Air Infiltration Rate Research Articles

Air infiltration characteristics in oxygen-enhanced and heated chambers on the Qinghai-Xizang Plateau

The Qinghai-Xizang Plateau is characterized by a low-pressure and oxygen-deficient environment due to its high altitude, causing discomfort and major safety problems for the inhabitants. To address this, oxygen-enriched chambers can be used to alleviate the plateau reaction. However, little consideration has been given to air infiltration in these chambers, with a lack of information on the corresponding infiltration heat loss phenomenon. This paper addresses this by investigating the phenomenon of air flow in an oxygen-enriched chamber using experiments and simulations. The results highlight that when there is a difference in oxygen concentration between the interior and exterior of the chamber, mass transfer occurs due to both the molecular diffusion in addition to a flow due to the air density difference caused by the variation in concentration. Also, the simultaneous stack effect is roughly equivalent to 10 times the oxygen pressure, and the two pressure effects act in opposite directions. It is also noted that both the oxygen pressure and the stack effect decrease as the atmospheric pressure decreases. Overall, the oxygen-enriched chambers exhibit less infiltration in plateau areas with a low atmospheric pressure compared to plains areas with a relatively high atmospheric pressure. Finally, this study establishes formulas that can be used to calculate air infiltration rates in oxygen-enriched chambers. This study fills a gap in the existing literature regarding the air infiltration mechanism in oxygen-enriched chambers at high altitudes and low pressures, providing a theoretical foundation for improving indoor environments in the Qinghai-Xizang Plateau and other high-altitude regions.

Effects of oxygen consumption characteristics of goaf on the low oxygen formation mechanism in the working face

Low oxygen at a coal mine's working face has a detrimental impact on working conditions and productivity. This study conducted an experiment on oxygen consumption at low temperatures, quantified the rate of air infiltration, and scrutinised and examined the zoning division of coal seam gas occurrences. The gas change rules in the return air corner and the goaf and the gas outflow rules in the goaf to the working face are analysed. Experiment results reveal that residual coal predominantly consumes oxygen through a combination of physical adsorption and chemical reaction, which is the key factor in the decrease in oxygen concentration. The examination showed, that the gas emission rate of air from the surface cracks to the working face is 0.09–0.13 m·s−1. Air leakage in the goaf results in the oxidation of residual coal and consequently leads to significant oxygen consumption. The release of low-oxygen gases from the oxidation of residual coal in the goaf to the working face is facilitated by atmospheric pressure and negative pressure ventilation methods, which act as sources of power. The research findings offer direction for examining and managing the problem of low oxygen in coal mine working faces.

Evaluating building-level parameters for lower-temperature heating readiness: A sampling-based approach to addressing the heterogeneity of Dutch housing stock

The Dutch government aims to eliminate natural gas for residential heating in 1.5 million homes by 2030. One strategy is connecting existing dwellings to lower-temperature district heating (DH) systems, although these dwellings might require energy renovations. The heterogeneous dwelling stock causes varying renovation needs that complicate the energy transition. The present study addresses this issue by assessing the building-level parameters affecting the readiness of the Dutch terraced-intermediate and apartment types for lower-temperature heating (LTH) supplied by DH systems. A sampling-based approach was employed to capture variability within these dwelling types, addressing the limitations of archetype-based methods. The findings suggest a sample size of 1300 to represent the variations in these dwelling types. Parametric simulations and machine learning methods were used to identify significant building-level parameters for medium-temperature (MT: 70/50 °C) and low-temperature (LT: 55/35 °C) supply levels. These include heating setpoints (desired indoor temperature) and ventilation-related parameters (ventilation system type and air infiltration rate), followed by fabric-related parameters (roof, glazing, wall, ground, and door insulation) and geometric properties (orientation, compactness ratio, and window-to-wall ratio). Additionally, radiator oversizing also impacts LTH readiness. These results broadly apply to the studied dwelling types, although feature importance varies by supply temperature and dwelling type. The findings can guide stakeholders in assessing current conditions and prioritising renovation measures, aiding the development of targeted renovation solutions. Encompassing the representative variations within studied dwelling types enhances the robustness of the results. However, incorporating more refined data could improve the accuracy of the findings, better supporting the energy transition of these dwellings.

