A building must meet requirements related to energy usage and good indoor environment. The building ́s ventilation system aims to maintain optimal air quality, thermal condition, and efficient energy usage. By being able to control and adjust airflow as needed with a Variable Air Volume (VAV) system, energy usage of the ventilation system can be reduced without sacrificing indoor air quality. The VAV system operates with a variable airflow, so the accuracy of the VAV terminal at low flows is important. The study aims to verify the accuracy of three different methods for measuring airflow: iris damper, hot- wire anemometer, and volume flow hood. Data collection was carried out through measurements in a laboratory environment. The collected data were managed in the Excel spreadsheet program. The three methods were tested on a prototype consisting of a supply airline and an exhaust airline, each equipped with a VAV unit that varied the airflow through a potentiometer, allowing different airflow values to be obtained for the experiment. The results of the iris damper method were chosen as reference for the other methods due to its ability to predict results using manufacturer tables, which provide useful information about airflow values when varying pressure drop and the iris damper loss k-factor. In this way, set points were stablished for all tests. Two experiments were conducted with different set points. In retrospect it is acknowledged that an air flow meter of higher accuracy had been needed to ascertain the results of the study. That said, the attained results indicate the following: In the experiments, measurements were taken for 12 different airflow values, ranging from 200 l/s to 20 l/s. The test results showed that the most inaccurate method was the volume flow hood, with an average error ranging from ±19% to ±49%, followed by the hot wire anemometer, which had a measurement error between ±15% to ±18%. The high inaccuracy of the volume flow hood was due to a lack of instrument recalibration, resulting in highly inaccurate measurements. All methods showed lower uncertainty between 20 l/s and 50 l/s. Finally, it was verified that the iris damper method improved its average reading error by increasing the pressure drop across the damper and reducing its loss k-factor, achieving the lowest error of the entire experiment at ±12%.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:hig-44406 |
| Date | January 2024 |
| Creators | Antoñanzas Fernández, Daniel |
| Publisher | Högskolan i Gävle, Energisystem och byggnadsteknik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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