Air-condition process for scalable fabrication of CdS/ZnS 1D/2D heterojunctions toward efficient and stable photocatalytic hydrogen production

We report the scalable fabrication of CdS/ZnS 1D/2D heterojunctions under ambient air conditions(i.e.,room temperature and atmospheric pressure)in which ZnS nanoparticles are anchored on the surface of CdS nanosheets.The as-formed heterojunctions exhibit a significantly enhanced photocatalytic H_(2) evolution rate of 14.02 mmol h^(-1) g^(-1) when irradiated with visible light,which is~10 and 85 times higher than those of pristine CdS nanosheets and CdS nanoparticles,respectively,and superior to most of the CdS-based photocatalysts reported to date.Furthermore,they provide robust photocatalytic performance with demonstratable stability over 58 h,indicating their potential for practical applications.The formation of 1D/2D heterojunctions not only provides improved exposed active sites that respond to illumination but also provides a rapid pathway to generate photogenerated carriers for efficient separation and transfer through the matrix of single-crystalline CdS nanosheets.In addition,first-principles simulations demonstrate that the existence of rich Zn vacancies increases the energy level of the ZnS valence band maximum to construct type-II and Z-scheme mixed heterojunctions,which plays a critical role in suppressing the recombination of carriers with limited photocorrosion of CdS to enhance photocatalytic behavior.

A Study on the Reduction of the Aerodynamic Drag and Noise Generated By the Roof Air Conditioner of High-Speed Trains

In order to investigate how the aerodynamic drag and noise produced by the roof air conditioner of a high-speed train can be reduced,the related unsteady flow in the near-field was computed using the method of large eddy simulation.In this way,the aerodynamic source for noise generation has initially been determined.Then,the far-field aerodynamic noise has been computed in the framework of the Lighthill’s acoustics analogy theory.The propulsion height and flow-guide angle of the roof air conditioner were set as the design variables.According to the computational results,a lower propulsion height or flow-guide angle is beneficial in terms of aerodynamic drag and noise mitigation.However,compared to the design scheme with propulsion height of 0mm,the aerodynamic drag coefficient of the configuration with propulsion height of 190mm and flow-guide angle of 30°is slightly larger,while the aerodynamic noise is obviously reduced.Thus,from the viewpoint of the aerodynamic drag and noise,the design scheme with propulsion height of 190 mm and flow-guide angle of 30°is the optimal configuration in the range of conditions examined in the present work.

Influence of Surrounding Structures upon the Aerodynamic and Acoustic Performance of the Outdoor Unit of a Split Air-Conditioner

DC-inverter split air-conditioner is widely used in Chinese homes as a result of its high-efficiency and energy-saving. Recently, the researches on its outdoor unit have focused on the influence of surrounding structures upon the aerodynamic and acoustic performance, however they are only limited to the influence of a few parameters on the performance, and practical design of the unit requires more detailed parametric analysis. Three-dimensional computational fluid dynamics（CFD） and computational aerodynamic acoustics（CAA） simulation based on FLUENT solver is used to study the influence of surrounding structures upon the aforementioned properties of the unit. The flow rate and sound pressure level are predicted for different rotating speed, and agree well with the experimental results. The parametric influence of three main surrounding structures（i.e. the heat sink, the bell-mouth type shroud and the outlet grille） upon the aerodynamic performance of the unit is analyzed thoroughly. The results demonstrate that the tip vortex plays a major role in the flow fields near the blade tip and has a great effect on the flow field of the unit. The inlet ring＇s size and throat＇s depth of the bell-mouth type shroud, and the through-flow area and configuration of upwind and downwind sections of the outlet grille are the most important factors that affect the aerodynamic performance of the unit. Furthermore, two improved schemes against the existing prototype of the unit are developed, which both can significantly increase the flow rate more than 6 %（i.e. 100 m3·h～（-1）） at given rotating speeds. The inevitable increase of flow noise level when flow rate is increased and the advantage of keeping a lower rotating speed are also discussed. The presented work could be a useful guideline in designing the aerodynamic and acoustic performance of the split air-conditioner in engineering practice.

Evaluation of Energy-Efficiency Standards for Room Air Conditioners in the US

This article describes an analysis of the energy and economic impacts of possible energy efficiency standards for room air conditioners on both U.S. consumers and the nation as a whole. We used two metrics to determine the effect of standards on a representative sample of U.S. consumers: life-cycle cost change and payback period. For the national impact analysis, we evaluated national energy savings attributable to each potential standard, the monetary value of the energy savings to consumers of room air conditioners, the increased total installed costs because of standards, and the net present value of the difference between the value of energy savings and increased total installed costs. Our analysis indicates that standards for room air conditioners at efficiency level 3, which is 17% more efficient than today’s typical unit in the case of room air conditioners less than 6000 Btu/h with louvers and 12% more efficient in the case of room air conditioners 8000 - 13,999 Btu/h with louvers, would save close to one quad of energy over 30 years and have a net present value of consumer benefit of between ?$0.14 billion and $1.82 billion, depending on the discount rate. In addition, such standards would reduce carbon dioxide emissions and NOx emissions.