Effects of an extreme heat event on indoor conditions of social heritage housing in Mediterranean climate

Social heritage housing in Mediterranean historic cities is particularly vulnerable to climate change hazards as protection policies lead to its exclusion from energy retrofitting programmes, leaving their residents - at higher risk of fuel poverty and the heat-island effect – defenceless. Increasingly frequent heatwaves can potentially produce “overheating” in these buildings, a thermal state that impedes people's comfort with harmful consequences to their health. Other indoor air quality factors, like humidity and CO₂ levels, also affect residents' health. The objective of this research is to evaluate the actual indoor environmental quality of three occupied dwellings in social buildings of high heritage value located in two historic cities in Andalusia (Spain) during the extreme heat events that occurred in 2022. A monitoring campaign was conducted and the data collected over the summer was analysed and evaluated using existing metrics. Our results show that the CO2 concentration rates generally remained below the upper limit of 1000 ppm in all cases, probably due to the high air infiltration rates measured (5.83 h−1, 4.39 h−1 and 14.65 h−1). On the contrary, the relative humidity rates were outside the acceptable range (45–60 %) for 90 % of the occupied hours in all cases. In the warmest city, overheating was continuous and severe in all rooms, according to the metric adopted (CIBSE standards TM52 and TM59 under the adaptive thermal comfort model). The situation was particularly critical in the free-running bedroom, but the overheating index values in the living rooms, where air conditioning was installed and used about 50 % of the occupied time, also deviated significantly from the acceptable limits.

Research on the air-infiltration rate shelter coefficient of building complexes based on building parameter clustering

The configuration of a building complex can significantly influence the air-infiltration rate, which subsequently affects the energy consumption for heating and cooling. Given the diversity of parameters associated with a building complex, it is challenging to study all combinations. This study proposed the k-means clustering method to identify representative building clusters, thereby facilitating the derivation of correction coefficient for the air-infiltration rate within a complex. Initially, data pertaining to district characteristics, such as the complex density, height, and building aspect ratio, were collected and clustered to obtain several representative groups of building clusters. Subsequently, a validated computational fluid dynamics program with the renormalization group (RNG) k–ε turbulence model was employed to investigate the spatial characteristics of the pressure coefficient (Cp) on building surfaces across various groups within the complex. Finally, the shelter coefficient (SAIR), which represents the ratio of an individual building to those in different groups, was determined to correct for the air-infiltration rate in diverse district types. The results show that SAIR varies considerably (from 0.15 to 0.53) owing to the different densities, heights, and layouts between buildings. The applicability of SAIR was further demonstrated and verified in a case study of a building in Dalian, China. The research results can provide a method for predicting the air-infiltration rate of building complex.

Synergistic approaches to elevate indoor air quality: A holistic examination of classroom refinement, air exchange optimization, and flooring material impact

This research endeavors to elevate indoor air quality within aging school environments by concentrating on refining interior finishing materials and windows. Renovations, encompassing window and floor remodeling in classrooms, aim to mitigate particulate matter (PM) infiltration and enhance air exchange rates. Utilizing SPS30 sensors for the analysis of 0.3–2.5 μm particles, with a focus on their implications for human health, the study evaluated air exchange rates, deposition rates, infiltration rates, and particle generation during classroom activities. Post-renovation results demonstrated a noteworthy decrease in air exchange rates, indicating an enhancement in airtightness. The investigation delves into particle generation with various flooring materials, accentuating the importance of opting for durable and low-particle-generating alternatives. Health risk assessments, considering multiple exposure routes (inhalation, dermal contact, and ingestion), revealed reduced risks post-renovation, particularly for children. To further optimize indoor air quality, the study suggests the implementation of air purification systems. Examination of PM generation during student activities showcased a substantial reduction post-renovation. This study underscores the positive influence of architectural enhancements on indoor air quality while acknowledging the necessity for holistic solutions and continuous research.

