Biodiesel Production Facilities from Vegetable Oils and Animal Fats

Abstract

Biodiesel is a renewable fuel that can be produced from vegetable oils, animal fats, and used cooking oil including triglycerides. Biodiesel, an alternative biodegradable diesel fuel, is derived from triglycerides by transesterification with methanol and ethanol. Concerns about the depletion of diesel fuel reserves and the pollution caused by continuously increasing energy demands make biodiesel an attractive alternative motor fuel for compression ignition engines. There are four different ways of modifying vegetable oils and fats to use them as diesel fuel, such as pyrolysis (thermal cracking), dilution with hydrocarbons (blending), emulsification and transesterification. The most commonly used process is transesterification of vegetable oils and animal fats. The transesterification reaction is affected by molar ratio of glycerides to alcohol, catalysts, reaction temperature, reaction time and free fatty acids and water content of oils or fats. In the transesterification, free fatty acids and water always produce negative effects, since the presence of free fatty acids and water causes soap formation, consumes catalyst and reduces catalyst effectiveness, all of which result in a low conversion. Biodiesel has over double the price of diesel. The high price of biodiesel is in large part due to the high price of the feedstock.     

New Options for Conversion of Vegetable Oils to Alternative Fuels

Biodiesel from transesterification of vegetable oils is an excellent alternative fuel. There is, however, a need to develop a direct process for conversion of vegetable oils into gasoline-competitive biodiesel and other petroleum products. Methyl esters of vegetable oils have several outstanding advantages among other new-renewable and clean engine fuel alternatives. The purpose of the transesterification process is to lower the viscosity of vegetable oil. Compared to No. 2 diesel fuel, all of the vegetable oils are much more viscous, whereas methyl esters of vegetable oils are slightly more viscous. The methyl esters are more volatile than those of the vegetable oils. Conversion of vegetable oils to useful fuels involves the pyrolysis and catalytic cracking of the oils into lower molecular products. Pyrolysis produces more biogasoline than biodiesel fuel. Soap pyrolysis products of vegetable oils can be used as alternative diesel engine fuel. The soaps obtained from the vegetable oils can be pyrolyzed into hydrocarbon-rich products. Zinc chloride catalyst contributed greatly to high amounts of hydrocarbons in the liquid product. The yield of ZnCl ₂ catalytic conversion of the soybean oil reached the maximum 79.9% at 660 K.     

Characteristics of transient heat transfer during quenching of a vertical hot surface with a falling liquid film

An experimental study has been conducted to elucidate characteristics of transient heat transfer during quenching of a vertical hot surface with a falling liquid film. The experiment was done at atmospheric pressure for the following conditions: an initial surface temperature from 200 to 400^°C, a subcooling of 20– 80 K, average velocity of 0.52– 1.24 m/s, and the block material is copper and carbon steel. The surface temperature and heat flux are estimated from the measured temperatures in the block during the quench by a two‐dimensional inverse solution. It follows that as the position of wetting advances downward, the position at which the heat flux becomes a maximum also advances downward. The time at which the position of maximum heat flux begins to move is one of the most important parameters and can be predicted by a proposed correlation. In addition, it is revealed that the maximum heat flux for copper depends on the length to which it occurs from the leading edge. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(6): 345– 360, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20167     

Experimental Investigation of Heat Transfer Characteristics and Cooling Performance of Mini‐ and Microheat Exchangers

This paper presents an experimental investigation of forced convection heat transfer in two heat sinks for electronic system cooling and investigated the comparisons of the thermal behavior of the mini‐ and microchannel heat exchangers. The hydraulic dimension of one of the heat sinks is 2 mm while that of the other is . Deionized water was used as the working fluid for studies conducted in both the heat exchangers. The effect of heat flux and volumetric flow rate (in laminar flow regime) on temperature and heat transfer coefficient is studied. Irrespective of the average heat transfer coefficient and the total thermal resistance, advantages and limitations of each device are analyzed and discussed in the light of experimental results. Furthermore, the results obtained from the experiments were in good agreement with those obtained from the design theory analyses.     

无内热源下R134a喷雾冷却瞬态过程研究

搭建以R134a为制冷工质的闭式喷雾冷却试验台,试验研究喷雾冷却瞬态传热过程,建立了准确描述其传热过程的试验曲线,分析了蒸发压力对传热性能的影响,并阐述了每个瞬态传热阶段的传热机理。试验蒸发压力变化范围为0.207~0.331 MPa,流量范围为0.140~0.164 L/min。结果表明:膜态沸腾区在瞬态冷却过程中所占时间最长,且表面温度冷却速率保持在0.10 ℃/s,热流密度维持在20 W/cm2以下,故穿越膜态沸腾区的耗时决定着喷雾冷却瞬态过程的冷却速率;增加蒸发压力,可以提升冷却速率,当蒸发压力从0.207 MPa增加到0.331 MPa时,表面温度从130 ℃冷却至30 ℃所需的时间从508 s降至381 s;喷雾冷却瞬态过程在过渡沸腾区存在表面温度突变点,随着蒸发压力提高,突变点对应温度增加。     

