Ventilation system design for a church pipe organ using numerical simulation and on-site measurement

Since old churches have had heating installed, more complaints have arisen of organs sounding out of tune. Sound frequency of organ pipes is dependent on air temperature. Old churches tend to have very large volumes, so are typically heated just before and during services in wintertime, in order to reduce energy usage. Warm air plumes rise at radiators and spread out into the room, finally reaching the cold organ casing where they cause a non-uniform temperature distribution within. If pipes standing in different temperature zones are played at the same time the organ sounds out of tune due to clearly audible beats (interference between two slightly different frequencies). The purpose of this study was to design a ventilation system inside the organ casing, able to create a uniform temperature distribution around the pipes. A computational fluid dynamic (CFD) model was developed for the St. Martin church in Oberesslingen, Germany. It was validated by on-site measurements that had been carried out in the organ casing of the church. Four organ divisions containing 300–500 pipes were represented by equivalent porous material zones. Their properties were determined using an auxiliary two-dimensional model of a staggered array consisting of 392 pipes. The effect of different ventilation system settings on the temperature field in the organ casing was examined. Best results were achieved by a system consisting of two ventilation lines together with a thin, synthetic net placed at the open interface between church and organ casing in order to reduce warm air inflow.     

An experimental study of naturally driven heated air flow in a vertical pipe

Specifications of warm air flow within a vertical pipe which is induced by the buoyancy effect were investigated in this study. Air from surroundings was directed into a heating chamber connected to a vertical pipe to establish a flow within the pipe. The temperature and the velocity were measured at different points within the stable flow and the mean values of these parameters were computed. Mass flow rate of air was evaluated using ideal gas assumption. In order to investigate the effect of the thermal boundary condition of the pipe, two tests were conducted; once for the pipe exposed to the surroundings and then for the pipe with a thermal insulation. A model for predicting the induced flow rate of warm air was developed and the predictions of the model were compared with the experimental data over the tested range of the parameters.     

透壁通风管路堤降温效应的室内试验研究

介绍了研究透壁通风管路堤降温效果的室内试验方法,对100cm×60cm×100cm尺寸的不同通风管路堤试样进行了实验研究。结果表明,采用透壁通风管能明显增强路堤的降温效果,而只在负温期间通风的透壁通风管路堤降温效果更为显着,路堤在通风管进风口附近的温度变化幅度以及负温区域的范围都明显大于通风管出风口处,形成了路基温度场沿着风向的不对称分布。     

低温热管蓄冷技术在人防工事中的应用

为了充分开发利用人防工事的地下空间和充分利用东北地区的冬季冷源,进行了把热管技术应用于人防工程中的研究试验工作,将天然冷源引入人防工程内,把工程改造为保鲜冷藏库。本文是对人防工事的改造、冷管研制和埋设及测试等的研究报告。     

Thermal comfort and IAQ assessment of under-floor air distribution system integrated with personalized ventilation in hot and humid climate

The potential for improving occupants’ thermal comfort with personalized ventilation (PV) system combined with under-floor air distribution (UFAD) system was explored through human response study. The hypothesis was that cold draught at feet can be reduced when relatively warm air is supplied by UFAD system and uncomfortable sensation as “warm head” can be reduced by the PV system providing cool and fresh outdoor air at the facial level. A study with 30 human subjects was conducted in a Field Environmental Chamber. The chamber was served by two dedicated systems – a primary air handling unit (AHU) for 100% outdoor air that is supplied through the PV air terminal devices and a secondary AHU for 100% recirculated air that is supplied through UFAD outlets. Responses of the subjects to the PV-UFAD system were collected at various room air and PV air temperature combinations. The analyses of the results obtained reveal improved acceptability of perceived air quality and improved thermal sensation with PV-UFAD in comparison with the reference case of UFAD alone or mixing ventilation with ceiling supply diffuser. The local thermal sensation at the feet was also improved when warmer UFAD supply air temperature was adopted in the PV-UFAD system.     