Comparison of models to predict air infiltration rate of buildings with different surrounding environments

Comparison of models to predict air infiltration rate of buildings with different surrounding environments

Dimensionless correlations of indoor thermal stratification in a non-enclosed large-space building under heating and cooling conditions

Indoor thermal stratification is a prevailing phenomenon in large-space buildings, which poses great pressure on their energy consumption and indoor built environment. This paper revealed the mechanism of indoor thermal stratification in a non-enclosed large-space building under heating and cooling conditions. It can be abstracted as a joint effect of the cold and hot air inflow (i.e., HVAC system and outdoor air infiltration), which are respectively depicted by two newly-defined Archimedes numbers (i.e., Arc and Arh). Then, we developed dimensionless correlations between the indoor thermal stratification (quantified by the dimensionless factor of the vertical temperature profile, CT) and the two streams of air inflow (quantified by Arc and Arh). For application, the dimensionless correlations can be coupled with our previously proposed theoretical model to accurately predict the air infiltration rate in a large-space building. Moreover, the dimensionless analysis reveals a principle of indoor vertical temperature profile control to minimize the buoyancy driving force of air infiltration in large-space buildings: Achieving a vertically uniform indoor thermal environment under heating condition and an effectively stratified indoor thermal environment under cooling condition. These findings help to provide practical guidelines to minimize buoyancy-driven air infiltration in large-space buildings.

HUBUNGAN LAJU INFILTRASI TERHADAP PERMEABILITAS TANAH DAN MUKA AIRTANAH DI DAERAH DESA TAJUR KECAMATAN CITEUREUP

Infiltration is an important process in a hydrological system and acts as a medium for air infiltration into the soil. The process of infiltration in soil can be influenced by several factors, namely, rainfall, vegetation, land slope, land use, and soil moisture. Apart from this, other factors such as groundwater level and soil permeability also have an influence on the infiltration process, both of which are related to each other in terms of the rate of infiltration or air infiltration into the soil. If the infiltration process is disrupted, it results in the pooling of air on the ground surface, which affects the hydrological system. It is necessary to know how factors such as groundwater levels and soil permeability influence the infiltration rate. Based on this, the aim of this research is to determine the relationship. between infiltration rate, groundwater level, and soil permeability and their influence. The research method was carried out by taking data from direct groundwater level measurements and infiltration rate measurements, as well as samples for soil permeability analysis. Then an interpretation of the data obtained is carried out and presented in a map of the infiltration zone and soil permeability zone. The research area in Tajur Village has 2 infiltration zones, namely the slow-medium zone and the medium zone with medium and rather fast soil permeability and low-medium groundwater depth.

Air infiltration rate distribution across Chinese five climate zones: A modelling study for rural residences

Air infiltration rate is one of the fundamental parameters in the design and analysis of building environment, which is the fundamental mode of air exchange between indoor and outdoor in non-mechanically ventilated residences when doors and windows are closed. Most Chinese residential buildings have no mechanical ventilation equipment installed. Previous researches on Chinese housing have primarily focused on urban residences. However, the number of both urban households and rural households accounts for almost half of Chinese households. Considering the significant urban-rural differences in Chinese housing, there is an urgent need for researching the air infiltration rate in rural area. This study employed a multi-zone network airflow model approach to simulate the air infiltration rate of 111 rural residential samples in 13 Chinese provinces, obtaining the hour-by-hour results for a whole typical weather year of each sample. Thus, the distributions of air infiltration rate for each rural region were finally summarized. Additionally, we performed field measurements in 23 samples to validate the simulation results. According to the results, the mean value of air infiltration rate is larger than that of urban residences, and its distribution in each climatic zone generally follows a log-normal distribution. The results are expected to be applied for indoor air quality studies, building energy consumption analysis, and other frontiers related to architectural environmental design and analysis.

