwide, adolescents and young people are at most risk of drug abuse. The predisposing factors to drug abuse among adolescents and young people include gender, age, family structure and relations, poverty, and the accessibility and affordability of drugs. This problem is common across developed and developing countries, including Nigeria This study was conducted to evaluate the association between school-based intervention programs and drug abuse among African American young people with the ages of 10 – 24 years. The theoretical framework for the study was based on the health belief model. The study utilized secondary data set from the 2014 National Survey on Drug Use and Health for the analysis. The dependent variable was drug abuse, while the independent variable was mentoring interventions. The Chi-square analysis revealed a significant association between participation in school - based intervention programs and drug abuse [(χ2 (1, N = 3533) = 8.567, p = .003]. The observed association between drug abuse and schoolbased mentoring intervention programs suggests that other mentoring intervention programs may be modified for effectiveness, which would result in positive social change. The social implications of drug abuse among adolescents and young people, particularly undergraduates, cannot be quantified and it is one of the health related problems among and African and specifically Nigerian youth and remains a source of anxiety to various stakeholders, including the educational stakeholders. In view of the profound public health implications of these dangerous drug abuse habits among adolescents and young adults in African and Nigeria, the findings of this study may be generalized and implemented to bring about a needed social change

Correlation of Forced-convection Heat-transfer Data for Air Flowing in Smooth Platinum Tube with Long-approach Entrance at High Surface and Inlet-air Temperatures

A heat-transfer investigation was conducted with air in an electrically heated platinum tube with long-approach entrance, inside diameter of 0.525 inch, and effective heat-transfer length of 24 inches over ranges of Reynolds number up to 320,000, average inside-tube-wall temperature up to 3053 degrees R, and inlet-air temperature up to 1165 degrees R. Correlation of data by the conventional Nusselt relation resulted in separation of data with tube-wall temperature. Good correlation was obtained, however, by use of a modified Reynolds number

Development of a biomarker for penconazole: a human oral dosing study and a survey of UK residents’ exposure

Penconazole is a widely used fungicide in the UK; however, to date, there have been no peer-reviewed publications reporting human metabolism, excretion or biological monitoring data. The objectives of this study were to i) develop a robust analytical method, ii) determine biomarker levels in volunteers exposed to penconazole, and, finally, to iii) measure the metabolites in samples collected as part of a large investigation of rural residents’ exposure. An LC-MS/MS method was developed for penconazole and two oxidative metabolites. Three volunteers received a single oral dose of 0.03 mg/kg body weight and timed urine samples were collected and analysed. The volunteer study demonstrated that both penconazole-OH and penconazole-COOH are excreted in humans following an oral dose and are viable biomarkers. Excretion is rapid with a half-life of less than four hours. Mean recovery of the administered dose was 47% (range 33%–54%) in urine treated with glucuronidase to hydrolyse any conjugates. The results from the residents’ study showed that levels of penconazole-COOH in this population were low with >80% below the limit of detection. Future sampling strategies that include both end of exposure and next day urine samples, as well as contextual data about the route and time of exposure, are recommended