Ventilation Demand Research Articles

A novel ventilation method: Experimental measurement and numerical simulation of vertical single-row inclined slit ventilation

Existing ventilation technologies often struggle to balance the limited airflow supply with the demands of indoor ventilation and air circulation in winter. This paper introduces a novel ventilation method, vertical single-row inclined slit ventilation (VSISV), which channels airflow through multiple inclined slits spaced at specific intervals along a vertical supply air duct. By ensuring continuity of the upstream and downstream slit jets, a continuous downward airflow is formed, enhancing both winter ventilation performance and indoor air circulation. The method was experimentally measured, with a focus on comparison to the IJV system. At the same airflow rate, it not only efficiently transports the supply air heat from the upper indoor area to the floor but also exhibits strong horizontal diffusion capability. The RNG turbulence model was selected for numerical simulation, focusing on indoor thermal comfort, air quality, and energy-saving potential. The results indicate that, at the same airflow rate, this method effectively maintains high indoor thermal comfort, directs airflow downward from the ceiling, reduces thermal stratification in the upper zone, achieves a more uniform and elevated indoor temperature, enhances indoor air quality, and demonstrates substantial energy-saving potential. This provides valuable insights for energy conservation, emission reduction, and the optimization in winter building ventilation systems.

Improving thermal environment and ventilation efficiency in high-temperature excavation tunnels via an innovative heat insulation and cooling baffle

An increasing number of tunnels inevitably encounter high-temperature environments induced by elevated geotemperatures. The energy demand for ventilation and cooling in excavation tunnels increases significantly as the temperature of the surrounding rock increases, thereby hindering the sustainable exploitation of deep resources. This paper presents an optimization method for airflow organization in excavation tunnels that integrates thermal insulation and cooling (TIC) baffles. The proposed approach significantly improves the cooling effect of the auxiliary ventilation system while reducing energy consumption. This method offers the advantages of simplicity, convenience, and cost-effectiveness. A multifield coupling model using COMSOL software was developed and validated to analyze the system, and the application scenario was explored. Several ventilation scenarios were examined, highlighting that TIC baffles effectively reduce the heat release from the surrounding rock and lower the airflow temperature in personnel areas in the excavation tunnel. By implementing TIC baffles, the average airflow temperature in the excavation tunnel decreases by 1.5 °C to 1.8 °C, resulting in a saving of approximately 5.11 kW in cooling energy. Increasing the circulating water flow in the heat-exchange pipe of the TIC baffles or reducing the initial circulating water temperature can enhance the cooling capacity of the TIC baffles and lower the tunnel airflow temperature to a certain extent. The distance between the TIC baffles and surrounding rock significantly affects the airflow temperature between the left and right TIC baffles. An excessive length of TIC baffles (L > 7 m) leads to heat accumulation and high-temperature airflow in localized areas. In This study, a method for optimizing the thermal environment and saving energy in high-temperature excavation tunnels is proposed.

Numerical analysis and evaluation of a tropical classroom for thermal comfort, indoor air quality, and energy consumption using ventilation with air-to-air total heat recovery system (MemHEX)

ABSTRACT Lecture rooms in the Philippines often experience unfavourable temperatures and elevated carbon dioxide (CO2) concentrations, impacting the well-being, health, and learning efficiency of both students and educators. This research seeks to evaluate the thermal comfort, indoor air quality, and energy usage in a standard Philippine lecture room by implementing a membrane-type total heat exchanger (MemHEX). The research used computational fluid dynamics (CFD) simulations, which were validated by field measurements and showed the effectiveness of the MemHEX. Energy consumption was modelled using EnergyPlus to compare potential impacts of various ventilation approaches. Room temperature and humidity fall short of thermal comfort standards, suggesting the need for a higher-capacity air conditioning unit (ACU). Average CO2 concentration exceeds 1000 ppm, signalling a demand for ventilation. Post-MemHEX installation, temperature and humidity slightly rise with increased air changes per hour (ACH), introducing warm outdoor air. Indoor air quality improves with rising ACH, reducing CO2 levels by exchanging fresh outdoor air. Comparing mechanical ventilation and MemHEX reveals MemHEX as more energy-efficient, maintaining better indoor conditions. These findings provide valuable insights for the field of research by demonstrating the feasibility and benefits of using MemHEX to improve the indoor environment and energy efficiency of a typical Philippine classroom.

