Health concerns of Iranian adolescents: Protocol for a mixed methods study

Background: Adolescents have particular health and developmental needs that suggest they should neither be treated as older children nor younger adults. Objectives: The aim of this paper is to report the protocol for a mixed methods study that set out to investigate the health concerns of Iranian adolescents and their sources of health information with the goal of identifying suitable strategies to address their health concerns. Materials and Methods: This mixed methods study consists of an explanatory sequential design to be conducted in two phases. The first phase was a population-based cross-sectional survey of 915, 14-18 year old adolescents who were selected by stratified cluster random sampling method from the 22 main municipal sectors of Tehran, Iran. They completed a series of self-administered questionnaires which were analyzed using quantitative approaches. The second phase was a qualitative study in which adolescents were selected using purposeful sampling for individual in-depth semi-structured interviews on the basis of the quantitative findings from the first phase. These data, together with a literature review and data obtained through nominal group technique, would then be used to in the development of strategies to reduce adolescents' health concerns. Results: The findings of this mixed methods sequential explanatory study are expected to provide unique information about the health concerns of Iranian adolescents and their sources of information, which to date have received little attention. Conclusions: These data will provide a rich source of information that can be used by intervention programs, health professionals and policy makers in addressing the health concerns of adolescents, with the goal of facilitating a successful passage to adult life. © 2014, Iranian Red Crescent Medical Journal

Asymmetric Graetz Problem: The Analytical Solution Revisited

Copyright © 2016 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Copies of this paper may be made for personal and internal use, on condition that the copier pay the per-copy fee to the Copyright Clearance Center (CCC). All requests for copying and permission to reprint should be submitted to CCC at www.copyright.com; employ the ISSN 0887-8722 (print) or 1533-6808 (online) to initiate your request. Foroushani, S. S. M., Wright, J. L., & Naylor, D. (2017). Asymmetric Graetz Problem: The Analytical Solution Revisited. Journal of Thermophysics and Heat Transfer, 31(1), 237–242. https://doi.org/10.2514/1.T4944Forced-convective heat transfer from the walls of an asymmetrically heated channel to the fluid passing through in a laminar, hydrodynamically developed flow is known as the asymmetric Graetz problem. Several analytical and numerical solutions for this problem have been published, and many variations and extensions have been investigated. Recently, there has been a renewed interest in this problem due to its applications in emerging areas such as microchannels and fuel cells. In the present work, the asymmetric Graetz problem is examined in a resistor-network framework. The formulation of the problem in terms of three convective resistances forming a delta network leads to temperature-independent Nusselt numbers that are free of the singularities found in previous results. The proposed approach also offers new information regarding the split of heat transfer between the channel walls and the flow. This work is part of an ongoing project on resistor-network modeling and characterization of multitemperature convection problems.Smart Net-Zero Energy Buildings Strategic Research Network (SNEBRN) || Natural Sciences and Engineering Research Council of Canada (NSERC) || University of Waterlo

Sensitivity of the Solar Heat Gain Coefficient of Complex Fenestration Systems to the Indoor Convection Coefficient

Accurate estimation of the solar gain of a fenestration system is important in analyzing the energy performance of buildings. Recently, models were developed for complex fenestration systems – glazing systems with attachments such as venetian blinds and insect screens. These models use a three-node network for modeling heat transfer at the indoor-side of a glazing system. Empirical expressions based on observation and known limits were originally proposed for the corresponding convection coefficients. To address any ambiguity or error associated with these expressions, a research project is underway to develop techniques for evaluating these convection coefficients more accurately. The purpose of the current paper is to quantify the sensitivity of the U-value and solar heat gain coefficient of complex fenestration systems to the indoor-side convection coefficients. Configurations comprised of low-e glazings, roller blinds, venetian blinds, drapes and insect screens are examined in design summer and winter conditions using the window analysis software VISION5. Results show that the presence of an indoor-mounted attachment can significantly change the solar heat gain coefficient of a fenestration system. Nevertheless, the solar heat gain coefficient and the overall heat transfer coefficient are not sensitive to the indoor convection coefficient

