Performance And Potential Application Of A Ventilator

When outdoor air is polluted by haze and fog,fine particles with aerodynamic size less than 2.5?m(PM2.5)can penetrate into buildings through various ventilation paths.In order to ensure indoor air quality,it is necessary to purify the air inside the room.The high efficiency particulate air(HEPA)filter can remove most of the airborne particles.However,the inferior features of the HEPA filtration are the high flow resistance and the associated maintenance or replacement cost.The outdoor PM2.5 concentrations vary greatly with time and location,and hence the HEPA filtration may only be required on some severely polluted days and in some specific climatic zones.Besides,the indoor particle filtration can remove airborne particles but may not remove gaseous pollutants.Thus,appropriate ventilation is still needed to dilute gaseous pollutants while filtering airborne particles.There is still lack of a ventilator that can respond to the outdoor weather and pollution conditions to provide the exactly demanded ventilation and particle filtration.This investigation proposed a ventilator with multiple modes of air filtration.The ventilator can be driven by either the outdoor wind or the mechanical fan installed inside the ventilator.Different efficiency of air filters are installed into the natural and mechanical ventilation passages and factors such as airflow rate,ventilation resistance and applicable condition are considered to design the ventilator and select the material.The ventilator can be controlled manually or by a control system.The control system can automatically choose the appropriate operating modes and the required air ventilation rate.The ventilator based on the above scheme was constructed and installed to a test room.The performance of the ventilator in terms of ventilation flow rate,wind pressure,fan power consumption,particle filtration efficiency was measured.The indoor conditions inside the test room and performance of the ventilator were modelled by the EnergyPlus software.The resistance-flow relationship and particulate filtration performance in different operating modes were specified into the EnergyPlus as known information.The experimental data obtained in the test room were used for modeling validation.The validated model was adopted to simulate the indoor air quality and operating energy consumption in a typical apartment utilizing such ventilators.It was assumed that the same apartment with such ventilators were located in representative cities in different climatic zones in China.The simulated annual indoor air quality and energy consumption were compared with those by replacing the ventilators with the market-available fresh air blowers.The results revealed that the power consumption per unit CADR of the ventilator is lower than the fresh air blower.If the outdoor air is sufficiently clean or slightly polluted,the wind-driven modes can be used.The natural ventilation with air filtration can provide the PM2.5 purification efficiency at approximately 40%.If the outdoor air is slightly polluted but without wind or rapid ventilation is required,the mechanically-driven middle-efficiency filtration mode of the ventilator can be used,which has a lower power consumption rate than the high-efficiency mode.The service life of the high-efficiency filter can also be prolonged by running the middle-efficiency filtration as much as possible.The comparison between the EnergyPlus modeling and the experimental test shows that the proposed numerical model can accurately resolve the indoor ventilation and PM2.5 concentrations for all of the operating modes.The numerical simulations in different cities also imply that the ventilator can reduce approximately 70% of the running time of the HEPA filtration as compared with the fresh air blower with the pure HEPA filtration.The annual operating energy consumption per unit floor area is approximately 30% lower and the energy consumption of heating and cooling is also lower.The simulation results are helpful for guiding selection of ventilators and air cleaners in different climatic zones.