Effect of air-conditioner exposure on semen quality

Aim: To investigate the effect of air-conditioner exposure on semen quality. Methods: The data came from the healthy male volunteers, aged 22 to 30 years, who went to centers for maternity and children health for premarital physical examination in Shanghai, Henan, Zhejiang and Hebei from December 1998 to February 2000. The sampling size is 304. Results: Among the subjects, 90 (29.6 %) had air-conditioner at home and the rest did not. X2-test and multiple logistic regression analyses showed that, the difference between the exposure and control groups was statistically significant in semen volume, sperm density and proportion of sperm with normal morphology. The three indexes were lower in the exposure group. Conclusion: Air-conditioner exposure possibly influences the semen quality.

Remote Control of Unitary Air Conditioner Based on Manufacturing Message Specification

Traditional air conditioner used to be in local control mode. However, with the development of modern information technology, the control of air conditioner will have to support many more functions. As a first step in such a development, we have implemented a remote monitoring system of unitary air conditioners, using the manufacturing message specification (MMS). MMS is an OSI application protocol designed for the remote control and monitoring of real devices. The functions supported are those that an operator would do normally at the console of the unitary air conditioner. Due to the accomplishment of UMCS (Unitary air conditioner MMS Control System), there will be a leap of the application of MMS and the control technology of unitary air conditioner.

基于ISSA-LSTM的热舒适短期预测模型

为解决在测试日内的短期预测过程中,农村城镇人体热舒适中建筑惰性及人员等随机因素使人体感受变化的样本对预测结果影响大而导致预测精准度低的问题,提出基于改进麻雀搜索算法(ISSA)优化长短期记忆神经网络(LSTM)的方法建立新型户用空调热舒适短期预测模型;首先,对测试日气象数据进行动态性分析,对数据进行有效性验证并构建多种热舒适预测模型;随后选用新型用户热舒适短期预测模型(ISSA-LSTM)对热舒适进行预测。结果表明,模型的最高预测均方误差(MSE)比麻雀搜索算法(SSA)和蜣螂优化算法(DBO)优化LSTM分别提高了0.02296和0.10827,采用ISSA-LSTM方法后改善了短期热舒适预测的精度问题,并提高了分体式空调通过热舒适来控制温度的性能。

基于神经网络与NSGA-Ⅱ算法的方舱温控优化设计

综合考虑车载方舱外部传热与舱内设备的功率负载等因素对舱内热环境的影响,以车载空调的布局与送风角等作为设计变量,以舱内电子设备耐受温度与乘员舒适度为目标函数,采用BP神经网络建立设计变量与目标的映射关系,利用改进型非支配排序遗传算法对舱内的气流布局与环境温度梯度进行优化,取得Pareto前沿解。优化结果表明,在制冷功率一定的前提下,最优解集主要集中在空调较接近电子设备且前出风角较平直时。此方法节省仿真优化成本,对方舱内温度与流场环境控制具有重要工程指导意义。

DISPLACEMENT CONTROL AND KINETIC ANALYSIS OF A NOVEL VARIABLE DISPLACEMENT COMPRESSOR FOR AUTOMOTIVE AIR CONDITIONER

A novel variable displacement compressor (VDC) for automotive air conditioner (AAC) is introduced, which inherits the advantages of common wobble plate type VDC. It has fewer parts and makes less noise, and instead of pneumatic valve the displacement is controlled by electronic control valve. In order to know the control mechanism well and get a good control effect, a mathematical model for the variable displacement mechanism is developed according to the geometrical and kinematical information of the compressor. Using the model, the effect of relevant parameters on variable displace control is estimated. It is helpful to make the optimum decision in the flow control of AAC. As the novel displacement control device, the structure and control rule of electronic control valve is introduced. It can get better effect than the conventional pneumatic valves. And by using this new electronic control device, the optimum systemic control of AAC is available.

