A Nonlinear Fin Design Problem in Estimating the Optimal Shapes of Longitudinal and Spine Fully Wet Fins

In the present nonlinear fully wet fin design problem, the optimum shapes for the longitudinal and spine fins are estimated by using the conjugate gradient method (CGM) based on the desired fin efficiency and fin volume. For many practical engineering applications, thermal conductivity and heat transfer coefficient of fin are a function of temperatures. This makes the design problem nonlinear and complicated. For this reason, the present work is focused on examining these kinds of design problems. The validity of this design algorithm using CGM to solve the nonlinear fin design problems are justified based on the numerical experiments. Results show that when the Biot number, relative humidity, and thermal conductivity are varied, the optimum fin efficiency and optimum fin shape are also subjected to change, and any reasonable designs for fully wet fins can always be obtained.     

An Analytical Approach to Determine the Optimal Resistance for the Three-Series-Resistor Method for Induction Generator Connection

This letter presents a set of analytical formulas to determine the optimal resistor size to be used in the three-series-resistor method of squirrel-cage induction generators connection. The analytical formulation is based on the short-circuit theory of induction machines.      

Neural-Network-Assisted Optimization of Rectangular Channels with Intersecting Ribs for Enhanced Thermal Performance

Abstract

Optimization of rectangular cooling channels with intersecting ribs was performed to determine optimal rib configurations for thermal performance enhancement using Reynolds averaged Navier-stokes equations at Reynolds number of 10,000. The study aims to achieve two-fold objectives: (1) to maximize the thermal performance in three different rectangular channels with aspect ratios equal to 1, 2, and 4, respectively at a fixed hydraulic diameter and (2) analyze the trend in optimum design variables with change in aspect ratio. Angle of attack, position of the intersecting rib relative to channel center-line, and height of rib were selected as design variables for optimization. The objective function viz. thermal efficiency was formulated using radial basis neural network and particle swam optimization was used to determine the optimal point. The thermal performance of the channel was found to be sensitive to the chosen design variables, and strongly governed by rib-induced secondary motion. As a result of optimization, the optimal design showed an enhancement of 14.4, 12.8, and 16.2% in overall thermal efficiency for channels with aspect ratios 1, 2, and 4, respectively. Finally, to achieve maximum thermal efficiency, shift in optimum design variables was observed with change in aspect ratios of rectangular channels.     

大功率喷油泵试验台的设计要点探讨

大功率柴油机喷油泵对试验台有许多特殊的要求．本文总结了作者长期研究设计油泵试验台的经验。     

摩托车化油器起动平稳性优化设计

根据化油器起动加浓阀总成的起动油道供油特性和PTC加热片的温度特性,调整化油器蜡式起动加浓阀总成的起动柱塞组件突出尺寸,优化设计化油器的起动柱塞、起动油针和起动块本体,同时提出了低温起动平稳性的评价方法,从而改善了摩托车在不同气候环境下的低温平稳起动性能.     

A Two-Dimensional Numerical Analysis for Thermal Performance of an Intermittently Operated Radiant Floor Heating System in a Transient External Climatic Condition

Abstract

Building thermal inertia and operation control strategies have impacted on the thermal performance of a radiant floor heating system. This study conducts a two-dimensional numerical analysis of an intermittently operated radiant floor heating system using the Re-Normalization Group model with Discrete Ordinates Radiation model. A detailed numerical simulation setups and various analyses are provided, including grid independency analysis, initial condition, time step sizes and external boundary conditions. Three different weekend day intermittent operation strategies are investigated. The results showed that Case 3 designed with pre-heating of 20?h has better performance compared to Case 1 designed with pre-heating of 8?h and Case 2 designed with pre-heating of 14?h. The average indoor air temperature differences of approximate 2.1, 1.6 and 1.2 K are observed for Case 1, Case 2 and Case 3, respectively, when comparing two-time slot at 8:00am on Friday morning and Monday morning. This significantly highlights the effect of thermal inertia and the potential of energy saving due to the utilization of intermittent operation. Therefore, the current study presents numerical simulation potential in evaluating the radiant floor heating effects on indoor thermal environment, taking into account building thermal inertia and transient external climatic conditions.     

冷却风扇变密流型扭叶片设计方法及其气动特性的数值研究

利用"径向平衡"原理,推导了轴流叶轮出口通流速度沿叶高的分布方程,并基于此提出了一种新的"变密流型"扭叶片设计方法.将该方法运用于某型叶轮的设计,并采用CFD技术,研究了该类扭叶片的气动特性.通过与传统的"等密流型"扭叶片及原始直叶片的气动性能的比较,发现"变密流型"扭叶片不仅能扩大小流量下风扇的稳定工况范围,而且其风压明显增加,有助于提高冷却风扇的散热性能.     

