Heating load and COP optimisations for a universal steady flow endoreversible heat pump model

The heating load and coefficient of performance (COP) of a class of universal steady flow endoreversible heat pump cycle model, which consists of one heating branch, two cooling branches and two adiabatic branches, are optimised using the theory of finite time thermodynamics. The analytical formulae for heating load and COP versus temperature ratio as well as COP versus heating load of the cycle model are derived. Effects of the total heat exchanger inventory on performances of heat pump cycles are shown by detailed numerical examples. The results obtained herein include the optimal performances of endoreversible Otto, Brayton, Atkinson, Diesel, Dual and Carnot heat pump cycles.     

Optimal performance for a steady-flow endoreversible refrigerator model including five typical cycles

The optimal performance of a universal endoreversible steady-flow refrigerator cycle consisting of a constant thermal-capacity heating branch, a constant thermal-capacity cooling branch and two adiabatic branches with heat transfer loss was analysed using finite-time thermodynamics. The analytical formulae about cooling load, coefficient of performance, exergy loss rate, exergy output rate and ecological criterion of the endoreversible steady-flow refrigerator cycle are derived. Moreover, analysis and optimisation of the model were carried out in order to investigate the effect of the cycle process on the performance of the cycles using numerical examples. The results obtained include the performance characteristics of endoreversible steady-flow Carnot, Diesel, Otto, Atkinson and Brayton refrigeration cycles. The results can provide some theoretical guidance for the design of practical refrigerators.     

Thermodynamic aspects of power generation in imperfect fuel cells: part II

This research continues the thermodynamic analysis of steady-state solid oxide fuel cells initiated in Sieniutycz (Sieniutycz, S., 2010, Thermodynamic aspects of power generation in imperfect fuel cells: part I. International Journal of Ambient Energy, 31 (4), 195–202). This analysis focuses on the effect of incomplete conversions in chemical reactions. A general approach is developed that attributes lowering of the cell voltage below its reversible value to polarisations and imperfect chemical conversions. Relevant model, appropriate for systems with complete conversions, is extended to imperfect cases. The performance curves of a fuel cell and the effect of typical design and operating parameters on the cell behaviour are analysed. A general result is obtained for power limits of fuel cells propelled by linear transport phenomena.     

High-efficiency remediation of cadmium (Cd2+) from aqueous solution using poultry manure– and farmyard manure–derived biochars

Farmyard manure (FYM-BC) and poultry manure (PM-BC) derived biochars were applied as adsorbents to remove Cd²⁺ from water. Results indicated that PM-BC was a more efficient adsorbent than FYM-BC at all experimental conditions. Maximum Cd²⁺ adsorption was observed at pH 4, temperature 318 K and contact time 1 h, regardless of biochar type. The Langmuir model predicted maximum adsorption capacity of 90.09 mg g^?1 for PM-BC. The data fitting to pseudo-second-order model proposed chemisorption of Cd²⁺ onto biochars. Thermodynamics indicated that adsorption was spontaneous and endothermic. Post-adsorption analysis provided evidences of strong chemical interactions between biochars’ functional groups and Cd²⁺ ions.     

A modified thermodynamic insight to deliquescence of a void‐containing nanocrystal confirmed by MD simulation

Existence of voids in crystalline structures can affect their physical and chemical properties considerably. When the size of the crystal reaches to nanoscale, experimental determination of its void fraction is difficult. In this work, a molecular dynamics approach is introduced to find equilibrium void fractions of a simple cubic (CsCl) and fcc (KCl) nanocrystals by determination of their deliquescence relative humidity (DRH) for different sizes and void fractions and extrapolation of the results to the bulk limit. To confirm the simulation results, the size dependency of DRH to the nanoparticle size was studied thermodynamically by inclusion of size‐dependent density of water nanodroplet which leads to a simple homographic equation. This method proposes the equilibrium void percents of CsCl and KCl nanoparticles to be 10 and 15%, respectively, which are obtained by extrapolation of the results to the bulk limit. The success of obtained Möbius function was also confirmed by fitting it to experimental data for deliquescence of NaCl nanoparticles which implies the importance of considering density of water nanodroplet as a size dependent quantity. Also, using the mentioned thermodynamic approach, void dependency of deliquescence for the nanoparticles was found to be as a quasi‐linear trend which is compatible with the simulation results. It is noticeable that the approach used this work for determination of equilibrium void fraction is only valid if the utilized force fields are accurate. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4066–4077, 2016     

Thermodynamics and separation process for quaternary acrylic systems

Vapor‐liquid equilibrium (VLE) and liquid‐liquid equilibrium (LLE) data of binary and ternary acrylic systems were systematically measured. Subsequently, VLLE phase diagrams of binary systems, tridimensional VLE phase diagrams of methyl acrylate (MA)‐methanol (Me)‐H₂O ternary system, and quaternary LLE phase diagrams of MA‐Me‐H₂O‐methyl acetate (MeOAc) system were constructed. These diagrams clearly demonstrated the effects of temperature on phase equilibrium. The experimental data was fitted by the NRTL and UNIQUAC models, and the best‐fitted parameters were used to predict interaction properties of ternary and quaternary mixture. Therefore, the phase equilibrium data were provided as reference for the design of acrylic systems rectification or extraction process. Residue curve was mapped out for MA‐Me‐H₂O system through Aspen plus software. Finally, using thermodynamics and residue curve as theoretical basis, two novel separation processes were proposed and applied to the quaternary acrylic systems. © 2015 American Institute of Chemical Engineers AIChE J, 62: 228–240, 2016     

苯酚与异丙醇烷基化合成异丙基苯酚的热力学和动力学

基于Benson基团贡献法研究苯酚与异丙醇烷基化反应过程,确定了主、副反应的反应热、平衡常数及平衡转化率,得到反映热力学性质的反应方程式并建立反应的网络结构,为该体系的工艺设计提供热力学依据。在苯酚与异丙醇物质的量比为0.5~2.0、温度(513.15~573.15)K、空速8 h-1和催化剂颗粒(40~60)目[相当于粒径(0.45~0.30)mm]条件下进行本征动力学实验。选用幂数型动力学模型,对参数进行估值。用Runge-Kutta法进行数值积分,Simplex法对参数进行优化,F统计法对模型进行检验,最终得到能较好描述反应的本征动力学模型。     

基于平衡态和非平衡态分子动力学模拟研究锗烯热导率

利用平衡态和非平衡态分子动力学模拟的方法计算了锗烯的热导率。首先,应用平衡态方法模拟了锗烯的热导率并进一步计算了热导率分解的各个分量。与石墨烯不同,锗烯热导率较小且 分量占主导。其次,应用非平衡态方法模拟计算了一系列长度的锗烯热导率,通过拟合得到不依赖长度的收敛热导率。最后,比较平衡态和非平衡态两种模拟方法得到的结果。发现不仅在数值上结果是一致的,而且通过拟合声子群速度将平衡态数据转换为长度依赖关系,也可以与非平衡态数据很好的重合。因此,基于平衡态和非平衡态两种方法应用GPUMD程序模拟计算的锗烯热导率都是有效且等价的。