Reversible decentralized ventilation: Experimental determination of efficiency by carbon dioxide level

Abstract

We studied decentralized ventilation devices based on a regenerative heat exchanger with a reverse mode of operation. These devices are capable of recovering up to 90% of the heat used for ventilation of premises. They are a cheaper alternative to central units, and can solve the problem of high heat consumption for ventilation of buildings. Such devices are of little use in practice, since their efficiency concerning providing the required air exchange is poorly studied. The reverse mode of operation is not typical for room ventilation, since the same device constantly changes its purpose between supply and exhaust, which constantly changes the air distribution pattern in the room and can affect the efficiency of dilution and removal of harmful substances. Taking this fact into account makes the study original. The aim of the study is to experimentally determine the efficiency of ventilation in the premises of civil buildings when using such devices. The efficiency criterion was the level of carbon dioxide concentration in the room with a specified limit value of 1000 ppm. People were the source of carbon dioxide. Ventilation was represented by two decentralized devices. The experiment consisted in determining the level of carbon dioxide concentration in natural conditions with a different number of people in the room and different ventilation performance. The results of the experiment were verified by analytical determination of the level of carbon dioxide in the room. As a result of the experiment, dependences of changes in CO2 concentration over time were obtained when one, two and five people were in a room with and without ventilation. To ensure the level of carbon dioxide concentration below the limit (1000 ppm), the required ventilation capacity for one person was 40 m3/h, for two people – 80 m3/h, for five people – more than 160 m3/h. The results allow us to make conclusions about the efficiency of decentralized ventilation devices with reversible mode for premises with a small number of people.