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

Zhonghua Zhang,Haowen Shen,Xuefei Zhou,Lina Wang,Hua Liu,Huixian Shi,Yalei Zhang,Lingjie Zeng,Jun Gao,Wenjun Yin,Libin Yang

doi:10.3390/en14248379

Abstract

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.

Highlights

Indoor air pollution is harmful to human health [1,2], causing issues such as respiratory infections, asthma, and lung cancer [3,4,5]
This study developed a user-defined function (UDF) in ANSYS Fluent to solve for mean age of air (MAA) [49]
The normalized ammonia concentration value gradually decreases with the increase in the air changes per hour (ACH)

Summary

Introduction

Indoor air pollution is harmful to human health [1,2], causing issues such as respiratory infections, asthma, and lung cancer [3,4,5]. We spend more than 90% of our time indoors [6]. Indoor air quality (IAQ) is vital to our well-being [7]. The toilet is frequently used, and it emits many undesirable odors such as ammonia and hydrogen sulfide [9,10]. The maximum ammonia and hydrogen sulfide concentration in first-class public toilets should be 0.3 mg·m−3 and 0.01 mg·m−3 , respectively [11]. It is essential to remove pollutants quickly and provide sufficient fresh air to achieve suitable IAQ [12,13,14]. Natural ventilation is an energy-efficient way to improve the IAQ, but it often cannot meet the ventilation needs

Methods

Results

Conclusion