Analysis of Cooling Characteristics in Datacenter Using Outdoor Air Cooling

Advancement of the information society has proceeded with the development of information and communication technology, and a demand on a data center has increased. In such a situation, the number of servers is increasing in a data center. Thus, the heat density in a data center is much higher than that of usual offices. And typically, almost 40% of the total power consumption is used for cooling servers in a data center. Thus, cooling effectiveness is one of the most important factors in evaluating the value of the data center. The data center taken up in this paper is located in Ishikari, where is a cold district in Japan. Using the cool outdoor air for cooling servers helps us to cut the power consumption for cooling. This paper first assesses the efficiency of Ishikari data center measuring the temperature of seven parts in a building where the cooling air flowing. Second, this paper describes the most efficient method for the operation and estimates 1.11 of PUE （power usage effectiveness）.

Surveillance-image-based outdoor air quality monitoring

Air pollution threatens human health,necessitating effective and convenient air quality monitoring.Recently,there has been a growing interest in using camera images for air quality estimation.However,a major challenge has been nighttime detection due to the limited visibility of nighttime images.Here we present a hybrid deep learning model,capitalizing on the temporal continuity of air quality changes for estimating outdoor air quality from surveillance images.Our model,which integrates a convolutional neural network(CNN)and long short-term memory(LSTM),adeptly captures spatial-temporal image features,enabling air quality estimation at any time of day,including PM_(2.5) and PM10 concentrations,as well as the air quality index(AQI).Compared to independent CNN networks that solely extract spatial features,our model demonstrates superior accuracy on self-constructed datasets with R^(2)?0.94 and RMSE=5.11 mg m^(-3) for PM_(2.5),R^(2)=0.92 and RMSE=7.30 mg m^(-3) for PM10,and R^(2)=0.94 and RMSE?5.38 for AQI.Furthermore,our model excels in daytime air quality estimation and enhances nighttime predictions,elevating overall accuracy.Validation across diverse image datasets and comparative analyses underscore the applicability and superiority of our model,reaffirming its applicability and superiority for air quality monitoring.

Indoor and outdoor BTX levels in Barcelona City metropolitan area and Catalan rural areas

Five aromatic hydrocarbons (benzene, toluene, and three isomeric xylenes) were monitored in indoor and outdoor air of 7 public buildings and 54 private homes, located in Barcelona City metropolitan area and in several rural areas of Catalonia. The sampling was carried out over four periods: spring-summer and winter of 2000, and summer and winter of 2001. Passive ORSA 5 Dra¨ger samplers were used for benzene, toluene, and xylenes (BTX) adsorption. BTX were extracted with carbon disulphide and analysed using ...

Assessment of Air Pollution,by the Urban Traffic,in University Campus of Bucharest

This study aims to measure traffic-related air pollution of vehicles with internal combustion, the main source of emissions of BTEX, organic compounds and NOx, NO2, NO, O3, CO, SO2, PM10 and PM2.5, inorganic compounds, in three sites of the University campus, surrounded by residential areas. According to the University data, around 8000 students are being exposed daily to the measured level of pollution, in all 3 studied places of campus. A mobile laboratory was used, which continuously measures above mentioned pollutants and mete-orological parameters. The diurnal variation of BTEX, in a sunny and rainy day showed two peaks of BTEX concentration in the morning and evening. In the rainy days, the non-polar (hydrophobic) compounds as BTEX are mechanically trained by rain into the ground, where either they enter into the groundwater, or volatilized and re-enter in the air. Particulate matter such as PM10 and PM2.5 is, in a large part, carried by the rain into the soil. The polar compounds (hydrophilic, NOx, SO2) dissolves in the rainwater and are absorbed in the soil (increasing soil acidity) and evaporated towards the clouds (leading to acid rain). In our study, BTEX compounds removed by the rain varied between 62% - 75%, NOx and SO2, 80% and 77% respectively. Particulate matters were washed out up to 68% for PM10, and 42% for PM2.5. In the sunny days the air pollution with measured concentrations of O3 (121.66 ± 7.02, 123.56 ± 4.89 μg/m3) remained for 7 hours close to the limit value (120 μg/m3). The maximum of solar radiation, with corresponding low concentrations in NOx and xylene, corresponds to photochemical reactions in the atmosphere, generating photochemical smog. In a sunny day and high traffic, we found the maximum value 5.4 μg/m3 for benzene, for 30 min., a known human carcinogen, exceeding the annual limit value de 5 μg/m3. The average background, from benzene, in three University campuses daily visited by around 8000 students was 0.97 μg/m3, exposed to 1.46 μg/m3 and the cancer risk is 1/100,000.

