Traditional Ventilation System Research Articles

EFFECTS OF NATURAL VENTILATION SYSTEM WITH UNDERGROUND PIPE ON CALF BARN CONDITIONS IN WINTER

The aim of the present study was to investigate the effects of natural ventilation system with underground pipe which is an alternative ventilation system for temperature, relative humidity and air flow rate parameters in the calf stall indoor environment during the winter, when animals continuously stay in the barn. The temperature, relative humidity and air flow rate values of stall interior and outdoor air were continuously measured during the months of December, January, February, March by applying natural ventilation system with underground pipe and traditional ventilation system with windows in a 48 head calf barn with a floor area of 150 m2. Measured parameters in both ventilation systems were statistically compared.In the wake of implementing; It has been observed that the natural ventilation system with underground pipe in the calf barn in frigid meteorological conditions has a statistically better good achieve on the temperature, relative moisture and air flow rate criteria inside the stall than the traditional ventilation system carried out with windows.In the natural ventilation system with underground pipe, the outside air is taken from the exterior surface of ones of the lengthy sides of the barn, passes under the barn floor transversely and enters the stall from inner surface of the other lengthy side of the barn. Thus, outside air coming in the stall through underground pipes becomes warmer than the outside air picked up into the barn by windows. In addition, since the air taken into the barn with the underground pipe ventilation system penetrates directly into the ground and comes out of the chimneys, it allows the air inside the barn to be cleaned faster than traditional ventilation systems. Keywords: calf stable, natural ventilation, underground piped natural ventilation, temperature, relative humidity

Indoor air quality in naturally ventilated dwellings in Spain

This article presents the results of the exploratory study on indoor air quality in existing dwellings with traditional ventilation systems based on natural ventilation. A preliminary study of the most representative typology of the Spanish housing stock has been conducted and, based on it, twelve dwellings located in Madrid have been monitored in different periods. Monitored indoor air quality has been compared to that required in the regulations in Spain, the Código Técnico de la Edificación (Technical Building Code). According to the results of the research, 50 % of the monitored dwellings do not comply with the CO2-based air quality quantification offset in the regulations. Such non-compliance is primarily caused by high CO2 concentrations in winter, especially in bedrooms. These high concentrations and their seasonality are attributed to the interference of the occupant’s behaviour, influenced by weather conditions, that is affecting the efficiency of the existing natural ventilation systems.

CFD modeling of air exchange in a room using a textile air duct with microperforations

The article is devoted to the issue of increasing the energy efficiency of ventilation systems and improving the air quality in the working environment of the premises of communication personnel for the maintenance of transport infrastructure when using a new types of air distribution devices. These include textile air ducts made of polyester. This material allows you to cut micro-holes. The advantage of diffusers with microperforation is the possibility of even distribution of air throughout the premises without creating drafts in the working area. The results of the analysis of literary sources on the issue of improving air quality in public buildings are presented. The data on the results of a comparative CFD modeling of the air distribution in the room with two supply air supply schemes: through the supply openings and with the help of a textile air duct with microperforation are presented. In the course of numerical calculation, the distribution fields of temperature and air velocity in the working area of the room were obtained. It is concluded that the textile air duct copes with the task of removing excess heat more efficiently than the traditional ventilation system.

Dynamic sensing and control system using artificial intelligent techniques for non-uniform indoor environment

Traditional ventilation systems have difficulty in effectively capturing the dynamic and non-uniform distribution of indoor environment, making it difficult to meet the dynamic demand of real-time indoor environment control. This results in a large amount of energy consumption, and the comfort of indoor personnel is not guaranteed. Microsensors are used to monitor indoor air quality for responding to indoor environmental conditions and providing real-time regulation of indoor ventilation system. However, the monitoring by a single microsensor cannot reflect the global non-uniform indoor environment and can easily lead to ineffective control of indoor environment and thermal discomfort for personnel. Increased number of sensors can lead to wasted monitoring resources and inconvenient installation in the room. Therefore, this study developed dynamic ventilation control system based on “limited monitoring - fast prediction - real-time control” method. The system realized online transmission and reception of indoor environment monitoring data through wireless communication technology. Combined with fast prediction model to obtain the optimal air change rate per hour (ACH) value of indoor environment, the real-time regulation and intelligent control of indoor ventilation system can be realized, further promoting a balance between energy consumption (up to 60% ventilation energy savings) and indoor environmental quality. This work can provide important strategies and technologies for the construction and implementation of intelligent ventilation control systems.

