Study of gas evolution in a sewer section

Summary

Transportation of wastewater through sewer networks is accompanied by the generation and evolution of gases from the flow. For a quantitative assessment of the gas evolution process a sewer section model has been developed in the ANSYS CFX finite element analysis package. The model takes into account the combined flow of wastewater, entrained air and sewage gas (e.g. carbon dioxide) coming from the collector tray. Monitoring was carried out in a section of the domestic sewage system (DN = 500 mm) in the industrial zone of Obukhovo in St. Petersburg. The measured values of the vacuum pressure are in the range of model calculations. The process of designing a computational area of the sewer section and establishing initial and boundary conditions is presented. As a result of modeling the dependences of the carbon dioxide concentration and the pressure of the gas-air environment in the underroof space of the pipeline with different slopes and filling levels were obtained. The results obtained can serve as a basis for the approach to predicting the process of gas evolution in sewer sections.

Key words

monitoring , simulation , ecological safety , sewerage network , carbon dioxide , hydrogen sulfide , methane , ammonia , gas evolution intensity

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Indoor air quality assessment in office buildings

Summary

The assessment of indoor air quality in an office building is given. The analysis of the results of reviewing Russian and foreign authors on this topic showed that at CO₂ concentration of 600–800 ppm and higher the well-being of people worsens, which leads to impaired productivity and increased fatigue. Prolonged exposure to carbon dioxide in humans can lead to chronic diseases. The results of an experimental study of the change in carbon dioxide concentration in an office of a public building with an area of 30 m² with continuing presence of five people are presented. The CO₂ concentration was measured using MT 8057 portable carbon dioxide detector during 24 hours. According to the measurement results a graph of CO2 concentration is plotted against the time. It was concluded that the air quality was not satisfactory during certain periods of the working day (from 10:40 to 13:30 and from 14:45 to 19:00 the CO₂ concentration exceeded 1000 ppm) which indicates problems with the ventilation system and excessive sealing of the room (because of plastic windows). The necessity of taking measures to improve the efficiency of inflow exhaust ventilation has been substantiated.

Key words

carbon dioxide , ventilation , personalized air terminal device , air quality , air exchange , public buildings , sick building syndrome,

Removing carbonate deposits from geothermal heating and hot water supply systems

Summary

The method of removing calcium carbonate deposits from geothermal heating and hot water supply systems is considered. The results of experimental studies of dissolving calcium carbonate deposits in geothermal water in heat-exchange equipment by increasing carbon dioxide partial pressure are presented. On the basis of the conducted experiments a method and a flow scheme of dissolving calcium carbonate deposits that provide for elimination of heat loss with geothermal water used for treatment are suggested.

Key words

geothermal water , calcium carbonate , hot water supply , carbon dioxide , heat exchanger , acidity