Performance Optimization of a Phosphoric Acid Fuel Cell/Absorption Refrigerator Hybrid System

A hybrid system that consists of a phosphoric acid fuel cell(PAFC),an absorption refrigerator and a refrigeration-space is proposed.The four-heat-source absorption refrigerator,which is driven by the waste heat produced from PAFC,provides cooling for a refrigeration-space.A numerical model is set up to analyze both the steady-state performance and transient performance considering the influences of the electrochemical and thermodynamic irreversibilities.Expressions of the equivalent power output and efficiency of the hybrid system are determined.Moreover,the transient behavior of cold-space temperature is performed and the time to reach a prescribed cold-space temperature is displayed.Thus,the operation regions of the current are optimized at different operating conditions.The results showthat in an appropriate current range,the overall power output and efficiencies of the hybrid system are enhanced.

Aqueous ammonia solution cooling absorption refrigeration driven by fishing boat diesel exhaust heat

A solution cooling absorption（SCA）approach is proposed to modify the aqueous ammonia absorption refrigerat-ion cycle using the strong solution from the absorber to cool the forepart of the absorption in the cycle for reclaiming some portion of absorption heat.As a consequence of raised temperature at the inlet,the strong solution partially boils at the outlet of the solution heat exchanger,and diminishes the thermal heat consumption of the heat source.The calculation results show that the coefficient of performance（COP）of this modified cycle is about 28.3% higher than that of the traditional cycle under typical conditions;while the required heat transfer area of the total heat exchangers of the cycle is somewhat less than that of the traditional one.The capacity of refrigeration with the new absorption cycle is more than doubled in contrast to the adsorption scheme with an identical configuration.It is sufficient to supply a fishing boat the chilling capacity for preservation of fishing products with the modified cycle chiller driven by its diesel engine exhaust.

Performance analysis of ammonia-water absorption/compression combined refrigeration cycle

In view of different compressor adding ways in the ammonia-water absorption/compression combined refrigeration AWA /CCR cycle combining the Schulz state equation of the ammonia-water solution the theoretical analysis and calculations on two combination ways by adding the compressor in the high-pressure area and in the low-pressure area are conducted respectively.The effects of several factors including the evaporation temperature Te heat-source temperature Th as well as the cooling water temperature Tw on the equivalent heat consumption in compression qCW heat consumption in absorption qG and the system coefficient of performance COP are analyzed under the two combination configurations.The results show that the effect of the equivalent heat consumption in compression on the COP is less than that of the heat consumption in absorption.Besides the compressor set in the high-pressure area uses more energy than that in the low-pressure area. Moreover the compressor in the low-pressure area is superior to that in the high-pressure area with respect to the COP. Under the given intermediate pressure there is an optimum heat-source temperature corresponding to the maximum COP of the AWA/CCR cycle.

Thermodynamic Calculation and Analysis of Biomass Energy Applied in the NH_3/He Absorption Refrigeration System

[Objective] The study aimed to discuss the factors influencing the application of shaping biomass energy in the NHJHe absorption re- frigeration system. [ Method] In the NHJHe absorption refrigeration system, the thermodynamic analysis of semi-gasification furnace based on sec- tional combustion technology and absorption refrigeration system was performed. [ Result] Biomass could burn cleanly and efficiently in the semi- gasification furnace, which can reduce the environmental pollution caused by the combustion of coal and other fossil fuels. The heating power of the furnace for the absorption refrigeration system could not be too high, so biomass energy and other low-grade energy can be used as heat sources, which opens up a new way for the utilization of biomass energy. [ Conclusion] Biomass energy was applied successfully in the absorption refrigera- tion system.

Computer Simulation of an Ammonia-Water Absorption Cycle for Refrigeration: Using a Distillation Tower to Replace the Generator

By using a distillation tower as the regenerator, the coefficient of performance (COP) of the ammonia-water absorption refrigeration cycle is calculated in this work. Two types of distillation towers, namely an equilibrium-stage tower with a total condenser and a packed-bed tower with a partial condenser, are used in the cycle. From the simulation results, it is found that both types of distillation towers can successfully increase the COP of the cycle due to increased ammonia concentration in the vapor phase of the ammonia-water refrigerant. It was also found that the tower equipped with a partial condenser provides higher COP than that of the tower equipped with a total condenser. The value of COP can be further increased when the generator is replaced by the packed-bed tower in this water-ammonia absorption cycle. The effects of the mass flow rate ratio of NH3/H2O, stage number, reflux ratio and energy duty of the tower on the COP of the cycle are also studied in the present paper.

