氨水吸收式制冷夹点分析法

氨水吸收式制冷需要消耗很大的公用工程,其性能系数(COP)不是很高,引入夹点分析法分析氨水吸收式制冷系统,该方法能够确定可回收的系统最大内部循环热,优化后的系统性能系数为0.623,比优化前的系统性能系数高11.58%。该方法对氨水吸收式制冷设计具有一定的指导意义。     

氨水喷射-吸收式制冷循环的研究

对喷射增压的氨水吸收式制冷循环进行分析和热力计算，分别与一般的氨水吸收式循环相比，前在相同的热源温度下，获取的最低蒸发温度能够降低10℃左右，单级喷射-吸收系统的COP一直保持在O．3左右，双级喷射-吸收系统的COP在O．2左右。虽然在较高的蒸发温度段该制冷循环的性能系数略有降低，但是它能够利用现实中许多低品位的热源获取更低的蒸发温度。     

太阳能与地热结合利用的氨水吸收式循环

利用氨水吸收式循环将太阳能与地热两个热源结合，提出了一种新颖的制冷与供热系统。由于热源温差的协调配置，该系统具有更高的能量利用特性。还研究了热源温度以及重要内部操作条件对系统制冷、供热效率的影响规律，探讨了该系统的可行性。     

利用低位能的氨水吸收式制冷（AAR）系统设计软件的开发及应用

介绍了氨水吸收式制冷系统设计中的计算机软件化过程,利用Visual Basic集成编译环境，采用OOP（面向对象编程）技术，编制基于Windows操作系统的应用软件，实现氨水吸收式制冷系统设计计算的图形化，可视化，用户可以在良好的界面和操作演示帮助的引导下完成流程选择，参数计算，设备计算等操作，对多种状态参数组合的计算结果与实际计算数据进行分析对比，得到令人满意的结果。     

利用工业余热的溶液冷却吸收式双级氨水制冷循环研究

溶液冷却吸收式氨水制冷循环利用吸收器出口经泵升压后的浓溶液来冷却吸收过程的前段,回收了部分吸收热,从而可使浓溶液在逆流式溶液热交换器中部分发生,减少了对外界热源蒸汽的需求量.该循环流程同样也适用于利用工业余热等低品位能量作为发生器加热热源的双级氨水吸收式制冷循环,计算表明该改进型循环比传统循环的COP提高23%左右,同时换热器所需的总传热面积也有所减少.     

新型太阳能吸收式制冷循环的性能分析

在两级溴化锂吸收式制冷循环的基础上,提出了一种由太阳能驱动的新型吸收式制冷循环,并对其进行性能分析。通过大量计算,分析结果表明,在现有太阳能集热器所能提供的热水温度范围内,新型太阳能吸收式制冷循环有较高的热力系数。该循环系统的中间压力、中间浓度对系统的热力系数和热源可利用温差有较大影响。     

工业余热氨水吸收式制冷系统优化研究

为了提高工业余热氨水吸收式制冷系统的综合性能,根据系统优化的三大原则,选择出影响系统性能的7个关键参数,并采用VC++编制了工业余热氨水吸收式制冷系统参数优化软件。该软件可以根据用户需要,快速准确地计算出优化后的参数,经优化软件计算得出以最小面积性能比为优化目标时,优化结果能够有效地提高系统的综合性能。     

利用工业余热的单级氨水吸收式制冷机在制冰生产中的应用

本文介绍了以工业余热为热源的单级氨水吸收式制冷机在工业制冰(蓄冰)与冰藏申的应用。通过生产性实验,初步得出了该机在生产中的性能变化规律及效率。并将该机与压缩式制冷机进行了技术经济比较,阐明了其在工业余热升级利用及节能增效中所起的作用。     

氨水吸收式制冷系统在渔船尾气中余热利用分析

渔船出海作业时,需携带冰块为渔产品保鲜,而100 t以下的中小型渔船因经济性的限制.不宜安装压缩式制冷机.文中介绍了一种渔船利用自身动力柴油机的尾气驱动氨水吸收式制冷机的技术,该技术采用可提高循环效率的溶液冷却吸收和溶液加热发生的循环方式,计算表明该改进型循环比传统循环的COP提高20%左右.     

吸收式制冷技术的应用与发展

溴化锂吸收式制冷技术在我国得到了飞速发展和广泛应用。介绍了溴化锂吸收式制冷技术在我国应用情况,对单效机,双效机及直燃机的应用场合进行了分析,同时对溴化锂吸收式制冷技术将来的发展进行了展望。     

Theoretical analysis of LiBr/H2O absorption refrigeration systems

A computational model is developed for the parametric investigation of single‐effect and series flow double‐effect LiBr/H₂O absorption refrigeration systems. The effects of generator, absorber, condenser, evaporator and dead state temperatures are examined on the performance of these systems. The parameters computed are coefficient of performance (COP), exergy destruction rates, thermal exergy loss rates, irreversibility and exergetic efficiency. The results indicate that COP and exergetic efficiency of both the systems increase with increase in the generator temperature. There exist different optimum values of generator temperature for maximum COP and maximum exergetic efficiency. The optimum generator temperature is lower corresponding to maximum exergetic efficiency as compared to optimum generator temperature corresponding to maximum COP. The effect of increase in absorber, condenser and evaporator temperatures is to decrease the exergetic efficiency of both the systems. The irreversibility is highest in absorber in both systems. Copyright © 2009 John Wiley & Sons, Ltd.     

