CFD Study on the Ventilation Effectiveness in a Public Toilet under Three Ventilation Methods

The indoor air quality (IAQ) of severely polluted toilets is associated with the transmission of diseases. Computational fluid dynamics (CFD) methods and experimental measurements were used to analyze the diffusion characteristics of pollutants. This study investigated the diffusion characteristics and normalized concentration of ammonia and hydrogen sulfide pollutants under three ventilation systems—mixing ventilation (MV), personalized ventilation (PV), and impinging jet ventilation (IJV)—in a public toilet. The mean age of air (MAA) and air exchange efficiency (AEE) were also analyzed in our study. The results show that the MV scheme has a poor removal effect on pollutants compared with PV and IJV. IJV has advantages in reducing the normalized concentration of pollutants and improving the IAQ. Increasing the number of air changes per hour (ACH) may lead to a longer MAA and reduced air exchange efficiency. Choosing an appropriate number of air changes is very important to improve the IAQ in the toilet.

Effects of Supply Parameters of Stratum Ventilation on Energy Utilization Efficiency and Indoor Thermal Comfort: A Computational Approach

Stratum ventilation shows the significant potential on energy conservation and indoor thermal comfort under cooling applications. Yet, only limited researches focus on the thermal performance of stratum ventilation under heating condition. The heating and cooling operation characteristic of stratum ventilation is different due to the distinct airflow characteristics. Therefore, this paper investigated the parameters that affect energy utilization efficiency and indoor thermal comfort under heating condition served by stratum ventilation via CFD simulations approach. The supply air parameters included temperature, airflow rate, angle, and return air outlet positions. The evaluation indicators adopt ventilation effectiveness and effective draft temperature (EDT) for assessing the energy utilization efficiency and indoor thermal comfort served by stratum ventilation under heating condition. The results demonstrated that, under the heating mode of stratum ventilation, different effects on the thermal performance were made by the mentioned parameters. The ventilation effectiveness was higher when the air supply temperature is 26°C, airflow rate is 7 air change per hour (ACH), and the air supply angle is 45°. The EDT range of the occupied zone is closest to zero K when the air supply temperature is 28°C, airflow rate is 12 (ACH), and the air supply angle is 60°. The related conclusions obtained from this study provide the theoretical basis for the stratum ventilation design and promote its heating application.

A COMPARISON OF MOUTH-TO-MOUTH, MOUTH-TO-POCKET FACE MASK AND BAG VALVE MASK VENTILATION DURING LIFEGUARDS’ CPR: A MANIKIN STUDY

Aim: To compare the effectiveness of ventilation of each of three methods: mouth-to-mouth ventilation using a foil face mask with a filter pad, mouth-to-mask technique with a pocket face mask and bag valve mask ventilation using a self-inflating bag and a face mask, performed during CPR by qualified non-medical rescuers. Material and methods: Ventilation effectiveness was assessed on manikin and compared for mouth-to-mouth, mouth-to-mask and bag valve mask ventilation method. 46 qualified non-medical rescuers-lifeguards participated in the study. Tidal Volume of 0,4-0,7L was considered as effective. The length of chest compressions pauses was recorded. The ventilation methods were also evaluated subjectively by participants in the questionnaire. Results: Effectiveness 90,75% vs. 92,38% vs. 69,5%; average number of effective rescue breaths: 7,26 vs. 7,39 vs. 5,65; average length of chest compressions pause: 7,7s vs. 8,1s vs. 9,9s for MTM, MPFM and BMV respectively. MPFM method was considered as the easiest, the second in terms of the difficulty in use was MTM, and BMV was described as the most difficult to use. Conclusions: Artificial ventilation using the pocket mask, in the course of resuscitation performed by one qualified non-medical rescuer, e.g. the water lifeguard, is an effective method ensuring adequate tidal volume and is more effective than mouth-to-mouth method and bag valve mask ventilation.

Numerical simulation of the CO2-diffusion effect on low turbulent mixed convection in a ventilated room heated by the bottom

A double-diffusive mixed convection within low-turbulent regime in a ventilated cavities filled with an air-CO2 mixture and heated from below has been numerically investigated. The lower wall was sustained at a uniform temperature and CO2-concentration. The vertical and upper walls were kept at external temperature and CO2-concentration. To analyze the behavior of flow, the ventilation effectiveness for temperature distribution and removal of CO2-contaminant, four configurations were dealt. These differ from each other by the location of the mixture inlet and outlet gaps. Likewise, three CO2-concentrations were considered (103, 2x103 and 3x103 ppm) to investigate the influence of the CO2-diffusion on the ventilation effectiveness. The numerical simulations were performed by considering closed Reynolds averaged-Navier-Stokes (RANS) equations using the Re-Normalization Group k-? model. The governing equations' set was then solved using the finite volume method, in which the pressure-velocity coupling was handled using the SIMPLEC algorithm. Validation of the numerical model was achieved by comparing our results with available experimental data. The obtained results indicate that the CO2-diffusion effect on the air movement and the ventilation effectiveness for temperature distribution can be neglected in the present study. However, the CO2-diffusion remains a key parameter in terms of indoor air quality index. Also, it was found that one of the studied configurations provides a better ventilation effectiveness to remove heat and CO2-contaminant, and insures a homogeneous temperature and CO2-concentration in the occupied zone. The three other configurations maintain an acceptable level of heat and can be used in temperate climate to ensure good indoor air quality.