Magnetic Field Enhancement in Ammonia-Water Absorption Refrigeration Systems

Absorption enhancement has been considered as an effective way of improving coefficient of performance (COP) of refrigeration systems and magnetic enhancement is one of these methods. A model of magnetic field enhancement in ammonia-water absorption systems is presented in this paper. A numerical model using finite difference scheme was developed based on the conservation equations and mass transport relationship. Macroscopic magnetic field force was introduced in the momentum equation. The model was validated using data obtained from the literature. Changes in the physical properties of ammonia solution while absorbing both in the direction of falling film and across its thickness were investigated. The magnetic field was found to have some positive effect on the ammonia-water falling film absorption. The results indicate that absorption performance enhancement increased with magnetic intensity. The COP of simple ammonia solution absorption refrigeration system increased by 1.9% and 3.6% for magnetic induction of 1.4 and 3.0 Tesla respectively.

Exergy Analysis of a Solar Absorption Refrigeration System in Ngaoundere

In this study, the first and second laws of thermodynamics are used to analyze the performance of a single-stage absorption refrigeration system powered by solar energy. The working pair used in this study is LiBr-H2O where water (H2O) is the refrigerant and the lithium bromide (LiBr) is the absorbent. A mathematical model based on exergy analysis is applied to analyse the system performance. Temperature, enthalpy, entropy, mass flow rate and exergy loss of each component including evacuated tube solar collector are evaluated. Furthermore, the overall coefficient of performance (COPcooling) and the overall exergetic coefficient of performance (ECOPcooling) of the solar absorption system (absorption system coupled to an evacuated tube solar collector) for cooling purpose are calculated from the thermodynamic properties of the working fluids under weather conditions of Ngaoundere city, Cameroon. The calculations were done on the basis of a half hourly analysis from 6:30 AM to 6:30 PM. The results were compared and they show that the exergy destruction highly occurs in the generator and the solar collector. The simulation results can be used for the thermodynamics optimization of solar absorption refrigeration systems.

Hydrogen absorption of LaFe_(11.5)Si_(1.5) compound under low hydrogen gas pressure

Hydrogen absorptions of LaFe11.sSi1.5 compound in 1-atm hydrogen gas at different temperatures are investigated. The hydrogen content in the hydrogenated sample does not increase with the increase of temperature of hydrogen absorption but changes complicatedly. The characteristic of first-order transition in LaFe11.sSil.5 compound is weakened after hydrogen absorption. It leads the peaks of magnetic entropy to become wider and the hysteresis loss to reduce significantly, but relative cooling power （RCP） is not changed considerably.

太阳能-余热联合驱动吸收过冷CO_(2)制冷-淡水联产系统性能分析

为了同时满足制冷和淡水的共同需求,提出了太阳能-余热联合驱动吸收过冷CO_(2)制冷-淡水联产系统(AbsCWCS),在提高CO_(2)制冷系统能效的同时可生产淡水。建立系统的热力学模型,分析了环境温度和太阳辐射强度对系统能效(COP)的影响。此外,为进一步分析气候条件的影响,选取5个典型缺水城市,对年度性能系数(APF)和年淡水产量进行了评估。结果表明:Abs-CWCS的COP和淡水产量均显著提升,与基础CO_(2)增压制冷-淡水联产系统(Base-CWCS)相比,COP提高了1.95%~41.02%,淡水产量增加了0.8~28.6倍,Abs-CWCS的CO_(2)制冷系统排气压力可降低7.86%;AbsCWCS可有效提高系统的APF,5个典型缺水城市的APF可提升3.66%,年淡水产量的提升率可达9.54%~64.62%。研究结果为同时解决制冷和淡水需求提供了可靠的解决方案。

