基于混合工质的LNG冷能分段利用研究

LNG冷能释放可分为液相区、气液两相潜热区和气相区,基于以上特点建立了与之相匹配分段的三级朗肯循环发电工艺,循环介质分别采用甲烷-乙烷-丙烷的混合物、乙烯和乙烷-丙烷-正戊烷的混合物。文章对此系统进行了模拟核算与热力学分析。结果表明,当气相区循环采用低温烟气余热时,LNG的冷能的效率可达到41.15%,比单级朗肯循环效率(21%)提高了20.15%。若三级循环均采用烟气余热作为热源时,LNG效率可达到54.33%,远远高于常规发电方式。当换热器1的出口温度为-98℃,换热器3的进口温度为-60℃时,该工艺的效率存在最大值58.45%。     

分离式热管蒸气压缩复合式空调的实验研究

因为基站机房内部的热流密度非常高,需要空调全年运行,导致用电量很大。为此,设计了一套分离式重力热管蒸气压缩复合式空调。它可以根据机房的工况在热管模式、空调模式和热管空调复合模式之间自由切换,从而降低系统的全年总能耗。实验结果表明:在室外温度为15℃、进风温度为35℃时,新系统制冷量达18.5kW,能效比为4.4;当室外温度为15℃、进风温度为25℃时,制冷量达14.6kW,能效比为3.5;与传统的空调相比,新系统的年节能率在20%到55%之间。     

HFC134a在太阳能喷射制冷系统中的性能分析

建立了系统热力学性能计算模型,分析了HFC134 a喷射系统的蒸发温度、喷嘴效率等参数对系统性能的影响。研究表明,冷凝温度改变对系统性能和喷射系数的影响大于蒸发温度的影响;混合效率每减小1%,系统COP减小5%左右;系统COP随蒸发温度的增而增,随冷凝温度的增而减。HFC134 a喷射系统设计时,尽量使蒸发温度在4—12℃,冷凝温度在30—36℃之间变化,该研究为HFC134 a在喷射系统中的设计和优化提供了技术支持。     

喷射式空调系统的实验与数值模拟研究

利用二维轴对称,真实气体模型对喷射式制冷空调系统的喷射器进行CFD计算。搭建喷射式空调实验系统,进行喷射式空调实验,验证CFD模型的可行性。利用验证的CFD模型,进行实验工况以外的数值计算,得到了喷射器在不同发生条件、蒸发条件和冷凝条件下的性能变化。在喷射器结构确定,其它条件不变时,发生温度tg必须要在一定范围内,71℃≤tg≤95℃,喷射器才能正常运行。在计算条件下,蒸发温度te越高,喷射器的性能越好。冷凝温度tc要在一定范围内:20℃≤tc≤40℃,喷射器才能正常工作。当冷凝压力低于临界压力时,喷射器的性能表现出恒能力特性。     

冬季工况条件对空调冷柜双联机性能的影响

利用中间冷却器将空调与冷柜系统连接构成空调冷柜双联机,其工作原理是利用空调冷凝器出口一部分制冷剂节流来过冷冷柜的冷凝液体。实验研究了冬季工况条件对空调冷柜双联机系统性能的影响。实验结果表明:在固定室内干、湿球温度19℃/11.5℃及冷柜温度条件下,联合运行时,冷柜排气压力及排气温度得到明显下降;随着室外温度的增加空调单位制热量与冷柜单位制冷量耗电量之和逐渐减小,相比于各自单独运行最大节省电量15.4%;在室外温度14℃条件下当制热量与制冷量之比9:1时,单独运行与联合运行耗电量相等。     

同步传热型溶液除湿空调机组的性能研究

空气调节过程中,冷凝除湿方式要求制冷剂的蒸发温度低于空气的露点温度,限制了空调器效率的提高.本文在传统的热泵空调机组的基础上,添加一个溶液除湿循环,利用吸湿性溶液调节空气的含湿量,此时制冷剂的蒸发温度可以较大幅度地提高,吸湿后的溶液用冷凝器的排热再生。文章计算了复合式空调机组在两种工作模式下的性能,研究了内部冷却流体温度、回热器效能和室外空气状态等因素对机组性能的影响。分析结果表明,溶液式复合空调机组具有较大的温、湿度调节范围,且机组效率较冷凝除湿机组显著提高。     

槽式集热器效率分析和互补电站镜场设计

为实现给水加热型互补发电系统中太阳岛与动力岛更好耦合,本文建立了槽式集热器炯效率的热力学模型,分析了200 kW典型集热器效率随运行参数的变化规律:平均辐照600 W/m~2时最大效率为33%左右,最佳温度范围为250～350℃,并进行了实验验证,最后分析了互补发电系统集热场效率在设计辐照和偏离设计辐照时的特性规律,初步给出了热互补电站设计的原则。本研究结果为太阳能与火电互补发电技术的集热场设计提供了一个基本依据,具有较好的工程实用价值。     