A Novel Mixed Finite/Infinite Dimensional Port–Hamiltonian Model of a Mechanical Ventilator

Mechanical ventilation is a life-saving treatment for critically ill patients who are struggling to breathe independently due to injury or disease. Globally, per year, there has always been a large number of individuals who have required mechanical ventilation. The COVID-19 pandemic brought to light the significance of mechanical ventilation, which played a significant role in sustaining COVID-19-infected critically ill patients who could not breathe on their own. The pandemic drew the attention of the world to the shortage of ventilators globally. Some of the challenges to providing an adequate number of ventilators include: increased demand for ventilators, supply chain disruptions, manufacturing constraints, distribution inequalities, financial constraints, maintenance and logistics difficulties, training and expertise shortages, and the lack of design and development of affordable mechanical ventilators that satisfy the stipulated requirements. This research work presents the formulation of a detailed Port–Hamiltonian model of a mechanical ventilator integrated with the human respiratory system. The interconnection and coupling conditions for the various subsystems within the mechanical ventilator and the coupling between the mechanical ventilator and the human respiratory system are also presented. Structure-preserving discretization is provided alongside numerical simulations and results. The obtained results are found to be comparable to results presented in the literature. Future work will include the design of suitable controllers for the system.

DIY Ventilator Using Arduino: Review

Abstract: The COVID-19 pandemic, caused by the novel coronavirus SARS-CoV-2, brought with it an unprecedented surge in the demand for ventilators. The resultant shortage of these life-saving medical devices exposed a critical gap in healthcare systems worldwide. In response, a global community of DIY enthusiasts, engineers, and healthcare professionals initiated projects aimed at designing and developing DIY ventilators. Many of these projects have harnessed the accessibility, affordability, and versatility of Arduino microcontrollers, an open-source electronics platform. The proposed system aims to fulfill the need of the portable ventilators by providing:  Cost effective  Easily accessible to everyone  Production Locally This comprehensive review paper delves deeply into these DIY ventilator projects, specifically those incorporating Arduinobased solutions, with a primary focus on their design principles, functionalities, safety considerations, regulatory compliance, technological advancements, and the associated challenges and opportunities. The analysis presented in this review is drawn from a wide range of references, including peer-reviewed articles, guidance documents, and original research.

Evaluation of MSCT severity scoring for prediction of mortality among patients with COVID-19

BackgroundLung CT imaging may reveal COVID-19 abnormalities earlier than RTPCR. CT may be more sensitive than RT-PCR for diagnosing COVID-19-related pneumonia.AimThis study assesses the accuracy of multi-slice computed tomography (MSCT) grading in predicting COVID-19 mortality.MethodsCOVID-19 RT-PCR. For severity scores, all patients’ clinical examinations, history, and chest MSCT data were collected.ResultsAccording to the chest MSCT score, 102 (51.5%), 70 (35%), and 28 (14%) patients had mild, moderate, and severe illness. Out of the patients, 62 (31%) died, and 69% survived. Patients with severe MSCT scores showed a considerably greater mean age than other groups (P < 0.001). Moreover, this group had a considerably higher mean BMI (P < 0.001), and a majority (57.1%) were obese (P < 0.001). Compared to the mild group, the moderate and severe groups had significantly increased rates of diabetes, hypertension, and liver disease (P < 0.001). The moderate group had a greater rate of no comorbidities (P < 0.001). A severe MSCT score was linked to increased leucocytes, C-reactive protein, ESR, ferritin, d-dimer, HbA1c, and fasting blood sugar, as well as decreased mean lymphocytes (P < 0.001). Severe MSCT scores were linked to increased ICU admissions (P < 0.001) and increased demand for advanced mechanical ventilation and oxygen assistance (P < 0.001). A severe MSCT score was associated with the highest death rate, followed by a moderate MSCT score. Low mortality rates were observed in mild MSCT-scored patients (P < 0.001).ConclusionMSC T score severity is a reliable and noninvasive way to predict COVID-19 mortality

Exploring the potential of fly ash cenosphere—capric acid composite phase change material in concrete incorporating supplementary cementitious material