具有时滞效应的air2stream河流水温模型及应用研究

高精度河流水温模型对于深入了解水温的时空变化特征和河流生态修复具有重要意义。基于数据驱动的air2stream模型在保证预测精度的同时,避免了计算的复杂性,已成为河流水温模拟常用的模型。由于水的热惯性及水文条件等的影响,河流水温变化往往显著滞后于气温变化,而air2stream原模型并未考虑滞后效应,导致该模型在流量未知情况下实际精度偏低。为解决该问题,采用气温-水温皮尔逊相关系数计算时滞天数,构建具有时滞的air2stream新模型,进一步根据长江中下游地区两个监测站的多年实测数据验证新模型的有效性和稳定性。结果表明:新模型在不引进额外观测数据的条件下具有更高精度且性能更稳定。相比原模型,在两个监测站新模型的均方根误差分别降低约4.29%和5.85%。新模型具有精度高、水文要素需求少的特点,可为长江中下游的水环境影响评价和生态保护提供依据。

高温环境因素对固-液混合燃料物理稳定性的影响

固-液混合燃料的物理稳定性对于燃料的质量和安全性均有重要的意义。高温环境引发的易挥发液体组分的气化将对燃料的物理稳定性产生极为复杂的影响。通过自主设计的实验装置模拟、加速燃料物理稳定性改变,并分别从液体燃料析出及密度分布变化趋势,分析高温环境因素的作用。结果表明:自然堆垛状态下燃料的顶部受饱和蒸汽压的改变影响较大,而中部、底部则由于燃料的紧密堆积,形成各自独立的气液平衡。同时,液体燃料于高温环境中对固体的润湿效果随之增强,更有利于液体组分完成对固体颗粒的吸附。在303~333 K的温度条件下,固液体积比为1.25∶1,硝基甲烷占液体组分40%的固-液混合燃料保持最佳的物理稳定性。

A PROSPECTIVE HYDROGEN STORAGE ALLOY PAIR FOR BUS AIR CONDITIONERS

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Girth welding system for vortex type refrigeration compressor of air conditioner

According to the requirements of welding process for vortex type compressor of air conditioner manufactured in product line, a special girth welding machine with PLC as control core was developed, which had both upright and 45 ° incline service positions. And some key technologies were researched, such as structural design of machine body, reliable conduction of rotary weldments and quality control of welding process and so on. The experimental results showed that this machine could satisfy the requirements of welding quality and girth welding technology, results also proved the machine was a high-effwiency and low-cost automatic welding device.

Impact of summer office set air-conditioning temperature on energy consumption and thermal comfort

To explore the relationship between summer office set air-conditioning temperature and energy consumption related to air conditioning use to provide human thermal comfort,a comparison experiment was conducted in three similar offices at temperatures of 24,26 and 28 ℃ respectively. A thermal comfort questionnaire survey was conducted. It is demonstrated that air-conditioner energy consumption at the set temperature of 28 ℃ is 113% and 271% lower than at 26 ℃ and 24 ℃,respectively. A linear relationship exists between air-conditioner energy consumption and the indoor and outdoor temperature difference. When comfortably dressed,over 80% of research participants accept the set temperature of 28 ℃. The regression analysis leads to a neutral temperature of 26.2 ℃ and an acceptable temperature of 28.2 ℃ for over 80% of the research participants subjects,indicating that the current 26 ℃ set temperature for offices in summer,required by Chinese General Office of the State Council,can be increased to 28 ℃. Moreover,analysis of predicted mean vote(PMV) index shows that a set temperature of 27 ℃,not 26 ℃,is sufficiently comfortable for office staff wearing long-sleeve shirts,long pants and leather shoes.

A Comparative Study on the Performance and Environmental Characteristics of Alternatives to R22 in Residential Air Conditioners for Tunisian Market

This paper presents the simulation results of a 9000 BTU/h air conditioner with some selected fluids that have been assessed for their suitability as alternatives to R22 for air conditioners. Only those refrigerants with zero Ozone Depletion Potential （ODP） are considered. The performances of 11 refrigerants were comparatively studied using the simulation software NIST Cycle_D. R134a, R290, R600, R404A, R407A, R407B, R407C, 407D, R410A, R410B, and R417A are considered in this study. The thermal performances, which are obtained with R 134a and R290, are very close to those of R22. The power consumptions of the unit operating with R404A, R407C, and R410A are higher in the range 22-31% with respect of R22. For the units operating with 407A, R407B, R407D, R407E, and R410B, the electric consumptions are higher in the range 10-23%. For R600, the power consumptions are in the range 6-8%. For all the fluids, the COP is lower by 7-24% than R22, except for R600 for which the COP is higher by 7-9%, and R134a and R290 which exhibit the same COP as R22. When considering the thermal and environmental parameters, R290 is identified as the best candidate for R22, provided the safety aspects of using R290 are addressed.

