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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES The strategy of Hybrid Ventilation (VH) or mixed mode (MM), switching between the use of natural ventilation (VN) and air conditioning (AC), is a way to reduce expenses with artificial conditioning systems and achieve thermal comfort residential use, in addition to the gains in internal air quality, since in VH the use of the artificial air conditioning system is partial, occurring only at times of day when the internal conditions are outside the established performance standards and integrated with the passive conditioning strategies (VN). The objective of this work is to evaluate the VH strategy regarding the thermal comfort and potential of energy saving in a residential building in the Brazilian Bioclimatic Zone 2 (ZB 2). The influence of hybrid ventilation on thermal comfort and energy consumption was investigated by means of a temoenergetic simulation of a single family residence, Casa Popular Eficiente, implemented in the city of Santa Maria / RS, using EnergyPlus software. Two reference simulations were defined, one with artificial air conditioning and the other only with temperature - controlled natural ventilation and 2 base cases with 3 climatization scenarios each, these scenarios were simulated with variations in the types of controls for hybrid ventilation (VH), the which also incorporate the control of solar radiation through the automation of blinds. Finally, openings for natural ventilation were controlled through the Energy Management System (EMS) advanced feature of the EnergyPlus software. The results obtained demonstrate that the strategy of hybrid ventilation in its best configuration reduced the consumption with air conditioning in 51.40% for the control based on the ASHRAE 55 standard and 16.05% in the temperature control optimized by means of algorithm via EMS, in relation to the configuration using only artificial air conditioning. The use of solar shading (blinds) was efficient in reducing 1.38% in the annual consumption of electric energy, when using the strategy in mixed mode of air conditioning, obtaining better performance for the control based on ASHRAE 55. With regard to thermal comfort, in the summer, the worst situation occurs when the building uses only natural ventilation (VN) controlled by temperature, reducing thermal discomfort by adopting hybrid ventilation, maintaining the internal temperature for longer in the range of desirable temperatures for the thermal comfort sensation and representing a reduction of 2337.71 GHR for the optimized temperature control through the control algorithm and 1645.62 GHR for the control based on. ASHRAE, compared to the reference configuration, with only natural ventilation. The use of sunscreens was also efficient in reducing the parameter Degrees-Hour Independent of the control adopted when opting for the mixed mode of air conditioning or hybrid ventilation, the building reduced the energy consumption, improving thermal comfort. Therefore, this research demonstrated that through the management, control and integration capabilities possible through automation, it is feasible to optimize the ambient air conditioning through the implementation of the hybrid ventilation in conjunction with the shading to control the thermal gains through the radiation and, in this way , improve levels of thermal comfort and reduce energy consumption. A estratégia de Ventilação Híbrida(VH) ou modo misto (MM), alternância entre o uso da ventilação natural(VN) e do ar condicionado(AC), é uma maneira de reduzir os gastos com sistemas de condicionamento artificial e atingir o conforto térmico residencial, além dos ganhos em qualidade do ar interno, uma vez que na VH o uso do sistema artificial de climatização é parcial, ocorrendo apenas nos momentos do dia em que as condições internas estão fora dos padrões de desempenho estabelecidos e de forma integrada com a estratégias passivas de condicionamento (VN). O objetivo deste trabalho é avaliar a estratégia de VH quanto ao conforto térmico e potencial de economia de energia elétrica em uma edificação residencial, na Zona Bioclimática Brasileira 2 (ZB 2). A Influência da ventilação hibrida no conforto térmico e consumo energético foi investigada por meio de simulação temoenergética de uma residência unifamiliar, a Casa Popular Eficiente implantada na cidade de Santa Maria/RS, com o software EnergyPlus. Foram definidas 2 simulações de referência, uma com climatização artificial e outra apenas com ventilação natural controlada por temperatura e 2 casos - base com 3 cenários de climatização cada, estes cenários foram simulados com variações nos tipos de controles para ventilação híbrida(VH), os quais incorporam também, o controle da radiação solar através da automação de persianas. Por fim, as aberturas para ventilação natural foram controladas por meio do Energy Management System (EMS) recurso avançado do software EnergyPlus. Os resultados obtidos demonstram que a estratégia de ventilação híbrida em sua melhor configuração reduziu o consumo com ar condicionado em 51,40% para o controle com base na normativa ASHRAE 55 e 16,05% no controle por temperatura otimizado através de algoritmo via EMS, em relação a configuração utilizando apenas a climatização artificial. O uso de proteções solares (persianas) se mostrou eficiente na redução de 1.38% no consumo anual de energia elétrica, quando utilizada a estratégia em modo misto de climatização, obtendo melhor desempenho para o controle baseado na ASHRAE 55. No que se refere a conforto térmico, no verão, a pior situação, ocorre quando a edificação se utiliza apenas da ventilação natural(VN) controlada por temperatura, havendo redução no desconforto térmico ao adotar a ventilação híbrida, mantendo a temperatura interna por mais tempo na faixa das temperaturas desejáveis para a sensação de conforto térmico e representando uma redução de 2337.71 GHR para o controle por temperatura otimizado através do algoritmo de controle e de 1645.62 GHR para o controle com base na. ASHRAE, comparados a configuração de referência, apenas com ventilação natural. O uso de proteções solares também mostrou-se eficiente na redução do parâmetro Graus-Hora Independente do controle adotado ao optar pelo modo misto de climatização ou ventilação híbrida a edificação reduziu o consumo energético melhorando o conforto térmico. Portanto, esta pesquisa demonstrou que através dos recursos de gerenciamento, controle e integração, possíveis através da automação, é viável otimizar a climatização ambiental através da implantação da ventilação híbrida em conjunto com o sombreamento para controle dos ganhos térmicos através da radiação e, desta forma, melhorar os níveis de conforto térmico e reduzir o consumo de energia elétrica.