AbstractIncreasing demand for energy globally, with the building sector being a significant contributor to energy consumption, is a major issue. To address this, efforts are being made to make buildings more energy efficient, including lowering the demand for heating, ventilation, and air conditioning to decrease energy demand. Phase change material (PCM) functions as a latent heat energy storage material that absorbs heat energy while transforming its phase from solid to liquid and then releases the heat energy when it transforms from liquid to solid state. Integrating PCM into building materials can considerably enhance their energy storage density. In this study, the potential of using fly ash cenosphere—capric acid (CeCA) composite PCM in concrete is evaluated. The mechanical, durability and thermal properties of the CeCA blended concrete were investigated. Furthermore, the CeCA‐concrete is enhanced with auxiliary cementitious substance, namely ground granulated blast furnace slag (GGBS). The optimal proportion of CeCA was determined to ensure a balance of compressive strength and thermal conductivity. The results indicated that the compressive strength of the CeCA blended concrete lowered with an increase in the percentage of CeCA. The thermal conductivity of the concrete specimen was lowered by 33.14% at a 25% incorporation of CeCA, resulting in improved thermal performance. The incorporation of GGBS has enhanced the mechanical and durability performance of CeCA‐Concrete. The optimal concrete specimen was found to be 25% CeCA +40% GGBS, which had greater thermal efficiency than the control specimen with similar strength performance. The findings were validated by field emission scanning electron microscopy analysis of the concrete specimen.

Ventilation Methods for Improving the Indoor Air Quality and Energy Efficiency of Multi-Family Buildings in Central Europe

In Poland and other countries in Central Europe, residential buildings from the second half of the 20th century dominate, which have recently undergone deep thermomodernisation. Research on the retrofitting of residential buildings has focused mainly on energy efficiency, with only a few studies on indoor air quality. The aim of this study was to present a comparative analysis of the impact of five ventilation scenarios (three natural and two mechanical) on CO2 concentration and energy demand for heating and ventilation in residential spaces of a multi-family building located in Poland. The analyses were based on the results of building performance co-simulation using the EnergyPlus and CONTAM programs carried out under dynamic conditions with a 5 min time step for the entire heating season. The calculations took into account the instantaneous occupancy variability of twenty apartments. In the buildings equipped with new tight windows, the natural ventilation system provided extremely low air exchange (on average 0.1 h−1) and poor indoor air quality (average CO2 concentration at the level of 2500 ppm). Opening windows to ventilate the rooms generated a multiple increase (up to 8 times) in heating demand during these periods, but average CO2 concentration was on the level of 930 ppm. The use of mechanical ventilation was profitable both in terms of energy savings (at the level of 50%) and improvement in the indoor air.

A view from the eye of the storm: An analytic autoethnographic account of ventilator procurement during COVID-19 first wave

An unprecedented spike in the demand for ventilators during the first wave of the COVID-19 caused significant disruption to the global supply and demand chain of medical devices. The characteristics of the disruption forced the Irish national health service to deviate from an established purchasing process as it pursued its objective of securing the delivery of ventilators for its ICUs. Utilising analytical autoethnography, this study presents a narrative account of the lead author's experiences (as a clinical procurement director) during the first wave of the COVID-19 crisis, with the objective of analysing the improvised resilient response of the medical device procurement function of the national health service. Incorporating process analysis to shape the narrative, four process deviations are identified and analysed using organisational mindfulness. The study provides a rich insight for practitioners and researchers into the realities of crisis response, with specific contributions to the field of resilience implementation through organisational mindfulness.

Advancing energy efficiency in livestock building: Simplified building energy simulation tool for geometric design of pigsty

Concerns related to food security and animal welfare have led to increasing interest in analyzing the energy demands of heating, ventilation, and air conditioning (HVAC) systems in livestock buildings. However, building energy simulation (BES) model, which facilitates precise HVAC systems energy analysis, is difficult to use for non-experts, and particularly, its usability drops significantly in livestock buildings, which are often constructed without involvement of building engineers. This study, therefore, developed a tool that can analyze the energy demand of pigsties by changing geometric design variables with only several numerical inputs without separate 3D modeling. Pigsty geometric design types were classified by examining pigsty architectural design manual and web portal map search. A simplified tool, utilizing EnergyPlus and MATLAB graphical user interface, was developed to analyze energy demand in pigsties by leveraging simple user inputs for geometric design modeling. This tool simplifies exploring potential energy savings through geometric design changes in the early design stages of livestock buildings. The methodology introduced in this study lays the groundwork for future enhancements, including the integration of various design-phase variables beyond geometric design.

