Search Results

In the present study, a model experiment is performed in order to clarify the ventilation characteristics of car cabin. This study also provides high precision data for benchmark test. As a first step, the ventilation mode is tested, which is one of the representative air-distribution modes. Part 1 describes the properties of the flow field in the cabin obtained by the experiment. Part 2 describes the ventilation efficiencies such as the age of air by using trace gas method. The properties of flow field are measured using particle image velocimetry (PIV). The mean velocity profiles, the standard deviation distribution, and the turbulence intensity distribution are discussed. The brief comparison between experiments and predictions of computational fluid dynamics (CFD) is also presented. In the comparison between experiment and CFD, the results showed similar flow field.

In order to evaluate the ventilation characteristics of car interior, a model experiment was performed. Part 1 deals with the air flow properties in a half-scale car model. In this paper, a trace gas experimental method equipped with Flame Ionization Detector (FID) systems is introduced to examine the local ventilation efficiency and inhaled air quality in the car, which was ventilated at a flow rate of 100 m3/h and kept in an isothermal environment of 28°C in the experiment. Here, ventilation efficiency was evaluated by means of the Scales for Ventilation Efficiencies (SVEs), and inhaled air quality in terms of the influences of passive smoke and foot odor was evaluated by means of the Contribution Ratio of Pollution source 1 (CRP1). Therefore, calculation methods using trace gas concentration values were suggested for these indices, which were proposed based on the Computational Fluid Dynamics (CFD) technique.

Following the previous reports, ventilation characteristics in automobile was investigated by using a half-scale car model which was created by the Society of Automotive Engineers of Japan (JSAE). In the present study, the ventilation mode of the cabin was foot mode which was the ventilation method for using in winter season. Supplied air was blown from the supply openings under the dashboard to the rear of the model via the driver's foot region in this mode. The experiment was performed in order to obtain accurate data about the airflow properties equipped with particle image velocimetry (PIV). Our experimental data is to be shared as a standard model to assess the environment within automobiles. The data is also for use in computational fluid dynamics (CFD) benchmark tests in the development of automobile air conditioning, which enables high accuracy prediction of the interior environment of automobiles.

Thermal comfort for car occupants is important factor for automotive design. We have been developing efficient solar reduction glass for vehicles. We also developed a numerical simulator to predict and evaluate the thermal environment and thermal comfort in vehicles. In this simulation, firstly distribution of solar radiation energy through the glass can be calculated actually, and then temperature and air flow distribution, and human comfort can be computed by a combined analysis of CFD (computational fluid dynamics), thermal radiation and body temperature control model which corresponds to shapes of a vehicle and human body. The thermal environment differences between solar reduction glass and normal glass should be clear, which makes the effects of functional glass clear from the view point of human comfort. We can calculate comprehensive situations and indices of thermal comfort evaluation.

Thermal comfort for car occupants is important factor for automotive design. We have been developing the numerical simulator for the prediction of the thermal environment and thermal comfort in vehicles. In the previous paper, the comprehensive combined analysis method with multi-node thermoregulation model, radiation model and CFD (Computational Fluid Dynamics) is proposed. In this paper, the applications of this method to car occupants are presented. We focused on investigating the effects of glass properties on thermal environment of compartment and thermal comfort for passengers. The calculated results were compared every part of glazing, front windshield, front sidelite and rear sidelite in summer condition. It was found that the differences of air temperature between normal glass glazing and functional one are not so much but the differences of human feeling are significant. Further more, the effects of functional glass on the reduction of air-conditioning power are simulated.

A numerical simulation method is presented for the evaluation of thermal comfort of car occupants under direct solar radiation. Present method is based on a comprehensive combined analysis with multi-node thermoregulation model, which is integrated by the 65-node thermoregulation model (65MN: Multi Nodes) based on the Stolwijk model, radiation model including thermal radiation and solar radiation, and CFD (Computational Fluid Dynamics). This paper focuses on the outlines of each numerical simulation method and discusses on the human body shape for predicting accurate boundary conditions of thermoregulation model. Applications of this method to car occupants are presented in the Part 2.

The transmissive and reflective performance of the glass according to the radiation sources are discussed for the accurate evaluation of the solar radiation through the glass window. They are quite different in radiation sources such as solar radiation from the sun or infrared solar lamps in the experiments because of the spectral properties of both glass and radiation sources. It is also discussed how differences of transmissive and reflective performance of the glass affect thermal comfort of car occupants. A numerical simulation method based on the comprehensive combined analysis with thermoregulation model within a human body, radiation models including thermal radiation and solar radiation, and CFD (Computational Fluid Dynamics) is conducted for this purpose.

The thermal fluid field in a headlamp based on the real 3D-CAD model is analyzed by a mesh free method. The conducted method is a new CFD (Computational Fluid Dynamics) solver based on the couples of the points whose density is controlled scattered in the analysis space including the boundaries, which leads to much reduce the hand-working time in the deformation of the 3D-CAD model for the mesh generation. This paper focuses on the steady state airflow field in a headlamp under the conditions of natural ventilation including the effect of the buoyancy and the heat generation of the lamp surface for the demonstration of the conducted method without not only the deformation of the real 3D-CAD model but mesh generation. The differences of the pressure outlet conditions and heat generation of the headlamp on the amount of the ventilation are also experimented.

This paper describes a method for evaluating the equivalent temperature in vehicle cabins based on the new international standard ISO 14505-4, published in 2021. ISO 14505-4 defines two simulation methods to determine a thermal comfort index “equivalent temperature.” One method uses a numerical thermal manikin, and the other uses thermal factors to calculate. This study discusses the latter method to validate its accuracy, identify the key points to consider, and examine its advantages and disadvantages. First, the definition of equivalent temperature and the equation to calculate the equivalent temperature using thermal factors, such as air temperature, radiant temperature, solar radiation, and air velocity, are explained. In addition, the experiments and simulation methods are described.

In the previous paper (Part 1), measurements of equivalent temperature (teq) using a clothed thermal manikin and modeling of the clothed thermal manikin for teq simulation were discussed. In this paper (Part 2), the outline of the proposed mesh-free simulation method is described and comparisons between teq in the calculations and measurements under summer cooling with solar radiation and winter heating without solar radiation conditions in a vehicle cabin are discussed. The key factors for evaluating teq on each body segment of the clothed thermal manikin under cooling and heating conditions are also discussed. In the mesh-free simulation, even if there is a hole or an unnecessary shape on the CAD model, only a group of points whose density is controlled in the simulation area is generated without modifying the CAD model. Therefore, the fluid mesh required by conventional CFD code is not required, and the analysis load is significantly reduced.

The present paper is Part 1 of two consecutive studies. Part 1 describes three subjects: definition of the equivalent temperature (teq), measurements of teq using a clothed thermal manikin in a vehicle cabin, and modeling of the clothed thermal manikin for teq simulation. After defining teq, a method for measuring teq with a clothed thermal manikin was examined. Two techniques were proposed in this study: the definition of “the total heat transfer coefficient between the skin surface and the environment in a standard environment (hcal)” based on the thermal insulation of clothing (Icl), and a method of measuring Icl in consideration of the area factor (fcl), which indicates the ratio of the clothing surface to the manikin surface area. Then, teq was measured in an actual vehicle cabin by the proposed method under two conditions: a summer cooling condition with solar radiation and a winter heating condition without solar radiation.