无沸腾喷雾冷却中流量和喷头高度对换热性能的影响

采用薄膜电阻加热器进行了喷头进口压力，喷头类型，喷头高度对换热系数影响的实验研究。研究了冷却介质的质量流量对换热性能的影响，并测量了同一喷头在不同喷头高度下的换热系数大小。实验发现当喷雾面积近似等于实验用薄膜加热器面积时冷却能力达到最大。根据以上实验结果可以最优化喷雾冷却性能。     

AGTB叶型前缘气膜冷却效果的数值模拟研究

以AGTB叶型为对象,对文献中获取换热系数的两种计算方法进行了对比研究,结果表明维持主流和射流温度一致的等温法不能很好地反映气膜冷却流动中的传热现象,而主流和射流有温差的非等温法使得传热现象和流动现象都得到了很好的反映,且更接近实际物理问题.而后以实际发动机中的AGTB叶型为研究对象,将开槽气膜冷却孔结构应用于该叶片,...     

热电(冷)联产系统的优化性能

依据有限时间热力学原理导出了不可逆热电联产和热电(冷)联产系统在系统最大火用输出时的基本优化关系,确定了热电(冷)联产系统优化参数和优化构形选取范围,得到了供热(制冷)和发电间的匹配优化特性,通过数值算例得出不同参数对系统性能影响的规律。所得结论可为热电(冷)联产系统的优化设计和最佳工况选择等提供理论依据。     

q∝△(T-1)的不可逆吸收式制冷系统的优化

以内可逆吸收式制冷循环模型为基础，建立一个不可逆吸收式制冷循环的模型，该模型的热传导规律为q∝△（T^-1），包括低温热源到制冷空间的热漏及工质内部耗散，工质与外部热源间的有限热传导率的不可逆性，并用于导出制冷系数与制冷率的关系及在优质状态下的传热面积的分配关系。确定了在q∝△（T^-1）规律不可逆吸式制冷系统的主要参数的实际优选范围。     

压电泵驱动闭式水冷环路传热实验研究

设计并研制全金属双腔串联有阀压电泵,利用压电泵驱动水工质在闭式环路内循环稳定流动。水冷环路热端设计为微通道结构,微通道结构能显著增强液相工质流动过程中与壁面换热速率。在压电泵驱动下,工质在微通道热端吸热,冷端放热,实现热量从热端到冷端高效传递。搭建实验测试系统,研究压电泵工作性能以及压电泵驱动水冷环路传热性能。结果表明,压电泵在开放系统和闭式系统工作性能一致。压电泵驱动电压越大,回路内液相工质流动速度越快,传热速率越高,系统热阻越低。双腔串联压电泵在120V驱动电压下,泵水流量达到167 mL/min,水冷环路热阻达到0.12℃/W。压电泵驱动闭式水冷环路具有热阻小,结构紧凑,能耗低,智能控制等优点,能更好地应用于大功率电子器件散热领域。     

工业炉炉体及烟气冷却技术分析

从能量利用，耗水量，安全性与经济性等多个方面对工业炉炉体冷地方式进行了分析与比较，指出了汽化冷却比水冷却更加节能降耗。并对加热炉与电炉烟气产邓过程－余热回收利用的两种形式进行了综合评价，从不同的角度肯定了各自的优点。     

太阳能制冷与供暖系统的设计与比较

根据上海的气候条件，以上海地区某写字楼为对象，提出4种太阳能驱动的溴化锂吸收式与电动蒸汽压缩式热泵联合制冷与供暖系统。这4种系统分别由热管式真空管集热器或抛物面槽形聚光集热器，单效或双效溴化锂吸收式制冷机，以及风冷热泵或水源热泵构成。分析比较这4种系统的节能型和经济性的结果表明，采用抛物面槽形聚光集热器＋双效溴化锂吸收式制冷机＋风冷热泵组成的系统，同时具备较好的节能性与经济性，一次能源利用率可降低约50％。     

吸附式制冷单元管的设计与性能研究

基于吸附制冷的理念,设计并研究吸附式制冷的核心部件——制冷单元管。工质对选择13X型沸石分子筛-水,设计单元管外径30 mm,吸附端长600 mm,冷凝/蒸发端长360 mm,添加可膨胀石墨以强化性能。为得到单元管的实际性能,通过实验研究制冷单元管的循环周期、温度与压力变化,并改变实验条件研究环境对制冷单元管的影响。研究结果为系统设计及吸附式制冷单元管的进一步改进提供参考。     

定量分析凝汽器冷却水管结垢对机组经济性的影响

以热力学第一定律为基础,应用传热学原理,定量分析了凝汽器冷却水管结垢对凝汽器真空、机组功率以及机组热耗率的影响。研究成果对提高电厂机组运行的经济性有着重要的现实意义。     

