Study on Temperature and Humidity of Plastic Greenhouse under Different Ventilation Modes in the Yangtze-Huai Region in Hot Season

In order to analyze the ventilation and cooling performance of single-tunnel plastic greenhouse in Yangtze-Huai region, the effects of two different ventilation modes （side window, side window＋roof window） on the temperature and humidity of plastic greenhouse were studied. The results showed that the ventilation mode of opening side window and roof window could effectively reduce the temperature and humidity at the plant canopy height, which was conducive to the growth of plant in greenhouse.

The Combination Effect of Night Ventilation and Thermal Insulation on Passive Cooling of Buildings in Baghdad

An experimental investigation of passive cooling buildings has been carried out for a typical summer days extended from July to December of Baghdad in Iraq. Six independent chambers were designed and constructed for different roof constructions. Night ventilation has been applied to study the possibility of reducing air temperature in buildings by testing different air changes per hour extended from 5 to 30. Measurements outside chambers including air temperature; relative humidity and solar radiation were achieved, while surface temperature and air temperature inside the chambers were recorded. The results show that the air temperature can be decreased with a range from 3 ℃ to 6 ℃ when using 50 mm polystyrene. This decrease can further be lowered by 2 ℃ to 4 ℃ if night ventilation of change per hours in buildings is allowed. The reduction in air temperature can be reduced to 5 ℃ by combination of external night ventilation and white paint.

Energy Design and Optimization of Greenhouse by Natural Convection

This study addresses the pressing need for energy-efficient greenhouse management by focusing on the innovative application of natural ventilation.The primary objective of this study is to evaluate various ventilation strategies to enhance energy efficiency and optimize crop production in agricultural greenhouses.Employing advanced numerical simulation tools,the study conducts a comprehensive assessment of natural ventilation’s effectiveness under real-world conditions.The results underscore the crucial role of the stack effect and strategic window positioning in greenhouse cooling,providing valuable insights for greenhouse designers.Our findings shed light on the significant benefits of optimized ventilation and also offer practical implications for improving greenhouse design,ensuring sustainable and efficient agricultural practices.The study demonstrated energy savings in cooling from November to April,with a maximum saving of 680 kWh in March,indicating the effectiveness of strategically positioning windows to leverage the stack effect.This approach enhances plant growth and reduces the need for costly cooling systems,thereby improving overall energy efficiency and lowering operational expenses.

Thermal-Fluid Coupling Simulation of Ventilation Cooling System of Generator Based on FLOWMASTER

By taking a 2.3 MW double-fed asynchronous generator as an example,a new method for fast simulation analysis of ventilation cooling system inside generator is proposed based on the one-dimensional simulation software FLOWMASTER.The thermal-fluid coupling simulation model of ventilation cooling system inside generator is established.Under the stable running state of the generator,the flow velocity distribution and temperature rise of the key parts of the generator are analyzed.The results prove that the ventilation structure design of the generator meets the temperature rise limit.The simulation results are compared with the theoretical calculation results and the experimental results,which verify the correctness of the thermal-fluid coupling simulation method proposed in this paper.

Thermal Management of Vehicle Cabins,External Surfaces,and Onboard Electronics:An Overview

Reducing heat accumulation within vehicles and ensuring appropriate vehicular temperature levels can lead to enhanced vehicle fuel economy,range,reliability,longevity,passenger comfort,and safety.Advancements in vehicle thermal management remain key as new technologies,consumer demand,societal concerns,and government regulations emerge and evolve.This study summarizes several recent advances in vehicle thermal management technology and modeling,with a focus on three key areas:the cabin,electronics,and exterior components of vehicles.Cabin-related topics covered include methods for reducing thermal loads and improving heating,ventilation,and air-conditioning(HVAC)systems;and advancements in window glazing/tinting and vehicle surface treatments.For the thermal management of electronics,including batteries and insulated-gate bipolar transistors(IGBTs),active and passive cooling methods that employ heat pipes,heat sinks,jet impingement,forced convection,and phase-change materials are discussed.Finally,efforts to model and enhance the heat transfer of exterior vehicular components are reviewed while considering drag/friction forces and environmental effects.Despite advances in the field of vehicle thermal management,challenges still exist;this article provides a broad summary of the major issues,with recommendations for further study.

