Evaluation Of Different Air Distribution Systems For Sleeping Spaces In Transport Vehicles

As a third part of the life,sleep has a great impact on quality of life and work efficiency.Both in the bedroom and small vehicle,sleep problems are worthy of attention.Vehicles as carriers of the modern society are indispensable whose prosperity is the embodiment of the modern social development vitality.Although sleeping time on a journey may not be as long as in bedroom,good sleep in vehicles such as trains,coaches,ships,airplanes,and spacecraft is essential to overcoming fatigue and sometimes jet lag.For steward work on all kinds of transportation,such as flight attendants,rest on narrow transportation is part of daily life.So creating a good sleeping environment is necessary.Creating a suitable air distribution of sleeping environment can control air temperature and velocity and pollutants.But sleeping space in transports compared with bedroom is small.It is challenging to satisfy the contradiction of pollutant emission and high speed.Thus we need to study air distributions in sleeping environment and provide design basis for such environment.This investigation used a verified computational fluid dynamics(CFD)method to obtain the distributions of air velocity,air temperature,and CO2 concentration in the sleeping space with displacement,personalized,and mixing ventilation systems.This study used the facial-area speed ratio,mean age of air,and draft risk obtained by CFD to evaluate the air distribution effectiveness.The distributions of air velocity,air temperature,and contaminant concentration computed by CFD were validated with corresponding experimental data obtained in a full-scale test rig.The research results show that the personalized system had the highest facial-area speed ratio for air velocity between 0.08 m/s and 0.20 m/s and had the lowest mean age of air which means it can provide the freshest air with highest draft risk,in comparison with the mixing and displacement ventilation systems..Nevertheless,the highest DR was acceptable and it can be greatly reduced by increasing the area of air supply outlet or supply air temperature.In addition,compared with the displacement ventilation and mixing ventilation,personalized ventilation can achieve thermal comfort and good air quality under the lowest supply air flow rate(1.5 m/min)which also reflected the personalized ventilation system can save energy.Thus,personalized ventilation is the most suitable ventilation system for sleeping space in transport vehicles amount three ventilation systems.At the same time,the agreement between the computed results and the measured data was generally good which was the evidence that the CFD method is an excellent tool for evaluating the air distribution in the sleeping space.