Wind-Thermal Environmental Characteristic of Multi-Variable Passive Enhanced Natural Ventilation System for High and Large Space Building

Natural ventilation effects in high and large space buildings of tropical areas greatlya ffect the air conditioning energy consumption.Aiming at nearly zero energy building design,thisp aper mainly contributes to provide theoretical basis and reference for thermal comfortable air conditioning system design of high and large space buildings.Taking a theatre in Hainan as study object,a newly composite enhanced natural ventilation system is proposed by integrating theu nderground tunnel-based earth to air heat exchange system and the solar chimney.Ventilationq uantity,air velocity and air temperature field,human vertical temperature gradient differenceu nder24simulation working conditions are considered and analyzed by using ANSYS Fluent.Fort he underground tunnel,results show that Group Two with double underground tunnels and side airs upply location shows its advantages in cooling effects and air supply uniformity.Then for the solar chimney,results show that the solar radiation intensity contributes to larger difference int ransmission power and leads to different cooling effects.On the whole,the system under workingc ondition No.7with120m long,side air supply,double underground tunnel and20m high,1mw ide,0.6°absorber plate angle solar chimney shows its priority in better comprehensive performance.

Influence of site selection on natural ventilation in Chinese traditional folk house

The relationship between the site selection of a hilly terrain and the natural ventilation of the Dangdamen building complex,which is a traditional folk house,is revealed by a computational fluid dynamics（CFD）simulation.The wind press and speed distributions around the building in four cases with different weather conditions and topographies are simulated.The simulation results show that a hill can reduce the absolute values of the wind pressure at the windward and leeward sides of the building.The encouraging effect of the patio on the natural ventilation in a terrain with a hill is greater than that without a hill.The same situation occurs when comparing the patio effects between summer and winter.The wind speed around the building can be reduced by the hill as it is an obstacle and the degrees of the influence of the hill in summer and in winter are quite different because of different wind directions.The analysis results show that this kind of site selection,with the hill to the north,is a suitable way to settle the conflict of the natural ventilation requirements in summer and in winter under subtropical climate conditions,especially in houses with patios.

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.

Performance Evaluation of Solar Chimney Draft: Application to Ventilation

Ventilation is one of the factors contributing to energy consumption in buildings and food preservation. The solar chimney proves to be an alternative for reducing conventional energy consumption. Thus, in this study, the performance of a solar chimney with two active faces for thermally drawing air from a chamber for preserving agri-food products was evaluated. These performances were experimentally assessed through data measurements: temperatures and velocities within the chimney, and their analysis using Excel and MATLAB. The obtained results were compared with those from literature to verify their validity. From this study, it is found that the maximum temperature at the chimney outlet reaches 49.4˚C with an average value of 43.7˚C. Additionally, the heating evolution of the chimney air presents four (04) identical phases in pairs, reflecting the chimney’s operation throughout day. The temperature difference between the outlet and inlet of the chimney reaches a maximum of 17˚C with an average of 12.6˚C. Regarding airflow, the maximum air velocity at the chimney outlet is 0.8 m/s, and the average velocities have consistently been greater than or equal to 0.46 m/s. Thus, it can be concluded that the solar chimney is capable of providing ventilation for the preservation chamber through thermal draft.

Numerical Simulation of Natural Ventilation in Northern Civil Pig Houses

With northern pig house as study objective,the 3-D numerical simulation of natural ventilation airflow field of five pig houses with different window area was done by using Fluent software,and the comparative analysis was carried out on simulation result and measured result.The results showed that the effect of ventilation was decided by the reasonable area ratio of window and earth and the ratio of length and width of window.According to this real pig house in experiment,there are the best uniformity of ventilation and the least area of having no ventilation by 1：10 of the area ratio of the window and earth in the pig houses,the smaller air retention zone by the smaller ratio of length and width of window,the better effect of ventilation;the results of simulation agree well with the results of measured,the max relative error and the average error was 11.1% and 7.7%,so the software of Fluent was proved effective in the numerical simulation of natural ventilation in the pig houses and the optimal design of pig houses＇ structure.