Ventilation system design and operation may significantly affect indoor air quality (IAQ). The aims of this case study were to investigate the functionality of a supply air fan-assisted hybrid ventilation system in a newly built school building with reported IAQ problems and to determine the effects of ventilation improvement on measured and perceived IAQ. The ventilation system function was researched simultaneously with IAQ measurements, with an analysis of total volatile organic compounds (TVOC), single volatile organic compounds (VOCs), and indoor mycobiota, and with questionnaires about perceived IAQ. At the baseline, an operational error of the ventilation system was found, which prevented the air from coming into the classrooms, except for short periods of high carbon dioxide (CO2) concentrations. After the ventilation operation was improved, a significant change in indoor mycobiota was found, the dominant, opportunistic human pathogenic species Trichoderma citrinoviride found in settled dust in the classroom before the improvement was no longer detected. In addition, the concentrations of CO2, TVOC, and some single VOCs, especially toluene and decamethylcyclopentasiloxane, decreased. The analysis of the questionnaire results indicated that the perceptions of unpleasant odors and stuffy air decreased, although a statistically significant improvement in perceived IAQ was not observed. The results provided evidence that the properly controlled hybrid ventilation system operating in mechanical supply mode provided adequate ventilation and was effective in decreasing the concentrations of some indoor-generated pollutants. With simple ventilation adjustments, microbiological exposure from building structures might be prevented.

Passive measures, particularly natural or hybrid ventilation rather than air-conditioning, can dramatically reduce primary energy consumption.

Building hybrid ventilation integrates the advantages of both natural ventilation and mechanic ventilation. Ventilation efficiencies and system costs are found to be associated with different control strategies. Two indoor thermal comfort indices, which are predicted mean vote (PMV) model and adaptive comfort standard (ACS) model, are chosen as the control objective in this paper. A hybrid ventilation system with these thermal models was developed. Experimental tests were conducted to compare the time percentage of thermal comfort in summer, and the running time of the exhaust fan between the two systems. The results show that the percentage of the interior thermal comfort time is between 64.5% and 86.4% when the outside air temperature is between 10 °C and 25 °C (the average temperature is about 17.5 °C, Period 1). The percentage is 45.2∼60.7% when the outside air temperature was 13∼32 °C (the average temperature is about 22.7 °C, Period 2), and 29.4∼49.3% when the outside air temperature was 18∼34 °C (the average temperature is about 26.5 °C, Period 3). The comfort time percentage is always higher with ACS model than that with PMV model in these three test periods. The results also indicate that the ventilation efficiency, which is defined as ratio of window opening time to the fan's running time, is higher with the ACS model than that with the PMV model in the period 2 and 3. The ACS model could be considered as the prior control objective for the hybrid ventilation system.

A hybrid ventilation system that uses both natural and mechanical ventilation has drawn attention with its low operation cost and constant ventilation rate. This paper describes a hybrid ventilation system mounted at a window including its performance for IAQ and energy use according to different control methods. The simulation results indicate that in maintaining the required IAQ level, the proposed hybrid ventilation system reduces energy use by approximately 19.2%, 25.3%, and 41.3% with its outdoor air temperature based control, enthalpy based control, and indoor CO2 density control mode, respectively, compared to a conventional heat recovery ventilation system.

Coal dust disaster is the most serious problem in a laneway of coal mine. Dust movement regularity for comprehensive mechanized heading face is the key scientific issues for the principle and technology of dust prevention. The special topic on systematic study of the variation regularity of dust movement and dust distribution is presented with hybrid ventilation for the comprehensive mechanized heading face: Euler–Euler method was firstly established on the numerical platform for gas–solid two phase flow in a laneway. And the forces and the dynamic model of dust particles were performed in three-dimensional flow field. Then based on the visible simulations, the movement characteristics of diffusion, sedimentation and accumulation of dust particles were investigated under the action of the complex air flow, and the spatiotemporal variation of dust distribution was studied with hybrid ventilation system. Meanwhile, the obtained dust distribution regularities were compared with the obtainable experimental results. Finally, selected method on different ventilation patterns for dust control was brought out for the heading face according to the gained regularity. The research results is helpful for further understanding of the essence of dust movement with air flow, which could provide more suitable guidance for the principle of dust control and technology of ventilation.

