Fresh Air Research Articles

Thermal performance of three-wheel and split-wheel air cycle systems for a civil aircraft environmental control system (ECS)

The conventional approach of regulating cabin temperature and pressure on aircraft is to utilize engine-bleed air through an environmental control system (ECS). The extraction of bleed air from the engine leads to a decrease in thrust and an increase in drag on the ECS ram air duct, resulting in higher fuel consumption. Consequently, the ECS transitioned from being engine-powered to being electrically powered. In this study, the thermodynamic characteristics of three-wheel and split-wheel air cycle systems (ACSs) with a high-pressure water separation system (HPWS) were investigated by developing a parameter decomposition model and an iterative algorithm using MATLAB for a state-of-the-art electrically driven ECS (EECS) on the Boeing 787 Dreamliner. The efficiency of the ACS was assessed by establishing analytical correlations for the coefficient of performance (COP) using relevant literature on endo-reversible thermodynamic model (ETM). By employing these analytical correlations, the thermal performance of both ACSs can be accurately predicted without the need for system modeling and simulation, considering variations in the input variables and operating conditions, such as the temperatures of fresh air and ram air, the ratio of the mass flow rates of ram air and fresh air, and component parameters, including the efficiencies of the primary and secondary heat exchangers and the pressure ratios of the fan and compressor. The implementation of a split-wheel ACS instead of three-wheel ACS in the Boeing 787 EECS led to an improvement in the COP from 0.31 to 0.43, and also resulted in a reduction of 14.35 % in the input power.

Gaseous contaminant transfer in membrane-based air-to-air energy exchangers

Membrane-based air-to-air energy exchangers (M−AAEEs) transfer heat and moisture between building exhaust air and fresh ventilation air streams through a membrane, thereby reducing the energy required for conditioning the fresh ventilation air. Energy exchangers are typically used in buildings with relatively clean building exhaust air, such as office buildings and schools. Recently interest in using energy exchangers in a wider range of buildings has grown, to reduce the energy consumption associated with the heating, ventilating, and air-conditioning (HVAC) systems in these buildings. However, if the building exhaust air is not clean, as would be the case for laboratories or factories, new risks are encountered when using energy exchangers. It is possible that gaseous contaminants in the exhaust air may also transfer along with the moisture through the membranes, contaminating the incoming fresh ventilation air. Current test standards provide a test procedure to determine the contamination of the fresh ventilation air by measuring the transfer of an inert tracer gas in an energy exchanger. However, the tracer gas test may not represent the transfer of common indoor air contaminants due to differences in their transport properties. Therefore, in this study, an experimental facility is developed to determine the transfer of seven different contaminants through two membranes (porous and dense) at different flow rates. Contaminant transfer is quantified using a parameter called the exhaust contaminant transfer ratio (ECTR), which gives the fraction of the contaminants transferred from the exhaust air to the fresh ventilation air. A theoretical model based on the effectiveness-number of transfer units (ε-NTU) correlation and moisture transfer resistance of the membrane is presented to determine transfer through porous membranes and validated with experimental results. The major contribution of this paper is that it presents a simple method to predict the transfer of different contaminants through a porous membrane based on the moisture transfer resistance of the membrane at different operating conditions. It is found that as contaminant diffusivity decreases, ECTR generally also decreases, and as the flow rate increases, ECTR decreases, which is consistent with the predictions from the correlation.

Factor analysis and GA-BP-ANN prediction of nitrogen diffusion behavior in underground laboratory under ventilation conditions

