- Access throughyour institution
- Section snippets
- References (23)
- Cited by (29)
- Recommended articles (6)
Transportation Research Part D: Transport and Environment
, Pages 433-440
Author links open overlay panelTong-BouChangaPersonEnvelopeJer-JiaSheubJhong-WeiHuangbYu-ShengLinaChe-ChengChanga
As the level of within the vehicle cabin increases, the risk of accidents as a result of driver drowsiness and a slowing of the reactions also increases. Accordingly, a CFD simulation model was developed in this study to explore the effects of outdoor air ventilation rate on vehicle cabin indoor air quality and the amount of outdoor air required for each person in a vehicle. The results show that using the outdoor air supply rate recommendations of ASHRAE Standard 62.1 (i.e. 2.5 l/s per person) the mean CO2 concentrations in the cabin are around 2850 ppm. The results also show that using the outdoor air supply rate recommendations of 4.0 l/s per person for improved human wellbeing, the corresponding mean CO2 concentrations in the cabin are around 1810 ppm. Moreover, the present study found that an outdoor fresh air flow rate of 9.2 l/s per passenger was sufficient to reduce the carbon dioxide concentration within the cabin to a safe value of 1000 ppm. Furthermore, an outdoor fresh air flow rate of 3.6 l/s per passenger resulted in a carbon dioxide concentration of around 2000 ppm.
With changes in modern lifestyle, people spend an increasing amount of time in vehicles. Accordingly, various ventilation methods and devices have been developed in recent decades for providing a comfortable thermal environment for vehicle occupants while simultaneously reducing the energy demand. One of the most effective strategies for achieving both goals is to use an auto air-conditioning system (also known as an Energy Saving Airflow System), which automatically adjusts the ventilation mode and supply air speed depending on the number of occupants in the vehicle and the outdoor/indoor temperatures (Dwiggins, 2000). However, due to the high traffic load in city areas, most drivers tend to close the window completely to prevent the ingress of pollutants and then set the ventilation system to full recirculation mode. Previous studies (Zhu and Eiguren-Fernandez, 2007, Qi and Stanley, 2008) have shown that such an approach yields a substantial reduction in the concentration of particle pollutants in the cabin. However, it also results in an accumulation of carbon dioxide (), which can lead to drowsiness and a slowing of the reactions, and hence the risk of accidents increases. Consequently, maintaining a healthy IAQ (indoor air quality) is an essential issue for vehicle designers and IAQ researchers.
Most previous studies on IAQ focus on buildings. Olesen (2004) reviewed the development of international standards for the indoor thermal environment and IAQ. ASHRAE Standards 55 (ASHRAE, 2013a) and 62.1 (ASHRAE, 2013b) provide general guidelines on thermal environmental conditions for human occupancy. Ahmed (2003) found that improvements in the outdoor thermal environment result in an enhanced indoor thermal environment and a lower energy strain on indoor thermal control systems. Candido et al. (2010) investigated air movement acceptability limits in ventilated buildings in Brazil, and found that subjects preferred air velocities of at least 0.4 m/s for operational temperatures of 26 °C and 0.9 m/s (higher than the 0.8 m/s ASHRAE limit) for temperatures of 30 °C. Arens et al. (2009) reported that many indoor occupants prefer a greater air movement than that prescribed by existing thermal comfort standards. Noh et al. (2007) performed field measurements and numerical simulations to investigate the thermal comfort and IAQ in lecture rooms with different HVAC systems. Yau and Chew (2009) conducted a thermal comfort study of hospital workers in Malaysia, and found that a higher temperature was required for comfort than that specified in the ASHRAE standards. Wang et al. (2012) performed an extensive field evaluation of thermal comfort and IAQ for a hospital in a hot and humid climate. Wang et al. (2014) recently conducted an investigation into the retrofitting of a total heat exchanger system in an office building in a hot and humid climate. The results showed that the CO2 concentration decreased and the thermal comfort increased after the installation of the total heat exchanger. However, the improvement in the IAQ and thermal comfort was obtained at the expense of a slightly higher power consumption.