Exploring assumptions for air infiltration rate estimates using indoor radon in UK homes

Radon, a known carcinogen, is one of the most commonly monitored indoor contaminants. This paper utilises findings from a previous study on indoor radon measurements in United Kingdom (UK) homes to explore the UK Government’s Standard Assessment Procedure (SAP) assumptions for air infiltration rates. These assumptions are important as they are used to assess the energy performance of dwellings and compliance with building regulations. Indoor radon data is aggregated by 16 combinations of home energy efficiency measures (loft and wall insulation, glazing upgrades and draught proofing) and fitted using a simple analytic radon model. We find indoor radon to be inversely proportional to air change rate and proportional to a fit coefficient, k, of 42.2 ± 3.1 (95% Confidence Interval (CI)). We also show that the assumptions within SAP used to estimate home infiltration rates can be modified to include the impact of home energy efficiency which improves the fit (R 2 from 0.38 to 0.51) to the radon data. This work provides evidence to help improve assumptions regarding the effects of home energy efficiency on infiltration rates.

Air infiltration and related building energy consumption: A case study of office buildings in Changsha, China

Past studies reveal that air infiltration through the building envelope and its impact on the indoor environment and energy consumption are significantly influenced by climate characteristics. However, little relevant information is available for buildings in southern China, where the building design traditionally follows a philosophy of being open and shaded. The present study employs both experimental measurements and numerical simulations to investigate the airtightness of buildings in Hot Summer and Cold Winter (HSCW) climate region of southern China and the associated energy consumption. The measurements and simulations are based on a typical office building in Changsha. Measurement results show that the air change rate of six tested spaces at the natural pressure difference ranges from 0.10 to 0.30 h−1 with an average of 0.17 h−1 in summer, and from 0.09 to 0.32 h−1 with an average of 0.16 h−1 in winter. The operation of the air-conditioning system affects largely air infiltration, and each unit change in setpoint air temperature can result in an average of one-third or more change in air infiltration rate. Simulation results show that a decrease in air infiltration rate from 0.17 h−1 to 0.01 h−1 reduces the infiltration-related cooling energy consumption from 14.29 to 0.75 kWh/m2·year and heating energy consumption from 8.20 to 0.39 kWh/m2·year. The same change in the setpoint air temperature of air-conditioning system in summer and winter results in different infiltration-related energy consumption. The findings would contribute to an improved energy simulation and assessment of buildings in southern China.

A Numerical Investigation of the Thermal Performance of a Gabion Building Envelope in Cold Regions with a Mountainous Climate

Applying rock-filled gabion to buildings in cold regions with mountainous climates has multiple potentials, such as utilizing rock resources, improving building sustainability and saving building energy. Therefore, it is necessary to analyze the thermal performance of gabion buildings. Based on the CFD method, this paper establishes a numerical model of buildings with gabion enclosure structures, analyzes the influence of the gabion structure on the external convective heat transfer coefficient (CHTC), wind pressure, air infiltration, room temperature and building load, and further uses the building energy consumption simulation method to analyze the heat load of gabion buildings. The results showed that the adverse impact of climate on the building thermal performance is significantly diminished by the gabion. Under different weather conditions, the CHTC, the maximum wind pressure difference on the exterior surface, and the air infiltration rate are reduced by different rates. Further, the room base temperature increases throughout the heating season, and the maximum heat load and the cumulative heat load of the building are, respectively, reduced by 10.6% and 24.8%. This work revealed that the gabion is an eco-friendly and adaptive measure to improve thermal performance and indoor thermal comfort.

Evaluation of phase change materials for a light-weight building in Morocco: Effect of building's volume, window orientation & infiltration

In this study, we will model a light-weight building made of phase change materials (PCMs) to analyze the impact of the building volume, window orientation, and air infiltration on the PCM performance. This is done by calculating the energy savings attained by the use of PCM across all of Morocco. We'll use the commercial Rubitherm panels with RT28HC as a phase change material in this work. Typically, the EnergyPlus simulation engine is chosen to perform the modeling. The impact of building volumes is also evaluated on the PCM activation for light-weight square buildings with different side lengths of 10 m, 9 m, 8 m, and 7 m. Also, we looked at how well the PCM performed in terms of energy savings and thermal regulation at different window orientation placements (south, north, west, and east) and various air infiltration rates (0.5, 1, 1.5, and 3 ACH). This paper's primary objective is to determine the energy savings for the PCM-enhanced building in Morocco, as well as the effect of building volume, window orientation, and infiltration on the PCM capabilities for stabilizing the indoor room temperature. The results show good indoor temperature stabilization during the summer, for the light-weight square building with a south-facing window and no air infiltration. This configuration was able to achieve a total fluctuation reduction of 1303.3 °C for the 10 m building in a semi-arid environment. Besides, a high energy savings percentage of 69.56% was achieved for the PCM-enhanced building with the south-oriented window and air infiltration of 0.5 air change per hour.