Natural ventilation performance of single room building with fluctuating wind speed and thermal mass

Natural ventilation is driven by either buoyancy forces or wind pressure forces or their combinations that inherit stochastic variation into ventilation rates. Since the ventilation rate is a nonlinear function of multiple variable factors including wind speed, wind direction, internal heat source and building structural thermal mass, the conventional methods for quantifying ventilation rate simply using dominant wind direction and average wind speed may not accurately describe the characteristic performance of natural ventilation. From a new point of view, the natural ventilation performance of a single room building under fluctuating wind speed condition using the Monte-Carlo simulation approach was investigated by incorporating building facade thermal mass effect. Given a same hourly turbulence intensity distribution, the wind speeds with 1 rain frequency fluctuations were generated using a stochastic model, the modified GARCH model. Comparisons of natural ventilation profiles, effective ventilation rates, and air conditioning electricity use for a three-month period show statistically significant differences （for 80% confidence interval） between the new calculations and the traditional methods based on hourly average wind speed.

Experimental Study of Tunnel Fire with Natural Ventilation

The 1/15 reduced-scale experiments using Froude scaling were designed to study the effect on the smoke control efficiency for subway tunnel fires with natural ventilation mode.The propane gas fires with heat release rate 11.48 kW was used,which corresponds to the heat release rate 10 MW in the full-scale tunnel.The temperature distributions under the ceiling were measured by K-type thermocouples to investigate smoke movement,and the velocity of smoke in shafts was measured by hot-wire anemometer to obtain the smoke extract amount of ventilation shafts.The results show that the smoke temperature under the ceiling varies with the longitudinal different distance from fire source.The results also show that the smoke temperature distributions and the smoke control efficiency in tunnel vary with the space between ventilation shafts and vary with the area and the height of ventilation shaft.

Effect of Window Opening Percentage on the Air Flow Rate of Wind-Driven Natural Ventilation Rooms

According to the investigations of window opening percentage (WOP) of Shanghai in 2011, the WOP varies significantly from season to season and thus affects the air flow rate of natural ventilation rooms. A three-dimensional computional fluid dynamic(CFD) model was applied to simulating the flow fields in a street canyon under different wind speed and WOP. The numerical simulations show that WOP has a significant influence on the static pressure distribution of the downwind building. Therefore, a correction factor k can be used for calculating the flow rate of wind-driven natural ventilation. The results show that k ranges from 0.43 to 0.49 when WOP is 4.44%; when WOP increases to 9.78%, the correction factor k lies in 0.32 and 0.36.

Study on the Optimization for Design of Indoor Natural Ventilation and Lighting Based on Passive Design Measurements

Based on the current indoor natural ventilation and lighting in the space of traditional residential buildings,this paper starts from the passive-design optimization of the spatial natural ventilation and lighting,and makes quantitative evaluation on the quality of current interior natural ventilation and lighting for two typical residential buildings by three indexes,including wind speed,static wind area ratio and satisfaction ratio about minimum lighting coefficient. Based on that, this paper conducts the passive design optimization, and establishes the quantitative association and reevaluation among the passive reformation design, natural ventilation,and lighting environmental quality,proposing the general strategy for the existing residential buildings to respond to the passive reformation design of the natural ventilation and lighting. The special reconstruction of core functionary space of integration of "the living room + dining room + partial space"is researched,and the redesign for the optimization and replacement of both indoor and outdoor enclosure parts is explored,which is expected to provide practical exploration on the strategies for passive construction of spatial natural environmental quality within a large number of highly-energy-consumed residential buildings in China,as well as the green design of residential buildings.

Prediction and analysis model of temperature and its application to a natural ventilation multi-span plastic greenhouse equipped with insect-proof screen

The natural ventilation widely used in greenhouses has advantages of saving energy and reducing expense. In order to provide information for climate control of greenhouse, a model was developed to predict the variation of air temperature in the naturally ventilated greenhouse equipped with insect-proof screen. Roof ventilation and combined roof and sidewall ventilation were considered in the model. This model was validated against the results of experiments conducted in the greenhouse when the wind was parallel to the gutters. The model parameters were determined by the least squares method. In the used model, effects of wind speed and window opening height on the air temperature variation were analyzed. Comparison between two types of ventilation showed that there existed a necessary ventilation rate which results in air temperature decrease in natural ventilation under special climatic conditions. In our experiments when wind speed was less than 3.2 ms?1, wind had a more gradual effect on greenhouse temperature for roof ventilation, compared with combined roof and sidewall ventilation, which had greater air temperature decrease than roof ventilation only.

