Experimental and numerical study of fluid flow and heat transfer in a twisted square duct

Heat transfer and friction factor characteristics of air flow inside twisted square duct are studied experimentally and through three-dimensional numerical simulations. Experiments were conducted for air with uniform wall temperature boundary condition, twist ratio of 11.5 and 16.5, and Reynolds number 600-70,000. Laminar to turbulent flow transition point was identified. The results show considerable enhancement in heat transfer and pressure drop in both laminar and also in turbulent flow regimes till Reynolds number of 9500. Twist ratio of 11.5 shows relatively higher heat transfer and pressure drop compared to straight square duct. Three-dimensional analysis of steady fully-developed laminar flow inside twisted duct of square cross section flow area is carried out for Reynolds number range of 100100,000 using commercially available software. The numerical study is conducted for a uniform wall temperature case, twist ratio of 2.5, 5, 10 and 20, for Prandtl number range of 0.7 to 20. The maximum value for product of friction factor and Reynolds number is observed for a twist ratio of 2.5 and a Reynolds number of 3000. The maximum Nusselt number is observed for the same values for Prandtl number of 20. Correlations for friction factor and Nusselt number are developed involving swirl parameter in the laminar flow regime. Correlations are also provided for the entire range of turbulent regime. Local distribution of friction factor ratio and Nusselt number across a cross-section is presented. Based on constant pumping power criteria, enhancement factor is defined to compare twisted ducts with straight ducts. Selections of twisted square duct are presented in terms of enhancement factor. It is found that twisted duct performs well in laminar and also to some extent in turbulent flow regime due to strong presence of secondary flow. It is recommended to use twisted square duct in laminar flow regime for entire range of Prandtl number studied. Maximum enhancements factor of 10.5 is obtained with twist ratio of 2.5, Prandt-1 number of 20 and Reynolds number of 3000. Guidelines are provided for selection of twisted square duct in terms of Reynolds number and Prandtl number. Comparison with twisted elliptic tube and twisted tape are discussed. These results would help in the design and development of compact heat exchanger. (C) 2014 Elsevier Ltd. All rights reserved

Laminar flow heat transfer studies in a twisted square duct for constant wall heat flux boundary condition

The problem of fluid flow and heat transfer was studied for flow inside twisted duct of square cross-section. Three-dimensional numerical solutions were obtained for steady fully developed laminar flow and for uniform wall heat flux boundary conditions using commercially available software. Reynolds number range considered was 100-3000. Twist ratio used are 2.5, 5, 10 and 20. Fluids considered are in Prandtl number range of 0.7-20. Product of friction factor and Reynolds number is found to be a function of Reynolds number and maximum values are observed for a twist ratio of 2.5 and Reynolds number of 3000. Maximum Nusselt number is observed for the same values along with Prandtl number of 20. Correlations for friction factor and Nusselt number are developed involving swirl parameter. Local distribution of friction factor ratio and Nusselt number across a cross-section is presented. Based on constant pumping power criteria, enhancement factor is defined to compare twisted ducts with straight ducts. Selection of twisted square duct is presented in terms of enhancement factor. It is found that twisted duct performs well in the laminar region for range of parameters studied. Heat transfer enhancement for Reynolds number of 3000 and Prandtl number of 0.7 for twist ratio of 2.5, 5, 10, and 20 is 20%, 17.8%, 16.1% and 13.7%, respectively. The results are significant because it will contribute to development of energy efficient compact size heat exchangers

Aetiology and Management of Epistaxis - A Prospective Clinical Study

Objective : Epistaxis is a common clinical problem and is an uncomfortable experience that can cause great apprehension and anxiety in patients. Most nose bleed are benign, spontaneous and self-limiting. Epistaxis can range from minor bleed to profuse bleed that can be life threatening and warrant urgent medical attention. By this means it becomes necessary to study aetiology, age and sex incidence, seasonal variation, site and management of epistaxis. Methods : This prospective study was carried out in Department of Otorhinolaryngology, School of Medical Sciences and Research, Greater Noida from January 2013 to June 2014. The study subjects included 100 patients who presented with epistaxis during the period under study. Results : The mean age of patients were 30.44±19.08 (SD) years and male to female ratio was 3:1. Epistaxis was more common during hot dry months and dry cold winter months. Trauma to the nose caused epistaxis in 35% of case. Neoplasms of nose, paranasal sinuses and nasopharynx were observed to be responsible for epistaxis in 13% of cases. Acute and chronic inflammatory conditions of nose were responsible for epistaxis in 13% of cases. High blood pressure was found in 10% of cases. In 7% of the cases, epistaxis was idiopathic. Anterior bleed was present in 69% of cases while posterior nasal bleed was seen in 34% of cases, in 12% cases site is undetermined. Conclusion : 79% cases treated successfully with conservative approach while 21% cases required surgical intervention. In this study conservative treatment was found effective in most cases

Efficacy of Epley’s Maneuver in Treating BPPV Patients: A Prospective Observational Study

Vertigo and balance disorders are among the most common symptoms encountered in patients who visit ENT outpatient department. This is associated with risk of falling and is compounded in elderly persons with other neurologic deficits and chronic medical problems. BPPV is the most common cause of peripheral vertigo. BPPV is a common vestibular disorder leading to significant morbidity, psychosocial impact, and medical costs. The objective of Epley’s maneuver, which is noninvasive, inexpensive, and easily administered, is to move the canaliths out of the canal to the utricle where they no longer affect the canal dynamics. Our study aims to analyze the response to Epley’s maneuver in a series of patients with posterior canal BPPV and compares the results with those treated exclusively by medical management alone. Even though many studies have been conducted to prove the efficacy of this maneuver, this study reinforces the validity of Epley’s maneuver by comparison with the medical management

Genome-wide analysis of AAAG and ACGT <i>cis-</i>elements in <i>Arabidopsis thaliana</i> reveals their involvement with genes downregulated under jasmonic acid response in an orientation independent manner

Abstract Cis-ciscis(N)(N)Arabidopsis thaliana(N)(N)(N)(N

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Not AvailableFertilizers are one of the costly inputs in agriculture and development of nutrient efficient fertilizers is need of the hour. Keeping in view of the above, slow release coated urea fertilizers are developed and the N loss from different coated urea fertilizers in a Vertisol was studied in comparison with normal urea. The coated fertilizers used were neem, 4% pine oleoresin (POR), 35% nano-rock phosphate and 2% nano-ZnO coated urea. In later two cases nanoparticles were loaded over 4% POR coated urea during preparation. Application of coated urea fertilizers such as neem coated urea and pine oleoresin coated urea in a Vertisol reduced the ammonia volatilization by 27.5% and 41.1%, respectively. Similarly, reduction of NO3-N leaching due to application of neem, resin, nano-rock phosphate and nano-ZnO coated urea were 18.3%, 28.0%, 25.7% and 35.1%, respectively. The reduction of N volatilization and leaching losses imparted by coated urea fertilizers could be a viable N source for crops. However field level validation experiments have to be carried out to assess the efficacy of these coated fertilizers in enhancing crop yield and nutrient use efficiency.Not Availabl