Field measurement of the impact of natural ventilation and portable air cleaners on indoor air quality in three occupant states

Natural ventilation(NV)has been considered a simple and effective method of ventilation.However,the intro-duction of NV does not achieve better indoor air quality(IAQ)when the outdoor atmospheric environment is polluted.Therefore,portable air cleaners(PACs)are increasing in use in recent years,but their effectiveness is highly dependent on the residents’habits.A typical residence in Xi’an,China was selected to examine the effects of the use of NV alone and the use of NV and PACs together on IAQ in the three occupant states,i.e.,unoc-cupied,sleeping and leisure.Parameters,such as temperature,relative humidity,CO_(2),and PM_(2.5)concentration were measured when changing the window opening and the position of the PAC.The results showed that in the unoccupied state,opening the inner door can promote a more uniform thermal and humid environment.In the sleeping state,the I/O ratio of the PM_(2.5)concentration was the lowest when the window opening of the bedroom was 1/2 or 3/4,with a mean value of 0.3.In the leisure state,only using NV,when the purification rate reaches 90%,the mean purification time of each window opening in the living room is 87.5 min.The mean purification time was reduced to 25 min when both NV and PAC were used.The on-site purification efficiencies were 91.0%and 94.5%,when the window opening was 1/2(i.e.,the PAC was placed in the center of the room)and 3/4(i.e.,the PAC was placed away from the outer window),respectively.

Airflow pattern and performance of attached ventilation for two types of tiny spaces

With the emergence of urban sentry boxes and capsule hotels,the development of tiny spaces with the concept of a reasonable minimum occupied space has attracted widespread attention from society.The ventilation mode that fits with the limited geometric characteristics of tiny spaces is worth exploring.Combined with the respective ventilation requirements of two types of tiny spaces,i.e.,sentry box space and tiny sleeping space,this paper proposes two attached ventilation modes.A full-scale experiment cabin was established,and the simulation method was optimized through experimental data.The airflow pattern and distribution performance of the two attached ventilation modes in two types of tiny spaces were studied by the CFD method.The results showed that the airflow attached to the vertical wall could form an air curtain at the opening windows of the sentry box space,but there is a phenomenon of air leakage.The installation of the deflector can improve the integrity of the air curtain,and the best installation angle of the deflector is 60 degrees.The double side-attached ventilation mode in the tiny sleeping space can not only relieve the draught of the occupants(DR<15%),but also firstly deliver fresh air to the occupied zone(expiratory zone MAA<92 s).The research conclusions will add new ideas to the diversity of ventilation modes in tiny spaces.