As for buildings, the aim of HVAC vehicle systems is not only to achieve thermal comfort, but also to maintain a healthy cabin environment. Chan and Chung (2003) investigated the effects of the ventilation mode on the air quality in a vehicle cabin, and recommended the use of the full fresh air mode (i.e., 0% recirculation) when driving in countryside environments in order to exhaust the cabin indoor pollution gas. Katarzyna (2011) showed that in the cabin of a small passenger vehicle, the continuous use of the full recirculation mode can result in a concentration of almost 4500 ppm, and may thus have significant adverse effects on driving safety. Jung (2013) developed a mathematical model for predicting the CO2 concentration in vehicle cabins when using the air-recirculation ventilation mode. Thirumal et al. (2015) used Gray Relational Analysis (GRA) and Response Surface Methodology (RSM) techniques to optimize the IAQ characteristics (temperature, level and relative humidity) of an air-conditioned car cabin over a specified range of input conditions. Chang et al. (2017) suggested that the total air leakage ventilation rate for a vehicle cabin comprises two components, namely (1) the car speed induced air leakage rate, and (2) the fan-supplied air speed induced air leakage rate. The authors further proposed a theoretical general equation for predicting the air leakage ventilation rate.
Each exhaled breath by an adult contains 35,000–50,000 ppm of CO2 (ASHRAE 2013b, Scott et al., 2009). For a vehicle, the indoor CO2 concentration is directly related to the number of occupants in the cabin, the ventilation rate, and the CO2 level of the outside air. As described above, an elevated CO2 level poses a significant risk to driving safety. Consequently, evaluating the concentration and distribution of CO2 in the vehicle cabin is an essential task for vehicle designers and IAQ researchers alike.
Vehicle road tests are expensive and time-consuming. Accordingly, the present study performs CFD simulations to evaluate the CO2 concentration in a typical vehicle cabin given various outdoor fresh air supply rates and numbers of occupants in the cabin. The validity of the numerical model is confirmed by comparing the simulation results with the experimental data reported in the literature. The results provide a valuable insight into the minimum fresh air supply rate required to achieve the ASHRAE criterion of a CO2 concentration of no more than 1000 ppm in the vehicle cabin.
The present study considered a Mitsubishi Galant having a cabin with the dimensions shown in Fig. 1. The cabin is fitted with four inlets on the upper surface of the dashboard (I1-I4 in Fig. 2) and four return air outlets on the lower side of the dashboard (R1-R4 in Fig. 2). For evaluation purposes, the present study additionally designed two fresh air inlets at the front of the cabin (L1 and L2 in Fig. 2) and one direct outlet at the rear of the cabin (O1 in Fig. 2). To simplify the CAD model,
Results and discussions
To validate the numerical model, the simulated CO2 concentration in the cabin was compared with that measured experimentally by Chang et al. (201) for a car speed of 50 km/h and five occupants in the cabin. The two sets of results are shown in Fig. 5 for various fan supply air speeds in the range of 3.93–8.29 m/s. It is observed that while the simulation results are slightly higher than the experimental measurements for all values of the fan speed, the discrepancy between the two sets of
ASHRAE Standard 62.1 suggests a minimum outdoor air requirement of 2.5 l/s per occupant in indoor building environments. Moreover, previous research has suggested a higher outdoor air supply rate of 4.0 l/s per occupant for improved wellbeing. However, vehicle interiors are quite different from those of buildings. Hence, there is no guarantee that the same recommendations also apply to vehicle cabin. Accordingly, this study has performed CFD simulations to examine the CO2 concentration in the
The authors gratefully acknowledge the financial support provided to this study by the Ministry of Science and Technology (MOST) of Taiwan under Grant number MOST 103-2221-E-415-029-MY3 and MOST 106-2221-E-415-013.
