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.     

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。     

升膜理论在氨水吸收式制冷循环中的应用

由于可以利用低品位热源制冷,氨水吸收式制冷系统得到了广泛的应用。氨水系统的精馏器要求很高的安装精度,限制了其应用范围。为了开发新型制冷器,将升膜理论应用到氨水吸收式制冷系统中,用一个冷凝发生器来实现精馏塔的作用。研究结果表明,本循环的热力系数比较高,这一成果可广泛应用于各种车、船等的制冷系统设计中。     

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。     

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。     

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.     

吸收式制冷技术在玻璃熔窑余热回收中的应用

本文着重从节能、环保和经济性等方面阐述了采用溴化锂吸收式制冷技术回收玻璃熔窑余热,替代窗式空调器进行空调的合理性。并以洛阳玻璃厂二浮法玻璃熔窑的热平衡测试数据为基础,对采用二种方式空调时的主要经济技术指标——设备初投资和运行费用做了对比和分析,结果表明,在玻璃熔窑余热回收中采用溴化锂吸收式制冷新技术,经济上合算,社会效益和环保效果明显,具有推广应用价值。     

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。     

结合制冷的新型吸收式热变换器热力分析

提出了一种能同时制冷的溴化锂喷射-吸收式热变换器系统。根据热质平衡理论和喷射器理论,对该新型系统进行了热力学模拟,分析了各参数对系统性能的影响。并将该系统用于回收55℃的废热,解决同时需要制热、制冷场所的冷、热源问题。结果表明:废热先流经蒸发器的串联流程的性能优于其它流程;低压蒸发器内冷冻水出口温度越高、冷凝器中冷却水出口温度越低,系统性能越好;而吸收器中用户供水温度越高,系统制热火用效率ηr越大,系统能效比COP却越低。     

两种新型氨水吸收式制冷空调系统的热力和(火用)对比分析

介绍了两种新型无溶液泵和精馏装置的氨水吸收式制冷空调系统(无回热式和回热式).首先对两系统的结构特点和循环过程进行了阐述,然后在不同发生器溶液存留倍数下对两系统进行了热力计算分析比较,然后对两系统进行了(火用)计算分析比较.经分析,在理想情况下无回热式系统的热力系数为0.249,总体(火用)效率为0.111;回热式系统的热力系数为0.454,总体效率为0.202.     

Performance of solar NH3/H2O absorption cycles in the athens area

The performance of solar driven NH₃/H₂O absorption units, operating in conjunction with high and intermediate temperature solar collectors in Athens, is predicted along the typical year, in the cases (a) of absorption refrigeration units working as refrigerators, (b) of absorption refrigeration units working as heat pumps and (c) of reversed absorption units working as heat transformers. In all cases, the operation of the units and the related thermodynamics are simulated by suitable computer codes, and the required local climatological data (i.e. the incident solar radiation and the ambient temperature) are determined by statistical processings of related hourly measurements over a considerable number of years. It is found that in the case of the refrigerator, for operation over the whole year, the theoretical coefficient of performance varies in the range from 72 to 75% and a maximum theoretical specific cooling power of 223 W/m² is observed on July at 13 hrs. In the case of the heat pump, for operation from November to April, a maximum theoretical heat gain factor of about 170% is obtained on December with corresponding specific heat gain power amounting to 213 W/m² at 14 hrs, while a maximum theoretical specific heat gain power of 344 W/m² is observed on April at 13 hrs with a corresponding heat gain factor of about 165.5%. Lastly, in the case of the heat transformer, for operation over the whole year, a maximum theoretical heat gain factor of about 48.3% is observed during winter at about 13 hrs but with very small specific heat gain power, while a maximum specific heat gain power of 175 W/m² is obtainable on July at noon with a corresponding heat gain factor of 44.5%.     

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.     

Thermodynamic study of a two-stage vapour absorption refrigeration system using NH3 refrigerant with liquid/solid absorbents

A systematic investigation is made of the two-stage vapour absorption refrigeration system employing the refrigerant absorbent combinations of NH₃---H₂O and NH₃---LiNO₃. The system consists of coupling two conventional absorption cycles so that the first-stage evaporator produces cooling water to circulate in the absorber of the second stage. The effect of operating variables such as generator temperature, evaporator temperature, absorber temperature and condenser temperature on the coefficient of performance (COP), heat transfer rates and relative circulation have been studied for both single-stage and two-stage absorption refrigeration systems. It is found that the COP is higher for NH₃---LiNO₃ than for NH₃---H₂O, in both single-stage and two-stage absorption systems, especially at higher generator temperatures. Furthermore, the minimum evaporator temperature achieved is lower for NH₃---LiNO₃, and the system can be operated at lower generator temperatures.     

A high-efficiency, compound NH3/H2O-H2O/LiBr absorption-refrigeration system

A high-efficiency, compound absorption-refrigeration system is considered, which is composed of two cooperating absorption units using NH₃/H₂O and H₂O/LiBr solutions, respectively. The heat output from the NH₃/H₂O unit is employed to drive the H₂O/LiBr unit. The thermodynamics of the new system are simulated by using a procedure which showed that very high theoretical coefficients of performance may be obtained (up to 230%) compared to the corresponding theoretical values for the usual single absorption units, which do not exceed 100%.     