Determining airflow requirements in mine workings based on field measurements of actual emissions from internal combustion engine equipment

The increasing complex geological and hydrogeological conditions ore deposit mining, deeper excavation sites, and ambitious business expansion strategies, necessitate the use of high-performance, heavy-duty self-propelled machinery and winning equipment. Such activities significantly strain mine ventilation systems and demand innovative safety measures during mining.This study assesses the influence of interconnected production variables on the aerological safety of mining operations. It provides real-world data on emissions from diverse sources within mines. The analysis includes an examination of current methodologies for estimating the air volume needed to dilute exhaust gases from diesel-powered machinery. Through numerical simulation that accounts for changes over time, the study was able to predict how exhaust gas concentrations would disperse within mines. These theoretical findings were then confirmed through empirical observations made in actual mining setting The field studies conducted, alongside their thorough analysis, underscored the necessity for adopting new, more sophisticated approaches to calculate airflow requirements in mines operating ICE machinery. A particular methodology developed by the MMI of the NUST MISIS (hereinafter referred to as the Methodology) was put forward as the primary tool for this purpose. The Methodology’s precision and benefits were closely scrutinized, revealing its effectiveness in ensuring aerological safety in mines.

Development and evaluation of a mechanical ventilator-sharing system.

During the COVID-19 pandemic surge in the hospitalization of critically ill patients and the global demand for mechanical ventilators, alternative strategies for device sharing were explored. We developed and assessed the performance of a system for shared ventilation that uses clinically available components to individualize tidal volumes under a variety of clinically relevant conditions. The feasibility of remote monitoring of ventilators was also assessed. By using existing resources and off-the-shelf components, a ventilator-sharing system (VSS) that ventilates 2 patients simultaneously with a single device, and a ventilator monitoring system (VMS) that remotely monitors pulmonary mechanics were developed. The feasibility and effectiveness of VSS and VMS were evaluated in benchtop testing using 2 test lungs on a single ventilator, and then performance was assessed in translational swine models of normal and impaired lung function. In benchtop testing, VSS and VMS delivered the set individualized parameters with minimal % errors in test lungs under pressure- and volume-regulated ventilation modes, suggesting the highest precision and accuracy. In animal studies, the VSS and VMS successfully delivered the individualized mechanical ventilation parameters within clinically acceptable limits. Further, we found no statistically significant difference between the target and measured values. The VSS adequately ventilated 2 test lungs or animals with variable lung conditions. The VMS accurately displayed mechanical ventilation settings, parameters, and alarms. Both of these systems could be rapidly assembled for scaling up to ventilate several critically ill patients in a pandemic or mass casualty disaster situations by leveraging off-the-shelf and custom 3D printed components.

Holistic design of energy-efficient temporary houses: Meeting ventilation, heating, cooling, and lighting demands

Recent disasters around the world have brought attention to the challenges faced by the homeless. Energy-efficient container houses (EECHs) offer a comfortable, sustainable, and temporary solution. A holistic design of EECH was conducted for mixed and hot climates using DesignBuilder software. The design, performed initially according to design criteria derived from ASHRAE Standards and previous studies, was subsequently examined for five passive strategies: envelope layering, WWR, windows opening ratio, glazing type, and shading. Optimal conditions were determined by the trade-off between heating and cooling demands, ventilation rate, and minimum daylight factor (DF) and uniformity (UDF). Results reveal that in mixed climates, using insulation materials and thermal mass is recommended, while in hot climates, it is advisable to avoid using them and instead rely solely on internal finishing layers. Complete reliance on natural ventilation is achieved by combining an opening ratio of 35 % with a WWR of 9%–25 % for south and north facades, and 6%–12 % for west façade. In mixed climates, argon gap double clear glazing is suitable, while a low-e layer is added for hot climates. Installing overhangs on south windows enhances UDF, unlike vertical fins on north and west windows. The designed EECHs consume 176 kWh/m2 of electricity annually.