Investigation of the performance of lateral ventilation in subway station fires

Lateral ventilation has been widely used in tunnel ventilation in recent years. But the effect of lateral ventilation in subway stations has received little attention and discussion. Based on numerical simulation, a real standard subway station is modelled in this paper to study the applicability of lateral ventilation in subway stations. Both the traditional ventilation system with vents located at the bottom of ventilation ducts and the proposed lateral ventilation system with vents located at the side of ventilation ducts are presented and compared. Parameters including temperature, CO concentration, and smoke layer height are adopted to qualitatively study the smoke control effect of different vent layouts. Parameters including ventilation efficiency and fractional effective dose are adopted to quantitatively model the ventilation performance of different vent layouts. The results indicate that: (1) The side vent layout is recommended in subway station emergency ventilation with slower horizontal smoke diffusion, slower vertical smoke settlement, and better smoke layer stability. (2) The advantage of side vent layout is quantitatively validated with higher ventilation efficiency in every vent and lower gas toxicity at eye-sight height. (3) Sensitivity analysis of fire location, heat release rate, vent amount, and vent size are conducted to verify the advantage of the side vent layout. In all scenario groups simulated, a better smoke control performance, higher ventilation efficiency, and lower fractional effective dose value is acquired in side vent layout. This research presents the application prospect and design method of lateral ventilation in subway stations.

A NOVEL OCCUPANT DETECTION-BASED VENTILATION CONTROL STRATEGY FOR SMART BUILDING APPLICATIONS

Traditional ventilation systems supply fresh air to the building on a consistent basis, however, do not ensure adequate comfortable areas in indoor environments. On the other hand, smart ventilation systems adjust indoor environment parameters optionally by occupancy schedules to provide desired indoor air quality while minimizing energy consumption. ASHRAE Standard 62, which shows ventilation strategies for acceptable indoor air quality, uses steady-state occupancy detection algorithms, however, dynamic methods are required behind simulation studies. To this aim, this study presents a dynamic novel ventilation control strategy by detecting occupants in an office building in Ankara-Turkey. The novel control strategy includes deployment of several sensors which measure carbon dioxide concentration, indoor air temperature and position of the door. A prototype of the controller is manufactured and tested in a real environment with the help of regulation of air flow in HVAC system. The proposed control strategy is tested between January 1st, 2020 and August 15th, 2020 and compared with traditional controller in terms of thermal comfort and energy consumption. The results showed that proposed controller decreased energy consumption by 16% while satisfying thermal comfort for the 94% of total number of occupants.

Prediction and control of aerosol transmission of SARS-CoV-2 in ventilated context: from source to receptor.

Global spread of COVID-19 has seriously threatened human life and health. The aerosol transmission route of SARS-CoV-2 is observed often associated with infection clusters under poorly ventilated environment. In the context of COVID-19 pandemic, significant transformation and optimization of traditional ventilation systems are needed. This paper is aimed to offer better understanding and insights into effective ventilation design to maximize its ability in airborne risk control, for particularly the COVID-19. Comprehensive reviews of each phase of aerosol transmission of SARS-CoV-2 from source to receptor are conducted, so as to provide a theoretical basis for risk prediction and control. Infection risk models and their key parameters for risk assessment of SARS-CoV-2 are analyzed. Special focus is given on the efficacy of different ventilation strategies in mitigating airborne transmission. Ventilation interventions are found mainly impacting on the dispersion and inhalation phases of aerosol transmission. The airflow patterns become a key factor in controlling the aerosol diffusion and distribution. Novel and personalized ventilation design, effective integration with other environmental control techniques and resilient HVAC system design to adapt both common and epidemic conditions are still remaining challenging, which need to be solved with the aid of multidisciplinary research and intelligent technologies.

Annual dynamics of the micro-climate parameters in pig farms and their impacts on the production qualities of lactating sows

The experiment compared the annual dynamics of microclimate parameters in sows and lactation rooms of sows under different variants of their ventilation and its effect on sows' productive qualities and growth of their offspring. Technological group of lactating sows with pigs are very sensitive to any climate change. They are basis for the next development and implementation of their genetic potential, therefore one of the most important issues of retention is the right choice of the microclimate creation system. One of the main tasks in this case is also the reduction of energy costs to ensure proper parameters, both for animals and for their serving staff. It was revealed that during the year the geothermal ventilation system of the premises, due to the heating of the air in the underground mines and its uniform distribution by the air duct system, created more comfortable temperature conditions of keeping for the pigs and sows, compared to the traditional ventilation system. Both traditional and geothermal ventilation systems during this period provided optimal gas composition of the air and maintained it within the normal range. Optimal indices of humidity in rooms were at both systems of creation of a microclimate in all seasons except summer. In the summer both ventilation systems failed to provide optimal indoor humidity. The best microclimate conditions created by the geothermal ventilation system in the pig yard for the farrowing contributed to the improvement the conservation of piglets by 1.05−2.03 % before weaning, the increase in individual weight by 2.87−9.83 %, nest weights by 3.82−11.57 % when weaned, and live weight gain of suckling piglets by 8.12−25.9 g in all seasons, compared to the traditional system. Key words: productivity, ventilation, microclimate, air, temperature, gas composition, sow, piglet, multiplicity.

