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The success of vapour phase soldering for electronic assemblies has led to the availability of several heat transfer fluids for the purpose. This paper aims to demonstrate the significance of the differing properties of fluids, illustrated by measurements on the three most commonly used in the UK. These three, as well as any future fluids, can be judged in terms of (i) vapour temperature and its influence on soldering yields and materials properties; (ii) stability of soldering temperature with time; (iii) heat transfer efficiency; (iv) power requirements and thermal control; (v) rosin solubility and flux wash‐off; (vi) toxicity, especially under thermal stress; (vii) corrosivity and its dependence on process control; and (viii) consumption of fluid.

This paper seeks to discuss a mechanistic modeling concept for local phenomena governing two‐ and multi‐phase flows and heat transfer.

An overview is given of selected issues concerning the formulation of multidimensional models of two‐phase flow and heat transfer. A complete computational multiphase fluid dynamics (CMFD) model of two‐phase flow is presented, including local constitutive models applicable to two‐phase flows in heated channels. Results are shown of model testing and validation.

It has been demonstrated that the overall model is capable of capturing various local flow and heat transfer phenomena in general, and the onset of temperature excursion (CHF) in low quality forced‐convection boiling, in particular.

Whereas the multiphase model formulation is applicable to a large class of problems, geometries and operating conditions, the closure laws and results are focused on forced‐convection boiling in heated channels.

The proposed approach can be used to predict multidimensional velocity field and phase distribution in two‐phase flow devices and components used in thermal power plants, nuclear power plants and chemical processing plants.

A complete mechanistic multidimensional model of forced‐convection boiling in heated channels is given. The potential of a CMFD approach is demonstrated to perform virtual experiments that can be used in system design and optimization, and in safety analysis.

The purpose of this paper is to develop new semi-empirical heat transfer correlations for turbulent flow of liquid metals in the tubes, and then to compare these correlations with the experimental data. The Prandtl and Reynolds numbers can vary in the ranges: 0.0001 ≤ Pr ≤ 0.1 and 3000 ≤ Re ≤ 10⁶.

The energy conservation equation averaged by Reynolds was integrated using the universal velocity profile determined experimentally by Reichardt for the turbulent tube flow and four different models for the turbulent Prandtl number. Turbulent heat transfer in the circular tube was analyzed for a constant heat flux at the inner surface. Some constants in different models for the turbulent Prandtl number were adjusted to obtain good agreement between calculated and experimentally obtained Nusselt numbers. Subsequently, new correlations for the Nusselt number as a function of a Peclet number was proposed for different models of the turbulent Prandtl number.

The inclusion of turbulent Prandtl number greater than one and the experimentally determined velocity profile of the fluid in the tube while solving the energy conservation equation improved the compatibility of calculated Nusselt numbers, with Nusselt numbers determined experimentally. The correlations proposed in the paper have a sound theoretical basis and give Nusselt number values that are in good agreement with the experimental data.

Heat transfer correlations proposed in this paper were derived assuming a constant heat flux at the inner surface of the tube. However, they can also be used for a constant wall temperature, as for the turbulent flow (Re > 3,000), the relative difference between the Nusselt number for uniform wall heat flux and uniform wall temperature is very low.

Unified, systematic approach to derive correlations for the Nusselt number for liquid metals was proposed in the paper. The Nusselt number was obtained from the solution of the energy conservation equation using the universal velocity profile and eddy diffusivity determined experimentally, and various models for the turbulent Prandtl number. Four different relationships for the Nusselt number proposed in the paper were compared with the experimental data.

Subcooled flow boiling phenomenon is characterized by coolant phase change in the vicinity of the heated wall. Although coolant phase change from liquid to vapour phase significantly enhances the heat transfer coefficient due to latent heat of vaporization, eventually the formed vapor bubbles may coalesce and deteriorate the heat transfer from the heated wall to the liquid phase. Due to the poor heat transfer characteristics of the vapour phase, the heat transfer rate drastically reduces when it reaches a specific value of wall heat flux. Such a threshold value is identified as critical heat flux (CHF), and the phenomenon is known as departure from nucleate boiling (DNB). An accurate prediction of CHF and its location is critical to the safe operation of nuclear reactors. Therefore, the present study aims at the prediction of DNB type CHF in a hexagonal sub-assembly.