新型吸收式制冷体系工质对溶液研究进展

吸收式制冷系统是一种低碳/零碳制冷技术,利用低品位热源(如工业余/废热、太阳能热源等)作为其驱动能源,能有效提高能源系统综合利用效率。当前商业吸收式制冷剂体系主要基于水-溴化锂和氨-水体系,水-溴化锂溶液存在腐蚀性强、易结晶和制冷效果差等问题,氨体系有毒性较强、爆炸性以及氨-水制冷设备无法小型化等缺点。新型制冷剂-吸收剂工质对的研发是设计更环保高效的新型吸收式制冷系统的核心。总结了近年来备受关注的新型工质对体系,从吸收剂角度出发,探讨了离子液体、低共熔溶剂、大分子有机溶剂以及其它吸收剂与制冷剂组成的工质对溶液热力学性质的计算和实验研究方法。特别讨论了吸收剂-制冷剂相互作用类型和机制,及其对工质对溶液热力学性质和制冷性能的影响规律。总结研究发现对于新型工质对体系,普遍存在的问题是工质对溶液对制冷剂蒸汽的吸收性能欠佳。通过调控吸收剂化学结构和工质对组成,增强吸收剂-制冷剂相互作用是进一步优化工质对体系的关键途径。该综述为优化、设计工质对溶液体系提供了参考。

吸收式制冷压缩CO_(2)储能系统性能分析

提出了一种结合了吸收式制冷循环的压缩CO_(2)储能系统,该系统采用分流的方式,将一部分CO_(2)引流至二级压缩机,将压缩产生的热量提供给吸收式制冷循环,使其启动工作并提供冷量给主路CO_(2),同时使用高压罐储存液态CO_(2),从而提高系统的储能效率。此外,对该系统进行了热力学分析和多目标优化。结果表明:在设计工况下,吸收器、一级压缩机、透平和级后换热器的[火用]损较大;本系统的储能效率随着冷凝压力、压缩机等熵效率和透平等熵效率的增加而提高,而储能压力的增大会使系统的储能效率降低;系统的最佳储能效率为68.70%,能量密度为0.153 kW·h/m^(3)。

离子液体吸收式制冷工质对气液相平衡研究及其分子动力学模拟

为了克服传统吸收式制冷工质对的种种缺陷,离子液体型制冷工质对被视作理想替代品,得到了广泛的开发与应用。采用静态实验和分子动力学模拟两种方法,对[EMIM]BF_(4)/CH_(3)OH离子液体二元体系的气液相平衡性质展开研究。研究结果显示,[EMIM]BF_(4)/CH_(3)OH离子液体二元溶液具有良好的气液相平衡性质,实验测得饱和蒸气压比其他醇类离子液体二元溶液低约21%;模拟结果与实验值有相同的数量级和变化趋势,相对误差普遍小于8%。研究结果为离子液体制冷工质对的筛选和进一步的理论循环系统研究提供了物性数据基础,另一方面也为离子液体基础物性研究提供了一种模拟预测的新方法。

吸收式溴化锂机组回收蒸汽凝液余热制冷技术改造分析

介绍了余热回收溴化锂制冷机组的工作原理,针对鑫润公司60万t/a草酸技改乙二醇装置存在的1.0 MPa(G)蒸汽冷凝液大量直排、所含余热未进行利用的问题,进行了技术改造,即在乙二醇冷冻站新增吸收式溴化锂制冷机组系统,利用凝液余热制取冷冻水。改造后,热能浪费问题得到了有效解决,每年可节约电能2740.53万kW·h,相当于节约标准煤3368.11 t、减少CO_(2)排放量15629.24 t。

太阳能吸收压缩制冷与真空膜除湿耦合系统性能优化

对于太阳能吸收式制冷系统,很难产生较低温的冷冻水用于除湿和冷却,并且面临间歇性的问题。提出了一种新型的温湿度独立控制系统(SACV),该系统集成了太阳能吸收式制冷(SSAR)子系统、蒸汽压缩制冷(VCR)子系统和真空膜除湿(VMD)子系统。VMD子系统和VCR子系统分别解决了除湿困难和全天候制冷问题。建立并验证了热力学数学模型,分析了集热器面积和热水流量对集热器出口热水温度的影响,以及对集热器、SSAR子系统和SACV系统性能的影响,并对SSAR子系统和SACV系统进行了性能优化。结果表明,集热器出口热水温度的增加,使得SSAR子系统存在最佳性能;通过变化热水流量来改变集热器出口热水温度,使得SACV系统存在最佳性能。集热器面积增加73.7%,SSAR子系统性能到达最佳,提升了0.24%,制冷量增长69.64%,同时SACV系统性能提升4.71%,耗功量减少36.18%,但系统成本增加,因此,需要综合考虑系统性能和经济效益。