Photoreduction of N2 to NH3 and H2O to H2 on metal doped TiO2 catalysts (M = Ce, V)

The photosynthesis of NH₃ from N₂ and the photogeneration of H₂ from H₂O under non-sacrificial conditions on M/TiO₂ (M = Ce, V) are reported. The yields are superior to those earlier reported for similar metal doped TiO₂ catalysts. The flat band potentials of these catalysts have been determined and correlated to their catalytic activity.     

Thermoeconomic optimization and exergy analysis of CO2/NH3 cascade refrigeration systems

In this paper, thermoeconomic optimization and exergy analysis are applied to a CO₂/NH₃ cascade refrigeration cycle. Cooling capacity, ambient temperature and cold space temperature are constraints of the optimization procedure. Four parameters including condensing temperature of ammonia, evaporating temperature of carbon dioxide, condensing temperature of carbon dioxide and temperature difference in the cascade condenser are chosen as decision variables. The objective function is the total annual cost of the system which includes costs of input exergy to the system and annualized capital cost of the system. Input exergy to the system is the electricity consumption of compressors and fans, and the capital cost includes purchase costs of components. Results show that, optimum values of decision variables may be found by trade-off between the input exergy cost and capital cost. Results of the exergy analysis for each of the system components in the optimum state are also given.     

CO2 methanation combined with NH3 decomposition by in situ H2 separation using a Pd membrane reactor

Combination of the reactions by means of membrane separation techniques are of interest. The CO₂ methanation was combined with NH₃ decomposition by in situ H₂ separation through a Pd membrane. The CO₂ methanation reaction in the permeate side was found to significantly enhance the H₂ removal rate of Pd membrane compared to the use of sweep gas. The reaction rate of CO₂ methanation was not influenced by H₂ supply through the Pd membrane in contrast to NH₃ decomposition in the retentate side. However, the CH₄ selectivity could be improved by using a membrane separation technique. This would be caused by the active dissociated H species which might immediately react with adsorbed CO species on the catalysts to CH₄ before those CO species desorbed. From the reactor configuration tests, the countercurrent mode showed higher H₂ removal rate in the combined reaction at 673 K compared to the cocurrent mode but the reaction rate in CO₂ methanation should be improved to maximize the perfomance of membrane reactor.     

Hydrogen permeation through a Pd-based membrane and RWGS conversion in H2/CO2, H2/N2/CO2 and H2/H2O/CO2 mixtures

This study investigated the effect of gases such as CO₂, N₂, H₂O on hydrogen permeation through a Pd-based membrane −0.012 m² – in a bench-scale reactor. Different mixtures were chosen of H₂/CO₂, H₂/N₂/CO₂ and H₂/H₂O/CO₂ at temperatures of 593–723 K and a hydrogen partial pressure of 150 kPa. Operating conditions were determined to minimize H₂ loss due to the reverse water gas shift (RWGS) reaction. It was found that the feed flow rate had an important effect on hydrogen recovery (HR). Furthermore, an identification of the inhibition factors to permeability was determined. Additionally, under the selected conditions, the maximum hydrogen permeation was determined in pure H₂ and the H₂/CO₂ mixtures. The best operating conditions to separate hydrogen from the mixtures were identified.     

Electrochemical property of NH4V3O8·0.2H2O flakes prepared by surfactant assisted hydrothermal method

NH₄V₃O₈·0.2H₂O is synthesized by sodium dodecyl sulfonate (SDS) assisted hydrothermal method and its electrochemical performance is investigated. The as-prepared material is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared (IR) spectrum, differential scanning calorimetry and thermal gravimetry (DSC/TG), cyclic voltammetry (CV), and charge-discharge cycling test. The results show a pure NH₄V₃O₈·0.2H₂O phase with flake-like morphology is obtained and the average flake thickness is about 150 nm. The NH₄V₃O₈·0.2H₂O electrode has a good lithium ion insertion/extraction ability with the highest discharge capacity of 225.9 mAh g⁻¹ during 1.8-4.0 V versus Li at the constant current density of 15 mA g⁻¹. After 30 cycles, it still maintains a high discharge capacity of 209.4 mAh g⁻¹, demonstrating good cyclic stability. Interestingly, at the discharge process a new (NH₄)Li_xV₃O₈·0.2H₂O compound is formed due to the new lithium ion from lithium metal anode.     

An improved H2/O2 mechanism based on recent shock tube/laser absorption measurements

An updated H₂/O₂ reaction mechanism is presented that incorporates recent reaction rate determinations in shock tubes from our laboratory. These experiments used UV and IR laser absorption to monitor species time-histories and have resulted in improved high-temperature rate constants for the following reactions: H+O₂=OH+OH₂O₂(+M)=2OH(+M)OH+H₂O₂=HO₂+H₂OO₂+H₂O=OH+HO₂ The updated mechanism also takes advantage of the results of other recent rate coefficient studies, and incorporates the most current thermochemical data for OH and HO₂. The mechanism is tested (and its performance compared to that of other H₂/O₂ mechanisms) against recently reported OH and H₂O concentration time-histories in various H₂/O₂ systems, such as H₂ oxidation, H₂O₂ decomposition, and shock-heated H₂O/O₂ mixtures. In addition, the mechanism is validated against a wide range of standard H₂/O₂ kinetic targets, including ignition delay times, flow reactor species time-histories, laminar flame speeds, and burner-stabilized flame structures. This validation indicates that the updated mechanism should perform reliably over a range of reactant concentrations, stoichiometries, pressures, and temperatures from 950 to greater than 3000 K.