Multi absorber stand alone liquid desiccant air-conditioning systems for higher performance

Achieving comfortable environment with the use of renewable energy or waste heat without creating the hazardous effects over the earth atmosphere are major challenges in the field of air-conditioning. Liquid desiccant technology is a promising option. For the past few decades research is going on worldwide to commercialize such systems. Hybrid liquid desiccant systems (combination of vapor compression (V-C) and liquid desiccant system) have got more attention probably due to higher COPs and lower regeneration temperature for such systems.In the present communication the steady-state performance of stand alone liquid desiccant systems has been simulated and analyzed. Falling film designs of absorber and regenerator have been selected for the study due to their lower pressure drops. The simulation of these components has been carried out by solving the basic mass and energy balance equations. These are nonlinear coupled first order differential equations, which have been solved by using fourth order finite difference Runge-Kutta method. The overall system has been simulated using Warner’s technique. Two new stand alone liquid desiccant cycles utilizing the potential of desiccant fully through multiple absorbers have been proposed. The proposed new cycles improve the COP of stand alone systems significantly. A parametric study has also been carried out on these liquid desiccant cycles to identify the key design parameters affecting the performance of the system.     

国产镁橄榄石砖在玻璃熔窑蓄热室上的使用

为了延长玻璃熔窑蓄热室格子体的使用寿命,应选用合理匹配的耐火材料。分析了国产镁橄榄石砖使用中存在问题及应注意的事项。     

蓄顶温度与火道温度关系模型辨识新方法

针对焦炉火道温度与蓄顶温度关系模型的辨识问题,提出了一种基于区间预估最小二乘法的模型辨识方法.此方法可以有效消除煤气交换给火道温度和蓄顶温度带来的趋势不同的影响.使用置信区间的预计算,能够避免辨识数据紧凑带来的拟合数据准确而物理意义不准确的问题.     

重油催化裂化再生器应力腐蚀开裂分析及处理

分析了再生器壳体裂纹产生的原因,认为应力集中及器壁温度低和酸性气的存在是产生裂纹的主要因素,采取对裂纹部位进行挖补、减薄衬里厚度以提高壁温的方法进行修复。投用后运行良好,有铲解决了再生器应力腐蚀问题,该方法既消除了设备隐患,顾修复工期,又节约了大量资金邮降本增效,可供同行业参考与借鉴。     

Dynamic operation of an active magnetic regenerator (AMR): Numerical optimization of a packed-bed AMR

A new, fast and flexible, time-dependent, one-dimensional numerical model was developed in order to study in detail the operation of an active magnetic regenerator (AMR). The model is based on a coupled system of equations (for the magnetocaloric material and the heat-transfer fluid) that have been solved simultaneously with the software package MATLAB. The model can be employed to analyze a wide range of different operating conditions (mass-flow rate, operating frequency, magnetic field change), different AMR geometries, different magnetocaloric materials and heat-transfer fluids, layered and single-bed AMRs, etc.This paper also presents an optimization of the AMR’s geometry, where the AMR consists of a packed-bed of grains (spheres) of gadolinium (Gd). The optimization of the mass-flow rate and the operating frequency of the AMR were performed by studying five different diameters of Gd spheres.     

Permanent magnet magnetic refrigerator design and experimental characterization

Magnetic refrigeration (MR) using permanent magnets is being investigated for near-room temperature applications. An MR prototype is described and results using gadolinium as refrigerant are presented. Important design features are simple sealing, compactness, high operating frequencies, and ease of use. Using a total of 110 g of refrigerant, the device produces a maximum temperature span under no thermal load of 29 °C, and 10 °C under 50 W. The overall COP determined by using the power to the drive motor is between 0.3 and 0.8 under most operating conditions and temperature spans. The maximum COP measured is 1.6 with a span of 2.5 °C when operating at 1.4 Hz and utilization of 1.28. If the inefficiency of the motor is removed the maximum COP is 2.2, and, when the magnet drive losses are excluded, the maximum COP becomes 10. The peak specific exergetic cooling power is 0.085 W T⁻¹ cm⁻³.     

Optimal performance of regenerative cryocoolers

The key component of a regenerative cryocooler is its regenerative heat exchanger. This device is subject to losses due to imperfect heat transfer between the regenerator material and the gas, as well as due to viscous dissipation. The relative magnitudes of these losses can be characterized by the ratio of the Stanton number St to the Fanning friction factor f. Using available data for the ratio St/f, results are developed for the optimal cooling rate and Carnot efficiency. The variations of pressure and temperature are taken to be sinusoidal in time, and to have small amplitudes. The results are applied to the case of the Stirling cryocooler, with flow being generated by pistons at both sides of the regenerator. The performance is found to be close to optimal at large ratio of the warm space volume to the regenerator void volume. The results are also applied to the Orifice Pulse Tube Refrigerator. In this case, optimal performance additionally requires a large ratio of the regenerator void volume to the cold space volume.     

Empirical estimation of regenerator efficiency for a low temperature differential Stirling engine

An experimental method of regenerator evaluation is proposed in this paper. The configuration of the experimental equipment used in the method is similar to that of an alpha-configuration Stirling engine with a phase angle of 180°. The temperature of the hot side heat exchanger is controlled by an electric heater, and the heat sink was room air. An air conditioner controlled the temperature of the room air. The temperature and pressure of the working fluid were measured during the piston motion. A #18 stainless steel mesh was used as a regenerator matrix for a low temperature differential Stirling engine (LTDSE). The regenerator efficiency can be calculated based on the measurement results. The product of the swept volume, the density of the working fluid, the specific heat and the difference in the working fluid temperatures between the hot side and the cold side is greater than the amount of the internal energy fluctuation. The reason for this is assumed to be the temperature fluctuation in the region between the two heat exchangers. The walls of the region are made of acrylic resin. The amount of the temperature fluctuation in the region is assumed to be uniform. The regenerator efficiency is calculated as a function of the temperature fluctuation in the region. The evaluation method does not require a fast-response thermocouple. The prediction of the regenerator efficiency is possible basted on some experimental results of same matrix. Polyurethane foam and #18 stainless steel mesh, layered parallel to the stream line of the working fluid, were each tested. These materials can realize a non-rectangular regenerator without the generation of waste. Non-rectangular regenerator includes regenerator that can be installed into narrow gaps. The regenerator efficiency of the stainless steel mesh layered parallel to the stream line of the working fluid was significantly less in comparison to that of the normal mesh layers. In the polyurethane foam case, a pressure loss was observed.     

改善催化再生器压力仪表控制质量提高能量回收机组发电量

在催化裂化装置再生器压力分程控制中,烟机入口蝶阀和双动滑阀是参与控制的重要执行机构,本文通过调整蝶阀和双动滑阀动作的线性度、受控精度、灵敏度,提高了能量回收机组(烟机-主风机-电动机/发电机)仪表的控制质量,达到了回收再生烟气中携带的大部分能量,降低了机组功率消耗,提高了机组回收效能.     

S-Zorb装置在线分析仪表配置与应用

采用S-Zorb吸附脱硫技术降低催化汽油硫含量是中国石化汽油产品质量升级的重要措施。为解决前期投用的S-Zorb装置中在线分析仪表配置与应用不当的问题,通过对在线分析仪表应用环境与系统优化配置方案的研究,分析了影响分析系统正常运行的原因,提出了该装置在线分析仪表系统配置注意事项及再生烟气氧分析仪与二氧化硫分析仪共用样品系统与采用引流器重建总硫分析仪回收系统等建议,可供同类装置参考。