Introducing a proper hydrogen liquefaction concept for using wasted heat of thermal power plants-case study: Parand gas power plant

A hydrogen liquefaction concept with an innovative configuration and a capacity of 4 kg·s^-1 (345.6 t·d^-1) is developed. The concept involves an ammonia absorption refrigeration system for the pre-cooling of hydrogen and MR streams from 25 ℃ to -30 ℃. The ammonia absorption refrigeration system is fed by exhaust gases of the Parand gas power plant that are normally dissipated to the environment with a temperature of 546 ℃. The simulation is performed by Aspen HYSYS V9.0, using two separate equations of state for simulating hydrogen and MR streams to gain more accurate results especially for ortho-para conversion. Results show that conversion enthalpy estimated by Aspen HYSYS, fits very well to the experimental data. Determining the important independent variables and composition of MRs are done using trial and error procedure, a functional and straightforward method for complicated systems. The minimum temperature limit in the cooling section is lowered, and an ortho-para converter is implemented in this section. The proposed concept performs well from energy aspects and leads to COP and SEC equal to 0.271 and 4.54 kW·h·kg^-1, respectively. The main advantage of this study is in the low SEC, eliminating the losses of the distribution network, and improving the ability of the hydrogen liquefaction for energy storage in off-peak times.     

Extended preservation of raw beef and pork meat by hyperbaric storage at room temperature

Hyperbaric storage (HS) was evaluated as a new food preservation methodology at room temperature (RT) for beef and pork meat, both minced and in pieces, and compared to refrigeration (RF) storage. The meat samples were stored at 50, 75 and 100 MPa and variable RT up to 60 days. HS at 75 and 100 MPa could not only inhibit microbial growth but also inactivate microorganisms. Regarding physicochemical analyses, an overall equal to better pH maintenance in HS samples was achieved, and similar colour differences between HS and RF were observed. Generally, similarities in moisture content and drip loss between HS (mostly 75 and 100 MPa) and RF were detected (tendency for lower values in the former and higher values in the latter for the higher pressure level). Protein solubility revealed a decrease of sarcoplasmic protein values during storage with a pressure level dependency in some samples.     

Performance analysis of a supersonic ejector cycle working with R245fa

A supersonic ejector chiller for industrial use is currently being developed and tested as part of a project cooperation between Frigel s.p.a and DIEF (Department of Industrial Engineering, University of Florence). The refrigerator was built following a “ready to market” setup criterion and is intended for applications on the industrial refrigeration market or in air conditioning. The plant has a nominal cooling power of 40 kW and is powered by low temperature heat (from 90 up to 100 °C). The ejector is equipped with a movable primary nozzle and 9 static pressure probes along the mixing chamber/diffuser duct. The working fluid is R245fa. An extensive numerical campaign was performed to analyze the internal dynamics of the ejector. All the simulations were carried out by accounting for the real gas properties of the refrigerant. Comparison with experimental data resulted in close agreement both in terms of global and local parameters. Analyses showed that in order to achieve an accurate matching with the experimental data, it is necessary to correctly account for the surface roughness of the ejector. This is especially true for off-design operating conditions.     

制冷压力容器中应力集中及改善措施探讨

对应力集中现象及概念进行了阐述,同时对制冷压力容器设计和制造过程中可能导致应力集中的因素进行归纳总结,并提出了具体的改善应力集中的措施,方便大家探讨。     

发动机尾气余热驱动的吸附式空调系统仿真与测试

针对在高太阳辐射地区，柴油车驾驶室内使用车载空调会增加车辆发动机的耗油量、降低柴油车经济效益的问题，搭建了一套由发动机尾气余热驱动的吸附式车载空调系统。系统由填充有氯化钙/氯化锰/硫化膨胀石墨复合吸附剂的吸附床、蒸发器、冷凝器、储液罐和阀门组成，使用氨作为制冷剂，利用车辆在行驶时接触到的自然风为吸附床冷却，在发动机尾气余热的驱动下，为驾驶室内提供连续的制冷效果。结合仿真和实验测试，对所设计系统的制冷性能进行了分析，仿真结果表明，系统最优循环时间为45 min，系统的理论平均制冷功率可达3.5 kW以上，系统COP处于0.2~0.25之间。实验结果表明，在230℃的尾气温度条件下，系统能产生3 kW的平均制冷量。在40℃环境温度条件下，系统在蒸发器进出口处的平均温差为6.5℃，平均制冷量为3.2 kW。     

Nb modified structural,magnetic and magnetocaloric properties of double perovskite Ba2FeMo1−xNbxO6

A systematic study focusing on the effect of Niobium (Nb) doping on the structural, magnetic and magnetocaloric properties of Ba₂FeMoO₆ samples is presented here. The samples of interest Ba₂FeMo_1?xNb_xO₆ (0 ≤ x ≤ 0.4) were prepared using the solid state reaction method and were confirmed to possess a cubic structure with Fm-3m space group using the X-ray diffraction analysis and Rietveld refinement. A second order of ferromagnetic phase transition was recorded in both the pure as well as the Nb doped samples using the temperature dependent magnetization and Arrott plots analysis. The pristine Ba₂FeMoO₆ (BFMO) sample indicated a spontaneous magnetization (34.6 emu/g at 100 K) with a relatively sharp magnetic transition at the Curie temperature (T_C) of 315 K as compared to the doped samples. A magnetic entropy change of 0.93 Jkg^?1K^?1 at an applied magnetic field of 2.5 T was measured for the pure BFMO sample. The doped BFMO samples with Mo partially substituted by Nb however, were observed to effectively modify the T_C accompanied by a decrease in magnetization. The results investigated in this work suggest that the magnetic and magnetocaloric properties of the BFMO can be tailored by controlled Nb doping which is of significant importance in order to realize the numerous potential applications of the material in the magnetic refrigeration technology.     

Surface Profile Optimization of Yankee Dryer Based on Finite Element Analysis

The deformation and stress distribution of cast iron Yankee dryer caused by outside linear load， inside steam pressure and self-gravity were calculated by numerical simulation with ANSYS software. The deformation curve of the linear load area was obtained and compared with the deformation in the actual working process. The surface profile of dryer was optimized and the deformation and stress of the optimized dryer were calculated and compared with the that of before optimization. In this paper， the method of the surface profile optimization of Yankee dryer was presented．     

基于金属Gd的室温旋转式磁致冷演示样机的设计

磁致冷是利用磁介质在其居里温度Tc附近具有较大磁热效应的特性实现的一种物理现象.以稀土金属Gd为磁致冷材料,对室温旋转式磁致冷演示样机进行了结构设计,演示样机可达4.4K的制冷温跨,用于设计性实验教学,具有良好的示范作用.     

桨叶-微粉干燥在纳米碳酸钙生产中的应用

纳米碳酸钙的生产过程中,干燥方式的选择是影响产品最终质量和成本的重要因素之一。本文介绍了纳米碳酸钙生产过程中的喷雾干燥、带式干燥和闪蒸干燥等几种干燥方式,重点对桨叶-微粉干燥的工艺流程、设备选型、生产特点等进行了介绍,并对几种干燥方式所存在的优缺点进行了比较。     

一种磁粉料浆干燥的新方法

通过对现有磁粉干燥方法的分析，提出了一种连续干燥磁粉的新方法。此种方法是根据磁粉料浆的特点，采用倾斜安装的螺旋输送机以及悬链式间接加热干燥机，使连续干燥粉份这－工艺过程得以实现，同时指出，用悬链式间接加风干燥机连续干燥磁粉的新方法是提高磁性材料行业整体装备水平的有效途径之一．