Nowadays, thermal comfort became one of the criteria in choosing a vehicle. In last decades time spent by people in vehicles had risen substantially. During each trip, thermal comfort must to be ...ensured for a good psychological and physical state of the passengers. Also, a comfortable environment leads to a higher power concentration of the driver thereby to a safe trip for vehicle occupants and for all traffic participants. The present study numerically investigated the effect of human body sited in the driver's place, over the air velocity distribution and over the thermal comfort in a passenger compartment. CFD simulations were made with different angles of the left inlet grill, in both cases, with and without driver presence. In majority of the actual vehicles environment studies, are made without consideration of human body geometry, in this case, the results precision can be affected. The results show that the presence of human body, lead to global changing of the whole flow pattern inside the vehicular cabin. Also, the locations of the maximum velocities are changing with the angle of the guiding vanes. The thermal comfort PMV/PPD indexes were calculated for each case. The presence of human body leads to a more comfortable environment.
With the increasing focus on indoor environmental quality, driven by the growing amount of time people spend in enclosed spaces, this study presents an approach to enhancing air distribution in ...office environments and confined spaces. A novel low-induction air diffuser is designed to deliver fresh, clean air in close proximity to occupants while maintaining their thermal comfort. Clean, unpolluted air is pivotal to healthy and productive workplaces. Yet, this paper underscores the importance of not sacrificing thermal comfort in the pursuit of improved indoor air quality. Inadequate thermal comfort may lead occupants to deactivate ventilation systems, negating the benefits of improved air quality. Inefficient temperature control can also result in discomfort, distractions, and reduced productivity. The innovative low-induction air diffuser resolves this issue, enhancing air quality near occupants without causing thermal discomfort. By directing air gently and efficiently, this solution is prepared to transform personalized ventilation systems, mitigating the discomfort associated with traditional jet flows while delivering high-quality breathable air. This research serves as a bridge between improved indoor air quality and thermal comfort, for office environments. It introduces a practical, energy-efficient solution that satisfies the core requirements of a healthy workspace—clean air and comfortable conditions.
Thermal comfort is very important for the well-being and safety of vehicle occupants, as discomfort can elevate stress, leading to distracted attention and slower reaction times. This creates a ...riskier driving environment. Addressing this, high-induction air diffusers emerge as a significant innovation, enhancing indoor environmental quality (IEQ) by efficiently mixing cool air from the heating ventilation and air conditioning (HVAC) system with the cabin’s ambient air. This process ensures uniform airflow, diminishes temperature discrepancies, prevents draft sensations, and boosts overall air quality by improving air circulation. In addition to enhancing thermal comfort in vehicles, the novel air diffuser also offers significant potential for personalized ventilation systems, allowing for individualized control over airflow and temperature, thereby catering to the specific comfort needs of each occupant. This study introduces a novel air diffuser that demonstrates a 48% improvement in air entrainment compared to traditional diffusers, verified through Ansys Fluent simulations and laser Doppler velocimetry (LDV) measurements. At a fresh airflow rate of 31.79 m3/h, the total air entrainment rate at 0.6 m for the standard air diffuser is 73.36 m3/h, while for the innovative air diffuser, it is 109.26 m3/h. This solution has the potential to increase the level of thermal comfort and air quality within vehicles, and also signals potential applications across various enclosed spaces, underscoring its importance in advancing automotive safety and environmental standards.
In confined spaces, such as vehicle cabins, airflow and temperature distribution are the most critical factors affecting thermal comfort and pollutant dispersion. To develop innovative and ...energy-efficient HVAC systems, a deep understanding of the interaction of the jet flow from the air diffusers on the development process of the human thermal plume became essential to improve the knowledge of airflow patterns for optimizing ventilation system design, thermal comfort, and, indirectly, the energy efficiency. The human thermal plume is one of the most challenging phenomena to capture with optical measurement methods and validate with complex numerical models, given its unsteady nature governed by the buoyancy forces. This study aims to validate the interaction of jet flows from classical and innovative air diffusers on the thermal plume by comparing measured data and numerical simulation results. This validation was made with a specific approach by comparing PIV fields from measurements and CFD results with boundary conditions of air velocity distribution from LDV data. The PIV measurements for flow distributions at the air vents and the thermal plume of an advanced thermal manikin in the driver’s seat were performed in a 1:1 scale mock-up of a Renault Megane car cabin in a climatic chamber. The results obtained with both methods showed good agreement regarding air velocity ranges and distributions. Despite the confined cabin space restricting the development of the thermal plume, a difference in maximum velocities of 0.08 m/s was observed when the distance between the top of the head and the ceiling was doubled. With innovative air diffusers, air velocity distribution showed a more uniform flow than classical diffusers.
