CHANGE IN THE STATE AIR IN THE ROOM UNDER THE INFLUENCE OF HEAT, WATER VAPOUR AND CO2 EMITTED BY THE HUMAN MODEL AND THE SUPPLY AND EXHAUST VENTILATION UNIT
DOI:
https://doi.org/10.32782/mathematical-modelling/2024-7-2-8Keywords:
mathematical model, air contaminant, aerodynamics, computational fluid dynamics, air change scheme, relative humidity, temperature, carbon dioxide concentration, room working area (WA), rebranding, supply and exhaust ventilationAbstract
The work continues to develop a mathematical model of the respiration process, taking into account the peculiarities of heat and mass transfer between humans and the environment, in particular, the release of carbon dioxide, water vapor and heat. Estimates of air pollution in an isolated room are obtained using a model of a dressed person. The time a person spends in the room and the number of people are taken into account. Based on these estimates, the inverse ventilation problem for the room was solved, i.e. the process of bringing the previously polluted air to the standard parameters was studied. Changes in the state of air parameters were modelled taking into account the impact of the following: – model of a dressed person; – the supply ventilation system (i.e., the intake of CO2, water vapor, and atmospheric heat); – exhaust ventilation system (i.e. removal of carbon dioxide from the air environment, reduction of humidity, air cooling). The ventilation scheme is studied when the supply is from the top of the room and the exhaust is from the bottom near the floor. The application of ANSYS CFD (Computational Fluid Dynamics) numerical modelling based on continuity equations and Reynolds-Averaged Navier-Stokes (RANS) equations has yielded the following results: – the inverse ventilation problem was solved – for the previously contaminated room space under study, the interaction of the systems ‘a dressed person and a working supply and exhaust ventilation unit’ was considered; – monitoring and visualisation of changes in the concentration of carbon dioxide CO2, temperature and relative humidity in the room, depending on the time of operation of the ventilation unit and the height of the room; – the efficiency of the adopted air exchange scheme in the room was compared to match its characteristics with the requirements of regulatory documents. The dynamics of the absorption of excess heat, humidity and carbon dioxide (CO2) made it possible to assess the efficiency of ventilation systems and predict an increase in their energy efficiency when air parameters are brought to standard values. Changes in the air environment are typical for rooms with mechanical supply and exhaust ventilation.
References
Kiosak V., Isaiev V., Fedorenko V., Gridasov A. Мodeling the entry of air contaminants into a room. Mechanics and Mathematical Methods, 2024, Vol. 6(2), P. 58–76. https://doi.org/10.31650/2618-0650-2024-6-2-58-76.
Опалення, вентиляція та кондиціонування. ДБН В.2.5-67:2013. Чинний від 2014-01-01. Київ : Держстандарт України, 2013. 135 с.
Розрахункові параметри мікроклімату приміщень для проектування та оцінки енергетичних характеристик будівель по відношенню до якості повітря, теплового комфорту, освітлення та акустики (EN-15251:2007, IDT). ДСТУ Б EN 15251:2011. Чинний від 2013-01-01. Київ : Держстандарт України, 2012. 71 с.
Mansour E., Vishinkin R., Rihet S., Saliba W., Fish F., Sarfati P., Haick H. Measurement of temperature and relative humidity in exhaled breath. Sensors and Actuators B: Chemical, 2020, Vol. 304, 127371. https://doi.org/10.1016/j.snb.2019.127371.
Elcner J., Lizal F., Jedelsky J., Jicha M. Study of airflow in the trachea of idealized model of human tracheobronchial airways during breathing cycle. EPJ Web of Conferences, 2015, Vol. 92, 02016. https://doi.org/10.1051/epjconf/20159202016.
Patankar S.V. Numerical Heat Transfer and Fluid Flow. CRC Press, 2018, Р. 214. https://doi.org/10.1201/9781482234213.
Coakley T. Turbulence modeling methods for the compressible Navier-Stokes equations. У 16th Fluid and Plasmadynamics Conference. American Institute of Aeronautics and Astronautics, 12 July – 14 July 1983. Danvers, MA, U.S.A., 1983, Р. 1–2. https://doi.org/10.2514/6.1983-1693.
Jones W.P., Launder B.E. The prediction of laminarization with a two-equation model of turbulence. International Journal of Heat and Mass Transfer, 1972, № 15(2), Р. 301–314. https://doi.org/10.1016/0017-9310(72)90076-29.