Examining the impact of stochastic multi-year weather and air infiltration on hygrothermal moisture risks

The analysis of heat, air, and moisture (H.A.M.) transport for building envelopes are known to be highly dependent on climate loads and air infiltration rates. Moisture content within the assembly is often a key H.A.M. analysis outcome to assess risk and transport behavior. ASHRAE Standard 160-2016 states that building envelope H.A.M. analysis should be done using moisture design reference data or using a minimum of 10 consecutive years of weather. While there has been progress and methods for selecting or designing moisture reference years there has been a lack of study in the impact of multi-year (particularly 10-year) weather scenarios on simulation results in comparison to reference year simulations. This paper presents research using stochastic 1, 2, and 10-year weather data and air infiltration rates to study the range of simulated moisture content outcomes for four wall assemblies in Philadelphia and compares these to the outcomes when using reference years. Results from the study show that air infiltration, starting month, and multi-year duration have significant impacts on simulated moisture content, mold, and corrosion analysis results. Regression analysis using annual averages of climate input parameters did not yield useable models for selecting weather years, however an estimated mold index value using outdoor climate data may be useful in selecting weather years with varying starting months for mold growth assessment.

Investigating the temperature distribution of non-enclosed atriums with air infiltration in winter

Low-temperature air infiltration and vertical thermal stratification lead to an unsatisfied bottom-occupied environment of the atrium and increase the space heating load in winter. An integrated prediction model was proposed regarding the interaction between thermal stratification and air infiltration. It includes the extended Block model for predicting the vertical temperature distribution in a non-enclosed atrium, the air infiltration model for calculating the buoyancy-driven air infiltration rate, and the Velocity propagating model for describing the airflow pattern within a foyer. By applying this model, we quantitatively analysed the indoor thermal characteristics in different atrium/foyer spatial morphologies. Beyond the indoor net height, the atrium diameter is also a dominant factor affecting the flow rate of air infiltration introduced from the foyer. The lower the section aspect ratio (SAR) and the higher the bottom floor height of the atrium, the warmer the bottom-occupied environment. The foyer's buffer effect mainly promotes occupants' thermal comfort, as lengthening the foyer length increases the heating load of air infiltration into the atrium while helping reduce the horizontal temperature gradient (HTG) when occupants walk across. This study clarified the indoor environmental characteristics in such spaces in winter and explored the interrelated influencing factors. The methodology and conclusions provide insights into practical engineering.

In situ virtual sensing for dwelling infiltration rates in multi-unit residential buildings

Wind- and stack-interacted dwelling infiltration is a major factor influencing heating and cooling loads, indoor environmental quality, and indoor air quality (IAQ) in high-rise or multi-unit residential buildings (MURB). However, it is challenging to observe the real-time infiltration rates in an entire building using existing sensors. Therefore, this study proposes a virtual sensing method for dwelling infiltration rates in MURB. Virtual sensing is developed in situ for the target MURB by a hybrid modeling approach combining forward simulation and inverse estimation using the building life cycle. It mainly consists of (1) multi-zone airflow network modeling with design information, (2) model calibration with intrusive commissioning data, and (3) virtual sensing with nonintrusive operation data. The proposed method can observe the outdoor air infiltration rates across the envelope and the interzonal airflow rates at the entrance door by dwelling units. In the validation case, the hybrid modeling approach could determine the reliable infiltration rate (with 97.16% accuracy). In the application, all dwelling units were rated by the thresholds in terms of the heating loads and IAQ based on the virtual sensing results. We strongly recommend observing dwelling infiltration in each household using the proposed virtual sensing method.