Nitrogen is widely used in various laboratories as a suppressive gas and a protective gas. Once nitrogen leaks and accumulates in a such confined space, it will bring serious threats to the experimental staff. Especially in underground tunnels or underground laboratories where there is no natural wind, the threat is more intense. In this work, the ventilation design factors and potential leakage factors are identified by taking the leakage and diffusion of a large liquid nitrogen tank in China Jinping Underground Laboratory (CJPL) as an example. Based on computational fluid dynamics (CFD) research, the effects of fresh air inlet position, fresh air velocity, exhaust outlet position, leakage hole position, leakage hole size, and leaked nitrogen mass flow rate on nitrogen diffusion behavior in specific environments are discussed in detail from the perspectives of nitrogen concentration field and nitrogen diffusion characteristics. The influencing factors are parameterized, and the Latin hypercube sampling (LHS) is used to uniformly sample within the specified range of each factor to obtain samples that can represent the whole sample space. The nitrogen concentration is measured by numerical value, and the nitrogen diffusion characteristics are measured by category. The GA-BP-ANN numerical regression and classification regression models for nitrogen concentration prediction and nitrogen diffusion characteristics prediction are established. By using various rating indicators to evaluate the performance of the trained model, it is found that models have high accuracy and recognition rate, indicating that it is effective in predicting and determining the concentration value and diffusion characteristics of nitrogen according to ventilation factors and potential leakage factors. The research results can provide a theoretical reference for the parametric design of the ventilation system.

Rencana Pelaksanaan Pembelajaran Dalam Kurikulum Merdeka

The Merdeka Curriculum is here as a breath of fresh air in the world of Indonesian education, bringing a spirit of independence for teachers and students to learn and teach with creativity. One of the important instruments in realizing the vision of Independent Learning is the Learning Implementation Plan (RPP) which has undergone a significant transformation compared to the 2013 Curriculum RPP (K13). The Independent Curriculum RPP is made more concise and focuses on essential points, so that it is easy for teachers to understand and use. Learning objectives are formulated clearly, measurably and oriented towards Learning Achievements (CP), ensuring learning is centered on the outcomes to be achieved. Teachers are encouraged to understand students’ learning profiles, including their interests, talents, learning styles and learning needs. This allows learning to be designed in a personalized and meaningful way for each individual.

Air Quality Index Assessment Of An Educational Organization

Abstract Uncontaminated and fresh air is an elementary prerequisite of every living being. But, in this day and age, atmosphere contamination-is certainly the most pervasive kind of environmental-degradation. In the ambience, there are several pollutants which have widespread causing contamination in the air. Pollutants of chief concern include gaseous pollutants like carbon monoxide, ozone, oxides of sulphur and nitrogen, lead etc. These are primary pollutants. Secondary pollutants are particulate matters of different types ranging from fine to high. Every single one of these pollutants can cause a severe menace to human-health. In the current research, sensor-based equipments have been used to monitor and measure the concentration of various pollutants in the air. In the present research work, the effect of different pollutants like PM2.5, PM10, NO2 C02, TVOC, H-CHO, Temperature, Humidity and Noise on air pollution at five stations in the education institute namely RCOEM campus is studied and presented. It had been observed that air pollutants like PM2.5, PM10, and NO2 primarily affected the air quality of RCOEM campus. So, these pollutants are mainly considered to monitor and evaluate air quality of RCOEM campus. After evaluation, air quality index of RCOEM campus was found to be around 94.5. It is within the range of 51-100. So, its falls in the range of satisfactory as per standard norms of central pollution control board and state pollution control board in terms of quality of the air and thereby its contamination.

A numerical study on transport of dust particles accompanied by air gouging process and energy consumption in a circulating ventilation workshop

A modified circulating layered ventilation system is proposed to address the issue of particulate pollutants in the casting cleaning workshop, taking into account the characteristics of end treatment and production processes. By combining Reynolds Average Navier-Stokes (RANS) turbulence model and Discrete Phase Model (DPM), the particle transport law in the coupled flow process of thermal plumes generated by purified circulating airflow and heat source was explored, and ventilation energy consumption was evaluated from the perspective of particle removal energy efficiency ratio. Comparing three ventilation modes: mixed ventilation (MV), wall-based attachment ventilation (WAV), and wall-based attachment ventilation with deflector (WAV-D), it was found that the large vortex region formed by the change in airflow direction during WAV played a key role in particle transport. Placing deflector helped to reduce the impact of vortex recirculation zones generated by the intersection of airflow and plumes on particles. A higher fresh air rate will weaken the diffusion effect of particles in the horizontal air lake region. Continuously increasing the air supply volume to a certain level has little effect on the transportation of low-inertia particles, yet it still manages to effectively enhance the removal efficiency of medium-inertia particles. However, for high-inertia particles, an increase in air supply can easily lead to excessive particle concentration in local areas. When the particle removal efficiency reaches a certain level, higher supply air volume and fresh air rate may lead to a significant decrease in energy efficiency ratio.