TFE/E181,TFE/NMP及NH_3/H_2O吸收式制冷系统性能研究

对以TFE(三氟乙醇)/E181(四甘醇二甲醚),TFE/NMP(氮甲基吡咯烷酮)和NH3/H2O为工质的吸收式制冷系统进行了评价,并基于系统的性能系数COP和循环倍率f分析了发生温度、蒸发温度、冷凝温度和吸收温度对系统性能的影响。研究结果表明:各项影响因素所造成的COP和f的变化趋势基本上一致。总体来说,在相同工况下,TFE/NMP系统的COP最大,TFE/E181次之,NH3/H2O最小,而循环倍率f正好相反,NH3/H2O系统最大,TFE/E181次之,TFE/NMP最小。     

Temperature–enthalpy/entropy charts of combined ejector–absorption cycle using NH3–H2O

This paper describes the performance of an ammonia–water combine ejector–absorption cycle as refrigerator and heat pump. This combination brings together the advantages of absorption and ejector systems. Also, thermodynamic cycles on the temperature–enthalpy and temperature–entropy charts are shown. The thermodynamics of the combined ejector–absorption cycles are simulated by a suitable method and a corresponding computer code, based on analytic functions describing the behaviour of the binary mixture NH₃–H₂O. It is found that in the case of the refrigerator and heat pump, the theoretical coefficient of performance (COP) or the theoretical heat gain factor (HGF) vary from 1.6 to 90.4 per cent and 0.7 to 37.6 per cent, greater than those of the conventional absorption system, respectively. The operation conditions were: generator temperature (205.5 to 237.1°C), condenser temperature (25.9 to 37.4°C) and evaporator temperature (−8.4 to 5°C). Copyright © 2000 John Wiley & Sons, Ltd.     

Thermodynamic properties and performance evaluation of [EMIM] [DMP]-H2O working pair for absorption cooling cycle

The combination of ionic liquid-refrigerant based [EMIM][DMP]-H₂O as an alternative working pair for single effect vapor absorption cycles (VACs) is assessed and optimized by using energy and exergy based performances. Thermodynamics properties of binary mixture of [EMIM] [DMP]-H₂O like Dühring's (P-T-x1) and h-T-X1 plots are computed from the activity coefficient based non-random two-liquid model (NRTL) model. Further modeling and simulation of VACs are accomplished in open source Scilab as mathematical programing software and used to ascertain the optimal generator temperature established on energetic and exergetic COP. Optimal results include an extensive range of temperatures like T_e from 2.5 to 15°C and T_a and T_c from 30 to 45°C. Simulation of the single effect VAC with SHE by using [EMIM][DMP]-H₂O mixture at T_e = 10°C, T_g = 100°C, T_a = 30°C, and T_c = 40°C were evaluated and compared with the 5 working fluids. Simulation outcomes depicted greater COP of 0.82 for [EMIM][DMP]-H₂O in comparison with NH₃-H₂O, EMISE-H₂O, [EMIM][BF4]-H₂O and nearly equal to LiBr-H₂O (COP = 0.83). In addition, the effect of T_g on the COP, ECOP f _, and composition are compared and optimized for the evaporation temperature range from 2.5 to 15°C, T_a/T_c from 30 to 45°C and cooling water (CW) flow in series and parallel. Additionally, the optimal T_g exhibited distinction based on energy and exergy analysis. Thus, it resulted in optimized performances of [EMIM] [DMP]-H₂O that can be suitable to replace corrosive aqueous LiBr in VACs.     

Experimental investigations on shell and helical coil solution heat exchanger in NH3-H2O vapour absorption refrigeration system (VAR)

This paper presents the performance investigation of a shell and helical coil type of Solution Heat Exchanger (SHX) in an ammonia–water vapour absorption system. In an absorption system, SHX is one of the major heat recovery components. The main objective of any heat exchanger design is to achieve minimum heat transfer area required for a given heat duty, as it governs the overall fixed cost content of such a system. The required surface area is decided by the overall heat transfer coefficient. Hence, the heat transfer coefficient (HTC) correlation plays a major role in optimizing the heat exchanger. In this paper, shell and helical coil type of SHX is investigated with more emphasis on the dimensionless correlation of shell side co-efficient, which decides the overall HTC and the size of heat exchanger. From the experimental study, shell side heat transfer coefficient of 510–650 W/m² K is obtained with the heat exchanger effectiveness of 0.84–0.9 for the tested conditions. A proposed Nusselt number correlation is compared with the experimental results.     