Resistor-Network Formulation of Multitemperature Forced-Convection Problems

Please note that this file contains the final draft version of this technical paper. Minor differences will be found between this version and the final version printed by the publisher. The reader should contact the publisher if the final version, as printed, is preferred. Copyright © 2016 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Copies of this paper may be made for personal and internal use, on condition that the copier pay the per-copy fee to the Copyright Clearance Center (CCC). All requests for copying and permission to reprint should be submitted to CCC at www.copyright.com; employ the ISSN 0887-8722 (print) or 1533-6808 (online) to initiate your request. Foroushani, S., Naylor, D., & Wright, J. L. (2016). Resistor-Network Formulation of Multitemperature Forced-Convection Problems. Journal of Thermophysics and Heat Transfer, 1–8. https://doi.org/10.2514/1.T4993Many convection heat transfer problems involve more than two isothermal heat sources/sinks. A network of multiple convective resistors connecting temperature nodes representing the isothermal sources (walls, inlet flows, etc.) can be used to represent this class of problem. However, the convective resistances that characterize this network cannot generally be evaluated using energy balances resulting from a single solution to the energy equation. A technique based on solutions of the energy equation with perturbed boundary conditions is developed to overcome this difficulty. The resulting technique is verified by comparison with energy-balance results previously obtained for a special symmetric case. The technique is also applied to a superposition solution for hydrodynamically developed laminar flow in an annulus and to numerical solutions of simultaneously developing flow in an asymmetrically heated annulus under both laminar and turbulent flow conditions. This work is part of an ongoing research project on the resistor-network modeling and characterization of multitemperature convection problems.Smart Net-Zero Energy Buildings Strategic Research Network (SNEBRN) || Natural Sciences and Engineering Research Council of Canada (NSERC) || University of Waterlo

Indoor-Side Convection Coefficients for Complex Fenestration Systems with Roller Blinds

© 2017 ASHRAE (www.ashrae.org). Published in ASHRAE Conference Papers, Winter Conference, Las Vegas, NV. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE's prior written permission.In order to characterize the resistor network that describes convective heat transfer on the indoor side of a complex fenestration system, three convection coefficients are needed. Although methods to obtain convection coefficients in glazing cavities are well established, the convection coefficients in the vicinity of an indoor-mounted attachment are not so readily available. In principle, convection coefficients of a three-resistor network cannot be obtained based on numerical solutions or measurement only. The ASHWAT models for simulating windows with attachments currently provide estimates of the three convection coefficients as functions of glass-to-shade spacing, based largely on known limits. Recently, a numerical technique, dubbed dQdT, was developed for evaluating the heat transfer coefficients of multi-temperature convection problems. This technique entails numerical solutions of the full set of governing equations and subsequent solutions of the energy equation with perturbed boundary conditions. In earlier work, dQdT was applied to a fenestration system with an indoor-mounted roller blind. To keep the flow laminar and the numerical solutions simple, a relatively short window was considered. Preliminary results suggested that ASHWAT gives good estimates of the convection coefficients and accurately predicts the general trends. Nevertheless, ASHWAT overestimated the glass-to-shade heat transfer coefficient for intermediate spacing, while underpredicting glass-to-air and shade-to-air heat transfer coefficients for larger spacings. The effect of spacing also seemed to be underestimated by ASHWAT. The present study was undertaken to further examine the accuracy of the ASHWAT estimates for windows with realistic dimensions, various glazing-attachment spacings and taking into account the transition of the flow to turbulence. Excellent agreement between the dQdT results and the ASHWAT predictions was obtained under summer design conditions, confirming the validity and utility of the current ASHWAT correlations. A minor adjustment to improve the accuracy of the current ASHWAT estimates is suggested.Smart Net-Zero Energy Buildings strategic Research Network (SNEBRN) || Natural Science and Engineering Research Council (NSERC) of Canada || University of Waterlo