VAV系统中新风量的控制

介绍了变风量系统新风量控制中的风阀控制、送回风机控制、独立设置风机、混合段静压控制、ＣＯ２浓度控制和人数估计控制等方法，分析了各种方法的特点和应用范围。

VAV系统中的新风量确定及控制

介绍了变风量(VAV)空调系统的特点以及末端装置的结构,详细阐述了变风量空调系统新风量的确定方法和控制的方法,并分析了各种方法的优、缺点及适用范围。

公共建筑中新风能量回收系统节能量计算和控制方法研究

结合GB 50189—2015《公共建筑节能设计标准》的相关规定,给出了新风能量回收系统全年节能量的分析计算方法。以北京的酒店建筑和办公建筑为例,讨论了新风能量回收系统在4种控制模式下的节能效益,并给出了各种应用形式下单位新风量的全年节能量,供相关技术人员参考,以决定在新风系统中是否采用、采用何种形式及何种控制模式的新风能量回收系统。

空调客车中新风量的控制

空调客车的耗能是惊人的,如何使空凋客车在不影响乘坐舒适度的条件下,降低能耗,减少空调客车的运行成本,具有重要的意义。针对空调客车新风量进行了分析,并提出合理控制新风量以达到节能的目的。

医院无凝水空调系统——新一代微生物控制手段

通过控制理念与理论分析,认为无凝水空调系统创新点在于将传统的空调系统除湿与降温解耦。由于无凝水不存在细菌滋生问题;彻底消除交叉感染以及滋菌引起的气味、毒素或过敏原等。适用于卫生条件要求高,新风比较大且热湿比大的场合。在新风终状态点选择上,采用“最小新风比优先”的原则,无论在满足干工况、卫生要求方面还是在节省新风能耗上均具有优越性。

Pollution characteristics of 15 gas- and particle-phase phthalates in indoor and outdoor air in Hangzhou

Phthalate esters(PAEs),typical pollutants widely used as plasticizers,are ubiquitous in various indoor and outdoor environments.PAEs exist in both gas and particle phases,posing risks to human health.In the present study,we chose four typical kinds of indoor and outdoor environments with the longest average human residence times to assess the human exposure in Hangzhou,including newly decorated residences,ordinary residences,offices and outdoor air.In order to analyze the pollution levels and characteristics of 15 gasand particle-phase PAEs in indoor and outdoor environments,air and particulate samples were collected simultaneously.The total PAEs concentrations in the four types of environments were 25,396,25,466.8,15,388.8 and 3616.2 ng/m^3,respectively.DEHP and DEP were the most abundant,and DMPP was at the lowest level.Distinct variations in the distributions of indoor/outdoor,gas/particle-phase and different molecular weights of PAEs were observed,showing that indoor environments were the main sources of PAEs pollution.While most PAEs tended to exsit in indoor sites and gas-phase,the high-molecular-weight chemicals tended to exist in the particle-phase and were mainly found in PM2.5.PAEs were more likely adsorbed by small particles,especially for the indoor environments.There existed a good correlation between the particle matter concentrations and the PAEs levels.In addition,neither temperature nor humidity had obvious effects on the distributions of the PAEs concentrations.