Computational fluid dynamics (CFD) simulations are performed to predict DNB in a hexagonal sub-assembly. The methodology uses an Eulerian–Eulerian multiphase flow (EEMF) model in conjunction with multiple size group (MuSiG) model. The breakup and coalescence of vapour bubbles are accounted using a population balance approach.

Bubble departure diameter parameters in EEMF framework are recalibrated to simulate the near atmospheric pressure conditions. The predictions from the modified correlation for bubble departure diameter are found to be in good agreement against the experimental data. The simulations are further extended to investigate the influence of blockage (b) on DNB type CHF at low operating pressure conditions. Larger size vapour bubbles are observed to move away from the corner sub-channel region due to the presence of blockage. Corner sub-channels were found to be more prone to experience DNB type CHF compared to the interior and edge sub-channels.

An accurate prediction of CHF and its location is critical to the safe operation of nuclear reactors. Moreover, a wide spectrum of heat transfer equipment of engineering interest will be benefited by an accurate prediction of wall characteristics using breakup and coalescence-based models as described in the present study.

Simulations are performed to predict DNB type CHF. The EEMF and wall heat flux partition model framework coupled with the MuSiG model is novel, and a detailed variation of the coolant velocity, temperature and vapour volume fraction in a hexagonal sub-assembly was obtained. The present CFD model framework was observed to predict the onset of vapour volume fraction and DNB type CHF. Simulations are further extended to predict CHF in a hexagonal sub-assembly under the influence of blockage. For all the values of blockage, the vapour volume fraction is found to be higher in the corner region, and thus the corner sub-channel experiences CHF. Although DNB type CHF is observed in corner sub-channel, it is noticed that the presence of blockage in the interior sub-channel promotes the coolant mixing and results in higher values of CHF in the corner sub-channel.

The paper aims to understand the process of transfer of agricultural technology, which comprises incubation of the technology business, valuation, evaluation, licensing and commercialization, to examine various dimensions of the process of technology transfer and the effectiveness of transfer object use criteria, to explore ways of sustaining incubation and commercialization through an autonomous unit responsible for technology transfer, to peruse the role of agribusiness incubators in creating an effective agri-entrepreneurship eco-system and to study the factors that promote or inhibit the sustainability of business incubators in an academic or research institution setting.

An innovative technology for production of liquid bio-fertilizers was developed and nurtured to market levels by Anand Agricultural University (AAU), a State Agricultural University in Gujarat. The technology for production of liquid bio-fertilizers, developed during 2009-2010 to 2013-2014 was licensed to some of the state public and private sector undertakings under the World Bank-financed National Agricultural Innovation Project (NAIP) implemented through Indian Council of Agricultural Research (ICAR). For commercializing the technologies from the University, a Business Planning and Development (BPD) Unit was set up at AAU along the lines of a technology transfer office, under the aegis of NAIP during later part of 2009. The NAIP funding from World Bank for BPD Units ceased in June 2014 with closure of the project. With funding no more available, Rajababu V. Vyas, a research scientist at the Microbiology and Bio-fertilizer Department of the University and Head of the BPD Unit, had serious concerns about the BPD unit’s sustainability, as well as sustaining the process of technology transfer from the University.

Anand Agricultural University (AAU), a state-run university in Gujarat, developed and incubated a technology to produce liquid biofertilizer, licensed the technology and marketed its product through a few state-run and private fertilizer firms. The technology was developed between 2009/2010 and 2013/2014 as part of the National Agricultural Innovation Project of the Indian Council of Agricultural Research with funds from the World Bank. A unit to incubate agri-businesses, referred to as Business Planning and Development Unit (BPDU), was set up in late 2009 to expedite the process of technology transfer from AAU to agribusiness firms. Rajababu V. Vyas, a research scientist at the Microbiology and Bio-fertilizer Department of the university, was concerned about the unit’s sustainability, because funding from the World Bank had ceased from June 2014, and wondered how to sustain the transfer of technology from the laboratory to the field in the light of the data available to him.

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Entrepreneurship

The purpose of this paper is to investigate thermal comfort performances of socks produced from cotton and regenerated cellulosic fiber yarns by thermal resistance (by a newly designed foot thermal manikin), moisture management tester (MMT) parameters and permeability (air and water vapor) tests.