Convective Heat Transfer In Hydrodynamically-Developed Laminar Flow In Asymmetrically-Heated Annuli: A Three-Temperature Problem

Heat transfer in hydrodynamically-developed flow in asymmetrically-heated channels and annuli has been studied extensively. This study is an extension of earlier work where heat transfer in an asymmetrically-heated parallel-plate channel was examined in a resistor-network framework. It was shown that the formulation of the problem in terms of a delta thermal-resistor network has several advantages. A delta network can also be used to represent heat transfer in asymmetrically-heated annuli. Nevertheless, the evaluation of the three paired convective resistances that characterize the network is not straightforward. In the present paper, a new technique based on solutions of the energy equation with perturbed boundary conditions is proposed. The proposed technique is first verified by comparison with the results previously obtained for the parallel-plate channel problem. A superposition solution to the energy equation is obtained for hydrodynamically-developed laminar flow in an asymmetrically-heated annulus. The developed technique is then applied to the annulus problem to obtain the corresponding resistances. Results are validated by examining limiting cases.Smart Net-Zero Energy Buildings Strategic Research Network (SNEBRN) || Natural Sciences and Engineering Research Council of Canada (NSERC) || University of Waterlo

Laminar Free Convection from a Pair of Horizontal Cylinders: A Three-Temperature Problem

The formulation of multi-temperature convection problems in terms of a single driving temperature difference and a single heat transfer coefficient does not properly reflect the physics of the problem. Paired heat transfer coefficients, which designate both the source and the sink of heat transfer, are a suitable alternative. A numerical technique, namely dQdT, is proposed to compute such paired heat transfer coefficients. The dQdT technique entails a numerical solution of the governing equations and consequent solutions of the energy equation with perturbed boundary conditions. In the present study, dQdT is applied to the three-temperature problem of steady-state laminar free convection from two horizontal cylinders, with equal diameters but different surface temperatures, aligned vertically at a center-to-center spacing of two diameters. A number of moderate Rayleigh numbers, 2×104<Ra<2×105, are considered. The baseline solutions are validated against experimental data from the literature. A grid convergence study is performed to assess the discretization error. The utility of dQdT in characterizing this three-temperature free convection problem, specifically in quantifying the interaction of the cylinders, is demonstrated. It has also been shown that the paired heat transfer coefficients obtained through dQdT provide detailed information about the local interaction of the cylinders, which are not available otherwise.Smart Net-Zero Energy Buildings Strategic Network (SNEBRN) || Natural Sciences and Engineering Research Council of Canada (NSERC) || University of Waterlo

Resistor-Network Formulation of Multi-Temperature Free Convection Problems

Copyright © 2016 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Copies of this paper may be made for personal and internal use, on condition that the copier pay the per-copy fee to the Copyright Clearance Center (CCC). All requests for copying and permission to reprint should be submitted to CCC at www.copyright.com; employ the ISSN 0887-8722 (print) or 1533-6808 (online) to initiate your request. Foroushani, S., Wright, J. L., & Naylor, D. (2017). Resistor-Network Formulation of Multitemperature Free-Convection Problems. Journal of Thermophysics and Heat Transfer, 1–6. https://doi.org/10.2514/1.T5024In recent work, the resistor-network formulation of forced-convection problems and a technique (dQdT) for evaluating the paired convective resistances that characterize the network were presented. This technique entails solutions of the energy equation with perturbed boundary conditions. In the present paper, the dQdT technique is extended to free convection. The analytical solution to the classical two-temperature problem of free convection at an isothermal vertical flat plate is used to verify the technique. Then, dQdT is applied to the three-temperature problem of free convection in an asymmetrically heated vertical channel based on numerical solutions of the energy equation. Sample results are presented and known limits are discussed to demonstrate the validity of the results. This paper is part of a series on the resistor-network formulation of convection problems.Smart Net-Zero Energy Buildings Strategic Research Network || Natural Sciences and Engineering Research Council of Canada || University of Waterlo