The Generation of Typical Meteorological Year and Climatic Database of Turkey for the Energy Analysis of Buildings

For sustainable development, a reduction in energy demand is essential. This could be achieved through improving energy efficiency, effective energy conservation and management. The weather conditions of a given region are the most important consideration for the proper design of space AC （Air Conditioning） systems. In this study, the typical meteorological year and climatic database of Turkey for the energy analysis of buildings were generated by SQL （Structured Query Language） database programmimg language. The Finkelstein-Schafer statistical method was applied to analyze the hourly measured weather data of a 23-year period （1989-2012） and select representative TMMs （Typical Meteorological Months）. The selection criteria were based on 13 meteorological parameters. These parameters are the daily mean, maximum and minimum values and ranges of temperature, dew-point and wind velocity and the daily values of global solar radiation. According to results of TMY （Typical Meteorological Year）, climatic database of Turkey including daily or hourly climate variables was created in SQL data tables.

Conscious Use of the Virtual Sphere Modeling in the Simulation of Passive Night Cooling of Buildings

Night cooling of building is considered as a technology with a high potential of impact on air conditioning energy needs. Natural ventilation should be the first option for night cooling, for obvious reasons of energy savings. The evaluation of the capacity of the building to cool down its structures during night ventilation is of primary concern during preliminary design stage, even though night cooling with natural ventilation is among the most complex problem to be modelled in details. Some modelling options are available, assuming different simplifications in space and time. Among them, virtual sphere modelling has been proposed in the past as a quick way to perform dynamic simulation of the night cooling of buildings. In this paper, the theoretical origin of the virtual sphere model is recalled, underlining its limits in case of application to buoyancy driven night cooling of buildings. The limits can explain the disagreements of virtual sphere prediction with other methods reported in literature and may stimulate a more conscious application of the model and further improvements of the method.

Predicting moisture condensation risk on the radiant cooling floor of an office using integration of a genetic algorithm-back-propagation neural network with sensitivity analysis

Pre-dehumidification time(τ_(pre))and pre-dehumidification energy consumption(E_(pre))play important roles in preventing the condensation of moisture on the floors of rooms that use a radiant floor cooling(RFC)system.However,there are few theoretical or experimental studies that focus on these two important quantities.In this study,an artificial neural network(ANN)was used to predict condensation risk for the integration of RFC systems with mixed ventilation(MV),stratum ventilation(SV),and displacement ventilation(DV)systems.A genetic algorithm-back-propagation(GA-BP)neural network model was established to predict τ_(pre) and E_(pre).Both training data and validation data were obtained from tests in a computational fluid dynamics(CFD)simulation.The results show that the established GA-BP model can predict τ_(pre) and E_(pre) well.The coefficient of determination(R^(2))of τ_(pre) and of E_(pre) were,respectively,0.973 and 0.956.For an RFC system integrated with an MV,SV,or DV system,the lowest values of τ_(pre) and E_(pre) were with the DV system,23.1 s and 0.237 kWh,respectively,for a 67.5 m^(3) room.Therefore,the best pre-dehumidification effect was with integration of the DV and RFC systems.This study showed that an ANN-based method can be used for predictive control for condensation prevention in RFC systems.It also provides a novel and effective method by which to assess the pre-dehumidification control of radiant floor surfaces.