Natural ventilation of all the floors of a multi-story building may require a tall stack. To provide satisfactory ventilation flow rates for a multi-story building and to restrict the height of the ventilation stack, this paper proposes a hybrid ventilation scheme of mechanical ventilation in the upper-level floors and natural ventilation of lower-level floors with the stack pressure induced by the warm discharge flows from all of the floors. This scheme is achieved by connecting the lower-level naturally ventilated floors to the upper-level mechanically ventilated floors via a common stack. A model is developed to optimize the quantity of mechanically ventilated floors required to provide satisfactory ventilation rates for the lower naturally ventilated floors and also minimize the energy consumption. The applicable conditions associated with the ventilation scheme are expressed explicitly. The model predictions are validated against a computational fluid dynamics (CFD) simulation. The results indicate that the proposed scheme is effective at energy savings if the key engineering parameters are appropriately designed. A larger exhaust opening of the stack and an optimized vent area of the ventilated rooms are helpful to both the increase in the quantity of naturally ventilated floors and the decrease in the energy consumption.

This study evaluated the effect of wind speed and direction and surrounding maize field on the air exchange rate (ACH) and indoor air velocity in a dairy cow building with hybrid ventilation, which combined auto-controlled natural and partial mechanical pit ventilation. The standard k − e turbulence model and standard wall function were applied in CFD modeling with extension of capability to account for the aerodynamics effect of surrounding maize plant canopy in the wind domain by using user defined functions (UDF). This extended model was validated by on-site measured velocities and temperatures. A reasonably good agreement was found between simulated and measured results. The wind speed influenced ACH greatly while modeling the maize field had little effect on ACH with low wind speed. With wind speed of 3.86 m s−1 in validation case, modeling the maize field reduced total ACH by 24%, ACH via bottom openings on the sidewall by 89.7% and air speed measured upwind by 71%. The results revealed that the plant canopy had the most significant effect on ACH through the opening on the sidewall. With the variation of wind direction from 0° to 90°, the difference of ACH could be 60%.

Based on the known geometric model of classrooms using hybrid ventilation with solar chimney, the solar radiation intensity of the solar chimney's effect on indoor air temperature and velocity is simulated and analyzed based on the Fluent software. Combined with the numerical simulation analysis, it can be seen that ventilation quantity increases with the increase of solar radiation and the variation of average temperature with a series of room heights under different solar radiation can be available. Study and Research on the solar chimney can provide the theoretical evidence for the ventilation effect of classrooms, however, a more accurate conclusion will be required for further study on the numerical simulation and experimental verification.

Reducing the energy demand for residential cooling systems is crucial in order to limit CO2 emissions, consistently with the EU climate change policy. Within this context, solar DEC (Desiccant, Evaporative Cooling) technologies can represent a valid answer to the energy saving targets. This experimental analysis aims to present the last results of a scientific campaign on a solar DEC prototype, named NAC-wall (Natural Air Conditioning), operating with a hybrid ventilation mode. Heat and mass transfer happens in an innovative dehumidification component, a finned coil coated with a layer of Zeolite SAPO-34, presenting very low pressure drops. Different tests have been performed in the flow regime Reynolds 750–3500 to analyze dehumidification effectiveness. For a better comparison between each test, a preliminary complete regeneration of the adsorbent mean have been always carried out with hot water circulation, produced by a solar thermal system. A theoretical optimized working cycle, i.e. one regeneration stage followed by one adsorption stage, has been studied starting from the experimental results and its performance has been compared with the optimized natural ventilation operating case, reported in a previous work.

Smoke is the element of a fire that causes the greatest loss of life. The importance of eliminating smoke is underscored in the fire safety engineering of underground subway stations. In this study, an experiment and a numerical simulation were performed to determine the efficacy of different ventilation modes. The experiment was conducted on a 1:50 scale model of a subway station and a complementary Fire Dynamics Simulator (FDS) simulation was performed on a full scale station. The influences of natural ventilation, mechanical ventilation and hybrid ventilation were examined. The results indicated that natural ventilation was good for smoke elimination when the fire source was under the dome, and the gas temperature measured in the middle of the basement 1 decreased significantly as the size of the vent increased. Smoke was exhausted from the basement 1 and fresh air supplied into the basements 2 and 3, which had the best efficacy when managing the smoke diffusion. No matter that the fire source was under the dome or out of the atrium, the carbon monoxide (CO) concentration was the smallest when the modified hybrid ventilation system was in operation. At the same time, changes in the natural ventilation vent had an influence on smoke elimination and the efficacy of smoke elimination became better with the increasing of the dimension of the vent when the fire location was under the dome.