Association between indoor environmental risk factors and pneumonia among preschool children in Urumqi：A case-control study

BackgroundPediatric pneumonia presents a significant global health challenge, particularly in low- and middle-income countries. This study aimed to investigate the incidence of pneumonia in preschool children in Urumqi and its association with indoor environmental factors. MethodsThis case-control study collected data from December 2018 to December 2019 on 1522 preschool children in Urumqi (779 boys and 743 girls) who were diagnosed with pneumonia by a physician. A control group of children who had never had pneumonia was matched in a 1:1 ratio based on gender, age, and ethnicity. Using questionnaires, data were collected on children's general characteristics, passive smoking, types of housing, flooring materials, and indoor dampness, analyzing potential factors associated with the incidence of pediatric pneumonia. ResultsMultivariate analysis revealed that cesarean birth (odds ratio [OR] = 1.27; 95 % confidence interval [95%CI] = 1.08–1.48), being an only child (OR = 1.32; 95%CI = 1.13–1.55), antibiotic treatment during the first year of life (OR = 2.51; 95%CI = 1.98–3.19), passive smoking during the mother's pregnancy (OR = 1.62; 95%CI = 1.24–2.13), living in multi-family apartment housing (OR = 1.64; 95%CI = 1.28–2.10) and other types of housing (OR = 1.47; 95%CI = 1.09–1.99), laminate flooring (OR = 1.31; 95%CI = 1.01–1.72), and tile/stone/cement flooring flooring (OR = 1.31; 95%CI = 1.06–1.61), and dampness in dwelling (during first year of mother's pregnancy) (OR = 1.30; 95%CI = 1.04–1.63) were risk factors for pediatric pneumonia. The use of fresh air filtration systems in children's residences (OR = 0.66; 95%CI = 0.50–0.86) was identified as a protective factor. ConclusionThis study underscores the importance of indoor environmental factors in the prevention of pediatric pneumonia. Public health strategies should consider these factors to reduce the incidence of pneumonia in children. Future research needs to be conducted over a broader geographical range and consider a more comprehensive range of factors influencing pediatric pneumonia.

DESIGN STRATEGIES OF APARTMENT HOUSING WITH SHELTERS TAKING PANDEMIC RISKS INTO ACCOUNT: CURRENT TRENDS AND DEVELOPMENT DIRECTIONS

The article explores the issue of adaptation of living spaces to pandemic risks. It was determined that the creation of special isolation zones in new residential complexes is one of the key aspects. These premises must be equipped with everything necessary for a comfortable stay during quarantine, including separate bathrooms and autonomous ventilation systems, which will minimize contact between residents and prevent the spread of infections. It is well-founded that the design of ventilation systems is an important element in preventing the spread of viruses. Modern ventilation systems must ensure a constant flow of fresh air and effective removal of contaminated air. an important direction is the change in planning and zoning of living spaces. New approaches to planning take into account the possibility of reducing population density and creating conditions for social distance, so common areas should be spacious and ensure the possibility of maintaining a safe distance between people. Research has shown that increasing privacy, creating workspaces, eco-design and flexibility are also defining trends in the field of residential design. The pandemic leveled the concept of "Open-space" in favor of interior separatism, which allows creating isolated areas for work, recreation and other activities, which provides comfortable conditions for residents who are forced to spend more time at home. Innovative technologies, such as health monitoring systems and smart home systems, can significantly improve the safety and comfort of living. The introduction of such technologies makes it possible to quickly identify potential threats and take the necessary measures to neutralize them. The importance of implementing eco-design, which contributes to improving the mental and physical health of residents, has been revealed. Green areas on balconies and terraces stabilize the emotional state of people, creating private gardens in the structure of living space. Organizing space for self-isolation and reducing pandemic risks requires new approaches to planning living spaces, common spaces, and infrastructure. These changes contribute to the creation of a safer, more comfortable and adaptive living environment during the pandemic.