Energy Efficiency in Building: Case of Buildings at the University of Ibadan, Nigeria

Nigeria today faces serious challenge in providing adequate energy to meet the needs of her citizenry. Efforts are currently geared towards generation of more energy to ease the problem. While these efforts are commendable, it is equally desirable to explore ways to minimize consumption of generated energy. The objective of this work is to investigate the effect of building orientation on energy demand in buildings. This paper considered the use of standard design considerations, fundamental cooling load equations and the guidelines stipulated by the American Society of Heating, Cooling and Air conditioning Engineers (ASHRAE). The study takes the designs of three buildings within the University of Ibadan, Nigeria into consideration with the view to harness the energy saving potentials through building orientation and selection of efficient cooling equipment. The results obtained were 155.34, 224.75, 86.35 kW and 163.60, 232.04 and 90.64 kW for the three lecture envelopes including the Faculty of Science, CBN and the Department of Chemistry lecture theatres using the North-South and East-West building orientations respectively. Increase in energy demand of 7.96, 7.29 and 4.29 kW was thus obtained with the East-West building orientation over North-South. Energy efficiency is thus guaranteed with North-South building orientation.

Technology and Studies for Greenhouse Cooling

Greenhouse technology is an efficient and viable option, especially for the sustainable crop production in the regions of adverse climatic conditions. High summer temperature is one of the worst effects on greenhouse crop production throughout the year. The main purpose of this paper is to present some technologies and studies for greenhouse cooling in summer. In the paper, some applicable and practical cooling technologies have been discussed. The choice of efficient cooling method depends on many aspects, such as local climate, agronomic condition, design and covering materials. To achieve desirable benefits, the combination of different cooling methods is necessarily used. Analysis of earlier studies revealed that a naturally ventilated greenhouse with larger ventilation areas (15% - 30%), provided at the ridge and side covered with insect-proof nets of 20 - 40 mesh size with covering material properties of NIR (near infrared radiation) reflection during the day and FIR (far infrared radiation) reflection during night was suitable for greenhouse production throughout year in some special regions. Evaporation cooling is the most effective cooling method for controlling the temperature and humidity inside a greenhouse. However, its suitability is restricted to the respective region and climate when the humidity level is high. The entry of unwanted radiation or light can be controlled by the use of shading. Researches show that shade net application with different perforated mesh size and their evaluation with respect to local climate and region are necessary to get cooling benefits in summer.

A state-of-the-art review on shallow geothermal ventilation systems with thermal performance enhancement-system classifications,advanced technologies and applications

Geothermal energy with abundance and large quantity can partially cover building heating/cooling loads and promote the carbon-neutrality transitions.Shallow geothermal ventilation(SGV)system,with a little initial in-vestment cost,is one of promising technologies to partly replace the conventional air-conditioning system for air pre-cooling/pre-heating.This paper reviews applications of SGV system for improving thermal performance over latest two decades,which mainly includes the reclassification of SGV system,coupling with other advanced energy-saving technologies,application potentials for building cooling/heating under various weather conditions.Heat transfer mechanism and mathematical modelling techniques have been reviewed,together with in-depth analysis on current research trends,existing limitations,and recommendations of SGV system.Phase change materials,with considerable latent energy density,can stabilize the thermal performance with high reliability.The review identifies that optimization designs and advanced approaches need to be investigated to address the existing urgent issues of SGV system(e.g.,large land occupation,difficulty in centralized collection of condensate water timely for horizontal buried pipe,bacteria growth,polluted supply air,and high construction cost for ver-tical buried pipe).A plenty of studies show that the SGV system could greatly expand the application scope and improve system energy efficiency by combining with other energy-saving technologies.This paper will provide some guidelines for the scientific researchers and engineers to keep track on recent advancements and research trends of SGV system for the building thermal performance enhancement and pave path for future research works.

Energy Performance and Condensation Risk of DCDV System in Subtropical Hong Kong

The combined use of dry cooling(DC) system and dedicated ventilation(DV) system to decouple cooling and dehumidification process for energy efficiency was proposed for subtropical climates like Hong Kong. In this study, the energy performance and condensation risk of the use of DCDV system were examined by analyzing its application in a typical office building in Hong Kong. Through hour-by-hour simulation using actual equipment performance data and realistic building and system characteristics, it was found that with the use of DCDV system, the annual energy consumption could be reduced by 54% in comparison with the conventional system(constant air volume with reheat system). In respect of condensation risk, it was found that the annual frequency of occurrence of condensation on DC coil was 35 h. Additional simulations were conducted to examine the influence of different parameters on the condensation risk of DCDV system. Measures to ensure condensate-free on DC coil were also discussed.

