Numerical analysis of the axial heat conduction with variable fluid properties in a forced laminar flow tube

This document is the Accepted Manuscript version of the following article: Lijing Zhai, et al, ‘Numerical analysis of the axial heat conduction with variable fluid properties in a forced laminar flow tube’, International Journal of Heat and Mass Transfer, Vol. 114: 238-251, November 2017. Under embargo until 22 June 2018. The final, definitive version is available online at doi: https://doi.org/10.1016/j.ijheatmasstransfer.2017.06.041.In this article, a theoretical model is developed to investigate the effects of the axial heat conduction on the laminar forced convection in a circular tube with uniform internal heat generation in the solid wall. In the current work, three different fluids, i.e. water, n-decane and air, are selected on purpose since their thermophysical properties show different behavior with temperature. The effects of the axial heat conduction with varying dynamic viscosity and/or varying thermal conductivity are investigated in a systematic manner. Results indicate that the variable-property effects could alleviate the reduction in Nusselt number (Nu) due to the axial heat conduction. For the case of Peclet number (Pe) equal to 100, wall thickness to inner diameter ratio of 1 and solid wall to fluid thermal conductivity ratio of 100, the maximum Nu deviation between constant and variable properties are up to 7.33% at the entrance part for water in the temperature range of 50℃, and 4.45% at the entrance part for n-decane in the temperature range of 120℃, as well as 2.20% at the ending part for air in the temperature range of 475℃, respectively. In addition, the average Nu deviation for water, n-decane and air are 3.24%, 1.94% and 1.74%, respectively. Besides, Nu decreases drastically with decreasing Pe when Pe≤500 and with increasing solid wall to fluid thermal conductivity ratio ( ) when ≤100. It is also found that variable properties have more obvious effects on the velocity profile at the upstream part while more obvious effects on the temperature profile at the downstream part.Peer reviewe

The amidine based colorimetric sensor for Fe³⁺, Fe²⁺, and Cu²⁺ in aqueous medium

An amidine based chemosensor AM-1 was synthesized and characterized by various spectroscopic (FT-IR, 1H-NMR and mass) data and elemental analyses. Sensor AM-1 exhibited high selectivity and sensitivity towards Fe³⁺, Fe²⁺ and Cu²⁺ in the presence of other surveyed ions (such as Sr²⁺, Cr³⁺, Co²⁺, Ni²⁺, Zn²⁺, Ag⁺, Al³⁺, Ba²⁺, Ca²⁺, Cd²⁺, Cs⁺, Hg²⁺, K⁺, Li⁺, Mg²⁺, Mn²⁺, Na⁺ and Pb²⁺) with a distinct naked-eye detectable color change and a shift in the absorption band. Moreover, the emission of AM-1 was quenched selectively only in the presence of Fe³⁺

A Convenient, TiCl_<b>4</b>/SnCl_<b>4</b>-Mediated Synthesis of <i>N</i>-Phenyl or <i>N</i>-Aryl Benzamidines and <i>N</i>-Phenylpicolinamidines

A new, TiCl4-or SnCl4-mediated, solvent-free method was developed for the synthesis of N-Aryl benzamidines and N-phenylpicolinamidines, in moderate-to-good yield, using suitable amines and nitriles as starting materials.</jats:p

Molecular Momentum Transport at Fluid-Solid Interfaces in MEMS/NEMS: A Review

This review is focused on molecular momentum transport at fluid-solid interfaces mainly related to microfluidics and nanofluidics in micro-/nano-electro-mechanical systems (MEMS/NEMS). This broad subject covers molecular dynamics behaviors, boundary conditions, molecular momentum accommodations, theoretical and phenomenological models in terms of gas-solid and liquid-solid interfaces affected by various physical factors, such as fluid and solid species, surface roughness, surface patterns, wettability, temperature, pressure, fluid viscosity and polarity. This review offers an overview of the major achievements, including experiments, theories and molecular dynamics simulations, in the field with particular emphasis on the effects on microfluidics and nanofluidics in nanoscience and nanotechnology. In Section 1 we present a brief introduction on the backgrounds, history and concepts. Sections 2 and 3 are focused on molecular momentum transport at gas-solid and liquid-solid interfaces, respectively. Summary and conclusions are finally presented in Section 4

Theoretical aerothermal concepts for configuration design of hypersonic vehicles

Convection coefficients and heat fluxes due to aerodynamic heating on critical surfaces of hypersonic vehicle are obtained analytically. The applicability of recovery temperature for stagnation regions is discussed. Convection coefficient for the bicurvature forward stagnation region is obtained directly from 2-D stagnation region correlation, using the two principal radii of curvatures. Convective heat flux to swept-back leading edge (SBLE) surface is obtained from the 2-D stagnation region and flat plate heat fluxes, using the respective velocity vector components. Results reveal the concepts of temperature-minimised-sweepback, and the thermally-benign sharp SBLE effect at high sweepback angles.© Elsevie

Heat transfer studies in microchannels

From a survey on studies on convection in microchannels, the Brinkman number is proposed as a parameter for correlating the Nusselt number. This proposal emerges from a dimensional analysis of the variables influencing the laminar forced convective heat transfer in microchannels, and explains the hitherto unusual behaviour of convective heat transfer in microchannels. The physical significance of the Brinkman number, as applicable to microchannels and its role in convective heat transfer are elaborated. The experimental data reported in the literature and those obtained from present experiments for the laminar regime heat transfer, correlate much better with the inclusion of the Brinkman number in the correlation. A dimensionless geometric parameter is also proposed in the correlation. The experimental data in the literature have also indicated that there are unexplained unusual behaviours associated with flow transitions in microchannels. In particular, the geometry of the microchannels and Reynolds number alone do not determine the flow regime boundaries and the transition range. The experimental data are processed based on the correlation of the single-phase convective heat transfer with the Brinkman number, from which the Reynolds and Brinkman numbers at the flow transition points are obtained for fixed microchannel geometry. The transition range is found to vary due to the difference in the extent of the rol6-played by the Brinkman number in determining the laminar-to-transition and transition-to-turbulent boundaries.Doctor of Philosophy (MPE