天津地区间接蒸发冷却能量回收系统能效的试验研究

根据天津地区的气象特点,该地区不适宜单独使用直接蒸发冷却空调,因此选用了间接蒸发冷却能量回收新风预冷系统.通过试验研究室内排风对新风的预冷过程,分析了干、湿工况下典型日的运行效果和能效,结果表明:在干工况运行状态下,系统显热节能量较大,没有潜热节能量,COP范围6.47～14.07,能够承担63.28％～144.54％...     

淡水与海水对蒸发冷却性能影响的试验研究

针对利用海水替代淡水进行蒸发冷却可行性的问题,首先,对厚度为100 mm的蒸发冷却用填料CELdek7060进行了试验研究,分别研究了淡水以及不同海水浓度(0.5倍、1倍和1.5倍海水)下的蒸发冷却性能,研究结果表明,用海水替代淡水进行蒸发冷却时,其引起的空气侧压降几乎无变化,冷却效率降低的不是特别大,在风速1,2 m...     

Experimental investigation of the performance of a reconfigurable fixturing system

A reconfigurable fixturing system has been developed for computer-integrated assembly environments. The fixturing system employs a number of fixture modules that are set-up, adjusted and changed automatically by the assembly robot without human intervention. A commercially available computer-aided design (CAD) package with the help of a dedicated software program is used for the design, analysis, and verification of the fixture layout. The robot program for setting-up, adjusting, and dismantling the designed fixture is generated automatically. This paper presents and discusses the accuracy of such a reconfigurable fixturing system in view of the off-line programming techniques. The experimental techniques to measure the accuracy and repeatability for setting-up the fixture are presented. The measured results of the robot positioning various types of locating fixture modules are presented and compared with the intended position settings. From the comparison, the accuracy that is to be expected from such an approach to fixturing and measures for improvement are discussed. The cycle times involved in setting-up the fixture modules are also presented and analysed. These results provide an initial guide for manufacturing industries interested in employing such systems in their computer-integrated assembly environment.     

Numerical study of a water distillation system using solar energy

This paper tackles an optimization approach in order to boost the fresh water production of a new design of a solar still which is located at Sfax engineering national school in Tunisia. This optimization approach is based upon the above mentioned design’s improvement by coupling the conventional solar still into at a condenser, solar air and water collector and humidifier. This new concept of a distiller solar still using humidification- dehumidification processes (HD) is exploited for the desalination purpose. As a result of this work, the humidification- dehumidification processes have an essential effect in improving the solar still performance. Performance has been predicted theoretically in terms of water and inner glass cover temperatures, the inlet temperature of air and water of the new concept of distiller on water condensation rate and fresh water production. A general model based on heat and mass transfers in each component of the unit has been developed in steady dynamic regime. The developed model is used, simulating the HD system, to investigate the influence of the meteorological and operating parameters on the system productivity. The obtained set of ordinary differential equations has been converted to a set of algebraic system of equations by the functional approximation method of orthogonal collocation. The developed model is used to simulate the HD system in order to investigate the steady state behavior of each component of the unit and the entire system exposed to a variation of the entrance parameters and meteorological conditions. The obtained results were compared with those of other studies and the comparison gives a good validity of the present results.

     

Experimental investigation on low energy impact behavior of foam cored sandwich composites

This study focuses on an experimental investigation of damage tolerance of the foam cored sandwich composite subjected to low energy impact. Tests are performed to correlate delamination length with failure loads and loss of damage tolerance of the sandwich composite. The impact force history is used to determine momentum imparted to the specimen, the work done on the specimen, and the kinetic energy in order to gain an understanding of the mechanisms involved in damage due to impact loading.     

独立式散热舱冷却空气侧流动特性试验研究

Aiming at the great differences between the detached cooling system and the traditional axial cooling system in aspects like system arrangement, matching relationships between the fan and radiators, the flow field distribution and so on, the detached cooling test bench was designed. Experimental study on the detached cooling system with different radiators’ installation angle and position was carried out on the new test bench. Dynamic characteristics like flow resistance and air speed distribution were measured by piezometer tubes and impeller anemometers. Relatively uneven coefficient of the air speed distribution and system matching curve were calculated and analyzed. The results indicate that when the radiator installation angle is within 30°, with the angle increasing, radiator flow resistance decreases and air speed distribution on the radiator surface is more uneven. When the position relationships between radiators change from opposed form to vertical form, radiator flow resistance increases and air speed distribution is more uneven. The matching area between the fan and the detached cooling system locates in the area where the fan pressure is low and the air flow is large. [ABSTRACT FROM AUTHOR]     

Phenomenological investigation of cutting oils: Antifriction and antiwear behaviour at low contact temperatures

The basic reason for the use of cutting fluids in machining processes is to increase cutting tool life and to decrease machining costs. An experimental simulation of tribological processes representing rear cutting tool contact was carried out in a ‘block‐on‐disc’ (BOD) tribotester. The coefficient of friction and block wear were measured under boundary (discontinuous fluid film) and elastohydrodynamic (quasi‐continuous fluid film) lubrication conditions for neat and semi‐synthetic cutting oils. Interesting data were obtained concerning a further cutting fluid classification, which is helpful for optimal cutting fluid selection via their antiwear and antifriction characteristics.     