Field observations of the thermal stability of permafrost under buildings with an underfloor open ventilation space and pile foundations in warm permafrost at high altitudes

Pile foundations combined with ventilation spaces under floors are the most common method in buildings over permafrost.The safety and stability of buildings are closely related to the temperature of permafrost.However,there are limitations of understanding on this method in the high-altitude,warm(>−1℃)permafrost areas on the Qinghai–Tibet Plateau.In this study,the thermal stability of permafrost foundation soils under buildings with an underfloor open ventilation space and pile foundations in warm permafrost at high altitudes was studied through field observations of ground and air temperatures,wind speed,net radiation from 2017 to 2021.The results indicated that the open ventilation space exerted an effective cooling effect on the underlying permafrost and pile foundations from March to October,while a thermal insulation effect was observed from November to February of the following year,but overall,the cooling effect dominated;the cooling effect of open ventilation spaces differed spatially.The permafrost temperature on the south-facing side was higher than that on the north-facing side,and those on the east and west sides were higher than that directly under the open ventilation space of the building.This study also demonstrated that radiation shielded by the building was a main factor of the cooling effect of open ventilation spaces,and the cooling effect of open ventilation spaces could accelerate the back-freezing of the cast-in-place(CIP)pile foundations.This structure could effectively maintain the frozen state of the underlying warm permafrost at high elevations on the interior Qinghai–Tibet Plateau.

动车检查库不同通风系统降温效果对比研究

基于实测数据开展了不同通风系统对夏热冬冷地区动车检查库降温效果的对比研究。结果表明:屋顶机械排风系统设计换气次数宜为2~4 h^(-1);直接蒸发冷却送风系统换气次数宜为3~4 h^(-1);诱导通风系统推荐采用中部送风、两侧排风的系统形式,机械送排风换气次数宜为2 h^(-1);各通风方案在推荐设计值下都能满足湿球黑球温度限值30℃的舒适性要求;综合对比各方案,机械排风系统造价最低,诱导通风系统效果最好,蒸发冷却送风系统适合于改善局部热环境。

典型核电厂址大型自然通风冷却塔对扩散的影响规律初探

近海核电厂采用二次循环冷却供水方式,配逆流式大型海水自然通风冷却塔。由于冷却塔作为高大建筑物以及冷却塔排放的雾羽对烟囱排放污染物扩散会造成影响,因此,需要针对工程布局,开展核电厂址大型自然通风冷却塔对扩散的影响规律研究。本研究联合风洞实验与数值模拟技术,发现核电厂大型冷却塔卷吸效应对放射性物质迁移途径和分布特征有显著影响。研究结果表明,无论是否排放雾羽,大型自然通风冷却塔都存在卷吸效应,烟囱排放的气载污染物会通过冷却塔底部进风口进入冷却塔,作为高架源进行二次排放。相比不排放雾羽,排放雾羽时的卷吸效应更加显著,通过冷却塔二次排放的污染物浓度显著增加。

高温独头巷道压抽混合式通风参数对人工制冷降温效果的影响

为了改善独头掘进巷道高温环境,以大红山铜矿西矿段-20m中段北沿脉西侧高温独头掘进巷道为研究对象,利用Fluent进行数值模拟,开展了风筒高度、抽出式风筒滞后压入式风筒距离及抽压比对独头巷道人工制冷降温效果的影响研究。结果表明:压入式风筒高度对降温效果影响明显,最佳高度为1.0m;抽出式风筒与压入式风筒高度持平时,降温效果最好,最佳高度为1.0m;抽出式风筒滞后压入式风筒距离过大不利于降温,最佳距离为5.0m;抽压比过小或过大均不能使掘进巷道形成良好的风流循环,降温效果较差,最佳抽压比为2.0。研究成果可为高温矿井通风辅助人工制冷降温参数选取提供指导。