- J.L. Scott et al.Occupational hazards of carbon dioxide exposure
J. Chem. Health Safety
- K.C. Noh et al.Thermal comfort and indoor air quality in the lecture room with 4-way cassette air-conditioner and mixing ventilation system
(2007)(Video) Air flow in a room by an Air Conditioner simulating using Ansys Fluent
- A.T. Chan et al.Indoor–outdoor air quality relationships in vehicle: effect of driving environment and ventilation modes
- C. Candido et al.Air movement acceptability limits and thermal comfort in Brazil’s hot humid climate zone
- K.S. AhmedComfort in urban spaces: defining the boundaries of outdoor thermal comfort for the tropical urban environments
- E. Arens et al.
Moving air for comfort
- ASHRAE, 2013b. ANSI/ASHRAE Standard 62.1-2013, Ventilation for Acceptable Indoor Air Quality. ASHRAE,...
- ASHRAE, 2013a. ANSI/ASHRAE Standard 55-2013, Thermal Environmental Conditions for Human Occupancy. ASHRAE,...
- T.B. Chang et al.
Vehicle air leakage ventilation and its effect on cabin indoor air quality
Proc. Inst. Mech. Eng., Part E: J. Process Mech. Eng.
- B.H. Dwiggins
Automotive Air Conditioning
- Modeling for vehicle cabin temperature prediction based on graph spatial-temporal neural network in air conditioning system
2022, Energy and BuildingsSee Also"Disposizioni per la formazione del bilancio annuale e pluriennale dello Stato (legge finanziaria 2007)"Restaurant Equipment Certification Marks ExplainedEl cuidado de enfermería ante los procesos quirúrgicos estéticosOSHA Announces Lockout/Tagout and Standards Improvement Project Developments | JD Supra
The vehicle HVAC (heating, ventilating, and air conditioning) system aims to keep passengers thermal comfort and reduce energy consumption. One effective measure is to use temperature prediction to optimize HVAC systems. This paper aimed to comprehensively investigate the potential of machine learning methods applied to cockpit temperature prediction and proposed a deep learning method considering the Spatio-temporal correlation of the temperature field. Specifically, this study constructs a topological description of the temperature field inspired by the spatial and temporal correlations revealed by the Navier-Stokes equations. The Graph Convolutional Network (GCN) is used to capture the topological structure to obtain spatial features, and the Gated Recurrent Unit (GRU) is used to capture the dynamic change of node attribute to obtain temporal features. Finally, the GCGRU model can extract Spatio-temporal features of the temperature field. The experimental results show that the prediction method using Spatio-temporal features for the temperature field is feasible. The prediction performance is better than all the baseline methods and has the robustness to the data noise. This work is enlightening and may have a further reference to the feasibility study of the vehicle cabin air temperature prediction model.
- Energy, economic, and environmental impacts of enhanced ventilation strategies on railway coaches to reduce Covid-19 contagion risks
In the last years, the Covid-19 outbreak raised great awareness about ventilation system performance in confined spaces. Specifically, the heating, ventilation, and air conditioning system design and operating parameters, such as air change per hour, air recirculation ratio, filtration device performance, and vents location, play a crucial role in reducing the spread of viruses, moulds, bacteria, and general pollutants. Concerning the transport sector, due to the impracticability of social distancing, and the relatively loose requirements of ventilation standards, the SARS-COV-19 outbreak brought a reduction of payload (up to 50%) for different carriers. Specifically, this has been particularly severe for the railway sector, where train coaches are typically characterized by relatively elevated occupancy and high recirculation ratios. In this framework, to improve the Indoor Air Quality and reduce the Covid-19 contagion risk in railway carriages, the present paper investigates the energy, economic and environmental feasibility of diverse ventilation strategies. To do so, a novel dynamic simulation tool for the complete dynamic performance investigation of trains was developed in an OpenStudio environment. To assess the Covid-19 contagion risk connected to the investigated scenarios, the Wells-Riley model has been adopted. To prove the proposed approach's capabilities and show the Covid-19 infection risk reduction potentially achievable by varying the adopted ventilation strategies, a suitable case study related to an existing medium-distance train operating in South/Central Italy is presented. The conducted numerical simulations return interesting results providing also useful design criteria.