新型复合固体除湿材料的吸附和解吸性能研究

为实现固体除湿系统吸附材料的低温再生及提高吸附材料的除湿效率,制备了新型复合固体除湿材料。新型复合固体除湿材料是以陶瓷纤维为基质,运用MgCl2浸渍改性硅胶及CaCl2二次强化方法而形成的复合物,复合固体除湿材料中MgCl2和CaCl2浓度均为25%。通过恒温恒湿空调室实验研究温度、风速、湿度对MgCl2/CaCl2改性复合材料除湿性能及再生特性。实验表明:在温度20℃、湿度70%条件下,复合固体除湿材料除湿量可达161 mg/g,是未改性除湿材料的3.2倍,是单一改性除湿材料的1.3倍;当系统平衡时,其除湿速率分别是未改性除湿材料的6.1倍,是单一改性除湿材料的2.6倍。除湿材料的平衡吸附量和吸附速率均与相对湿度成正比,与温度成反比;且风速在0.5 m/s条件时具有最大的除湿量。同时,在约70℃较低的脱附温度,8 min可脱附≥90%的总吸附水量,每1 g吸附剂可脱附水量高达145 mg;脱附再生6次后,除湿量依然较高为138 mg/g,且基本不再变化。     

机房专用空调性能研究

以名义制冷量为40kW的机房专用空调为对象,研究被控温度24℃、相对湿度50%,冷凝器进风温度-5~35℃条件下的机房空调性能。用焓差实验室测试空调机在不同冷凝温度条件下的性能参数,从而分析系统各部件的匹配关系、整机性能及在变冷凝温度下的综合性能。实验结果表明,调整蒸发器结构、增加风速、合理匹配热量膨胀阀,降低系统部件和管道阻力等,能使机房空调机在标准制冷工况下COP、变工况下COP以及综合COP都有较大幅度提高。     

水蒸气超高温热泵系统的实验研究

近年来以低温室效应(GWP)的制冷剂的蒸汽压缩式高温热泵一直是余热回收领域的研究热点。为获得更高的输出温度,本课题组搭建了一台采用自然工质水作为循环冷媒的超高温热泵样机并进行了实验测试。实验结果表明蒸发温度为80℃,冷凝温度从115℃升至145℃时,热泵的COP从4.88降至1.89。在85℃蒸发,117℃冷凝时,最高COP为6.1,制热量为285 kW,同时在85℃蒸发时,该热泵的最高冷凝温度可达到150℃,此时COP为1.96。在相同的温升下,热泵的COP和卡诺效率都随着输出温度的升高而增加,因此我们认为该热泵更适合高温输出的应用场合。     

The effect of geometrical characteristics of wavy strip turbulator and thermodynamic properties of fluid on exergy loss and heat transfer in a tube in tube heat exchanger

The present work conducts an experimental investigation into the influence of flow, thermodynamic and geometrical characteristics of the wavy strip on exergy loss and dimensionless exergy loss in a tube in tube heat exchanger. The working fluid is water with hot water passing the inner tube and cold water passing annulus. Wavy strips with four different angles and three widths were investigated experimentally. The result of exergy loss and dimensionless exergy loss for various conditions is presented and on the basis of curve fitting, three empirical correlations are suggested to predict dimensionless exergy loss in a double tube heat exchanger.     

Exergy Analysis Using a Theoretical Formulation of a Geothermal Power Plant in Cerro Prieto,México

The purpose of this research is the calculation of the exergy destruction of the single-flash and double-flash cycles of a geothermal power plant located on the ladder of the 233 m Cerro Prieto volcano, on the alluvial plain of the Mexicali Valley, Mexico. The methodology developed in this research presents thermodynamic models for energy and exergy flows, which allows determining the contribution of each component to the total exergy destruction of the system. For the case-base, the results indicate that for the single-flash configuration the efficiency of the first and second law of thermodynamics are 0.1888 and 0.3072, as well as the highest contribution to the total exergy destruction is provided by the condenser. For the double-flash configuration, the efficiency of the first and second law of thermodynamics are 0.3643 and 0.4983. The highest contribution to the total exergy destruction is provided by the condenser and followed by the low-pressure turbine.     