An experimental study on aging effects of fuel-cut events including sound optimized torque reduction on modern three-way catalysts

Continuously increasing country-specific emission standards for passenger vehicles demand additional development steps in complex exhaust gas aftertreatment systems for a more effective reduction of harmful gases. The efficiency of the aftertreatment system declines over its lifecycle due to specific load profiles and other boundary conditions, resulting in increasing emissions over vehicle mileage. As a result, the durability of the exhaust system becomes more important. Fuel cut is an intended, temporary interruption of the fuel supply of modern combustion engines of passenger cars to reduce fuel consumption and emissions. During this fuel reduction event, unconsumed oxygen of rich and cool fresh air is introduced to the combustion chamber and to the exhaust system. Besides a catalyst cool down, oxidation effects are provoked by enhanced oxygen reactions processes within the catalyst’s washcoat and surface layers. In this publication, specific aging cycles with a variation of fuel-cut programs were examined on their effects on a modified modern eight-cylinder turbo-charged engine, especially on their oxidation effects correlating to catalyst aging. Light-off curves and conversion heat maps were used to evaluate possible damaging impacts of fuel-cut events on the aging behavior of the catalyst systems. Results indicate that higher frequency of fuel-cut events results in a reduced catalyst conversion efficiency, whereas thermal sintering might be reduced due to overall lower temperature load. Temporary oxidation processes on catalyst’s surfaces occur only in a short timespan after changing the air fuel ratio to lean, resulting in a weaker thermal sintering during longer fuel-cut events. Sound optimized torque reduction functions, used in sports cars for a better drivability and powertrain response, exhibit a stronger aging influence due to additional thermal shock effects on the catalysts front face, as demonstrated via optical infrared sensor technology during catalyst aging cycles on the modified engine bench setup. A theoretical calculation of aging processes as a combination of thermal sintering by Arrhenius equation as well as oxidation process is discussed to describe an aging classification induced via oxidation processes. Additional physisorption measurements of different catalyst probes support the results which indicate the direction of future experimental approaches.

Synergistic Impact on Indoor Air Quality: The Combined Use of Air Conditioners, Air Purifiers, and Fresh Air Systems

As concerns about indoor air quality increase, air purifiers and fresh air systems are increasingly being used in conjunction with air conditioners in office buildings. To study the synergistic effects of multisystem joint operation on indoor air quality, this study used a combination of experimental and simulation methods to study the indoor particulate matter with a diameter of less than 2.5 µm (PM2.5) and carbon dioxide (CO2) concentrations under different operation conditions. The purification time and the PM2.5 concentration distribution under different conditions were compared with the condition in which the purifier was used alone. The results showed that the purification time required for the condition that the air conditioner runs together with the purifier was shortened by 15.2%. When the fresh air system is running together with the purifier, the purification time can be reduced by 30.4%. It was reduced by 32.6% when the three systems were operating at the same time. The PM2.5 concentration distribution under the joint operating condition was much more even than that under the condition in which the purifier was running alone. To analyze the impact on the CO2 distribution, the CO2 distributions under different joint operations were compared. The results show that the fresh air system can effectively dilute CO2 below 1000 ppm in 30 min. The air conditioner and purifier could help to mix the indoor air to provide a much more uniform indoor CO2 distribution.

Influence of ventilation and air filtration system on indoor air quality within a residential apartment in Hanoi, Vietnam

Most households in major cities in Vietnam use air conditioning equipment for better indoor thermal comfort. However, to save electricity cost, the houses’ rooms are often closed when the air conditioner is running. This habit causes the raising of indoor CO2 concentration especially during the sleep night time. Therefore, mechanical ventilation is recommended to provide fresh air in. However, high polluted particle outdoor will follow outdoor air to get in the room. To comprehensively solving the above issues, the combination of central ventilation and air purification system have been applied. Their influence on indoor air quality within a residential apartment were tested and evaluated in this study. When the central ventilation and air filtration system was operated, not only indoor CO2 concentrations but also indoor PM2.5 concentrations were reduced significantly compared to those when the system was turn off. On the other hand, the study also found that the air purification capacity of the ventilation and filtration system was strongly depend on the air flow of the system, it increased when raising the air flow going through the system.