Simulation of thermal comfort and energy demand in buildings of sub-Himalayan eastern India - Impact of climate change at mid (2050) and distant (2080) future

The global warming associated with climate change predicted by the Intergovernmental Panel on Climate Change (IPCC) is expected to deteriorate the indoor climate of free-running buildings. Features like proper orientation and wall thickness are important for the design of a building that is resilient to the impact of climate change. However, the implementation of these features is sometimes difficult, especially in a rugged hilly location. A whole building simulation was performed using DesignBuilder for an existing 3-storey free running multi-family concrete building located in the sub-Himalayan region of eastern India, for thermal comfort and energy demand during the present and the climate change scenarios of 2050 and 2080. The results show an increasing trend in the indoor operative temperature during the future climatic scenario, with the condition inside the top roof-exposed floor deteriorating the most. A decrease of 59.8% and 81.2% in the annual heating energy and an increase of 221.9% and 467.0% in the annual cooling energy were predicted for the future climate of 2050 and 2080 compared to the present. Parametric analysis performed considering orientation, wall U-value, infiltration rate and window-to-wall ratios revealed that the east/south-east facing orientation would perform the best with regard to overheating due to climate change. Further, the use of autoclaved aerated concrete (AAC) brick is recommended along with the decrease in air infiltration rate and window-to-wall ratio to improve the thermal performance of the indoor environment. In addition, we have also proposed a method to assess the under-cooling of an indoor environment.

Energy Performance Assessment of the Container Housing in Subtropical Region of China upon Future Climate Scenarios

Being continuously abandoned in huge amounts year-round by freight industry, shipping containers meet increasing regenerative utility in forms of temporary buildings, small public facilities, etc., especially in fast-developing countries with large populations and high living intensities like China. Although recycled containers have been nicely entitled with green building visions, their characterized inferior thermal properties (low inertia, poor insulation, etc.) when compared to conventional building forms and materials will greatly hinder their energy-saving potential, especially under the serious future extreme climate expectations. It therefore becomes particularly necessary to uncover the actual energy and thermophysical behaviors of the container building typology, upon extreme future climate scenarios targeting zero carbon forms for small-scale and temporary buildings in the upcoming future. In reference to existing data, this study made reasonable predictions of future extreme climate conditions (2050 and 2080), employing the Morphing method, and examined the cooling energy performances of the typical container housing in a subtropical climate through dynamic simulations. The energy-saving effectiveness of key design variables including insulation types, thicknesses, window opening areas and air infiltration rates has been validated and quantitatively revealed for such a building typology among the tested hot summer and warm winter region. Results imply that the additional energy burden brought by future extreme weather conditions cannot be ignored. The heat gains from envelopes and hot air infiltration are both key design factors of cooling energy increments for such building types upon future extreme climates. Compared with expanded pearl- and vermiculite-type insulation materials, thinner (70~90 mm) plastics and mineral wool-type ones have better energy-saving performance and therefore are worth consideration. High air infiltration rates and window openings in eastern or western orientations shall be carefully selected. The research outcomes can provide key references for design decisions made for the energy-efficient and low-carbon design of the container building typology among subtropical zones, or similar climate regions in response to future climate conditions.

An experimental method for evaluating vehicle cabin airtightness and ventilation performance

An experimental method is proposed for evaluating the airtightness of a vehicle cabin and the ventilation effects of three components of the vehicle ventilation system. The measurement results are used to derive a theoretical equation to predict the total air infiltration rate of the cabin as a function of the pressure difference between the cabin interior and exterior, respectively. The validity of the predictive equation is demonstrated by means of fan pressurization experiments performed with the vehicle air-conditioning system set in the fresh air mode. It is shown that the prediction results for the total ventilation rate deviate from the experimental results by less than 10%. The infiltration ventilation effect of natural diffusion in the vehicle cabin is measured using the CO2 tracer gas method. The air exchange rate (ACH) of the cabin is found to be 0.816 in the recirculation air mode and 3.554 in the fresh air mode.