单耗分析理论与结构系数法的对比分析

本文简要阐述了结构系数法和能源利用的单耗分析理论,并针对链式系统进行了初步的对比分析;尽管都是基于热力学第二定律的分析方法,并且它们的结果有一定的相似性,但结构系数法存在某些错误。比较而言,单耗分析理论显得更全面,也更实用。本文以锅炉供热系统为对象进行了详细的单耗分析,对系统中间子系统的(火用)耗损变化所带来的影响进行了详细的分析,结果证明结构系数法所作的“某一子系统(火用)效率变化,其他子系统(火用)效率不变”的假设是不恰当的, 其结论也是不准确的。     

Performance and Exergy Analyses of a Solar Assisted Heat Pump with Seasonal Heat Storage and Grey Water Heat Recovery Unit

The main research objective of this paper was to compare exergy performance of three different heat pump (HP)-based systems and one natural gas (NG)-based system for the production of heating and cooling energy in a single-house dwelling. The study considered systems based on: 1. A NG and auxiliary cooling unit; 2. Solely HP, 3. HP with additional seasonal heat storage (SHS) and a solar thermal collector (STC); 4. HP with SHS, a STC and a grey water (GW) recovery unit. The assessment of exergy efficiencies for each case was based on the transient systems simulation program TRNSYS, which was used for the simulation of energy use for space heating and cooling of the building, sanitary hot water production, and the thermal response of the seasonal heat storage and solar thermal system. The results show that an enormous waste of exergy is observed by the system based on an NG boiler (with annual overall exergy efficiency of 0.11) in comparison to the most efficient systems, based on HP water–water with a seasonal heat storage and solar thermal collector with the efficiency of 0.47. The same system with an added GW unit exhibits lower water temperatures, resulting in the exergy efficiency of 0.43. The other three systems, based on air–, water–, and ground–water HPs, show significantly lower annual source water temperatures (10.9, 11.0, 11.0, respectively) compared to systems with SHS and SHS + GW, with temperatures of 28.8 and 19.3 K, respectively.     

立式升温型溴化锂吸收式热泵的设计与变工况研究

本文对立式升温型溴化锂吸收式热泵循环和各部件建立了数学模型,并设计了85℃热水驱动产110℃热水的立式降膜升温型溴化锂吸收式热泵,吸收器输出功率为50 kW。然后对其在热源热水温度和流量变化、冷却水入口温度和流量改变等非设计工况下的工作特性进行了计算与分析研究,得到变工况对于机组性能系数,效率和机组负荷的影响关系图。发现在我们的研究范围内,热源水参数的变化对机组性能的影响要大于冷却水。并且在热源水参数变化过程中,机组性能存在性能急剧变化的拐点,实际运行中应当避免。     

能··传递链式发展的相贯性及必然性

依据热力学第一、第二定律(下文简称一、二定律)阐述了能具有量和质的双重属性,能量与能质系于同一属体而不可分离。(火用)是由热力学第二定律所赋予的用以表征能质的参数。能量传递必然伴随着能质(火用)的传递,(火用)传递如同热传递一样是客观存在的。由(火用)概念发展到(火用)传递有其必然性。     

喷射-闪蒸复合制冷性能研究

为充分利用工业废热、提高能源利用效率、减少热排放,将喷射制冷与闪蒸制冷进行有机结合,以工业生产中产生的大量废热蒸汽为动力,利用喷射器的抽吸原理,通过蒸发冷却将闪蒸器中的水冷却至5～10℃,混合冷凝器则可输出50～60℃热水,达到同时实现制冷和制热,满足不同用户要求的目的.     

混合制冷剂循环液化天然气流程(火用)分析

带丙烷预冷的混合制冷剂循环液化天然气流程具有高效及流程相对简单的优点.本文在对流程进行热力学分析的基础上,对流程进行(火用)分析.计算了流程中各设备的(火用)损失,计算结果表明,压缩机的(火用)损失约占整个流程(火用)损失的50%,换热器的(火用)损失约占总(火用)损失的26%.本文还分析了产生(火用)损失的原因,提出降低(火用)损失的措施.     

Exergy Analysis of a Bio-System: Soil–Plant Interaction

This paper explains a thorough exergy analysis of the most important reactions in soil–plant interactions. Soil, which is a prime mover of gases, metals, structural crystals, and electrolytes, constantly resembles an electric field of charge and discharge. The second law of thermodynamics reflects the deterioration of resources through the destruction of exergy. In this study, we developed a new method to assess the exergy of soil and plant formation processes. Depending on the types of soil, one may assess the efficiency and degradation of resources by incorporating or using biomass storage. According to the results of this study, during different processes from the mineralization process to nutrient uptake by the plant, about 62.5% of the input exergy will be destroyed because of the soil solution reactions. Most of the exergy destruction occurs in the biota–atmosphere subsystem, especially in the photosynthesis reaction, due to its low efficiency (about 15%). Humus and protonation reactions, with 14% and 13% exergy destruction, respectively, are the most exergy destroying reactions. Respiratory, weathering, and reverse weathering reactions account for the lowest percentage of exergy destruction and less than one percent of total exergy destruction in the soil system. The total exergy yield of the soil system is estimated at about 37.45%.     

与节能

是在热力学和能源科学中出现的新概念，是评价能量价值的重要参数，它对能源的开发和合理利用具有重大的理论意义和实际意义．文章介绍了的概念、效率、分析法和的合理利用．