渗流条件下地埋管换热器传热特性研究

基于有渗流工况下地埋管管群的有限长线热源模型,通过Matlab软件模拟计算了深度为50 m平面处的地下温度场,根据地下温度场的温度分布,分析了布管方式,运行年限,孔隙率对地埋管管群传热效果的影响。研究表明:在物性参数,地埋管布管区域及地埋管总数不变的情况下,将地埋管等间距布置在布管区域内最有利于地源热泵系统的运行。地埋管布管区域冷热量累积效应在初始阶段较为明显,随着运行年限的增加,冷热量累积将在某一时刻达到动态平衡,此后将不随时间的增加而继续累积。对于冬夏季冷热负荷不平衡地区,孔隙率越大的区域越有利于地源热泵系统的运行。     

Analytical investigation of pre‐stressed,pre‐cast beams with steel pipe sleeves

This paper presents an analytical investigation of the structural performance of a pre‐stressed, pre‐cast concrete beam with steel pipe sleeves. The hybrid pre‐cast beam consists of reinforcing steel, a pre‐stressing tendon, pre‐cast concrete and cast‐in‐place concrete. Steel sections are installed at both ends of the beam, and steel pipe sleeves are installed at the locations of pipes. The steel pipe sleeves in the pre‐cast, pre‐stressed beam allow the installation of piping and facility equipment. A strain‐compatibility approach was used to predict the influence of the sleeves and pre‐stressing on the structural behavior of the hybrid pre‐cast beams. It was found that reinforcing rebar, used to reinforce the sleeve openings for circular steel pipes with a diameter of 125 mm, contribute 20% to the flexural load resisting capacity, suggesting that rebar reinforcement can be considered one of the structural components of the beam. The pre‐stressed, pre‐cast beam with steel pipe sleeve openings exhibited performance similar to that of beams without openings when the reinforcements placed for the sleeve opening were considered part of the flexural stiffness of the beam.     

管幕冻结暗挖工法冻结止水效果分析

管幕冻结法是利用管幕配合冻结止水措施解决复杂建设条件下暗挖施工的一种创新性工法,该工法利用管幕顶管内冻结管路对管间土体进行冻结止水,在顶管管幕和冻结土体的超前支护下实施隧道暗挖施工。文章以港珠澳大桥珠海连接线拱北隧道冻结方案为例,利用数值模拟手段对积极冻结期不同土层的冻结效果及圆形冻结管、异形冻结管开启时间进行了研究,结果表明圆形冻结管和异形冻结管宜同步开启。对维护冻结期开挖断面温度、风速进行模拟分析,结果表明开挖断面内空气温度宜控制在25 ℃,风速对冻结效果影响不大。     

Frost formation and condensation in stone–wool insulations

This paper reports on a laboratory experiment concerning frost formation and moisture condensation in fibrous insulation based on stone–wool. Frost formation in samples of stone–wool open to air was noted in cases when temperature field over the specimen was between +20 and ?20 °C and air on the warm side was saturated with moisture.Frost accumulated with time in the part of the specimen facing the cold air. In the part of the specimen facing the warm humid air condense formation occurred. In this part the material had moisture content considerably higher than what could be anticipated from data such as moisture isotherms.Border between frost and liquid condensate was quite sharp in the specimens of higher density. Moisture content mass by mass has an upward trend with decreasing density of the material sample. Moisture resistance factor was found to be quite high at these circumstances. Reason for this is not clear.     

寒区隧道环向排水管的条带保温及温度场分析

排水管过早地冻结与过晚地解冻是引起寒区隧道冻害的主要原因。针对冻结期和消融期隧道衬砌壁后围岩温度的变化特点,提出了一种条带状保温隧道环向排水体系:(1)隧道环向排水管自上而下直通隧道的中央排水管,隧道纵向排水管径三通向环向排水管汇水;(2)间隔地对环向排水管进行局部保温,在衬砌壁后采用条带状保温层,在路面之下采用带有保温层的排水管;(3)条带状保温层有两层防水板密封夹裹,其中一层防水板与隧道的防水板形成一个整体。衬砌围岩温度场有限元模拟分析表明:由于有、无保温层的环向排水管相间布置,两类排水管的冻融状态存在时差,该时差有利于解决衬砌后在冻结期和消融期的排水不畅问题。     

Thermal comfort,perceived air quality,and cognitive performance when personally controlled air movement is used by tropically acclimatized persons

In a warm and humid climate, increasing the temperature set point offers considerable energy benefits with low first costs. Elevated air movement generated by a personally controlled fan can compensate for the negative effects caused by an increased temperature set point. Fifty‐six tropically acclimatized persons in common Singaporean office attire (0.7 clo) were exposed for 90 minutes to each of five conditions: 23, 26, and 29°C and in the latter two cases with and without occupant‐controlled air movement. Relative humidity was maintained at 60%. We tested thermal comfort, perceived air quality, sick building syndrome symptoms, and cognitive performance. We found that thermal comfort, perceived air quality, and sick building syndrome symptoms are equal or better at 26°C and 29°C than at the common set point of 23°C if a personally controlled fan is available for use. The best cognitive performance (as indicated by task speed) was obtained at 26°C; at 29°C, the availability of an occupant‐controlled fan partially mitigated the negative effect of the elevated temperature. The typical Singaporean indoor air temperature set point of 23°C yielded the lowest cognitive performance. An elevated set point in air‐conditioned buildings augmented with personally controlled fans might yield benefits for reduced energy use and improved indoor environmental quality in tropical climates.     