Aerodynamic quantification of inlet vent flaps in controlled ventilation system. The impact of installed inlet vent flaps in the window structure on the overall aerodynamic properties of conventional triple glazed window and window glazed by the triple glazing with improved acoustic properties. The methodology and results of the measurement.

The aim of this paper is to identify which method to assess thermal comfort is the most appropriate to be used in hybrid commercial buildings located in hot and humid summer climate. Three methods to assess thermal comfort were analysed: (1) ASHRAE 55 for determining acceptable thermal conditions in occupied spaces, (2) ASHRAE 55 for determining acceptable thermal conditions in naturally ventilated spaces and (3) Givoni's chart for hot and humid climates. Models with two geometries, two room sizes per geometry, two solar orientations and three window areas per model were analysed. Simulations were performed using the EnergyPlus programme, with the TRY climate file of Florianopolis. Thermal comfort was evaluated applying the simulations output data into the three methods. Thus, the amount of time (number of hours per year) in which the use of air-conditioning is necessary to bring thermal comfort for the users throughout the year was determined using each method. Such number of hours of use of air-conditioning was also compared with the pattern of use of air-conditioning observed in Florianopolis. The main conclusion is that the most suitable method for use in hot and humid summer climates is the method proposed by Givoni.

The objective of this paper is to combine sensitivity analysis and simulation-based optimisation in order to optimise the thermal and energy performance of residential buildings in the Argentine Littoral region. An actual house was selected as case study. This is a typical, local, single-family house having some rooms conditioned only by natural ventilation, and other rooms with natural ventilation supplemented by mechanical air-conditioning (hybrid ventilation). Hence, the total degree-hours at the naturally ventilated living room and the total energy consumption by air-conditioning at the bedrooms were chosen as objective functions to be minimised. The global objective function characterising the thermal and energy performance of the house was defined as the weighted sum of these objective functions. This objective function was computed using the EnergyPlus building performance simulation programme. Then, we performed a sensitivity analysis using the Morris screening method to rank the influence of the design variables on the objective function. This showed that the type of external walls, the windows infiltration rate and the solar azimuth were the most influential design variables on the given objective function for the considered house, and also that the azimuth either had a highly nonlinear effect on the objective function or was highly correlated to the others variables, deserving in any case a finer discretisation. Finally, we solved an optimisation problem using genetic algorithms in order to find the optimal set of design variables for the considered house. The results highlighted the efficiency and the effectiveness of the proposed methodology to redesign a typical house in the Argentine Littoral region, improving hugely its thermal and energy performance. Fil: Bre, Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; Argentina. Universidad Tecnológica Nacional. Facultad Regional Concepción del Uruguay; Argentina Fil: Silva, Arthur Santos. Universidade Federal de Santa Catarina; Brasil Fil: Ghisi, Enedir. Universidade Federal de Santa Catarina; Brasil Fil: Fachinotti, Victor Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; Argentina

A reduced-scale model of an atrium with displacement ventilation and natural exhaust in the ceiling was applied in experimental investigation, where its air velocity field was measured by particle image velocimetry (PIV). By computational fluid dynamics (CFD) method, the indoor airflow in both the reduced-scale and real-size atrium model with hybrid ventilation under cooling conditions was simulated. The experimental and calculated results show that the hybrid ventilation that coupled natural exhaust with mechanical air supply of air conditioning can satisfy the thermal environments requirements. Moreover, with the same heat gain and supply air parameters, space cooling load of the atrium can be a little less when applying displacement ventilation. In addition, the vertical temperature gradient in the atrium, the cooling load of handling return air and the temperature difference between supply and exhaust air decrease with the increase of exhaust air rate. An optimal exhaust-supply air ratio for the minimum cooling load of the air conditioning system in the atrium was obtained under a given heat gain and fresh air parameters.