Application of the twin-tube complementary ventilation system in large-slopping road tunnels in China

To solve the imbalanced problem of wind pressure between left tunnel and right tunnel in the large-slopping tunnel, the complementary ventilation system is proposed, and the design theory and calculation method are also discussed. Results from a experiment carried out in a model tunnel (1:10) with complementary ventilation are presented and applied to the Dabieshan tunnel. It is found that the twin-tube complementary ventilation system can bridge two tunnels and exchange air between tunnels to ensure adequate air quality. The fresh air in the downhill tunnel can be transfer into the uphill tunnel to dilute air in the uphill tunnel. Field measurements were performed in the Dabieshan tunnel on wind speed, CO concentration, and VI (visibility index) concentration. Measurement results also indicate that the twin-tube complementary ventilation system can meet the ventilation requirements for tunnels. Compared with traditional ventilation systems, the complementary ventilation can be used to ensure adequate air quality in tunnels by eliminating the ventilation shaft in uphill tunnel and saving initial investments and operation costs.

Numerical Analysis for Smoke Spread in an Aircraft Hangar

Smoke is one of the most dangerous factors in aircraft hangar in case of fire. As it causes reduce in visibility and deaths due to high temperature or toxicity also prevents applying evacuation plan for workers. This study present numerical analysis for improving traditional system of ventilation system to manage smoke produced due to push-back vehicle on fire at hangar. By studying effect of changing extraction and supply rates, the number of extraction and supply fans, and the arrangement of extraction and supply fans on the visibility, temperature and air velocity at human level to insure not to exceed limits stated by NFPA 130[1] to apply evacuation plan for workers. The study is performed using Fire dynamic simulator to simulate 16 case studies in the hangar of airports in Brandenburg. The hangar has the outer dimensions of 83.40 m width and 77.60 m depth and thus an inner area of approx. 6,472 m2. The hangar has a medium interior height of approximately 18.20 m. The results show that using extraction fans with rate (ACH) double the supply rate for the traditional ventilation system gives very good results in controlling the smoke. As well as, decreasing the number of supply fans will make the smoke spread rate inside the hangar lower, which helps to control the smoke spread of fire in less time.

Turkey meat quality (Meleagris gallopavo) submitted to different ventilation systems during fattening

The present investigation evaluated the quality of turkey meat produced in two production systems, according to the following parameters: water loss in cooking, drip water loss, texture (shear strength), pH, color, humidity, protein, ashes and lipids. A total of 200 turkey breast samples of 500 g, separated by a batch of 20 samples, from ten aviaries from Santa Catarina, Brazil, were used: five from breeding with a traditional ventilation system and five with a mechanical ventilation system. Samples were obtained after slaughter and frozen at -15°C for 30 days. The results were submitted to variance analysis and the Tukey test. Significant differences were found only in the analysis of drip water loss. The birds of the traditional ventilation system presented 14.26% loss of water drip, while those of the ventilation exhaust system presented a loss of 19.21%. There were no differences in the chemical composition of poultry meat in relation to the production systems.

Ocena zmniejszenia strat energii cieplnej budynku wielorodzinnego w wyniku przeprowadzonej termomodernizacji

W artykule przeanalizowano wpływ wentylacji mechanicznej nawiewno-wywiewnej, z odzyskiem ciepła, na zmniejszenie zapotrzebowania na energię cieplną w budynku wielorodzinnym. Sprawdzono również wpływ rodzaju docieplenia na rozkład temperatur i ciśnień w przegrodzie. Obliczeń dokonano za pomocą programu Purmo OZC 6,0 dla zabytkowego budynku wielorodzinnego, 3-kondygnacyjnego, który poddany zostanie głębokiej termomodernizacji. Na podstawie obliczeń stwierdzono, iż rodzaj docieplenia ściany nie wpływa w znaczący sposób na straty ciepła przez przegrodę, a jedynie na grubość samej przegrody. Największe obniżenie zapotrzebowania energetycznego następuje w skutek zastosowania w budynku wentylacji mechanicznej. Analiza strat wykazuje, że tradycyjne systemy wentylacyjne wywołują duże straty ciepła na poziomie 46,9%. Obliczenia wykazały, iż wentylacja mechaniczna nawiewno-wywiewna z odzyskiem ciepła zmniejsza współczynnik strat ciepła do poziomu 26,5%.