高温掘进巷道中双压风筒布设位置及降温效果研究

为解决高温掘进巷道中冷却方法和冷却成本问题,量化分析双压风筒布置方式对巷道中人工作业区的通风降温效果,利用Fluent软件对不同通风布置模型进行数值模拟。首先,提出双压风筒通风降温思路,并分别建立3种风筒布置巷道的三维几何模型;其次,在送风速度v=8 m/s,送风温度T=293.15 K且相同环境模拟参数的条件下,对不同布置方式的降温效果进行对比研究;最后,分析得出布置2模型的温度场分布及降温效果最好,并总结其在不同送风温度时的降温规律,确定经济适用的通风降温方案。研究表明:风筒布设位置是决定巷道温度分布的关键因素,双压风筒的间距影响风流流向的对称性,而风筒位置高度影响温度均匀分布的距离;当送风速度v=8 m/s时,布置2通风降温效果明显且满足矿井通风需求标准,送风温度T=298.15 K时能为矿山生产最大限度节约经济成本。

浅圆仓不同运行方式对粮堆通风调温效果影响

浅圆仓在粮食储藏中有着广阔的应用前景,探究垂直通风与径向通风系统不同运行方式的通风降温效果,有助于为粮食的安全储存提供支持。文章以浅圆仓内粮堆(大豆)为研究对象,通过有限体积法,数值模拟了3种不同风道在正压上行通风和负压下行通风为期14 d的调温过程,获得了粮堆内部的气流和温度分布情况,并对比分析了通风降温速率、均匀性与能耗等。结果表明:各通风方式下均无通风死角,形式差异导致流向与涡团的位置差异;垂直风道正、负压方式下通风7 d后仓内无高温区域,其他两种风道出现高温区域,14 d时各种工况均无高温区域;只有径向风道的负压通风的降温速率与最终温度低于正压通风;径向风道的通风均匀性优于其他两种风道,正压通风的均匀性优于负压通风的;而正压通风的能耗普遍低于负压通风。

黄金矿山深井开采研究进展与发展趋势

详细阐述了黄金矿山深井开采国内外研究现状及所面临的技术难题,围绕采动岩石力学理论、岩体结构识别与岩体质量分级、矿山三维工程灾害建模、深部采矿设计方法研究、深部采场爆破落矿技术、采动地压调控、采动地压监测、自承载主动释压支护技术、深部采动对地表岩移影响、通风降温技术、智能开采技术、超深竖井建设等展开了详细的讨论与分析;对于黄金矿山非爆采矿机器人研制、采动岩石力学、深部采动地压灾害防控、深井降温技术、超深竖井建设、基于采动地压均衡的深部连续智能化开采技术等方面的未来发展趋势提出了展望,为黄金矿山深井开采的系统研究提供参考依据。

压入式通风条件下高地温隧道降温效果研究

为分析压入式通风对高地温隧道的降温效果,基于典型双线铁路隧道建立三维计算模型,重点研究风速、风温、岩温、风管出风口与掌子面间距及风管布置对降温效果的影响,并与理论计算结果进行了对比。结果表明:掌子面附近存在涡流现象,有利于局部温度降低,随着风流远离掌子面,逐渐向层流过渡,隧道平均温度也逐渐升高;风速越高,隧道内温度越低,温度场越均匀,越能快速达到温度稳态;风温越低,隧道温度也随之降低,且降温效果较提高风速更显著;围岩温度越高,隧道内空气温度越高,且通风对围岩温度场的影响深度十分有限;风管与掌子面间距越大,通风后隧道温度越高,施工中应及时跟进风管,以最大程度降低隧道温度,而风管布置对降温效果影响不大;理论分析较数值计算得到的温度场沿隧道纵向温度分布均匀性更差;总体来看,采用压入式通风可有效降低隧道内温度,风速20m/s、风温14℃时,降温率可达66%。