太阳能驱动的溴化锂吸收式制冷性能模拟研究

利用AspenPlus软件搭建系统仿真模型,系统循环流程采用有限Wegstein收敛方法并选用ELECNRTL物性方法作为溴化锂溶液物性计算方法,对系统的驱动热源流量、溶液换热器温差、溴化锂浓度溶液分配比例等参数进行研究;进而得出参数变化对系统性能的影响规律。

耦合溴化锂制冷机组的燃气-蒸汽联合循环性能分析

燃气-蒸汽联合循环机组的运行性能容易受到环境温度的影响,使得机组在电力负荷需求高峰期面临出力不足的问题.为了解决这一问题,基于EBSILON软件,对耦合溴化锂制冷机组的SGT5-4000F型燃气-蒸汽联合循环进行仿真建模,并将冷却装置加装到压气机入口处,模拟分析进气温度对联合循环输出功率和循环效率的影响规律.研究表明:通过改变压气机进气温度可知降低进气温度可使得联合循环发电功率提高4.73%-6.10%.在温度较高的夏季工况,在燃气轮机的压气机进气口处加装进气冷却装置可以提高机组的性能,并且温度越高,联合循环输出功率提高的效果更好.

太阳能吸收式制冷系统及其蓄能技术研究

在分析国内外现有太阳能吸收式制冷系统的基础上,从太阳能集热器、蓄能形式、辅助热源、吸收式冷水机组以及太阳能集热器与吸收式冷水机组的匹配等方面详细阐述太阳能吸收式制冷系统及其蓄能技术的发展现状,并对太阳能制冷空调系统的控制策略、优化分析及理论研究进行总结,最后指出太阳能吸收式制冷系统及其蓄能技术的发展方向。

工业余热回收系统优化策略原理

介绍有机朗肯循环发电系统在工业余热回收上的应用,选取某燃煤电厂为例,介绍其回收装置及节能分析,并在此基础上进行余热回收的优化策略分析。首先通过引入湿硫酸工艺,将烟气中的二氧化硫催化氧化为三氧化硫并在特殊换热器中冷凝并回收为硫酸副产品,以此打破烟气低品位余热深度利用的酸露点限制。然后通过有机朗肯循环和吸收式制冷集成的余热回收系统对烟气余热进行深度利用。通过数值模拟的方法对余热回收系统进行研究,通过模型验证确保数值模拟的可信度和准确性。

基于核能综合利用的吸收式制冷方案研究

详细介绍了吸收式制冷的工作原理,分析了吸收式制冷的优缺点,介绍了典型的热电汽冷等联产的方案。以华龙一号核电堆型和泳池反应堆为例,分析了热能供给侧的参数条件,以及需求侧的用冷方案与用冷规模,结合供需双方的特点形成了基于核能综合利用的热水供能和蒸汽供能的吸收式制冷方案,并对方案的可靠性和经济性进行了对比。结果表明,基于华龙一号堆型的蒸汽型吸收式制冷机组方案和基于泳池反应堆的热水型吸收式制冷机组方案,均具有显著的技术经济性和社会经济性。

低温余热回收系统能量管理优化策略研究

低温余热回收系统在提高能源利用效率和减少排放方面具有重要作用。探讨了低温余热的来源、特性及其在不同行业中的应用潜力,分析了低温余热回收系统的设计方案和能量管理策略,综述了各种低温余热回收技术(如有机朗肯循环、吸收式制冷等)的原理及应用,指出现有系统在余热收集、传输和利用过程中存在的技术难题和效率瓶颈,提出了一系列创新的能量管理策略,旨在优化系统性能,包括改进热交换器设计、引入智能控制系统及采用多能源互补配置等。通过案例分析,验证了所提策略在提高系统能效、降低运营成本及促进可持续发展方面的有效性,此成果可为低温余热回收系统的设计与优化提供理论指导和实践参考,对推动能源高效利用和环境保护具有重要意义。