Internal Contaminant Source Dilution and Filtration in Dedicated Outdoor Air Systems

Heating, ventilation and air-conditioning (HVAC) systems account for more the 50% of energy use in residential buildings [1] and approximately three-quarter in healthcare environments [2]. Hence, HVAC systems are a favorable sector for sustainability with a great potential of energy savings. The engineering approach to this issue has led to the advent of newer and more sustainable technologies. Dedicated outdoor air systems (DOAS) are a case in point. By decoupling the sensible and latent loads, an enormous saving can be achieved in the amount of air to be conditioned. Ventilation systems are designed to satisfy three predominant requirements: (1) to deliver fresh air to occupants and dilute the indoor generated contaminants, (2) to control the temperature and humidity in indoor spaces, and (3) to pressurize the space.There is ample evidence that the DOAS facilitates the last two requirements with more quality and less cost, which makes it more sustainable. This work, however, focused on the effect of using this system on the first requirement, particularly with regard to the indoor generated contaminants. The results showed that compared to the traditional ventilation systems, the DOAS system less effectively treats the indoor generated contaminants. Therefore, other mechanisms such as filtration must be properly implemented to limit the contaminants level below their standard threshold.

Experimental assessment of the inhalation zone of standing, sitting and sleeping persons

In exposure studies and risk assessments, the intake of a pollutant through inhalation is often estimated using the well mixed concentration in the room. Less traditional ventilation systems such as stratum ventilation, displacement ventilation or personal ventilation systems aim to achieve higher ventilation effectiveness by delivering supply air directly in the occupants' vicinity, thus creating flow conditions that divert from the well mixed condition. Also, with sources in the near proximity of occupants, the concentration in the occupants breathing zone is often much higher than the one predicted assuming well mixed conditions, and assessment of exposure often requires calculation of pollutant concentrations in the inhalation zone. In this paper, we present the results of experiments with a breathing thermal manikin in an environmental chamber that define the geometrical extend of the inhalation zone of standing, sitting and sleeping persons breathing through the nose. These results allow to determine the inhaled fraction of a near field source of a gaseous pollutant and determine a geometrical zone around the nose where the intake fraction is equal to 1 as a reference for the selection of sampling positions in exposure studies. The experiments show that a person's thermal plume has a large impact on the shape of the inhalation zone, limiting the inhalation zone of standing and sitting persons to the area situated almost directly under the nose. For a sleeping person, the breathing zone is stretched down along the cheeks due to this same effect. The transient effect of the breathing cycle has only a minor influence on the inhalation zone.

“Breathing House” – New Air System for Healthy Residential Buildings

As the continual improvement of human living standards, healthy housing became a hot topic and was attached more and more emphasis whatever from the profession or the public. Professionally, better ventilation is one of the most important facets of the healthy housing. Compared with the traditional ventilation system, this paper illustrates the new air system that makes a full use of natural resources, directly and simply changes the normal traditional housing to the healthy housing, through the concept, philosophy, typology and property of the new air system. Additionally, it takes the "Dong Ya Shi Ji Cheng" in Batou as typical example of healthy housing, in order to demonstrates the advantages of the new air system more clearly.

Removal characteristics of particulate matter with different return air system designs in a nonunidirectional cleanroom for integrated circuit (Ic) testing processes

In a conventional arrangement of the airflow pathway in nonunidirectional airflow cleanrooms with wall return schemes, the supply air is introduced from ceiling air grills and the return air, close and vertical to the floor, is extracted from the wall air grills. However, such a wall return ventilation system is theoretically not an optimal design for removing heat and particles released from processing machinery. The conventional wall return system currently used in cleanrooms aims to create an environment with diluted particle concentration in which downward cold supply air from ceiling filters encounters upward air currents generated by drifted particles from processing machinery. To solve the problem, we introduced a new design called fan dry coil units (FDCUs). In this article, we compare the performances of both innovative and traditional ventilation systems in a full-scale cleanroom. For each return air ventilation system, we investigated the effects of air change rates on the removal of 0.1∼5 μm particles. Based on the results, it is noted that the FDCU-return system eliminates about 60% more particles from the cleanrooms, compared with conventional wall-return system.