Single jersey fabrics and socks were knitted from 30 Ne yarns produced from cotton, different regenerated cellulosic fibers (viscose, modal, bamboo, micromodal, Tencel®, Tencel LF®) and their blends. Thermal resistances of the socks were compared by a newly developed thermal foot manikin in a more realistic way than measurements in fabric form. Besides air and water vapor permeability, moisture management parameters of the fabrics were tested to differentiate performances of cellulosic fibers.

Results show that air permeability, liquid absorption and transfer parameters measured by MMT are generally identical and better for regenerated cellulosic fabrics than cotton. Micromodal and Tencel® have better performances for liquid transfer and overall moisture management capacities are superior for bamboo and Tencel LF®. Thermal resistances of the socks are minimum for Tencel LF® having a cross-linked structure and maximum for viscose socks.

It is thought that thermal resistance measured in socks form is more realistic than fabric measurements and results of this study that can be valid for all knitted garments. Moreover, comprehensive material plan of the study is valuable for getting reliable results for regenerated cellulosic fibers that have small differences in cases of thermal resistance and liquid transfer.

Sleep quality, a crucial parameter for health and life performance, is affected by mattress components; particularly mechanical and thermal comfort management ability of the upper layers. The aim of this study is to investigate effects of quilted mattress ticking fabric material (polyester, polypropylene, viscose, lyocell and their blends) on thermal comfort of the bedding system by objective and subjective measurements.

The permeability (air and water vapour), heat transfer, water absorption, transfer and drying behaviours of knitted quilted fabrics which influence the thermal comfort of the bedding system were investigated. Subjective coolness and dampness evaluations were gathered by forearm and hand-palm tests to provide more realistic discussion in light of fabric characteristics.

According to the results, polypropylene can be suggested for winter use with its higher air and water vapour permeabilities, lower thermal absorption and conductivities and warmer evaluation results. Lyocell can be suggested for summer use with also high permeabilities, higher thermal absorption and conductivities and cooler evaluation results. Polyester and viscose may also be considered for winter and summer in turn as a result of thermal feelings they create.

In addition to fabric thermal, permeability, liquid absorption and transfer properties, this study also includes subjective coolness and dampness evaluations which can provide realistic results regarding the coolness-to-touch and liquid transfer performances of mattress ticking fabrics. The relationships among objective and subjective data were investigated and the proposed subjective evaluation techniques can be used for different products.

A Lagrangian finite element algorithm is described for solving two‐dimensional, time‐dependent free surface fluid flows such as those that occur in industrial printing processes. The algorithm is applied using a problem specific structured meshing strategy, implemented with periodic remeshing to control element distortion. The method is benchmarked on the problem of a stretching filament of viscous liquid, which clearly demonstrates the applicability of the approach to flows involving substantial free surface deformation. The model printing problem of the transfer of Newtonian liquid from an upturned trapezoidal trench (3‐D cavity with a large transverse aspect ratio) to a horizontal substrate, which is pulled perpendicularly downwards from the cavity, is solved computationally using the Lagrangian scheme. The idealized 2‐D liquid motion is tracked from start‐up to the point where a thin sheet forms – connecting the liquid remaining in the cavity to a “sessile” drop on the moving substrate. The effect of varying substrate separation speed is briefly discussed and predictions are made for approximate drop volumes and “limiting” domain lengths.

The paper aims at studying numerically a vapour bubble growth in uniformly superheated liquid.

Time dependent mathematical and numerical models are developed. Based on the Stefan boundary condition, the rate of heat transfer at the vapour‐liquid interface and the rate of bubble growth are calculated.

It is found that, at the initial stage of bubble growth, both the growth rate and the mean Nusselt number at bubble interface have the maximum values, then they decrease with time; the rate of bubble growth also has a significant effect on bubble deformation; the growth tends to keep the bubble at its initial shape. In addition, the growth and deformation of a vapour bubble have much influence on temperature propagation in the vicinity of the bubble‐liquid interface; the temperature wake at the rear of the bubble occurs at high Reynolds number but does not appear at low Reynolds number.

The paper is based on the authors' original work, focusing on the behaviour of a vapour bubble in uniformly superheated liquid–an issue of importance in the field of boiling and two phase flow.

THE problem of the dissipation and transfer of heat is one that is becoming of increasing importance in aircraft with the introduction of gas‐turbines and jet propulsion as well as in view of the prospects of flight at high altitudes. We are therefore printing below summaries of all the papers read at the recent Anglo‐American conference on the subject, although some of them are not directly concerned with aeronautical applications.