Mixed-mode buildings (MM), which use both natural ventilation and mechanical cooling to provide thermal comfort and energy savings, have a high potential in climates where it is favorable to use natural ventilation (e.g., Brazil). In these buildings, operable windows are the source of natural ventilation, lighting and heat gains, and their characteristics can influence energy consumption. This work aims to evaluate the energy and luminous performance of mixed-mode office buildings with operable windows in a high-altitude tropical climate in Brazil. The performance is evaluated concerning energy savings, air-conditioning operation hours, the period of use of natural ventilation and balance between energy demand and illuminance levels. It is considered variations in envelope parameters (window-to-wall ratio and solar orientation). The method is composed of computer simulations on Daysim and EnergyPlus programs. The results showed that the mixed-mode strategy has great potential to reduce air-conditioning energy consumption. The most significant reductions occurred with larger WWRs, reaching 39.4% of energy savings (north facade, WWR = 80%). Nevertheless, while the larger WWR provided more natural ventilation availability, it increased the discomfort by high illuminance, which reached about 90% of the office’s area. Therefore, when the mixed-mode system was used, the cases with a better balance between adequate illuminance levels and low energy consumption were the south facade with all WWRs and the east and west facades with WWR of 30%. It is important to emphasize that the adoption of these solutions depends on the building's design requirements. Edifícios de modo misto (MM), os quais usam ventilação natural e resfriamento mecânico para proporcionar conforto térmico e economia de energia, tem um grande potencial em climas onde o uso da ventilação natural é favorável (ex. Brasil). Nesses edifícios, as janelas operáveis são fontes tanto de ventilação natural quanto iluminação e ganhos internos, e suas características podem influenciar no consumo de energia. Este trabalho tem como objetivo avaliar o desempenho energético e luminoso de edifícios de modo-misto com janelas operáveis em um clima tropical de altitude no Brasil. Considerando variações nos parâmetros do envelope (percentual de abertura na fachada e orientação solar), o desempenho é avaliado em relação à economia de energia, tempo de uso do ar condicionado, período de utilização da ventilação natural e o balanço entre a demanda de energia e os níveis de iluminância. O método é composto por simulações computacionais nos programas Daysim e EnergyPlus. Os resultados mostraram que a estratégia de modo-misto tem um grande potencial para reduzir o consumo do ar condicionado. As grandes reduções ocorreram nos maiores PAFs, atingindo 39,4% de economia de energia (fachada norte, PAF = 80%). Apesar disso, enquanto o maior PAF forneceu maior disponibilidade de ventilação natural, aumentou o desconforto devido a elevadas iluminâncias, atingindo cerca de 90% da área do escritório. Portanto, quando o modo misto foi usado, os casos com melhor equilíbrio entre níveis adequados de iluminância e baixo consumo de energia foram a fachada sul com todos os PAFs e as fachadas leste e oeste com PAF de 30%. É importante ressaltar que a adoção destas soluções depende dos requisitos de projeto do edifício.

The Nucleus-type Hospital in Glenfield comprises connected cruciform blocks with numerous small court- yards between. The hospital has mechanical ventilation and perimeter heating. The wards have a hybrid ventilation strategy with a low rate of mechanical ventilation. Ventilation through windows is the main source of summer time cooling. This paper investigates the summer time performance of spaces that are mechanically ventilated but passively cooled. The paper presents the measured indoor temperatures in selected hospital spaces and compares them with thermal comfort criteria. Finally, future summer conditions for the ward space are predicted using a calibrated multi zone dynamic thermal model. During June to September 2010, the maximum indoor temperatures in the case study spaces varied between 27.3◦C and 29.3◦C. The nurse station was found to be the hottest area. During this period the performance of most of the monitored spaces was reasonably within the thermal comfort threshold as defined by HTM03-01. The simulation results demonstrate that light-touch low carbon interventions could produce comfortable conditions in bedrooms into the 2050s in UK Midlands.

Hybrid ventilation is a two-mode system, including mechanical and natural ventilation, which can be used in large space to exhaust excessive heat while minimize energy consumption. One mathematical model is developed to calculate indoor vertical temperature distribution by the hybrid ventilation. Here, the mathematical model is proposed to illustrate the running operation of the hybrid ventilation, especially the control strategies of the natural ventilation in this paper. An experimental and theoretical investigation of natural ventilation in the hybrid system in an atrium building has been conducted. A simplified approach for calculating critical outer temperature and a mathematical model of the natural ventilation in the hybrid system are both proposed in this paper. We have restricted our attention to the natural wind within the upper zone of the large space, in which the effects of the outer air temperature, indoor heat, the natural air rate, and the inlet location of the natural wind are discussed by the mathematical model and experimental data.

FLUENT software and SIMPLE algorithm which was based on parity grid was used to carry out the numerical simulation of spraying dust gas-particle two-phase flow field of the mechanized working face with a single pressure pumping hybrid ventilation system. The dust distribution law of the mechanized working face was mastered and the main dust prevention area was determined to be the middle of the roadway and wall-attachment fan drum enclosed dust removal system of mechanized working face was also planned to be established according to the simulation result. It had been proved that fully-mechanized coal winning machine enclosed dust removal system had a large advantage in reducing dust by computer simulation and field application, the dust suppression effect was remarkable.

Complex commercial buildings consume a significant amount of energy through their ventilation and cooling systems. Hybrid ventilation can help reduce these loads while providing building occupants with a comfortable environment. This research develops a generic automated hybrid ventilation control for public spaces of complex commercial buildings, and identifies a commissioning methodology which determines the best way to operate a hybrid ventilation system in a retrofitted or occupied building. This control was verified through a case study of a complex building. The results show that the system could be used through 28% of the 128-day cooling season resulting in 20% energy savings in comparison to traditional mechanical ventilation in the public space. The implementation of the automated control helped develop a hybrid ventilation operation protocol through commissioning during the operation phase in lieu of developing complex air-flow models for the installed system in the case study building.