Vibrational characteristics of piping system in air conditioning outdoor unit

The modal analysis of piping system in air conditioner (AC) outdoor unit is essential to investigate the vibration properties of the system. In view of the growing significance of numerical finite element (FE) model for vibration behaviour prediction, the AC piping elastic end support characterization has been explored. The axial and radial stiffness variables (ka, kr1, kr2) of the compressor-piping mounting are obtained and represented by dynamic stiffness of compressor grommet. They are obtained from dynamic load deflection test based on compressor operating condition such as excitation frequency and amplitude. The unknown stiffness variables of the other tube end (chassis-piping mounting) are determined by parameter fine tuning. An experimental modal analysis using impact hammer test has also been employed to determine the vibration properties such as natural frequencies, mode shapes and damping ratio of the piping structures. The modal parameters acquisition using SCADAS mobile acquisition system and LMS Impact Testing software is compared with the corresponding simulated modal properties using Abaqus. Most of the simulated natural frequencies achieve good correlation with the measured frequencies and it is reasonably a good prediction model to predict vibration behaviour of AC piping structures.

Outdoor air pollution and the onset and exacerbation of asthma

Exposure to outdoor air pollution has been consistently associated with asthma.In this study,we reviewed the epidemiological studies published within the last 5 years on the association between outdoor air pollution and exacerbation and onset of asthma.A large number of studies have been published within the last 5 years.Short-term exposure to outdoor air pollution is associated with exacerbation of pre-existing asthma,manifested as worsening of symptoms and increasing of asthma-related emergency room visits and hospital admissions.Furthermore,increasing evidence suggests that long-term exposure to outdoor air pollution can result in onset of asthma.Children are more susceptible to outdoor air pollution.Future studies should be conducted to explore the mechanisms underlying the association between air pollutants and onset of asthma,including gene involvement.In addition,disentangling the effect of a mixture of air pollutants and identifying the key components of air pollution will complete the existing evidence.More importantly,a better understanding is required on the future impact of air pollution on asthma under a changing climate.

Improving outdoor air quality based on building morphology:Numerical investigation

Due to rapid urbanization around the world,high concentrations of vehicular pollutants have deteriorated the outdoor air quality,which can affect the physical and psychological well-being of humans.Numerous strategies have been proposed to overcome these harmful impacts by improving the dispersion of air pollutants.Consequently,a question arises regarding the potential effects of building morphology on the dispersion of pollutants.Subsequently,transient three-dimensional Computational Fluid Dynamics(CFD)simulations are performed to examine the effect of building morphology on PM10 dispersion.Eleven cases with various prototypes and morphological methods are compared with a simple building form to identify the patterns of PM10 dispersion within a given time sequence under a prevailing inflow condition.The results indicate that the different designs of building morphology with varying Relative compactness(RC)indicator highlight the importance of considering morphological factors to improve outdoor air quality.In addition,the proposed prototypes can reduce PM10 concentrations by approximately 30%e90%at specific points in the studied time sequence.In particular,the vertical,horizontal,and grid folded prototypes can be considered more effective as an approximate decrease between 70%and 90%in PM10 concentrations is observed,which reflects the influence of building morphology on improving outdoor air quality.

基于正交试验的空调室外机顶板优化设计

In this paper,the modal analysis of an air conditioner outdoor unit is carried out and the simulation results are compared with the experimental results to verify its accuracy.Aseparate structural optimization analysis is performed for the top plate,and the compression bars of the top plate are changed from transverse to vertical placement.The simulation results show that the natural frequency and stiffness of the top plate are improved.Under the premise of vertical placement of the compression bars,a three-factor,three-level orthogonal test is conducted to find the optimal combination of low-order natural frequency and high-order natural frequency in the given range.

Six-day measurement of size-resolved indoor fluorescent bioaerosols of outdoor origin in an office

Indoor airborne bioaerosols of outdoor origin play an important role in determining the exposure of humans to bioaerosols because people spend most of their time indoors. However, there are few studies focusing on indoor bioaerosols originating from outdoors. In this study, indoor versus outdoor size-resolved concentrations and particle asymmetry factors of airborne fluorescent bioaerosols in an office room were measured continuously for 6 days （144 h） using a fluorescent bioaerosol detector. The windows and door of this room were closed to ensure that there was only air infiltration; moreover, any human activities were ceased during sampling to inhibit effects of indoor sources. We focused on fine particles, since few coarse particles enter indoor environments, when windows and doors are closed. Both indoor and outdoor fluorescent bioaerosol size distributions were fit with two-mode lognormal distributions （indoor R2 = 0.935, outdoor R2 = 0.938）. Asymmetry factor distributions were also fit with lognormal distributions （indoor R2 = 0.992, outdoor R2 = 0.992）. Correlations between indoor and outdoor fluorescent bioaerosol concentrations show significant concentration-attenuation and a time lag during the study period. A two-parameter, semi-empirical model was used to predict concentrations of indoor fluorescent bioaerosols of outdoor origin. The measured and predicted concentrations had a linear relationship for the studied size fractions, with an R2 for all size fractions of larger than 0.83.