叶型表面曲率对离散孔气膜冷却性能的影响

由于型面曲率的影响,涡轮叶片前缘和吸力面的冷却气膜易于脱离型面,气膜冷却效果下降。本研究将叶片型线分段拟合,建立了多个单一曲率的曲面模型(R/D=-30、-75、120、∞),研究涡轮叶片表面曲率对于气膜冷却的影响。流动与传热的数值模拟采用Fluent软件,湍流模型选择RNGk-ε模型,模拟方法经平板流动进行的结果验证是可靠的。在不同吹风比(M=0.5、1.2、2.0)条件下,计算比较了不同曲率曲面上气膜单孔下游的壁面传热系数以及局部平均气膜冷却效率。结果表明:涡轮叶片型面曲率对气膜冷却效果的影响与吹风比有关。不同曲率的型线部分,应该设计采用不同的吹风比,气膜冷却效果可能取得最佳。低吹风比M<1时,凹面曲率对气膜换热系数是强化,凸面基本没有作用。高吹风比M>1时,曲率不影响换热能力,冷却效果则取决与气膜相对于型面的流动状态和与主流的掺混能力。     

Analysis of Heat Dissipation Performance between a Horizontal and Longitudinal Battery Pack Based on Forced Air Cooling

A battery pack is the main energy storage element, and directly affects the performance of an electric vehicle. Battery thermal management system research and its development for a modern electric vehicle is required. This paper selects the forced air cooling of battery pack as the research object, and uses simulation methods to research the heat dissipation performance with different structures of battery packs. The results indicate that according to the four types of transient state conditions, the rising temperature of both battery packs are significantly higher than the temperature difference, the maximum temperature rise and temperature difference of a horizontal battery pack are lower than a longitudinal battery pack. When an electric vehicle begins to decrease speed, the curves of temperature rising and temperature difference increase. This shows the internal heat is continuously rising, so even in a electric vehicle beginning to decrease speed, the fan must work. The reference basis for choosing battery pack type and an analysis of heat flow field characteristics, including fan run‐time control, are offered.     

供冷系统能耗评价模型及应用

随着人民生活水平提高,供冷系统日益普及。受全球气候变暖和能源资源短缺问题影响,供冷系统能耗控制日益受到广泛关注。为科学表征供冷系统能源消耗状况,将供冷系统划分为六个子系统,从总能系统层次上给出了适合于各类供冷系统的广义化的能耗评价一般模型。在此基础之上,结合单耗分析方法,提出了供冷系统能耗的定量计算方法。采用了热力学第一定律、热力学第二定律分析,对供冷过程的热力学本质、冷量?、供冷能力等方面展开研究,系统阐述了供冷系统的理论节能极限及理论最低能耗,并立足总能系统对供冷过程的理论极限－可逆供冷作出了说明。在北京市目前设计标准下,供冷系统理论最低燃料单耗为0.82kg/GJ,当前供冷系统能耗水平（25.27 kg/GJ）与之相比,节能潜力甚大。为验证所构建的供冷系统能耗评价一般化模型,结合北京市通州区供冷系统的实施方案,对分散电制冷、集中电制冷、分散热制冷、集中热制冷四个基本类型的供冷模式进行了实例计算分析,并与四种模式的?分析计算结果进行了比较,结果显示：所提能耗模型与?分析结果一致,电制冷燃料单耗低于热制冷,分散制冷燃料单耗低于集中制冷,集中热制冷能耗较高,应慎重发展。所提出的能耗分析评估模型为各种类型供冷系统的一般化对比评估提供了理论分析方法,同时可为城市供冷系统的规划设计提供参考。     

燃气轮机入口空气冷却系统的技术经济性能

符号说明P—发电出力Q—燃料输入热量T—大气环境温度W—燃气轮机年净增发电量price—能源价格TR—冷吨Cost—运行能耗成本下标amb—大气环境peak—峰电期间aver—平电期间fuel—燃料saving—年所节省的1前言燃气轮机作为一种启动迅速、易于实现能源梯级利用及污染排放相对较少     

某中速柴油机冷却液流动及流固耦合传热计算分析

为获得直观的流场和温度场数据,对某16缸中速柴油机建立了完整的冷却水三维模型,采用FLUENT流体计算软件对其进行了绝热CFD计算分析,得到了冷却水流速、压力等数据。考虑到各缸冷却水套为并列排布方式,各缸之间相对独立,建立了单缸的缸盖-缸套-冷却水耦合传热模型,对其进行了缸盖-缸套-冷却水耦合传热仿真,获得了各部件比较精确直观的温度场分布。结果表明:仿真结果与实测数据吻合较好,从而为柴油机冷却水套的优化设计提供了依据。     

间接空冷机组空冷塔塔群内空气流动及传热性能研究

由于具有巨大的节水优势,间接空冷机组在我国富煤少水区域得到广泛应用。研究环境风对间接空冷系统的影响机理对指导电厂运行具有重要意义。以某电厂间接空冷机组为基础,构建水平布置散热器的空冷塔群物理和数学模型,通过数值模拟方法分析环境风对塔内空气流场及空冷散热器换热性能的影响。结果表明:环境风对空冷系统塔内空气流场影响较大,进而影响空冷散热器的散热性能。随着风速的增加,空冷塔的换热性能不断恶化。在临界风速时额定负荷下,下游空冷塔换热量比上游空冷塔减少2.5%。