Low-frequency ultra-broadband ventilated muffler based on a resonance-labyrinthine metamaterial

We present a theoretical and experimental study of a ventilated metamaterial muffler operating at a low-frequency range. The muffler combines two Helmholtz resonance cavities with the spatial labyrinthine microstructures to achieve a large bandgap. A central hole ensures efficient air circulation. The adjustable cavity allows for precise control over the performance and bandwidth of sound insulation. By cascading multiple metamaterial units, the muffler exhibits a large transmission loss with broad bandwidth. Both simulations and experiments demonstrate transmission loss is over 10 dB in the frequency range from 230 Hz to 816 Hz. The overall dimensions of the muffler are 216 mm in length and 15 mm in diameter, much smaller than the operating wavelength. The high-efficiency sound insulation under the ventilation condition originates from local resonance with labyrinthine structures. This muffler exhibits potential for diverse applications in the field of acoustic engineering, where there is a demand for simultaneous noise reduction and ventilation.

Predictive Value of C-Reactive Protein/Albumin Ratio for Acute Kidney Injury in Patients with Acute Pancreatitis.

This study aims to evaluate the predictive efficacy of the C-reactive protein/albumin ratio (CAR), a cost-effective, easily accessible, and reproducible biomarker obtained from standard blood tests, in forecasting acute kidney injury (AKI) among patients undergoing acute pancreatitis (AP). Considering that changes in the CAR are associated with AKI incidence in AP cases, this work aims to explore whether CAR can be used as the innovative, inflammation-based diagnostic marker for AKI in AP patients. The current retrospective cohort study consecutively enrolled AP patients admitted to First College of Clinical Medical Science of China Three Gorges University during the period from January 2019 to October 2023. Data were extracted systematically in electronic medical records from these hospitalized individuals, including baseline demographic and clinical characteristics. To ascertain the association of the CAR level with the development of AKI, we carried out multivariate logistic regression, adjusting for potential confounders. These confounders were initially identified through univariate regression. Furthermore, the potential effect modifiers in the relationship between CAR and AKI occurrence were explored by stratified logistic regression. Totally, 1514 AP were recruited, including 257 (16.9%) with AKI. CAR was positively correlated with AKI. When adjusting for potential confounders, the AKI risk in patients in the upper CAR tertile (2.628-22.994) increased by 83% relative to those in lower tertile (0.05-0.289) (OR 1.83, 95% CI 1.13-2.96, P = 0.013). The AKI risk tended to increase according to the increasing CAR tertile (P for trend = 0.013). No significant interactions were observed among subgroups based on age, sex, BMI, admission to ICU, hypertension, DM, chronic obstructive pulmonary disease, severity of AP, etiology of AP, demand for CRRT, mechanical ventilation, and blood transfusion (all P > 0.05). A higher CAR is significantly related to the higher AKI incidence in AP patients in the Chinese population.

The Green Cooling Factor: Eco-Innovative Heating, Ventilation, and Air Conditioning Solutions in Building Design

This research investigates the compatibility of conventional air conditioning with the principles of green building, highlighting the need for systems that enhance indoor comfort while aligning with environmental sustainability. Though proficient in regulating indoor temperatures, conventional cooling systems encounter several issues when incorporated into green buildings. These include energy waste, high running costs, and misalignment with eco-friendly practices, which may also lead to detrimental environmental effects and potentially reduce occupant comfort, particularly in retrofit situations. Given the emphasis on sustainability and energy conservation in green buildings, there is a pressing demand for heating, ventilation, and air conditioning (HVAC) solutions that support these goals. This study emphasises the critical need to reconsider traditional HVAC strategies in the face of green building advances. It advocates for the adoption of innovative HVAC technologies designed for eco-efficiency and enhanced comfort. These technologies should integrate seamlessly with sustainable construction, use greener refrigerants, and uphold environmental integrity, driving progress towards a sustainable and occupant-friendly built environment.

Novel functional materials capable of humidity regulation and thermal storage for building energy conservation

Functional materials with large hygrothermal inertia can passively mitigate indoor temperature and humidity variations, thus improving indoor environmental quality and reducing energy demand for heating, ventilation, and air-conditioning (HVAC) systems. In this study, a novel functional phase-change humidity control material (PCHCM) was developed based on the integration of microencapsulated phase-change material (MicPCM) and novel moisture adsorbent: Metal-Organic Frameworks (MOFs). The novel MOF-based PCHCM is a dual-functional composite material. It can simultaneously uptake/release heat and humidity from indoor air and control the hygrothermal environment passively. The materials characterizations show that the new MOF-based PCHCM has better thermal and moisture buffering ability than most conventional building materials. The effect of the new material on building energy conservation was calculated by a newly developed HAMT-enthalpy model. The simulation results show that MOF-based PCHCM can effectively moderate the fluctuations of temperature and relative humidity and reduce building energy consumption in most climates worldwide. The maximum energy-saving potential could reach up to 35% in hot-dry climates. The paper will guide the application and further development of dual-functional PCHCM composites under different climates.