- Research on the characteristics of micro-pressure waves in high-temperature geothermal railway tunnels and a self-satisfying mitigation method
2022, Journal of Wind Engineering and Industrial Aerodynamics
In this study, through experiments and numerical simulations, micro-pressure waves (MPWs) resulting from the movement of high-speed trains through high-temperature geothermal tunnels were studied, and a self-satisfying MPW mitigation method was proposed. First, a model experiment of a moving high-speed train under local high-temperature conditions was carried out. Then, a relationship between the MPW and length of the heating zone (LH) and the length of the train streamline (12.5m) was established via numerical simulation. For LH<12.5m, the MPW amplitude gradually decreases with increasing LH. For LH>12.5m, the MPW amplitude remains basically unchanged. The influence of the circumferential distribution of the heating zone along the tunnel wall on the MPWs was further studied. The research results inspired an MPW mitigation method for tunnels, considering a heating length of 12.5m and an angle of 225°. Moreover, in a tunnel, electric energy could be generated under slipstream action through a wind turbine installed to provide heating equipment with power, thereby achieving self-satisfaction. This research proposed a new MPW mitigation method for research on MPW mitigation. Moreover, new mitigation methods could facilitate the construction of an environmentally friendly society and provide a new approach to the sustainable development of cities.
- A Eulerian-Lagrangian approach for the non-isothermal and transient CFD analysis of the aerosol airborne dispersion in a car cabin
2022, Building and Environment(Video) Reduce Vehicle Development Costs with Real-world Simulations
Car cabin micro-environment represents a potential hotspot for transmission of respiratory infections related to possible high concentration levels of viruses and bacteria and to reduced social distance between occupants. Since Heating, Ventilation and Air Conditioning (HVAC) system in a vehicle influences velocity and temperature fields, the position of inlet air vents, the air flow rate entering the car cabin, the air recirculation, the passenger number and location etc. highly influence the thermal comfort and potential health risks for occupants.
In this paper, a Eulerian-Lagrangian model is adopted to numerically analyse transient non-isothermal aerosol airborne dispersion in a passenger car cabin. Numerical results are validated against PIV measurements and the performances of different turbulence models are analysed. The validated numerical model is applied to the simulation of aerosol droplets emitted by a contagious subject in a car cabin during a 15-min journey. Two occupants are present in the car cabin and different scenarios for the ventilation system and the occupant position are investigated.
The aim of the present paper is to provide a properly validated numerical tool that can be applied on one side to the assessment of thermal comfort of occupants and, on the other side, to the analysis of potential infection risk with aerosol transmissible pathogens (e.g. SARS-CoV-2 virus) during short journeys.
- A control strategy for cabin temperature of electric vehicle considering health ventilation for lowering virus infection
2022, International Journal of Thermal Sciences
A cooperative control strategy is proposed for the air conditioning (AC) system and ventilation system to reduce the risk of COVID-19 infection and save the energy of the AC system. This strategy integrates the dynamic model of the AC-cabin system, infection risk assessment, model predictive control (MPC) of the thermal environment inside the cabin, and ventilation control that considers passengers' sneezing. Unlike other existing AC system models, the thermal-health model established can describe not only the system performance but also the virus concentration and risk of COVID-19 infection using the Wells-Riley assessment model. Experiments are conducted to verify the prediction accuracy of the AC-cabin model. The results prove that the proposed model can accurately predict the evolution of cabin temperature under different cases. The cooperative control strategy of the AC system integrates the MPC-based refrigeration algorithm for the cabin temperature and intermittent ventilation strategy to reduce the risk of COVID-19 infection. This strategy well balances the control accuracy, energy consumption of the AC system, and the risk of COVID-19 infection, and greatly reduces the infection risk at the expense of a little rise in the energy consumption.
- Air quality assessment in indoor and outdoor environments: A review
2022, Materials Today: Proceedings
Air quality impacts both the environment and health conditions of people in living space. The air quality assessment in indoor and outdoor environments is essential to resolve the health impacts caused by environmental degradation. The present investigation is focused on the study of air quality assessment in three major areas including Vehicle Cabins, inside buildings and outdoor environments. The studies of air quality by scientists and researchers for the past 33years have been reviewed and reported. As the air spreadable disease can blowout when people with positive infections cough, sneeze, spewing nasal and throat secretions into the air including COVID-19 transmitted through contact with respiratory droplets through the air, this comprehensive report on air quality characteristics will provide awareness for human safety and promote more research for the invention of comfort air quality in human living space.