Complex buildings such as hospitals and laboratories require intensive ventilation and cooling loads in order to meet operational demands. One way to reduce energy use while meeting these demanding requirements in complex buildings is the incorporation of hybrid ventilation in areas that do not require high and continuous loads such as public spaces. This research establishes an experimental approach to test and analyze various hybrid ventilation strategies in an occupied, complex building utilizing hybrid ventilation in public spaces. To optimize the use of hybrid ventilation, this research focuses on tracking three performance criteria: energy savings, occupant comfort and indoor-air quality. The framework establishes a variety of hybrid ventilation strategies to test, and outlines how to analyze results graphically and through linear regression modeling. This experimental approach is illustrated through a case study example of a laboratory building located in Madison–Wisconsin. The selection of the ideal hybrid ventilation strategy for the public space studied resulted in 56 percent average savings in ventilation and cooling load when HV is in use, and established a potential to use hybrid ventilation for 28 percent of the 111 day cooling season (20 percent savings in mechanical cooling over the summer).

The technology underlying the development of novel ventilatory modes for long-term noninvasive ventilation of patients with chronic hypercapnia is continuously evolving. Volume-targeted pressure-controlled ventilation is a hybrid ventilation mode designed to combine the advantages of conventional ventilation modes, while avoiding their drawbacks. However, manufacturers have created different names and have patented algorithms and set-up variables, which can result in confusion for physicians and respiratory therapists. In addition, clear evidence for the superiority of this novel mode has not yet been established. These factors have most likely hindered more widespread use of this mode in clinical practice. The current review presents the rationale, working principles, characteristics and set-up recommendations associated with volume-targeted modes. In addition, it summarises the clinical and laboratory studies that have challenged this mode.

Zadatak ovog rada bio je analizirati godišnju potrošnju energije za hlađenje konvencionalnog kontejnera za telekomunikacijsku opremu te na temelju provedene analize ponuditi rješenja za poboljšanje energetske učinkovitosti. Opis konvencionalnog kontejnera te parametri rada dani su od strane telekomunikacijskog operatera. Disipacija topline ugrađene opreme u kontejneru iznosi 2,2 kW, hlađenje kontejnera izvedeno je pomoću split-sustava, a jedini uvjet je da temperatura prostora u kontejneru tijekom godine ne poraste iznad 45°C. U prvom dijelu rada provedena je analiza potrošnje energije za konvencionalni kontejner s izoliranom ovojnicom i kontejner bez izolacije. Uspoređivanjem rezultata analize pokazano je da je potrošnja električne energije smanjena sa 4187 kWh na 1172 kWh godišnje. U drugom dijelu rada provedena je daljnja optimizacija sustava pasivnog hlađenja, u svrhu smanjenja potrošnje energije, korištenjem hibridne ventilacije (prirodna i mehanička ventilacija) te je odabrana oprema sustava hibridne ventilacije, postignuta ušteda električne energije iznosi 3899 kWh godišnje u odnosu na konvencionalnu izvedbu kontejnera. Na kraju rada uspoređena je godišnja potrošnja energije za sve izvedbe kontejnera opisane u ovom radu. Analiza godišnje potrošnje energije za hlađenje kontejnera provedena je korištenjem meteoroloških podataka standardne godine za meteorološku postaju Zagreb, Maksimir. The purpose of this study was to analyze annual cooling energy consumption of the conventional container for telecommunication equipment and based on that analysis offer solutions for improving energy efficiency. Description of the conventional container and work parameters are given by the telecommunication operator. Equipment installed in the container dissipates 2,2 kW of heat, container is being cooled by the split-system, and the only requirement is that the temperature of the air in the container does not exceed 45°C during the year. In the first part of the analysis energy consumption is being analyzed for conventional container with insulated shell and container without insulation. Comparison of analysis results has shown that electrical energy consumption was reduced from 4187 kWh to 1172 kWh annually. In the second part of the paper further optimization of the system for passive cooling was carried out to reduce energy consumption by using hybrid ventilation (natural and mechanical ventilation) and therefore equipment for hybrid ventilation system was chosen, achieving electricity savings in the amount of 3899 kWh annually as compared to the conventional container. At the end of the paper annual energy consumption was compared for all instances of the container described in this paper. Analysis of the annual energy consumption for cooling containers was conducted by using standard meteorological data for the meteorological station Zagreb, Maksimir.