Application of Indoor Natural Ventilation Simulation in Residential Space Layout

Tatural ventilation of indoor air flow and thermal comfort space plays an important role, especial y in the interior design of passive cooling factors, indoor space layout, and the location of doors, windows and other factors on the indoor natural ventilation effect has great influence. Using the method of fluid mechanics, and Airpak3.0 software, indoor natural ventilation for residential buildings was simulated, and the thermal comfort of indoor natural ventilation in a residential building in Xuzhou City was analyzed to explore the effect of indoor spatial layout, location of doors, window opening types on indoor natural ventilation. The results showed that indoor spatial layout played an essential role in indoor natural ventilation, application of numerical simulation for the simulation of the indoor natural ventilation and assessment of indoor natural ventilation effect was a scientific instruction for the indoor spatial design.

Formula Revision of Natural Ventilation Driven by Hot Pressure in Single Large Window Opening

This paper investigated the natural ventilation driven by hot pressure on a typical office building with single window opening.The actual result indicates that the ventilation rate of natural ventilation driven by hot pressure in the actual single window opening construction is very different from that obtained by the theoretical formula,since the ventilation conditions between actual environment and ventilation driven by hot pressure in the single window opening are different.Therefore,the theoretical formula is amended,and it becomes more consistent with the actual ventilation rate of natural ventilation driven by hot pressure under conditions that the construction is in the form of single window opening.

Application of natural ventilation of residential buildings in hot-humid regions

The current ventilation condition of the hot and humid regions was analyzed through on-site investigation. It is found that residents in this region expect to improve indoor thermal environment through natural ventilation as much as possible. Then,it comes to a conclusion by the field test that natural ventilation has certain practical effect on improving indoor thermal environment. CFD simulation software is employed to verify the test result. Based on PMV modified model,and according to norms,geography and climate combined with the measured and simulated results,the application of the time and effectiveness of natural ventilation in hot and humid region were analyzed,to some extent,providing a basis for reducing the air-conditioner's runtime with natural ventilation.

Study on Model of Indoor Air Pollution Forecast for Decoration Under Natural Ventilation Condition

To establish the model of indoor air pollution forecast for decoration. Methods The model was based on the balance model for diffusing mass. Results The data between testing concentration and estimating concentration were compared. The maximal error was less than 30% and average error was 14.6%. Conclusion The model can easily predict whether the pollution for decoration exceeds the standard and how long the room is decorated.

Natural Ventilation of Modern Residences in Rural Area in Guangdong Meishan City of China

By taking a modern residence in Meishan area as an example,15 measuring points have been set,and the wind speed of the parlor on the first and second floor and that of many bedding rooms have been measured every other hour from 7:00 to 22:00.Based on the measuring data and indoor architectural pattern,indoor ventilation has been analyzed.The results show that good natural ventilation could be created in modern rural residence by making use of plane layout,orientation and openings' organization,so that indoor air can be distributed evenly,helping to reduce temperature and remove humidness;indoor wind speed of the openings of architectures is the largest;and architectural orientation and opening's position can guide air flow and help to improve natural ventilation obviously.

Towards Enhancing the Effectiveness of Classroom Designs for Natural Ventilation Comfort in Yola, Nigeria

Given the perennial incidence of thermal discomfort, health issues, as well as energy costs associated with naturally ventilated classrooms in Yola, the study aimed at enhancing the effectiveness of classroom designs for natural ventilation comfort by examining the effects of six architectural design variables—size and position of openings, form of buildings, orientation of buildings, site planning, topography, and physical features, on the ventilation coefficients of 61 classrooms selected from nine stratified clusters in Yola, Adamawa State, Nigeria. Data were analyzed using percentages, ratios, means as well as standard deviation, and then sorted in groups using tables. The study revealed that the form and orientation of the classroom-buildings, as well as topography, site planning and other physical features, have no significant effect on ventilation coefficient. In addition, a new mean ventilation coefficient was obtained in ten classrooms against an earlier claim that ventilation coefficient cannot exceed a fixed average regardless of the ratio of wall opening to floor area.

Potential of Natural Ventilation in Mexico According to Its Hours of Hygrothermal Comfort

This work shows, through monthly maps, the potential of natural ventilation in order to cool down buildings in the different climatic regions of Mexico. By using the method of energy evaluation of buildings in Brazil applied to Mexico, a monthly electric-power saving factor is calculated to use natural ventilation for the forty-three biggest cities of the country according to their hours of hygrothermal comfort. Then, with the Geographical Information System Map Maker, monthly maps were created from the potentials of saving for the Mexican territory. Then, energetic, economic and environmental benefits were estimated for year 2006, in comparison to the realistic energy consumption in the same year.