Ventilation of air-conditioned residential buildings: A case study in Hong Kong

More and more studies reported that there were insufficient ventilation and excessive CO_2 concentration in air-conditioned residential buildings, but few solutions were provided. This study investigates the overnight evolution of CO_2 concentration in air-conditioned residential buildings and then focuses mainly on the evaluation of three ventilation strategies, including overnight natural ventilation, short-term mechanical ventilation and short-term natural ventilation. On-site measurements were conducted in a typical residential bedroom in Hong Kong in September. The indoor and outdoor CO_2 concentration, air temperature and relative humidity as well as the outdoor wind speed during the measurements were analysed. Ventilation rates were calculated based on the time series of CO_2 concentration. This study confirms that additional ventilation is usually needed in air-conditioned residential buildings. Overnight natural ventilation with even a small opening is associated with excessive energy consumption and deteriorated indoor thermal environment. Short-term natural ventilation strategies are inefficient and uncontrollable. Compared to the best short-term natural ventilation strategy, a reasonably designed short-term mechanical ventilation strategy requires only a 41% of ventilation period to complete one full replacement of indoor air and to reach a lower indoor CO_2 concentration. Nighttime case studies and a theoretical analysis suggest that a few several-minute mechanical ventilation periods could potentially maintain an acceptable indoor air quality for a normal sleeping period of 8 h.

Optimal Scheduling of Air Conditioners for Energy Efficiency

Energy saving is one of the most important research hotspots, by which operational expenditure and CO2 emission can be reduced. Optimal cooling capacity scheduling in addition to temperature control can improve energy efficiency. The main contribution of this work is modeling the telecommunication building for the fabric cooling load to schedule the operation of air conditioners. The time series data of the fabric cooling load of the building envelope is taken by simulation by using Energy Plus, Building Control Virtual Test Bed （BCVTB）, and Matlab. This pre-computed data and other internal thermal loads are used for scheduling in air conditioners. Energy savings obtained for the whole year are about 4% to 6% by simulation and the field study, respectively.

Quality Testing of Air Conditioner Condensate and Its Potential in Water Conservation

A major part of world is facing water shortages today. While the world’s population has grown to more than 7.75 billion, the quantity of sweet water has remained the same. The ever increasing use of water by such a large population has resulted in pollution of many water sources. The developing world where a large fraction of total world population is located faces water scarcity in a more severe manner than the developed world. The developed world has managed to control human population and preserve natural water resources more effectively. As a result of this and also due to stabilized population, they face lesser problems for water availability. Indian population stands at 1.386 billion as nowadays. The erratic monsoon rains over last few years have resulted in floods and subsequent water shortages in summer months in major part of the country. A similar situation is faced by many Asian and African countries. The means of recycling and using every possible source of water are always welcome in these countries. Since many of these countries lie in tropical or semitropical zone, the average relative humidity is more than 50% for most of the year. Changing life styles in these countries and spread of information technology based sectors have resulted in a growth spurt in air conditioning facilities. An air conditioner draws heat from surrounding air and cools the premises to desired temperature. During this process, a large amount of moisture in the atmosphere gets condensed and is drained out. There are no efforts made to recover this water in India and neighbouring countries. We have undertaken studies to check the quality of this water and see the feasibility of its use in a decentralized but effective manner. The results show that this water condensate from air conditioners is highly pure, substantial and available almost round the year. This can help in recovering millions of litres of good quality water daily. This water would find uses in industries, laboratories, households and farming. It would also create good business opportunities.

Critical assessment of R410A alternatives for mini-split air conditioners in the Egyptian market

In this study,the potential implementation of three different low-GWP refrigerants(R32,R452B,and R454B)as replacements for R410A was investigated.The study was performed using a simulation tool developed by the authors called RACHP-Lab,which is a vapor compression system simulation tool developed based on physics-based simulation for typical mini-split air conditioners.The simulation study was carried out and validated using experimental performance data of 10 different air conditioning units available in the Egyptian market.The units included fixed-speed or variable-speed compressors and operated in cooling or heating modes.Drop-in replace-ment with the new refrigerants was carried out.For R32,the capacity increased between 4.9%and 13%for cooling cases,and 6.3%and 12.4%for heating cases.However,COP did not improve in all cases.For R452B and R454B with direct replacement,the capacity nearly remained the same,with an increase of COP between 1.6%and 8.0%.Soft optimization was also conducted on cooling cases where compressor suction superheat,condenser subcooling,and compressor volumetric speed were optimized to maximize COP while maintaining the original capacity of R410A.R32 showed an improvement of COP over R410A between 4.6%and 15.5%,while for R452B and R454B between 2.2%and 13.2%.