RETRACTED: Optimizing energy and quantifying dispatchable potential of holistic HVAC systems

The increasing demand for flexible resources in power systems, coupled with the evolution of smart buildings, underscores the significance of optimizing energy use and quantifying dispatchable potential in heating, ventilation, and air conditioning systems. This work develops an energy optimization framework for these systems, accounting for external factors like solar radiation, temperature, and humidity. The goal is to minimize the energy consumption of holistic systems and devise optimal control strategies for each subsystem. The framework includes a mechanistic model that accurately describes the performance of cooling towers, a three-damper control strategy for air-side economizers, and three operational modes for air handling units. Furthermore, the relationship between the fresh air ratio and the supply/return air duct pressure drop obtained through analysis simplifies the optimization problem and reduces the difficulty of solving it. Subsequently, the framework utilizes indoor temperature and humidity ranges to ascertain optimal control strategies for both maximal and minimal energy consumption in the system. Simulation results for a hypothetical building reveal that dispatchable potential of the system can account for up to 13.055% of maximal energy consumption.

The influence of injection pressure and exhaust gas recirculation on a VCR engine fueled by microalgae biodiesel

AbstractBiodiesel has been chosen as a decent alternative to diesel in the context of establishing environmentally pleasant conditions and saving petroleum‐based resources for future generations. It is well‐established that biodiesel‐powered diesel engines may achieve outcomes equivalent to those of diesel engines. The current investigation was conducted to study the effect of injection pressure (190, 210, and 230 bar) and exhaust gas recirculation (EGR) (5%, 10%, and 15%) on a single‐cylinder variable compression ratio (VCR) diesel engine running using a B20 (20% MB + 80% PD) blend of microalgae biodiesel (MABD). This experiment was conducted in two stages. During the first stage of experimentation, the efficiency and emission characteristics of a diesel engine with a B20 blend of MABD at various fuel injection pressures and fresh air were investigated. During the second phase, fresh air was mixed with 5%, 10%, and 15% exhaust gases, and the experiment was conducted. It was discovered that increasing injection pressure to 230 bar provided considerable improvements. Brake thermal efficiency increased by 2.35%, brake‐specific fuel consumption decreased by 3.57% and pollutants such as carbon monoxide (CO), hydrocarbon, and smoke were reduced by more than 50% compared to conventional diesel. These reductions were similarly significant (over 22%) as compared to the B20 blend at lower injection pressure (210 bar). However, there was a slight trade‐off: nitrogen oxide (NOx) emissions increased partially (3.14%), while exhaust gas temperature (EGT) increased by 1.72% at a higher pressure. The study then investigated the influence of EGR (5%, 10%, and 15%) at various injection pressures. The optimal value seems to be 10% EGR at 230 bar injection pressure. This combination substantially reduced NOx emissions (by over 41% compared to the normal B20 blend) and EGT (by more than 8%), while having no notable effect on other performance or emission variables. Overall, the results show that employing a B20 MABD blend with high injection pressure (230 bar) and moderate EGR (10%) improves engine performance while reducing hazardous emissions.

Air-conditioning load characteristics and grey box predicting model in subway stations

With the continuous expansion of metro, energy conservation of air-conditioning system in subway stations draws the attention of the whole world. Most of the researches are focused on improving the energy efficiency of the system, while the load characteristics of subway stations are paid little attention. The inaccurate load prediction in the designing of air-conditioning system results in redundancy and low operating efficiency. Therefore, accurately predicting the air-conditioning load is crucial for energy saving in subway stations. In this paper, an innovative three-stage subway air-conditioning load test method was proposed and implemented in nine subway stations in Qingdao. Based on the test data, the special air-conditioning load characteristics of subway stations as underground buildings were analyzed. The results showed that electrical equipment load accounted for the largest part, reaching 53.7 %, while only 42 % of the equipment power was converted into air-conditioning load. The positive role of the envelope should not be ignored, especially in the case of entrance and exit walls, which bore almost all of the fresh air load. Based on the three-stage test, a grey box model was established and the error was validated to be within 6 %. With this model, the load of air-conditioning system can be calculated by inputting passenger flow, power of electrical equipment and public area. This paper provides a reference for the design and operation of air-conditioning system in subway stations.