The currently running International Energy Agency, Energy and Conservation in Buildings, Annex 62 Ventilative Cooling (VC) project, is coordinating research towards extended use of VC. Within this Annex 62 the joint research activity of International VC Application Database has been carried out, systematically investigating the distribution of technologies and strategies within VC. The database is structured as both a ticking-list-like building-spreadsheet and a collection of building-datasheets. The content of both closely follows Annex 62 State-Of-The- Art-Report. The database has been filled, based on desktop research, by Annex 62 participants, namely by the authors. So far the VC database contains 91 buildings, located in Denmark, Ireland and Austria. Further contributions from other countries are expected. The building-datasheets offer illustrative descriptions of buildings of different usages, sizes and locations, using VC as a mean of indoor comfort improvement. The building-spreadsheet highlights distributions of technologies and strategies, such as the following. (Numbers in % refer to the sample of the database’s 91 buildings.) It may be concluded that Ventilative Cooling is applied in temporary European and international Low Energy buildings. Still it’s not really widespread. Obstacles are challenges as regards noise, dust, weather and burglary, proving the research efforts of the Annex being necessary. The VC database forms a worthwhile basis for both dissemination and further research targets.

Maintaining IAQ (Internal Air Quality) and thermal comfort of occupants in buildings have been a challenge to overcome satisfying the two ends: criteria for sustainability and cost effectiveness. Although there was a movement for mechanical ventilation systems in the recent past, in addition to the cost involved, they are found to not deliver the desired air quality, lead to social consequences such as sick building syndrome, contribute to environmental consequences related to ozone-depleting substances with increasing energy consumption, generate noise and having difficulties in cleaning and maintaining. These consequences compelled research on natural ventilation systems, which were used in ancient buildings. Although it has been found that natural ventilation of buildings can become a substantial architectural design tool that leads to “breathing architecture,” fluctuations in indoor temperature and air quality makes depending entirely on natural ventilation less effective. The combination of natural and mechanical ventilation, the hybrid ventilation or mixed-mode ventilation, systems utilizes advantages and eliminates drawbacks from both mechanical and entirely dependent natural ventilation systems. Hybrid ventilation systems, which have been utilized in historical buildings, with less investment cost and reduction of energy usage have been found to be a solution to provide acceptable standards of IAQ and thermal comfort through natural air circulation in buildings. This research study was carried out to verify the effectiveness of a hybrid ventilation system in an auditorium built around 60 years back for its effectiveness as a provider of thermal comfort to its occupants. Computational Fluid Dynamic (CFD) modeling was carried out on a Finite Element (FE) model owing to its capability of offering a wide range of flexible analytical solutions, lower realization time and comparative cost effectiveness to experimental methods of modeling. This verification of the system has revealed that hybrid ventilation systems could provide effective thermal comfort in buildings designed specifically to allow circulation of air through the system. The results of the study were in agreement with measured data and the expected flow of air through the building when the thermal load due to metabolism of occupants was not included in the analysis. In addition, the expected results complied with similar studies on natural/hybrid ventilation systems. With the addition of the thermal load, as a uniform heat flux from the flow of the auditorium, it was observed that the conditioning of the air throughout the space was better than the without thermal load scenario. In the case modeling people as cylinders, with a convective heat flux, it was observed that the air flow direction changes and the seating level of the auditorium do not get sufficient air flow to maintain a comfortable air quality. Ineffective simulation of the inlet louver was assumed to be the primary reason for this scenario and other reasons such as the seating arrangement modeling too could have effects on the result. As conclusions of the study it was found that the whole building system properties have to be selected, as the control component to produce operating commands, to circulate air through the building in accordance with the air flow: both velocity and patterns, required to maintain thermal comfort of all occupants. Air inflow could be through windows as acquisition components to collect indoor and outdoor climatic parameters and air outflow could be mechanically controlled through exhausted fans turning on or off as the operating component in the system. The result of the study ensures the method of solutions through CFD to be utilized to provide effective and less costly path to verify systems such as natural or hybrid air flow systems through buildings. The whole system studied could be applied with suitable contextual modifications to any new location, with similar cost effective modeling, to produce less fuel consuming building systems leading to sustainability of built environment.

Numerous studies have shown that ventilation in classrooms is often insufficient or inadequate, leading to health risks, discomfort and a decrease in student learning performances. The aim of this study was to compare the performances of four ventilation modes used in identical and adjacent classrooms at the University of La Rochelle in terms of indoor environmental quality, overall comfort perception by the occupants and energy consumption. The different ventilation strategies included the use of balanced mechanical ventilation and natural ventilation by manual or automated window opening. Parameters related to air quality as well as thermal, visual and acoustic comfort were measured, and questionnaires were filled out by the occupants during the courses. The monitoring approach was conducted during summer and winter 2010 in order to classify the tested strategies during both seasons with reference to the requirements of standards and French regulations. The results showed that the automated window opening system controlled by air temperature and lighting level was really efficient in summer. In winter, none of the ventilation modes was clearly more adaptable for classrooms than the other. Thus, a good use of natural ventilation, controlled by well chosen parameters can provide a satisfactory solution for the academic environment.