对高炉本体冷却系统的技术分析及探讨

高炉本体冷却系统能否正常工作,是决定一代高炉寿命的关键因素.从高炉冷却方式的选择、冷却设备的设计安装、检漏技术的发展应用、高炉生产的操作维护等方面,详细论述了目前高炉应采用的冷却新技术.为延长高炉寿命提供了必要的依据.     

低温环境下MEMS微构件的动态特性及测试系统

研究了微机电系统(MEMS)微构件的谐振频率等动态特性在低温环境下的变化规律,从理论上分析了改变环境温度对微悬臂梁谐振频率的影响,并对低温环境下微构件的动态特性测试技术进行了研究。研制了低温环境下MEMS动态特性测试系统,采用半导体冷阱实现低温环境,利用压电陶瓷作为底座激励装置的驱动源,通过底座的冲击激励,使微悬臂梁处于自由衰减振动状态,使用激光多普勒测振仪对微悬臂梁的振动响应进行检测,从而获得微悬臂梁的谐振频率。利用研制的测试系统,在-50℃～室温的环境下对单晶硅微悬臂的谐振频率进行了测试,结果表明,随着温度的降低,微悬臂梁的谐振频率略有增大,其谐振频率的温度变化率约为-0.263 Hz/K,与理论分析的结果基本一致。该测试装置能够有效地完成在-50℃～室温环境下微构件的动态特性测试。     

Experimental investigation on sliding and fretting wear of steam generator tube materials

In nuclear power steam generators, high flow rates can induce vibration of the tubes resulting in fretting wear damage due to contacts between the tubes and their supports. In this paper, the sliding and fretting wear tests were performed using Inconel 600HTMA and 690TT against STS 304, which are the steam generator tube materials. The sliding wear tests with a pin-on-disk type tribometer were carried out under various applied loads and sliding speeds at air environment. The fretting wear tests were carried out under various vibrating amplitudes and applied normal loads.

The result of sliding and fretting wear tests show that the heat-treated Inconel 690TT has better wear resistance than Inconel 600HTMA in air. The fretting wear regimes were plotted using the test results and the wear coefficient was calculated also. From the results, it was observed that the wear and tear by stick-slip has very strong effect on the fretting wear behavior.     

Experimental study on the thermal performance of a KNO2-KNO3 mixture in a trapezoidal solar pond

Journal of Mechanical Science and Technology - Salt gradient solar ponds (SGSPs) are thermal devices used for storing solar energy for low-temperature applications. The thermal performance analysis...     

Experimental investigation of a process cooling system retrofitted with HFC-404A refrigerant for precise manufacturing application

Precise-manufacturing facilities, which emphasize accurate and stable machining of the working components to be used in semiconductor industry, cannot function properly without appropriate and precise cooling. HCFC (hydro-chloro-floro-carbon) has been commonly used as the coolant for precise manufacturing facilities; but it is facing the pressing schedule to be phased out. Additionally, the dramatic variation of heat load during high-accuracy and high-speed applications need a critical control of coolant (brine or water) temperature. Use of eco-friendly HFC 404A to replace HFC has been suggested as an effective alternative to alleviate the problems. In this study, the performance of a process cooling system retrofitted with HFC-404A refrigerant was evaluated; the energy efficiency ratio and accuracy of temperature control specific to −15°C precise manufacturing application were examined. Effects of using thermostatic expansion valve associated with hot-gas by-pass control scheme under different loading conditions have been investigated extensively. The energy efficiency ratio and accuracy of temperature control for the cooling system were measured and analyzed for comparing and evaluating HCFC-22 and HFC-404A using different throttling devices under specific coolant temperatures. The comprehensive studies on improving the accuracy of temperature control and energy-saving efficiencies through different temperature control strategies are presented in this paper.     

An experimental study on the spray characteristics of a dual-orifice type swirl injector at low fuel temperatures

The objective of this study is to investigate the effects of fuel temperature on the spray characteristics of a dual-orifice type swirl injector used in a gas turbine. The major parameters affecting spray characteristics are fuel temperature and injection pressure entering into the injector. In this study, the spray characteristics of a dual-orifice type swirl injector are investigated by varying fuel temperature from — 30°C to 120°C and injection pressure from 0.29 to 0.69 MPa. Two kinds of fuel having different surface tension and viscosity are chosen as atomizing fluids. As a result, injection instability occurs in the low fuel temperature range due to icing phenomenon and fuel property change with a decrease of fuel temperature. As the injection pressure increases, the range of kinematic viscosity for stable atomization becomes wider. The properties controlling the SMD of spray is substantially different according to the fuel temperature range.     

