Ventilation system with spiral recuperator

A new kind of longitudinal flow spiral recuperator for the heat recovery in ventilation systems of buildings was studied experimentally and analytically.The aim of this work is to analyze the possibility of using air handling units with new type of spiral recuperator in order to recover heat in ventilation systems of buildings. For the reason that the air flows are parallel to the symmetry axis of the longitudinal flow spiral recuperator, in this unit pressure drops are smaller than in commonly known spiral exchangers. Because of the counter flow, a greater value of thermal effectiveness ? is reached for the same value of the number of transfer units in comparison to cross-flow recuperators.The exploitation of the new type of spiral recuperator in winter periods brings significant savings. The results obtained from computations are very encouraging for a widespread use of these devices.     

Uncertainty in airflow rate calculations due to the use of surface-averaged pressure coefficients

Mean wind pressure coefficients (C_p) are key input parameters for air infiltration and ventilation studies. However, building energy simulation and stand-alone airflow network programs usually only provide and/or use a limited amount of C_p data, which are based on several assumptions. An important assumption consists of using surface-averaged C_p values instead of local C_p values with a high resolution in space. This paper provides information on the uncertainty in the calculated airflow rate due to the use of surface-averaged C_p data. The study is performed using published empirical data on pressure coefficients obtained from extensive wind tunnel experiments. The uncertainty is assessed based on the comparison of the airflow rate (?) calculated using the surface-averaged C_p values (?_AV) and the airflow rate calculated using local C_p values (?_LOC). The results indicate that the uncertainty with a confidence interval of 95% is high: 0.23 ?_AV < ?_LOC < 5.07 ?_AV. In cases with the largest surface-averaged ΔC_p, the underestimation or overestimation is smaller but not negligible: 0.52 ?_AV < ?_LOC < 1.42 ?_AV. These results provide boundaries for future improvements in C_p data quality, and new developments can be evaluated by comparison with the uncertainty of the current methods.     

Upgrading the Arlberg tunnel to current safety standards

Austrian road tunnels within the Trans-European Road Network (TERN) must fulfil the requirements of the Directive 2004/54/EC (European Commission, 2004) not later than April 2019. This regulation has to be applied to all tunnels in the TERN with a length of more than 500 m, whether they are in operation, under construction or at design stage, and aims at ensuring a minimum level of safety for road users. One of the main features of this directive is the requirement for providing an egress possibility to a safe environment every 500 m throughout the whole tunnel.The Arlberg road tunnel has a length of some 15.5 km and is in operation for more than 35 years. It is a single tube tunnel operated with bi-directional traffic, but carries a quite low traffic volume. Hence, the construction of a second tube is not really cost effective. Currently the tunnel is equipped with a transversal ventilation system with remotely controlled smoke extraction dampers providing smoke extraction every 100 m. The maximum distance between egress possibilities to a save environment is some 1500 m. Due to the high costs of a construction of a second tube or a parallel running escape gallery, a novel solution was found. The existing fresh air duct will be used as safe escape way between the existing egress possibilities. This solution has big impacts on the ventilation system and on the requirements for thermal structure protection of the new egress ways, i.e. the fresh air duct. In order to overcome this problem, massive changes in the ventilation design have to be performed, accompanied by the installation of a high-pressure water-mist system for structure protection.     

Effects of ventilation rate per person and per floor area on perceived air quality,sick building syndrome symptoms,and decision‐making

Ventilation rates (VRs) in buildings must adequately control indoor levels of pollutants; however, VRs are constrained by the energy costs. Experiments in a simulated office assessed the effects of VR per occupant on perceived air quality (PAQ), Sick Building Syndrome (SBS) symptoms, and decision‐making performance. A parallel set of experiments assessed the effects of VR per unit floor area on the same outcomes. Sixteen blinded healthy young adult subjects participated in each study. Each exposure lasted four hours and each subject experienced two conditions in a within‐subject study design. The order of presentation of test conditions, day of testing, and gender were balanced. Temperature, relative humidity, VRs, and concentrations of pollutants were monitored. Online surveys assessed PAQ and SBS symptoms and a validated computer‐based tool measured decision‐making performance. Neither changing the VR per person nor changing the VR per floor area, had consistent statistically significant effects on PAQ or SBS symptoms. However, reductions in either occupant‐based VR or floor‐area‐based VR had a significant and independent negative impact on most decision‐making measures. These results indicate that the changes in VR employed in the study influence performance of healthy young adults even when PAQ and SBS symptoms are unaffected.     

单扇混合式受控循环通风法的现场试验

通过现场试验,证朋了单扇混合式受循环通方法是一种在技术上可行、经济上合理的新型通方法,可以直接应用于实际生产.     

储粮通风降水系统的研究

通过对9种机械通风降水系统的研究,优选出全敞式地槽鼓风降水系统、地上风道鼓风降水系统、排风扇等负压通风降水系统等三类通风降水系统。对含水量为16～17％的玉米进行试验,能够有效地降低到安全水分13％,对保持储粮品质具有良好的作用。其风网设计较为合理,气流分布较为均匀。通风降水系统中,单位风量、管道风速、表层风速、静压、开孔率、途径比等测定数据均符合设计要求,具有效果好、能耗低、费用少的经济效益和社会效益。     

大型同步发电机定子多元流场与表面散热系数数值计算与分析

文中根据流体力学理论,采用有限体积法计算出定子通风沟内多元流场流速的分布,进而确定出表面散热系数,并把所得出的各表面的散热系数代入温度场进行计算.通过对考虑流场具体分布时的温度场计算结果与传统的计算结果、解析法计算的结果和实测值的比较,说明了本方法计算结果的准确性.将不同入口风速和不同入射角的径向通风沟内流场和散热系数的分布分别进行了比较和分析,得出了一些有益的结论.     

Modeling Ventilation Phenomenon in Sanitary Sewer Systems: A System Theoretic Approach

Municipal wastewater collection systems, due to the nature of their functions, carry varying concentrations of odorous gases. The production rate and transport of these gases within and out of sewer systems depend on air flow rate in the system piping. However, municipal sewers are generally designed to only transport sewage flow without giving consideration to the air flow field. As a consequence, the movement of air into, along, and out of collection systems is for the most part uncontrolled. The purpose of this paper therefore is to provide a new design protocol based on system theoretic techniques to be used by municipal engineers and environmentalists involved in odor control and sewer foul air transport studies. The modeling formulation accounts for combined wastewater drag and pressure-induced air flows, and manhole pressurization. The developed framework is applied to both hypothetical and real sewer systems to only illustrate the applicability of the modeling formulation.