In-situ fan curve calibration for virtual airflow sensor implementation in VAV systems

Alejandro Rivas Prieto, Wesley M. Thomas, Gang Wang, Li Song

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Due to high installation costs and space limitations, airflow measurements with physical meters in air-handling units (AHUs) are not adequate or/and accurate for energy efficient operations. Virtual airflow sensors that calculate airflow rate based on measurable operational data using fan curves provide a promising alternative. However, in-situ fan curves, rather than the manufacturer's fan curves, are needed for accurate airflow calculations. This paper explores a comprehensive procedure for accurate in-situ fan curve calibration in variable-air-volume (VA V) systems by addressing three technical challenges. First, the sampling time is studied to minimize the turbulence impact on the air velocity measurements. Second, for extended periods of airflow measurements using a limited number of velocity probes, the velocity distribution profile across a traverse section is evaluated. Third, in order to correct the flow rate measurement bias for volume tracking controls, a synchronized calibration between the supply air and return air fans is developed and studied. To validate this procedure, the in-situ fan head versus, airflow and efficiency versus airflow curves for both the supply and return fans of a test AHU are calibrated and compared with the manufacturer's fan curves. The investigation shows that the longer sampling time for velocity measurements can compensate for accuracy losses when the spatial traverse coverage is sacrificed. For example, for the 30 by 30 in. (0.76 by 0.76 m) duct in this study, the velocity mean by 25 sampling points on a traverse plane using a 3-second sampling time has an accuracy equivalent to that measured by three sampling points using a 60-secondsampling time. A coefficient of 1.276 is identified to correct the supply fan airflow measurements based on the return side through synchronized calibrations due to a less ideal traverse plane location in the supply duct. The large discrepancy between the calibrated and manufacturer curves suggests that in-situ fan curve calibration is necessary for the implementation of virtual fan airflow sensors.

Original languageEnglish (US)
Title of host publicationASHRAE Transactions - ASHRAE Winter Conference
PublisherAmer. Soc. Heating, Ref. Air-Conditoning Eng. Inc.
Pages215-229
Number of pages15
Volume123
ISBN (Electronic)9781939200655
StatePublished - 2017
Event2017 ASHRAE Winter Conference - Las Vegas, United States
Duration: Jan 28 2017Feb 1 2017

Other

Other2017 ASHRAE Winter Conference
CountryUnited States
CityLas Vegas
Period1/28/172/1/17

Fingerprint

Fans
Calibration
Sensors
Sampling
Air
Velocity measurement
Ducts
Velocity distribution
Turbulence
Flow rate

ASJC Scopus subject areas

  • Building and Construction
  • Mechanical Engineering

Cite this

Prieto, A. R., Thomas, W. M., Wang, G., & Song, L. (2017). In-situ fan curve calibration for virtual airflow sensor implementation in VAV systems. In ASHRAE Transactions - ASHRAE Winter Conference (Vol. 123, pp. 215-229). Amer. Soc. Heating, Ref. Air-Conditoning Eng. Inc..

In-situ fan curve calibration for virtual airflow sensor implementation in VAV systems. / Prieto, Alejandro Rivas; Thomas, Wesley M.; Wang, Gang; Song, Li.