Heat recovery system to power an onboard NH3-H2O absorption refrigeration plant in trawler chiller fishing vessels

This paper is concerned with the design, modelling and parametric analysis of a gas-to-thermal fluid heat recovery system from engine exhausts in a trawler chiller fishing vessel to power an NH₃-H₂O absorption refrigeration plant for onboard cooling production. Synthetic oil was used as heat transfer fluid and recirculated. The major components of the system are fluid-to-solution and gas-to-fluid heat exchangers. Both heat exchangers and the complete system have been modelled. Models are implemented in several computer programs. These models have been used to study the influence of geometric design parameters and thermal operating conditions on heat exchangers and system thermal performance. The analysis of the results allowed us to find the optimum thermal operating conditions that minimise total heat transfer area. Optimal design based on real data was performed and the operating function of exhaust gases by-pass control was obtained and is presented.     

Eutectic structure evolution of Al2O3-ZrO2-Y2O3 system for potential hybrid solar cell application

Abstract

Ternary Al₂O₃-ZrO₂-Y₂O₃ samples with a eutectic composition were prepared by slow cooling. The microstructural evolution was observed with X-ray diffraction (XRD), scanning electron microscopy (SEM).

The SEM observation of the ternary samples agreed with the XRD with a completion of crystallisation by slow cooling. The target materials commonly have ‘cantaloupe skin’ microstructures as shown in the previous studies by Han et al. The nanocomposite may have experienced different cooling rates with two different microstructures, near the surface having experienced optimal conditions for the eutectic reaction during their cooling and thus formed the eutectic microstructure, near the centre having experienced a slower cooling rate. The crystallised eutectic ternary Al₂O₃-ZrO₂-Y₂O₃ system had three different phases with a 3Y₂O₃-5Al₂O₃ (yttrium-aluminium garnet phase), an alumina phase formed by the eutectic reaction, and a solid solution of ZrO₂ and Y₂O₃.     

Effects of NH3 on N2O formation and destruction in fluidized bed coal combustion

The NH₃ oxidation and reduction process are experimentally and kinetically studied in this paper. It is found that NH₃ has contributions not only to N₂O formation, but also to N₂O destruction in certain conditions. The main product of homogeneous NH₃ oxidation is found to be NO rather than N₂O, but some bed materials and sulphur sorbents have catalytic contributions to N₂O formation from NH₃ oxidation. In reduction atmosphere, NH₃ can promote the KC destruction. It is deduced that the ammonia injection into fluidized bed coal combustion flue gas can decrease both NO_x and N₂O emissions. The ammonia injection process is kinetically simulated in this study, and the reduction rates of NO_x and N₂O are found to depend on temperature, O₂ concentration, initial NO_x and N₂O concentrations, and amount of injected ammonia.     

N2O在锰系低温催化剂上的生成途径

实验对比了由浸渍法、共沉淀法以及溶胶凝胶法制备的锰系低温催化剂在选择性催化还原(SCR)反应中的差异,发现溶胶凝胶法制备的催化剂在整个测试区间内都具有最高的脱硝效率,但是也有最多的 N2O 生成。针对溶胶凝胶法,进一步研究了N2O在SCR过程中的生成情况。发现N2O主要来源于NH3的直接氧化以及NH3和NO的反应,后者为N2O的主要生成途径。添加Ce、V后,随着反应温度升高,NH3的直接氧化逐步成为N2O主要来源。     

Comparative analysis of a solar‐driven novel salt‐based absorption chiller with the implementation of nanoparticles

The present study exemplifies the comprehensive thermal analysis to compare and contrast ammonia‐lithium nitrate (NH₃‐LiNO₃) and ammonia‐sodiumthiocynate (NH₃‐NaSCN) absorption systems with and without incorporation of nanoparticles. A well‐mixed solution of copper oxide/water (CuO/H₂O) nanofluid is considered inside a flat‐plate collector linked to an absorption chiller to produce 15‐kW refrigeration at ?5°C evaporator temperature. Enhancements in heat transfer coefficient, thermal efficiency, and useful heat gain of the collector are evaluated, and the effect of these achievements on the performance of both absorption chillers have been determined for different source temperatures. A maximum 121.7% enhancement is found in the heat transfer coefficient with the application of the nanofluid at 2% nanoparticle concentration. The maximum coefficient of performance observed for the NH₃‐NaSCN chiller is 0.12% higher than that for the NH₃‐LiNO₃ chiller at 0°C evaporator temperature. Contradictory to this, the average system coefficient of performance of the NH₃‐LiNO₃ absorption system has been found 5.51% higher than that of the NH₃‐NaSCN system at the same evaporator temperature. Moreover, the application of the nanofluid enhanced the performance of the NH₃‐NaSCN and NH₃‐LiNO₃ systems by 2.70% and 1.50%, respectively, for lower generator temperature and becomes almost the same at higher temperatures, which altogether recommends the flat‐plate collector–coupled NH₃‐LiNO₃ absorption system be integrated with a nanofluid.