In view of the warming climate, there is increasing concern about the likelihood of overheating inside UK buildings that are not mechanically cooled. A number of studies are examining this matter, of which the DeDeRHECC project is one. The recent availability of the UKCP09 future climate data projections has acted as a stimulus to such work. This paper illustrates how field measurement, thermal modelling and the generation of current and future typical and extreme weather years, can be used to provide a picture of the resilience of buildings to climate change. The unified framework for assessing both measurements and current and future predictions that is offered by the BSEN15251 thermal comfort standard is a crucial component. The paper focuses on internal temperatures during the day and at night in wards within the tower building at Addenbrooke’s hospital, which has a hybrid ventilation strategy. The maintenance of thermal comfort in such spaces is critically important and installing air-conditioning in response to climate change is expensive and potentially energy intensive. Fans appear to be a simple retrofit measure that may substantially improve the wards’ resilience to climate change even in extreme years. Whilst healthcare provides the back cloth, the methodology developed has a much wider utility for assessing thermal comfort in buildings in the current and future climate of the UK.

The whole rock fully-mechanized excavation with big cross section, high rock hardness and strong cutting intensity of fully-mechanized coal winning machine has a higher dust concentration than coal roadway excavation, so ventilation dust removal technology is in need in whole rock face. Based on the dust migration and distribution numerical simulation in whole rock tunnel excavation, optimization design of long pressing and short pumping hybrid ventilation and dust removal system were carried out. Eventually, the comprehensive dust prevention measures with air curtain closing dust source, dust electromotor exhausting dust and retaining curtain capturing dust were realized in this paper, which achieved a good removal efficiency of dust.

The purpose of this study was to evaluate the applicability of hybrid ventilation system in apartment housings and present a design method to improve the performance of hybrid ventilation system using the CFD simulation. As the object of CFD simulation, a small apartment houses with area of and were selected and evaluated. The test hybrid ventilation system are window frame natural air supply & duct exhaust hybrid system(Hybrid 1) and window frame natural air supply & bathroom and livingroom exhaust hybrid ventilation system(Hybrid 2). To evaluate the ventilation efficiency, we used the locations of diffuser installed for each system as the variables through the CFD simulation. In the case of Hybrid 1, the ventilation efficiency of the exhaust duct diffuser located on the inside room was higher rather than the exhaust duct diffuser located on the entrance. In the case of Hybrid 2, the most efficient system was the system that the diffuser connecting the bathroom static pressure fan is installed on the center of the living room. The ventilation efficiency of the Hybrid 2 in the case of type was more than 20% of the Hybrid 1. But, The ventilation efficiency of the Hybrid 2 in the case of type was more than 14% of the Hybrid 1. Therefore, to apply the Hybrid ventilation, a study that considers various variable should be conducted.

Air quality is very important for classrooms where high density of students study for long time. Enhanced ventilation is an idea way to introduce more fresh air to classroom. Hybrid ventilation combined natural ventilation with mechanical ventilation is a economic way for ventilation improvement. factors Influencing hybrid ventilation such as heat source intensity, location of air inlet, air velocity were studied by simulation in this paper. The characteristics of temperature distribution of the classroom were also analyzed. The simulation research was validated by model experiments. A low position of air inlet in the room makes high temperature efficiency, the optimal value of the air inlet velocity is about 0.5 m/s.

In order to improve effect of hybrid ventilation, the paper discussed a solar chimney to enhance natural ventilation. Some factors influencing solar chimney hybrid ventilation in classroom, such as heat sources, air inlet arrangements, air velocity and solar radiation were studied by simulation and validated by experiments. The characteristics of temperature distribution and temperature efficiency in classroom were obtained and analyzed. A low position of air inlet in the room makes high temperature efficiency, the optimal value of the air inlet velocity is about 0.5 m/s. The research provides a better way to enhance hybrid ventilation by solar chimney.

Hybrid ventilation systems combine the superior properties of natural and mechanical ventilation systems to reduce energy consumption. In this study, hybrid ventilation simulations were performed for several cities in Turkey, which have different climate conditions. Matlab/Simulink was utilized to perform the simulations. The results of these simulations were compared with that of regular air conditioning units in terms of energy consumption. A hybrid ventilation system which shows the general behaviour of a fan-assisted natural ventilation system with temperature-based control and which provides both heating and cooling, is shown to be effective for four cities in Turkey that have different climate conditions. Results showed potential savings of around 25–30% when compared to a regular AC system.

In this paper, the simulation software was applied to evaluate a hybrid ventilated combined mechanical and naturally ventilated (atrium area to be naturally ventilated) building. In order to understand the impact of the usage of natural ventilation on thermal comfort in atrium, we utilized TAS to simulate the air temperature and air velocity distribution for the atrium. A modeled three-storey commercial office building was used as the main subject of this analysis. To determine the thermal comfort level of the central atrium, Parameters will be set in such a way that the full height windows will be 100% open. Results were tabularized to determine and analysis the output of the simulation. Recommendations will be then given based on the output performance of the building.