Impact of climate change on outdoor design conditions and implications to peak loads

This study exams the impact of climate change on outdoor design conditions and peak loads of five Chinese cities over the five major climate zones for the winter and summer conditions.The design dry-bulb temperature(DDBT)and the coincident wet-bulb temperature(CWBT)for two 30-year periods;1971–2000 and 1984–2013 were analysed.It was found that the DDBT of the period 1984–2013 was higher than that of the period 1971–2000,whereas the CWBT and the corresponding outdoor enthalpy of the period 1984–2013 was lower than that of 1971–2000 at the various cumulative frequencies.This trend implies that the increment in conductive heat gain through the building envelope due to the rising temperature can be lower than the reduction in fresh air load due to the lower outdoor air enthalpy.In this case,the peak cooling loads may reduce in all five cities under study,and this is different from the widely held view that global warming will lead to more stringent outdoor design conditions,higher peak cooling loads and larger heating,ventilation and air conditioning(HVAC)plants than the current or historical status.The implications to the“free-cooling”of HVAC systems with enthalpy control are discussed as well.

A cost-effectiveness assessment of the operational parameters of central HVAC systems during pandemics

The present study develops a cost-effectiveness assessment model to analyze the performance of major operational parameters of central HVAC systems in terms of airborne transmission risk,energy consumption,and medical and social cost.A typical multi-zone building model with a central HVAC system is built numerically,and the effect of outdoor air(OA)ratio(from 30%to 100%)and filtration level(MERV 13,MERV 16,and HEPA)are assessed under the conditions of five climate zones in China.Compared with the baseline case with 30%OA and MERV 13 filtration,the airborne transmission risk in zones without infector is negligibly reduced with the increase in OA ratio and the upgrade of filtration level,owing to their slight modification on the equivalent ventilation rate of virus-free air.However,depending on climate zone,a 10%increase in OA ratio results in 12.5%-78.6%and 0.1%-8.6%increase in heating and cooling energy consumption,respectively,while an upgrade of filtration level to MERV 16 and HEPA results in an increase of 0.08%-0.2%and 1.4%-2.6%,respectively.Overall,when compared to the use of 100%OA ratio and HEPA filtration,the application of 30%or 40%OA ratio and MERV 13 filtration would save annually an energy and facility related cost of$29.4 billion in China,though giving an increase of approximately$0.1 billion on medical and social cost from the increased number of confirmed cases.This study provides basic method and information for the formulation of cost-effective operational strategies of HVAC systems coping with the airborne transmission,especially in resource-limited regions.

医院门诊公共空间人流量特性及新风量需求

为掌握医院门诊公共空间的人流量,为新风系统的设计与运行提供基础条件。本文对典型医院2012年及2013年的人流量和门诊量进行了实地调研,采用相关性分析法、时间序列相似和聚类分析等方法,并采用规定性和性能化设计方法对新风量需求做了对比分析。结果表明:门诊公共空间人流量与门诊量存在显著线性相关,人流量特征即门诊量特征,由此构建了人流量模型;可采用月、周和小时分布指数来表征门诊量时间序列特性;门诊量时间序列是以周为基本变化周期,可将一周内不同周次的日门诊量时间序列分为四类,分别为周一,周二至周五,周六及周日;日门诊量时间序列呈双峰特性,上午与下午高峰的小时分布指数相差2.1~2.6倍,且夏秋季上午高峰较冬春季提前约1 h,下午则延后约1 h;采用性能化设计比规定性设计可使新风机组选型减小约5%,运行总风量减少5%~18.6%。本文可为医院门诊公共空间新风系统的设计与节能运行提供参考。