In the short and medium term, it is estimated that electric mobility will play an important role in greenhouse gas emissions reduction strategy. However, vehicles with electric propulsion system come ...with a new series of challenges, some of them affecting more or less the well-being of vehicle users. The purpose of this article is to present in an exhaustive manner a review of data existing in the technical and scientific literature regarding thermal comfort of the passengers in the vehicular ambient, with a perspective on specific issues related to the design of the Electric Vehicles. Firstly, a general outline about the subject area is presented and the aspects of the vehicular environment are discussed. Next, a short introduction in the theories of the human thermal comfort, presenting the physiological bases of thermal comfort and a short discussion of the aspects of the vehicular spaces. The standards currently in use for thermal comfort assessment in vehicles are also discussed in the context of their suitability along other experimental methods for research and development. We will discuss in the final part of the article the particularities of Electric Vehicles and some solutions that are worth to be considered. Compared with buildings indoor environment, the vehicle cabin ambient is very different in terms of thermal comfort parameters magnitude and weight and also due to highly transient condition. The present vehicle standards for thermal comfort are constructed based on the building services standards. In regard to all the aspects presented in the present review, the main conclusion of this article is related to the need to develop specific methods for assessing the thermal comfort, solely for vehicles.
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•Literature review on 105 publications — thermal comfort of the vehicle passengers.•Current vehicle thermal comfort standards are based on the building standards.•Need to develop specific methods for assessing the thermal comfort for vehicles.•A thermal sensitivity test device was built to perform tests for humans.•Perspective on specific issues related to the design of the Electric Vehicles.
Abstract
Reducing energy consumption and CO2 footprint in existing buildings without requiring extensive construction work is one of the biggest challenges facing the globe today. Although heating ...contributes for the majority of energy use in buildings, residential hot water demand is also relatively high, particularly when daily usage is high and especially for certain applications. The use of technologies that recover energy from sources other than fossil fuels to heat water has grown crucial, and one such technology involves recovering thermal energy from wastewater. Typically, heat recovery from wastewater is made to collect any remaining energy from the hot drainage water, and this energy is then applied to heat pumps or to warm up incoming cold water. The paper presents numerical simulations using a SST k-ω turbulence model in order to compare a regular geometry of heat exchanger with a helicoidal one. The second one provides a more turbulent flow that allows an intensification of the outer flow, thus allowing the enhancement of the heat transfer from the inner heated flow to the outer flow.
In the last decade, there has been an increase in ease and affordability of air travel in terms of mobility for people all around the world. Airplane passengers may experience different risks of ...contracting airborne infectious diseases onboard aircraft, such as influenza or severe acute respiratory syndrome (SARS-CoV-1 and SARS-CoV-2), due to nonuniform airflow patterns inside the airplane cabin or proximity to an infected person. In this paper, a novel approach for reducing the risk of contracting airborne infectious diseases is presented that uses a low-momentum personalized ventilation system with a protective role against airborne pathogens. Numerical simulations, supported by nonintrusive experimental measurements for validation purposes, were used to demonstrate the effectiveness of the proposed system. Simulation and experimental results of the low-momentum personalized ventilation system showed the formation of a microclimate around each passenger with cleaner and fresher air than produced by the general mixing ventilation systems.
The main declared goal of all car manufacturers is to ensure high comfort inside the cabin and to reduce the fossil fuel. It is well-known that the time spent by the people indoor has raised in the ...last decade. The distance between the home and the workplace increased due to diversity of activities and hence job diversity. The thermal comfort during the travel must to be ensured to reduce the occupant’s thermal stress. The present study is investigating a comparison between the measured data and the numerical simulation results in the case when the ventilation system is functioning. It was evaluated the effect of the boundary conditions air flow and air velocity distribution in a passenger compartment in two cases: first is the general used constant inlet flow and the second is a new approach of importing the measured data obtained during the experimental measurement session as a boundary condition.CFD simulations were made taking as input the measured data obtained during experimental session. We have observed differences between initial simulation results and the measured data, therefore, for more accurate results, a new approach is needed, to impose as boundary conditions the measured data.
Among the factors that influence the resilience and sustainability of cities in general, and of inhabited spaces in particular, there are extreme temperatures and, in particular, for people, thermal ...comfort is something that should be considered. This problem includes all aspects of comfort for users of inhabited spaces in both buildings and vehicles. The purpose of this paper is to present the details of a recently designed and created thermal manikin that comprises 79 superficial zones with independent neuro-fuzzy temperature regulation. Both the component parts of the manikin and the acceptance strategy are described. Flexible heating elements were used to control the temperature, on which five digital sensors are positioned. In order to establish the relationship between heat loss and ambient temperature, the thermal manikin was calibrated in a climatic chamber. The thermal manikin was able to predict local sensations through the equivalent temperature concept of the so-called Predicted Mean Vote.
Thermal comfort evaluation for vehicle occupants is very complicated due to the transient nature and non-uniformity of the vehicle interior. The thermal sensation of an automotive occupant is ...affected by the surrounding environment. More than this, the actual standard is proposing three evaluation indexes and was developed for steady state and controlled conditions and some of the indexes are not adapted for this complex environment. In this article the three standardized indexes values are compared in term of thermal comfort, in a vehicle passenger in summer season. The results are showing that the mean values of PMV/PPD model calculated in a single point with Comfort Sense equipment are far from the TSV mean values which was collected in questionnaires, while the teq index which was calculated with an advanced thermal manikin are closer to the TSV comfort votes. This may be explained by the fact that the TSV and teq consider the sensation for each body part at the local level. For a correct evaluation of the thermal comfort in non-uniform and transient environments like in the vehicles, is not enough to measure in a single point and the results to be considered in all the ambiance. The main conclusion is that the PMV/PPD indexes are not very well adapted to the vehicle environment.
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