Comparison of Clinical Outcomes of Tracheostomy between COVID-19 and Non-COVID-19 Patients

Background and Objectives: We compared decannulation-related factors between COVID-19 and non-COVID-19 patients who underwent tracheostomy. Subjects and Methods: We conducted a retrospective study of patients who underwent a tracheostomy. The clinical factors were compared between the successful (decannulation within 3 months) and failed decannulation (decannulation over 3 months) groups in COVID-19 and non-COVID-19 patients. Results: The successful decannulation rates were 41.1% in COVID-19 and 45.1% in non-COVID-19 patients, with no significant differences in demographic and clinical factors between the two groups. In the non-COVID-19 patients, the failed decannulation group had a higher proportion of cerebrovascular and pulmonary diseases. Ventilator dependency or increased oxygen demand was the primary cause of decannulation failure in both groups, with no significant differences except for a higher prevalence of swallowing problems in the COVID-19 group (42.4% vs. 20.0%). Conclusions: The predominant cause of decannulation failure was ventilator and oxygen demand in both the non-COVID-19 and COVID-19 patients. In the non-COVID-19 patients, underlying cerebrovascular diseases were considered to have a significant impact on the decannulation process. On the other hand, swallowing problems significantly influenced decannulation among the COVID-19 patients. Therefore, we should consider early and active respiratory and swallowing rehabilitation to facilitate successful decannulation in COVID-19 patients.

Multi-objective optimization of building HVAC operation: Advanced strategy using Koopman predictive control and deep learning

Predictive control is an effective method for addressing the increasing demand for heating, ventilation, and air conditioning (HVAC) systems to operate with greater flexibility and efficiency. In this paper, the multi-objective problem of energy-efficient HVAC operation while tracking desired setpoints is addressed through an advanced control strategy, including a novel supervisory data-driven predictive control (DPC) and a local loop with a PI controller. The supervisory level is based on the integration of the DPC framework and the bilinear Koopman predictor. A deep neural network architecture is developed to realize the bilinear building thermal predictor. In addition, the integral input-to-state stability (iISS) constraint is enforced in the training procedure to obtain a global iISS control-oriented thermal predictor that enables the application of predictive control purely based on historical data. The effectiveness of the proposed approach is demonstrated through the simulation of a three-zone office in the transient system simulation software (TRNSYS). The proposed control configuration is implemented using a coupled TRNSYS-MATLAB simulation framework. It has shown significant potential for keeping the desired environment in line with energy conservation. Furthermore, a comparison is conducted between the proposed approach, the conventional controller, and another recent DPC approach, which demonstrates the suggested method’s superiority.

Enhancing indoor environmental quality: Personalized recommendation method for demand-oriented indoor ventilation strategy

In the context of indoor environmental control, users have varying preferences with respect to their ventilation demands. Currently, the design and control of ventilation schemes do not consider user preferences adequately. To optimize the ventilation strategies based on user demands, the weight coefficients of occupant ventilation demands were extracted in this study using questionnaire surveys. The distinctive characteristics of ventilation preferences among individuals were then analyzed. Computational fluid dynamics (CFD) was used to simulate ventilation schemes with multiple air supply parameters within an office environment, and a database of ventilation performance under different conditions was generated. A multi-index evaluation was conducted to determine the recommended air supply scheme. Finally, a backpropagation neural network was employed to establish a personalized recommendation model for the ventilation scheme. The model inputs include the environmental weight coefficients assigned by the occupants and objective environmental parameters. Its outputs include the ventilation performance and air supply parameters. The results demonstrate that the recommended model can align with user demands, providing suitable ventilation performance and air supply parameters. For user-oriented indoor environment construction, this method enables the rapid and accurate determination of recommended air supply parameters and performance, facilitating the creation of a healthy built environment.