A novel evacuation passageway formed by a breathing air supply zone combined with upward ventilation

With the development of transportation, the tunnel has become one of the important facilities of railway, highway and subway transportation. However, fire hazards occurring inside the tunnel may incur huge numbers of casualties and property losses. In this paper, a breathing air supply zone combined with an upward ventilation assisted tunnel evacuation system (BTES) is introduced. It can be used to create a safe, smoke-free evacuation passageway out of the tunnel. The BTES is optimized to achieve high-performance. The impacts of heat release rates, fire source locations and fire detection times are also discussed.The carbon monoxide (CO) concentrations found when utilizing the BTES were significantly lower than that found when utilizing the traditional ventilation system. An obvious, clean evacuation passageway was created by the BTES. The maximum CO concentrations in the BTES evacuation passageway were below 10 PPM throughout the entire combustion process. A larger CO concentration gradient in the vertical direction was detected with the BTES than that found in other ventilation systems. This finding means that the lower part of the tunnel has a lower CO concentration with the BTES, which benefits the evacuation process. The impacts of fire source locations and fire detection times were tested to ensure the system reliability, and it was found that the performance of the BTES was not sensitive to them.

Study of a proposed tunnel evacuation passageway formed by opposite-double air curtain ventilation

Subway tunnel fires often result in catastrophes and heavy casualties. To help people evacuate from a tunnel fire, an opposite-double air curtain ventilation assisted tunnel evacuation system (OTES) is introduced. It can be used to create a safe evacuation passageway that is free of smoke through out the length of the tunnel. The performance of the OTES is compared with that of the traditional ventilation systems: longitudinal ventilation and natural ventilation. The effect of the heat release rate, fire source location, and fire detection time are also discussed.This study also shows that compared with natural ventilation and longitudinal ventilation, the carbon monoxide, CO, concentration with OTES is significantly lower. Given the same HRR, the CO concentration values with OTES are only 0.58–2.41% of natural ventilation or 0.52–3.12% of longitudinal ventilation at the back end of the tunnel. An obviously clear evacuation passageway is created by OTES. The effects of changes in fire source location and fire detection time on tunnel ventilation are tested. Also the effect of these changes on the formation of an evacuation passageway by OTES is reported.

Effects of the Removal of 0.1 µm Particles in Industrial Cleanrooms with a Fan Dry Coil Unit (FDCU) Return System

A wall-return ventilation system, containing ceiling-supply and wall-return air grilles, is traditionally used in non-unidirectional airflow cleanrooms. In such a wall-return cleanroom, the pathways of return airflow towards the wall-return grilles may be affected by locations and layouts of the production lines and tool equipment; moreover, especially considering the needs for relocation of production lines and rearrangement of tool equipment in the industrial cleanrooms, this study proposed a fan dry coil unit (FDCU) return system, containing ceiling-supply and ceiling-return air grilles, and conducted experimental works in a full-scale cleanroom to investigate the performance of the innovative and traditional ventilation systems. The influences of air change rates and supply air plenum pressures on the removal of 0.1 μm particles were examined in the experiment. Results presented in this paper were subject to the particle size of 0.1 μm. The FDCU-return ventilation arrangement may provide viable solutions to effective contamination control. The results showed that the innovative FDCU-return system can effectively eliminate about 50% of 0.1 μm particles from the cleanrooms more than the conventional wall-return system. Moreover, the outcomes from this study suggested that particle removal rates for the given cleanrooms were significantly affected by air change rates.

Stability criteria for airflow patterns in livestock buildings

The environment experienced by stock housed in intensive livestock buildings depends on the ability of the ventilation system to control not only the air temperature but also the pattern of air movement. Although traditional ventilation systems aim to keep a constant temperature at the detector by varying the ventilation rate, as the external temperature changes both the internal air movement and consequently the distribution of internal air temperatures vary. This is because the small quantities of air required in cold weather and large quantities required in hot weather enter through the same inadequately adjusted vents with the result that both the buoyancy and dynamic pressures in the inlet air jet are continuously varying. Consequently to provide the most desirable environment for livestock at all times it is necessary to maintain a stable airflow pattern by exercising control over these two factors. It is shown that the airflow pattern depends on the buoyancy and dynamic pressures the ratio of which is defined as the Archimedes number. It is concluded that the jet remains horizontal for an Archimedes number less than 30 and falls when it is greater than 75, thus causing stable air flows with opposite directions of rotation. Intermediate values should be avoided to prevent unstable patterns and unstable environmental conditions near to the stock.