Research articleVertical ventilation concepts for future passenger cars
Building and Environment, Volume 129, 2018, pp. 142-153
We compared three vertical ventilation concepts to dashboard ventilation in a generic car cabin with the aim to improve thermal passenger comfort and energy efficiency of future cars. Temperatures were analyzed with an infrared camera and local temperature sensors. Omnidirectional velocity probes were used to capture the fluid velocities and temperatures in the vicinity of thermal passenger dummies, which were used to simulate the thermal impact of the passengers. Further, the ventilation efficiency was measured with the tracer gas technique using humidity sensors in the vicinity of the dummies and in the air outlets. Besides the experimental investigations, the relevant flow cases were studied by Computational Fluid Dynamics simulations using the RANS method, providing insight into the complex and three-dimensional flow structures of the passenger compartment. Validation of the simulations with the experimental data revealed acceptable consistency, however, with local deviations indicating further need for experimental investigations. The ventilation efficiencies of the vertical ventilation concepts were at least comparable or even better as compared to dashboard ventilation. Regarding the comfort-relevant flow parameters, dashboard ventilation stood out with the lowest temperature stratification but revealed comfort-critical flow velocities. The vertical ventilation concepts allowed for comfortable velocities, but tended to produce comfort-critical temperature stratifications. Pursuing the equivalent temperatures, the vertical systems revealed an improved heating performance over dashboard ventilation. During summer and spring/fall conditions, low momentum ceiling ventilation as well as the combination of cabin displacement ventilation and low momentum ceiling ventilation were able to provide comfortable equivalent temperature distributions.
Research articlePredicting self-pollution inside school buses using a CFD and multi-zone coupled model
Atmospheric Environment, Volume 107, 2015, pp. 16-23(Video) Wei Liu: Deep Learning to Replace, Improve, or Aid CFD Analysis in Built Environment Applications
The in-cabin environment of a school bus is important for children's health. The pollutants from a bus's own exhaust contribute to children's overall exposure to air pollutants inside the school bus cabin. In this study, we adapted a coupled model originally developed for indoor environment to determine the relative contribution of the bus own exhaust to the in-cabin pollutant concentrations. The coupled model uses CFD (computational fluent dynamics) model to simulate outside concentration and CONTAM (a multi-zone model) for inside the school bus. The model was validated with experimental data in the literature. Using the validated model, we analyzed the effects of vehicle speed and tailpipe location on self-pollution inside the bus cabin. We confirmed that the pollution released from the tailpipe can penetrate into the bus cabin through gaps in the back emergency door. We found the pollution concentration inside school buses was the highest when buses were driven at a medium speed. In addition, locating the tailpipe on the side, behind the rear axle resulted in less self-pollution since there is less time for the suction effect to take place. The developed theoretical framework can be generalized to study other types of buses. These findings can be used in developing policy recommendations for reducing human exposure to air pollution inside buses.
Research articleIs in-cabin exposure to carbon monoxide and fine particulate matter amplified by the vehicle’s self-pollution potential? Quantifying the rate of exhaust intrusion
Transportation Research Part D: Transport and Environment, Volume 54, 2017, pp. 225-238
In-cabin exposure has increased in recent years due to longer commute and/or prolonged times in cars. The intrusion of the vehicle’s own exhaust into the passenger’s compartment has been recognized as a process that amplifies in-cabin passenger exposure. Quantifying its contribution is hampered by uncertainties associated with its measurement method such as trace tests and the lack of data regarding certain critical physical parameters, particularly those pertaining to air exchange rate (AER) and particulate matter deposition rate (DR). In this study, we present a hybrid methodology combining field measurements with a single-zone mass balance to estimate these parameters as well as the source term that represents vehicle self-pollution. In- and out-vehicle carbon monoxide (CO) and fine particulate matter (PM2.5) were monitored concurrently in test vehicles under idle and moving conditions using several common ventilation modes. In addition to defining a hybrid methodology to characterize the underlying physical parameters, this study found that vehicle self-pollution can account for approximately 15 and 30% of CO and PM2.5 exposure experienced by vehicle occupants respectively. Vehicle self-exhaust intrusion may constitute a significant PM exposure route for vehicle-based occupations or commuters with prolonged time in vehicles.