Peculiarities of the use of "outdoor activity" with persons of the second mature age in health fitness

The article examines the peculiarities of the use of "outdoor activity" means with persons of the second mature age in improving fitness. Materials and methods: The research was conducted on the basis of the "Freestyle" fitness club in Kyiv. A total of 45 people of different sexes (41 men, 4 women), aged from 36 to 60 years (second mature age) took part in the research (survey). Results: We analyzed video recordings of "outdoor activity" training sessions on the Internet and evaluated their effectiveness for people of the second mature age according to the following criteria: physical component of programs, social component of programs, natural conditions for classes, variability of programs, effectiveness of programs, safety of programs, availability of programs, psychological advantages of programs, financial aspect of programs. The most effective measures and fitness programs with "outdoor activity" that can be considered the most useful for those who engage in independent or group training sessions in the health direction in the second mature age among women and men and the prevalence of using "outdoor activity" programs were also determined in order of decreasing significance. Conclusions: based on the results of a comparative analysis of various "outdoor activity" programs, it was established that outdoor fitness classes improve mood, reduce stress levels and increase emotional well-being. In today's wellness fitness outdoor activity programs for adults can have varying popularity based on various factors, such as accessibility, effectiveness, advertising, social support, physical limitations of participants, and others. With the help of a questionnaire, it was determined what was the main motivation for the respondents (n = 45) to use "outdoor activity" (improvement of physical fitness and endurance - 53.3%, weight loss - 24.5%, relaxation and stress reduction - 17.7%, feeling of nature and fresh air - 2.5%), which are the most relevant obstacles and problems when using "outdoor activity" (no obstacles - 20%, weather conditions - 37.7%, lack of time - 42.3%, lack of motivation - 2, 2%).

Cost-Effective Automatic Portable Air Purifier

Indoor air pollution has become a severe concern on human health due to improper ventilation, pets and fine dust particles. The demand for efficient air purifiers has surged, yet many existing solutions are generally pricey and lack portability. The suggested air purifier uses modern filtration technologies, including activated carbon filters, to remove a wide range of airborne contaminants, such as dust, allergies, pet hair, and volatile organic compounds (VOCs). By adopting a tiny and lightweight design, the purifier offers outstanding portability, enabling customers to experience clean and fresh air wherever they go. The proposed air purifier possesses a distinctive design that integrates a high electric field generator and UV light source. The high electric field technique effectively accumulates and neutralizes airborne particles, including dust, pollen, mold spores, and germs. Simultaneously, the UV light component kills dangerous microbes, such as viruses and bacteria, by breaking their DNA structure, offering cleaner and healthier air. To achieve best performance and energy economy the air purifier adopts an automated operation mode. The device operates only upon the detection of motion a human being.

Opaque ventilated façades: Energy performance for different main walls and claddings

Ventilated façades can reduce heat gains through the opaque envelope of buildings, and consequently help to lower the cooling energy demand and the relative greenhouse gas emissions. However, the influence of the design features and climatic variables on their energy performance is not known enough.In this article, the influence of different parameters of the ventilated façade has been assessed. The cladding material, the relative position between mass and thermal insulation in the main wall, the air cavity geometry, and the open/closed joint configurations have been evaluated through a numerical calculation with a model that considers all these parameters, validated with experimental data.It has been observed that, in summer conditions, the best strategy to prevent heat gains is to block the energy in the outermost layers. This suggests adopting non-thermal conductor materials for claddings and the insulation of the main wall on the outer layer. Higher cavities imply a reduction of the ventilation benefits; the air remains more time in the cavity, and thus heat fluxes per unit façade area increase. On the contrary, lower air cavities allow more fresh air entrances from outside, as occurs for open joint claddings, reducing net heat gains. Additionally, widening the air cavity, up to 10 cm, results in lower average heat flux.All these different façade configurations are compared in a cradle-to-gate environmental impact assessment demonstrating that the lowest energy-demanding solution during the service life might not be the best one in the whole life cycle, thus a deeper study is needed.