柴木铁路热棒试验断面冷却效果研究

柴达尔至木里铁路是青海省地方铁路,全线均有多年冻土分布,依据青藏铁路热棒应用的成功经验,其部分路段施行了热棒冷却措施。不同于青藏铁路沿线气候和冻土条件,柴木铁路热棒应用效果有待于检验。设置三个试验断面,分析了气温条件,比较研究了热棒和无热棒路基地温变化的不同,结果表明:(1)柴木铁路大风频繁、气温低、温差大的气候条件有利于热棒的应用;(2)无热棒断面路基地面深度3 m以下地温波动较小,长期稳定在-1 ℃附近;(3)在第二个冻融周期的冬季,热棒能够有效地降低路基温度;(4)热棒断面路基第二年的冬季降温效果非常显著,冻土上限最大抬升了1.5 m。热棒冷却措施能够保障柴木铁路多年冻土路基稳定,为铁路的正常运营提供保证。     

承台施工期水管冷却的影响因素分析

本文以某特大悬索桥的索塔承台为例,利用ANSYS有限元分析软件,在模拟其分层浇筑过程的基础上,分析了承台在水管冷却作用下的温度场分布,从而得出水管的降温效果。其中,本文重点分析了冷却水管间距、开始通水时间、管材对冷却效果的影响。     

数据机房用分离式热管散热器运行特性分析

信息化水平的不断提高直接带来了数据中心耗电量的急剧增加。数据机房不同于一般的公共建筑,考虑到隔热、隔湿及洁净度的要求,即使在冬季也需供冷降温。而在满足散热需求的前提下,最大限度利用自然冷源则是降低空调能耗的最有效方法。但目前自然冷源的利用中常出现受环境影响大、节能效率低等问题,热管式散热器能将室内外空气完全隔绝,具有启动温差小、体积小、安装灵活等优点,在机房节能中有很大的应用潜力。以节能和良好的环境适应性为目标,对数据机房应用分离式热管的被动式散热方式进行了理论分析。以本学科工程领域现有技术为基础,理论分析了应用分离式热管的意义及优势,定义了分离式热管蒸发段及冷凝段的换热效率,建立了数据机房应用分离式热管散热系统的理论分析模型,以某名义排热量为30 kW的管翅式换热器为例,研究换热效率随风量的变化关系,得出分离式热管散热下可运行的最高允许室外温度、全年运行时间、功耗及全年节电量等关键参数。以某一30 kW冷负荷数据机房为模型进行CFD软件模拟,获得了采用分离式热管散热器的机房内部温度场分布,并与普通空调进行了比较。针对室外温度下降所引起的室内侧送风温度过低问题,提出减小室外侧风量的具体改进措施。利用理论模型设计分离式热管换热系统蒸发段和冷凝段,提出可根据热负荷及实际机房灵活配置,建设成本低,有效适应机房现有散热系统的方法。主要结论如下:(1)分离式热管散热器应用于数据机房散热,换热效率随着风量增加而减小,分离式热管散热器应用于数据机房散热,换热效率随着风量增加而减小,但可利用室外冷源的温度升高,可利用室外冷源的时间也随之增加,可根据换热器及所在地区设计最佳风量。(2)分离式热管散热下风量较大时,机柜进风温度比普通空调散热更为均匀,机房内热环境更好,可减少机房内局部热点。(3)若风量不变,分离式热管散热器蒸发段送风温度随室外温度降低,并有可能低于机房送风的标准温度。可通过减小室外侧风量使室内蒸发段出风温度满足数据机房送风温度,同时散热器的能效也可进一步提高。     

The influence of environmental and geometrical factors on air-ground tube heat exchanger energy efficiency

More and more efficient solutions of thermal insulation of buildings result in an increasing role of ventilation in the energy balance of buildings. This leads to a necessity for seeking unconventional heat sources, as well as development of the exhaust air heat recovery methods. The use of heat accumulating potential of the ground perfectly fits into this trend, allowing natural pre-heating and pre-cooling of the inlet air. There appears to be very limited research and published data on their thermal performance in Poland. This paper introduces a developed method of air-ground heat exchanger (AGHX) performance evaluation together with its validation and research results of conducted simulation. The AGHX model (based on a quasi 3D finite elements method) allows analysis of energy performance dependence on a wide range of parameters including AGHX geometrical configuration, mode of operation and environmental factors. The simulation results indicate that the analyzed parameters in various degrees affect the thermal efficiency of AGHX; various is also the nature of their impact. For some of them it is possible to set a value to maximize heat or cold yield (pipe diameter and placement depth, number of parallel pipes, bypass system, soil thermo-physical parameters, ground area shading and ground surface cover). In other cases, the influence of parameters has an asymptotic nature for which the maximum heating or cooling efficiency is achieved for parameter values tending to infinity (pipe length and distance between parallel pipes).     