Research article1D/3D transient HVAC thermal modeling of an off-highway machinery cabin using CFD-ANN hybrid method
Applied Thermal Engineering, Volume 135, 2018, pp. 406-417
A comprehensive thermal model of a combine harvester air conditioning system is developed to study the transient cool-down phenomena in the cabin. The proposed simulation framework encompasses a 3D computational fluid dynamics (CFD) model that relies on an artificial neural network (ANN) which actively receives data on the performance of the refrigeration cycle in order to update the thermal state of the cabin. The refrigeration cycle is modeled using a 1D methodology to predict the heat absorption capacity of the evaporator at a wide range of operating conditions. The data generated by the 1D model is then utilized to train the ANN model with airflow, relative humidity (RH) and air temperature as input parameters and evaporator heat absorption as the output. The trained ANN model is integrated with the CFD model of the cabin allowing a realistic transient response of the evaporator based on the instantaneous thermal state of the cabin air. The proposed simulation framework exploits the versatility of ANN to simplify the overall complexity of the model and removes the necessity of 1D/3D co-simulation being the conventional method for this type of problems. The predicted transient thermal state of the cabin air is validated against experimental data and a substantial coherence of the numerical and experimental results is demonstrated.
Research articleTransient thermal model of passenger car's cabin and implementation to saturation cycle with alternative working fluids
Energy, Volume 90, Part 2, 2015, pp. 1859-1868
A transient thermal model of a passenger car's cabin is developed to investigate the dynamic behavior of cabin thermal conditions. The model is developed based on a lumped-parameter model and solved using integral methods. Solar radiation, engine heat through the firewall, and engine heat to the air ducts are all considered. Using the thermal model, transient temperature profiles of the interior mass and cabin air are obtained. This model is used to investigate the transient behavior of the cabin under various operating conditions: the recirculation mode in the idling state, the fresh air mode in the idling state, the recirculation mode in the driving state, and fresh air mode in the driving state. The developed model is validated by comparing with experimental data and is within 5% of deviation. The validated model is then applied for evaluating the mobile air conditioning system's design. The study found that a saturation cycle concept (four-stage cycle with two-phase refrigerant injection) could improve the system efficiency by 23.9% and reduce the power consumption by 19.3%. Lastly, several alternative refrigerants are applied and their performance is discussed. When the saturation cycle concept is applied, R1234yf MAC (mobile air conditioning) shows the largest COP (coefficient of performance) improvement and power consumption reduction.
Research articleImprovement of the performance of a simple box model using CFD modeling to predict indoor air formaldehyde concentration
Building and Environment, Volume 124, 2017, pp. 450-459
The purpose of this study is to improve the predictive potential of a simple box model by using CFD simulation. In this easy-use box model, the material/air mass transfer is governed by a convective coefficient of pollutant through the boundary layer settling on the surface of material (hoi) which is a key parameter for the prediction of indoor air pollution. The aim of this study is to better assess this parameter as function of several variables (material surface emissions, room configurations and ventilation conditions) by means of CFD simulations. First, dimensional analysis method is applied to CFD results to establish a new relationship between physical parameters involved in the transfer of compounds in air, particularly room characteristic length, mean air velocity in inlet section area and molecular diffusion of formaldehyde in air. Thus, the validity of this relation is tested by CFD modeling for large range of room sizes, mean air velocities and inlet section locations. Lastly, results of a first measurement campaign show the improvement of the prediction of the box model compared to the previous version including this new relation by a better assessment of indoor material contributions to indoor air formaldehyde concentration.(Video) CFD Simulation of Expired Air in an Open Air Vehicle (Jeepney)
© 2018 Elsevier Ltd. All rights reserved.