Effectiveness of natural ventilation through single-sided window opening in air-conditioning rooms

Since many buildings are not equipped with fresh air systems, many people open windows to allow for natural ventilation while the air conditioner is running. However, prolonged window opening may cause unnecessary energy consumption. Additionally, the diverse ways of window opening lead to significant variations in indoor airflow distribution, consequently impacting ventilation efficiency. Therefore, this study used field experiments and computational fluid dynamics (CFD) to determine the air exchange efficiency and air change rate of single-sided natural ventilation in air-conditioning rooms by fitting the decay curves of tracer gas. CFD simulation was performed using the unsteady Reynolds-averaged Navier-Stokes (RANS) model to examine how window openings affect the room’s air distribution, and the computed indoor CO2 concentration was compared to the corresponding field experiment data. The results show that natural ventilation through the window opening induced constant heat and mass exchange between indoor and outdoor air, which caused extra cooling losses but was globally effective in eliminating indoor contaminants. The air exchange efficiency is influenced to varying degrees by factors such as the air supply register’s position, window opening percentage, and window opening position. The air supply register’s position exerted the most significant impact at 46.45%. Efficient indoor-outdoor air exchange can be achieved by opening windows intermittently. When the window is opened from one side and the opening percentage is 100%, the indoor environment can be improved by opening the window for about 10 min every 39 min for X-direction air supply and about 7 min every 39 min for Y-direction.

Characteristics and Application Analysis of a Novel Full Fresh Air System Using Only Geothermal Energy for Space Cooling and Dehumidification

To effectively reduce building energy consumption, a novel full fresh air system with a heat source tower (HST) and a borehole heat exchanger (BHE) was proposed for space cooling and dehumidification in this paper. The cooling system only adopts geothermal energy to produce dry and cold fresh air for space cooling and dehumidification through the BHE and HST, which has the advantage of non-condensate water compared to BHE systems integrated with a fan coil or chilled beam. Based on the established mathematical model of the cooling system, this paper analyzed the system characteristics, feasibility, operation strategy, energy performance, and cost-effectiveness of the proposed model in detail. The results show that the mathematical model has less than 10% error in estimating the system performance compared to the practical HST–BHE experimental set up. Under the specific boundary conditions, the cooling and dehumidification capacity of this system increases with the decrease in the air temperature, air moisture content, and inlet water temperature of the HST. The optimal cooling capacity and the system COP can be achieved when the air–water flow ratio is at 4:3. A case study was conducted in a residential building in Shenyang with an area of about 1800 m2. It was found that this system can fully meet the cooling and dehumidification demand in such a residential building. The operation strategy of the cooling system can be optimized by adjusting the air–water flow ratio from 4:3 to 3:2 during the early cooling season (7 June–1 July) and end cooling season (3 August–1 September). As a result, the average COP of the cooling system during the whole cooling season can be improved from 6.1 to 8.7. Compared with the air source heat pump (ASHP) and the ground source heat pump (GSHP) for space cooling, the proposed cooling system can achieve an energy saving rate of 123% and 26%, respectively. Considering that the BHE of the GSHP can be part of the proposed HST–BHE cooling system, the integration of the HST and GHSP for space cooling (and heating) is strongly recommended in actual applications.

Influential factors on the energy efficiency of fresh air systems in nearly zero energy buildings

Ensuring precise control of fresh air volume is crucial for minimizing energy usage in nearly zero energy buildings. Research shows that automatic pressure-independent dampers offer a promising solution for maintaining the desired fresh air volume. However, the energy performance of damper-controlled fresh air systems is influenced by multiple factors that have not been thoroughly investigated. This study focuses on examining the impact of influencing factors on the energy efficiency of fresh air systems. Laboratory experiments and field testing were conducted on a typical fresh air system. Subsequently, based on the experimental data, an energy saving model of the damper-controlled fresh air system was developed and validated. The main influencing factors were comprehensively investigated according to the energy-saving model. Results show that damper resistance is one of the main influencing factors on energy efficiency. Pressure-independent damper with a low resistance ratio of less than 48 % are recommended; When the average PM2.5 concentration increases by 1 µg/m3, the energy saving rate decreases by approximately 0.3 %, indicating that pressure-independent dampers are more suitable for use in regions with cleaner air; In the heating season, the energy saving rate increases by approximately 0.075 % when the dry bulb temperature decreases by 1 °C; In the cooling season, the energy saving rate increases by 1.19 % when the wet bulb temperature rises by 1 °C. This study contributes to the development of sustainable building practices by identifying key factors that influencing the energy usage of damper-controlled fresh air systems and further guiding the selection and utilization of pressure-independent dampers in nearly zero energy buildings.