某浮式生产储油装置中央空调风道降噪改造

文昌油田群海洋石油116自投产以来,一直存在房间内噪声较大的问题,监测发现部分房间噪声超标,致使一些员工睡眠质量不佳,听力下降。油田采取技术改造,增大送风管的截面积,降低静音箱进风口的压差和风速;安装具有消音功能的波纹软管;采用新型静音箱,安装调节风闸平衡温度。改造之后,噪声明显降低,环境得以明显改善。     

使用塑料冻结管的液氮冻结温度场试验研究

温度场分析是判断冻结土体性状进而反映冻结效果的重要手段,而盾构出洞液氮冻结加固中使用塑料冻结管对温度场的分布有较大影响。为获得使用塑料冻结管液氮冻结温度场的分布规律,以相似理论为基础,使用塑料冻结管进行上海淤泥质黏土的液氮冻结物理模拟试验,得出结论如下:沿塑料冻结管长度方向,冻结管壁的温度差别较大,造成不同位置冻结壁的发展范围不均匀,在冻结循环的末端管壁温度最高,冻结效果相对较差。冻结形成冻结区内的温度分布曲线较陡直,而在冷却区的温度分布曲线较平缓,其温度梯度较使用钢管的液氮冻结时小。在土层性质确定的情况下,液氮灌注状况、冻结管间距、冻结时间是影响液氮冻结效果的主要因素。冻结过程中,采用较小的冻结管间距,可以加快冻结速度,缩短冻结时间,发挥液氮冻结优势。研究结果表明,塑料冻结管可以应用于液氮冻结加固施工,研究成果可以为液氮冻结的工程应用提供有益的参考。     

Thermal Sensations Resulting From Sudden Ambient Temperature Changes

This paper investigates the conscious experience of thermal transients, both experimentally and by means of a model of dynamic thermoreception. The experiments involved a sample of twelve human subjects, each undergoing twelve different ambient temperature step-changes. The research design included both temperature up-steps and down-steps, clothed and naked subjects, and transients both away from, and towards, neutrality. Each experiment lasted three hours, with the step- change occurring after 1.5 h when the subjects crossed between the twin climate chambers. Immediate sensations resulting from the temperature up-steps closely resembled later steady-state responses to the warmer environment, while initial impressions of temperature down-steps were typically twice the magnitude of their up-step counterparts. These experimental findings were accurately simulated by a simple thermoreceptor model coupled to a numerical model of heat transfer through clothing and cutaneous tissue. This heightened subjective sensitivity to temperature down-steps was achieved with the model by taking the subcutaneous depth of cold thermoreceptors to be less than that of the warm units, as noted by Hensel in his review of this specialized field (1981).     

武钢冷轧厂扩建爆破对环境的影响

武钢冷轧厂扩建镀锡作业线,要求对现有通风机室进行拆除。通风机室位于冷轧厂五机架东北端,西南面距离9m处有电控室,29m处有电子计算机房,北面30m处有开关站,东北面架空斜度5m处有煤气管道,屋顶上和两旁紧靠压缩空气管道和水管,靠近将爆破拆除的通风机室四角距离仅380mm有四个厂房柱,其柱基紧靠爆破拆除的风道。这些建筑物,设备仪表,特别是电子计算机,对爆破振动敏感,煤气管道在爆破时必须绝对安全,所以该拆除工程系高难度爆破,关键是爆破对周围环境的影响。首先要确保绝对安全,同时要保证正常生产。     

新风免费冷却节能研究

采用室外空气干球温度与比焓作为风侧经济器使用与否的判定条件,对新风免费冷却节能状况进行分析,提出了新风免费冷却节能效果评价指标———新风免费冷却节能率。应用该指标分析了我国不同气候条件下6个典型城市的3种不同类型建筑新风免费冷却节能效果,结果表明,北方严寒及寒冷地区节能率较高,夏热冬冷及夏热冬暖地区次之,温和地区节能率较低。宾馆建筑全年新风免费冷却节能率低于同一地区办公建筑和商场建筑。