Numerical investigation of dual-fuel direct injection on RCCI combustion performance at low load condition

Journal of Mechanical Science and Technology - A numerical study was performed to investigate the combustion characteristics of hydrogenated catalytic biodiesel (HCB)/gasoline reactivity controlled...     

太阳能光伏发电二轴跟踪机构的研究现状及发展趋势

首先综述了国内外太阳能单轴跟踪、二轴跟踪系统的研究现状,介绍了目前已有的5种二轴跟踪机构组成及其工作原理,在此基础上提出了差动式及并联式两种新型的太阳能二轴跟踪机构的概念设计,对发明的并联式太阳能二轴跟踪机构进行了结构及工作原理的阐述,表明该机构结构简单,制造方便,输入输出呈解耦性,控制容易,为一种理想的太阳能二轴跟踪机构.     

A study on energy saving of cooling/reheating system using compact heat exchanger

When circulated air passes through the cooling coil in an air-conditioning system, the air is over-cooled to eliminate the moisture and decrease the temperature. The cooled air is then reheated to recover the temperature. The purpose of the present study was to evaluate the performance of a cooling/reheating system with regard to both cooling and reheating energy savings affected by exchanging heat between the cooled air and the reheated air with a compact heat exchanger. The thermal and dehumidification behaviors of the system were evaluated experimentally and then compared with simulation data. The results show that the energy saving rate was as high as 50% under the present experimental conditions and was affected by the face velocity of the heat exchanger, the inlet temperature, the inlet humidity ratio, and the effectiveness of heat exchanger. Furthermore, the experimental data were found to be in fairly good agreement with the simulation data.     

Numerical simulation and design of a parabolic trough solar collector used as a direct generator in a solar-GAX cooling cycle?

In this work, a solar parabolic trough collector (PTC) has been dimensioned and its technical feasibility has been evaluated in order to be used as ammonia direct vapor generator in an advanced absorption air-cooled Solar-GAX cycle of 10.6 kW cooling capacity. A detailed numerical simulation model that takes into account the geometry and the optical, thermal and fluid dynamic behavior of the PTC has been developed. The model has been solved in order to reach minimal thermal losses through the PTC, and maximum coefficient of performance (COP) of the Solar-GAX cycle. Under design conditions, the solar PTC efficiency, the COP of the Solar-GAX cycle and the global efficiency of the system were 0.62, 0.87 y and 0.54 respectively. The calculated efficiency is 25.5 % higher than that provided by a single effect water-lithium bromide cycle coupled in an indirect form with a solar PTC system.     

Design and implementation of RELab system to study the solar and wind energy

It is well known that renewable energy, today more than ever, has undergone an exponential development. Thus, it is necessary to create an efficient, compact and relatively cheap system to be used in education and research, which allows studying these types of energy. The concept, design and implementation of such a system – RELab are presented in this paper. The RELab system is a very useful tool for students and engineers to learn about the two types of renewable energy: solar and wind energy. The system has two components: the NI ELVIS platform and the RELab add-on. The RELab add-on is a modular one and it can be easily redesigned for using the photovoltaic cell, the wind turbine and the solar thermal collector. The software used is built in the graphical programming language LabVIEW, and it is flexible and open.     

太阳能海水淡化与发电系统的研究

提出了一种可以利用低品位太阳能同时产生淡水和电能的太阳能海水淡化与发电系统,并给出其工作原理及其详细的热力学过程。利用温—熵图,通过理论分析,得出了热海水在不同的真空室温度下所产生的淡水量和电能,最后通过实验证明了该系统的在实际中的具有可行性,并且通过实验所测得的淡水量和理论值基本一致,表明热力学平衡模型是准确而可靠的,但是实验所测的发电量与理论值相差较大,主要是由于海水的不充分膨胀和摩擦磨损等因素所造成。     

An investigation of a heat pipe cooling system for use in turning on a lathe

A novel proposal is presented in this paper for reducing the thermal inaccuracy of turning on a lathe by removing the portion of the heat generated during the cutting process which is transferred to the carbide cutting insert by installing a heat pipe in the toolholder. The ability of the heat pipe to affect the temperature of the carbide cutting insert and the elongation of the toolholder is inferred from the response of thermocouples and strain gauges mounted on the toolholder to the heat generated during various cutting conditions. The results of the experimental investigation have proved the feasibility of the concept and recommendations have been made for continuing the research and improving the performance of the system.