A Field Assessment on Natural Ventilation and Thermal Comfort of Historical District--A Case of the Wugoushui Settlement in Taiwan

Due to the urban and town development, it is common to see historical buildings and new buildings intermingled with one and another inside historical regions in Taiwan. With the increase of new buildings, natural ventilation becomes harder, which leads to the impact on the preservation of historical building and the reduction of thermal comfort for residents. Besides, problems of new buildings＇ construction and design affect the developments of cities and towns in historical district, which has existed for hundreds of years. The Wugoushui Settlement is located in Pingtung County, the southernmost part of Taiwan, and its hot season of a year is pretty long and belongs to warm and humid tropical climate. In 2008, the Pingtung County Government officially registered and announced Wugoushui as traditional settlement and meanwhile, provided the maintenance and preservation for buildings in this region on government subsidies. This paper is based on one-year-long field experiments of Wugoushui Settlement. Residents in Wugoushui Settlement continue constructing new buildings near by the traditional buildings. With the fact that constructions of new buildings result in huge impact on the circumstances of natural ventilation and thermal comfort, which have been for hundreds of years, the simple weather station is set up to collect the data of local microclimate. In addition, four representative traditional architectures were selected to be measured their indoor and outdoor temperature, humidity, wind speed, wind direction and thermal radiation both in winter （December to February） and in summer （May to September）. The measurement time of each building is one week and every data record is kept every minute. Besides, residents were asked to fill out the comfort survey. Based on these data, the distributions of indoor and outdoor thermal environment as well as the thermal comfort of living space under the condition of the natural ventilation are assessed. Finally, focused on the indoor living space of historical districts in southern Taiwan, there are two main suggestions given in the essay： first, a provisional comfort zone in summer is planned and proposed; second, the preliminary suggestions for the design and norms of new buildings in historical district are provided.

Thermal Behaviour in Buildings with Green Covers Combined with Natural Ventilation, Green Facades and Green Roofs

The main aim of this paper was to study the influence of ventilation during a typical experimental day, in the internal air temperature as well as in internal surface temperatures under the conditions of the outer environment, using an experimental method which allows a comparison of the thermal performance between four cell tests： a prototype called control （no vegetation） and three with different combinations of vegetation （roofs and facades） installed in a region of tropical climate. The experiments were developed in four test cells with dimensions 2.0 m × 2.50 m × 2.7 m. Measurements of internal surface temperatures and internal air temperatures were collected with the use of specific equipment, a data logger （CR1000, Campbell Scientific Inc.）, connected with two multiplexers 32 channels （416AM Campbell Scientific Inc.）. Data were recorded over a year and a typical heat day was selected, which was September 24, 2015. The results show that ventilation affects the internal temperature of the air, so that this gets even surpass the external temperature. Regarding surface temperatures, increased temperature, except those which are provided with vegetation, namely, the surfaces which have green walls and green roofs file the lower temperatures. Therefore, we can confirm the ability of vegetation to maintain more pleasant internal conditions compared to the test cells built with conventional materials, thus it can reduce cooling load efficiency.

Numerical Analysis of Natural Smoke Ventilation Design System under External Wind Effect in Factory Compartment

This study applied the numerical simulator tool FDS （fire dynamics simulator）, Version 5.53, and focused on the simulation of the natural smoke flow ventilation design system, an innovative ventilation design using the parallel processing technology MPI （message passing interface）. The design was then compared with the exhaust efficiency of a typical natural smoke vent. The natural smoke flow ventilation design system was located at the top of the factory, where smoke streams effectively converged. Therefore, the source of fire was designed to be 2 MW, which has a better exhaust efficiency than typical natural smoke vent with same area. The simulation discovered that the exhaust efficiency of the natural smoke ventilation design systems is higher than that of typical natural smoke vent with 2 times the opening area and that was not affected by external wind speed, Instead, external wind speed can help to enhance the exhaust efficiency. Smoke exhaust of typical natural smoke vents was affected by external wind speed, even leading them to become air inlets which would disturb the flow of air indoors, leading to smoke accumulation within the factory.