Thermal modeling of a natural convection greenhouse drying system for jaggery: An experimental validation

The aim of this work is to develop a thermal model so as to predict the jaggery temperature, the greenhouse air temperature and the moisture evaporated (jaggery mass during drying), during the drying of jaggery under natural convection conditions. The experiment was conducted separately for 0.75 kg and 2.0 kg of jaggery pieces having dimensions of 0.03 × 0.03 × 0.01 m³ for complete drying. The jaggery was dried in a roof-type even span greenhouse with floor area of 1.20 × 0.78 m². Experiment was carried out during February 5–8, 2004 at IIT Delhi (28°35′N 72°12′E) from 10 am to 5 pm. A computer program was developed in MATLAB software so as to calculate the jaggery temperature, the greenhouse air temperature and the moisture evaporated and was also used to predict the thermal performance of the greenhouse on the basis of solar intensity and ambient temperature. The software developed was experimentally validated. It was shown that the analytical and experimental results for jaggery drying are in good agreement.     

An advantageous method for methanol oxidation: Design and fabrication of a nanoporous PtRuNi trimetallic electrocatalyst

In this study, an advantageous method of methanol oxidation is developed using a nanoporous structured PtRuNi trimetallic catalyst fabricated by dealloying Ni from a high Ni-content PtRuNi alloy precursor. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are used for catalyst characterization. The nanoporous PtRuNi trimetallic catalyst shows enhanced CO oxidation, higher activity and better stability than solid commercial PtRu/C catalyst. The method developed in this study is well suited to synthesize other high performance, nanoporous-structured, multimetallic electrocatalysts for fuel cells.     

Thermal management of metal hydride hydrogen storage using phase change materials for standalone solar hydrogen systems: An energy/exergy investigation

This paper reports on an energy/exergy analysis of a standalone solar-hydrogen system with a metal hydride (MH) system thermally managed using a phase change material (PCM). This is a self-contained thermal management arrangement that stores the heat released from the MH unit, when it is being charged and transfers it back to the MH while discharging hydrogen. The first and second laws of thermodynamics were used to develop a mathematical model in MATLAB to simulate this system and quality its performance from the energy and exergy viewpoints. The model was then applied on a passive standalone house, with ～3.8 MWh/year electricity demand, located in southeast Australia. The exergy efficiencies of the solar PV, electrolyser, fuel cell and the whole solar hydrogen system were found to be 6.5%, 88%, 50.6%, and 3.74%, respectively. The paper also provides the detailed entropy generation and exergy analysis on the MH hydrogen storage unit together with its PCM-based thermal management arrangement. The results show that the annual entropy generation, exergy destruction and exergy efficiency of the MH hydrogen storage unit were 173 Wh/K, 51.5 kWh, and 98.8%, respectively.     

薄板坯连铸连轧CSP工艺缓冲性能的研究--直通式辊底炉传热模型及其数值分析

CSP工艺是薄板坯连铸连轧的主要生产工艺之一,直通式辊底炉在CSP工艺中起到加热、均热薄板坯和缓冲作用,是十分重要的热工设备.建立了描述直通式辊底炉炉内换热的长炉模型,应用预解区域法解算其辐射换热,提出了新的"显式"迭代法,对直通式辊底炉的设计和操作参数的影响进行了数值分析.     

An evaluation of energy-environment-economic efficiency for EU,APEC and ASEAN countries: Design of a Target-Oriented DFM model with fixed factors in Data Envelopment Analysis

This paper aims to offer an advanced assessment methodology for sustainable national energy-environment-economic efficiency strategies, based on an extended Data Envelopment Analysis (DEA). The use of novel efficiency-improving approaches based on DEA originates from the so-called Distance Friction Minimisation (DFM) method. To design a feasible improvement strategy for low-efficiency DMUs, we develop here a Target-Oriented (TO) DFM model. However, in many real-world cases input factors may not be flexibly adjusted in the short run. In this study, we integrate the TO-DFM model with a fixed (inflexible) factor (FF) approach to cope with such more realistic circumstances. Super-efficiency DEA is next used in our comparative study on the efficiency assessment of energy-environment-economic targets for the EU, APEC and ASEAN (A&A) countries, employing appropriate data sets from the years 2003 to 2012. We consider two inputs (primary energy consumption and population) and two outputs (CO₂ and GDP), including a fixed input factor (viz. population). On the basis of our DEA analysis results, EU countries appear to exhibit generally a higher efficiency than A&A countries. The above-mentioned TO-DFM-FF projection model is able to address realistic circumstances and requirements in an operational sustainability strategy for efficiency improvement in inefficient countries in the A&A region.