ASHRAE Transactions - ASHRAE Winter Conference. Vol. 123 Amer. Soc. Heating, Ref. Air-Conditoning Eng. Inc., 2017. p. 215-229.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Prieto, AR, Thomas, WM, Wang, G & Song, L 2017, In-situ fan curve calibration for virtual airflow sensor implementation in VAV systems. in ASHRAE Transactions - ASHRAE Winter Conference. vol. 123, Amer. Soc. Heating, Ref. Air-Conditoning Eng. Inc., pp. 215-229, 2017 ASHRAE Winter Conference, Las Vegas, United States, 1/28/17.
Prieto AR, Thomas WM, Wang G, Song L. In-situ fan curve calibration for virtual airflow sensor implementation in VAV systems. In ASHRAE Transactions - ASHRAE Winter Conference. Vol. 123. Amer. Soc. Heating, Ref. Air-Conditoning Eng. Inc. 2017. p. 215-229
Prieto, Alejandro Rivas ; Thomas, Wesley M. ; Wang, Gang ; Song, Li. / In-situ fan curve calibration for virtual airflow sensor implementation in VAV systems. ASHRAE Transactions - ASHRAE Winter Conference. Vol. 123 Amer. Soc. Heating, Ref. Air-Conditoning Eng. Inc., 2017. pp. 215-229
@inproceedings{420d9f628b9a48cf9dd66ceea441010e,
title = "In-situ fan curve calibration for virtual airflow sensor implementation in VAV systems",
abstract = "Due to high installation costs and space limitations, airflow measurements with physical meters in air-handling units (AHUs) are not adequate or/and accurate for energy efficient operations. Virtual airflow sensors that calculate airflow rate based on measurable operational data using fan curves provide a promising alternative. However, in-situ fan curves, rather than the manufacturer's fan curves, are needed for accurate airflow calculations. This paper explores a comprehensive procedure for accurate in-situ fan curve calibration in variable-air-volume (VA V) systems by addressing three technical challenges. First, the sampling time is studied to minimize the turbulence impact on the air velocity measurements. Second, for extended periods of airflow measurements using a limited number of velocity probes, the velocity distribution profile across a traverse section is evaluated. Third, in order to correct the flow rate measurement bias for volume tracking controls, a synchronized calibration between the supply air and return air fans is developed and studied. To validate this procedure, the in-situ fan head versus, airflow and efficiency versus airflow curves for both the supply and return fans of a test AHU are calibrated and compared with the manufacturer's fan curves. The investigation shows that the longer sampling time for velocity measurements can compensate for accuracy losses when the spatial traverse coverage is sacrificed. For example, for the 30 by 30 in. (0.76 by 0.76 m) duct in this study, the velocity mean by 25 sampling points on a traverse plane using a 3-second sampling time has an accuracy equivalent to that measured by three sampling points using a 60-secondsampling time. A coefficient of 1.276 is identified to correct the supply fan airflow measurements based on the return side through synchronized calibrations due to a less ideal traverse plane location in the supply duct. The large discrepancy between the calibrated and manufacturer curves suggests that in-situ fan curve calibration is necessary for the implementation of virtual fan airflow sensors.",
author = "Prieto, {Alejandro Rivas} and Thomas, {Wesley M.} and Gang Wang and Li Song",
year = "2017",
language = "English (US)",
volume = "123",
pages = "215--229",
booktitle = "ASHRAE Transactions - ASHRAE Winter Conference",
publisher = "Amer. Soc. Heating, Ref. Air-Conditoning Eng. Inc.",

}

TY - GEN

T1 - In-situ fan curve calibration for virtual airflow sensor implementation in VAV systems

AU - Prieto, Alejandro Rivas

AU - Thomas, Wesley M.

AU - Wang, Gang

AU - Song, Li

PY - 2017

Y1 - 2017

N2 - Due to high installation costs and space limitations, airflow measurements with physical meters in air-handling units (AHUs) are not adequate or/and accurate for energy efficient operations. Virtual airflow sensors that calculate airflow rate based on measurable operational data using fan curves provide a promising alternative. However, in-situ fan curves, rather than the manufacturer's fan curves, are needed for accurate airflow calculations. This paper explores a comprehensive procedure for accurate in-situ fan curve calibration in variable-air-volume (VA V) systems by addressing three technical challenges. First, the sampling time is studied to minimize the turbulence impact on the air velocity measurements. Second, for extended periods of airflow measurements using a limited number of velocity probes, the velocity distribution profile across a traverse section is evaluated. Third, in order to correct the flow rate measurement bias for volume tracking controls, a synchronized calibration between the supply air and return air fans is developed and studied. To validate this procedure, the in-situ fan head versus, airflow and efficiency versus airflow curves for both the supply and return fans of a test AHU are calibrated and compared with the manufacturer's fan curves. The investigation shows that the longer sampling time for velocity measurements can compensate for accuracy losses when the spatial traverse coverage is sacrificed. For example, for the 30 by 30 in. (0.76 by 0.76 m) duct in this study, the velocity mean by 25 sampling points on a traverse plane using a 3-second sampling time has an accuracy equivalent to that measured by three sampling points using a 60-secondsampling time. A coefficient of 1.276 is identified to correct the supply fan airflow measurements based on the return side through synchronized calibrations due to a less ideal traverse plane location in the supply duct. The large discrepancy between the calibrated and manufacturer curves suggests that in-situ fan curve calibration is necessary for the implementation of virtual fan airflow sensors.

AB - Due to high installation costs and space limitations, airflow measurements with physical meters in air-handling units (AHUs) are not adequate or/and accurate for energy efficient operations. Virtual airflow sensors that calculate airflow rate based on measurable operational data using fan curves provide a promising alternative. However, in-situ fan curves, rather than the manufacturer's fan curves, are needed for accurate airflow calculations. This paper explores a comprehensive procedure for accurate in-situ fan curve calibration in variable-air-volume (VA V) systems by addressing three technical challenges. First, the sampling time is studied to minimize the turbulence impact on the air velocity measurements. Second, for extended periods of airflow measurements using a limited number of velocity probes, the velocity distribution profile across a traverse section is evaluated. Third, in order to correct the flow rate measurement bias for volume tracking controls, a synchronized calibration between the supply air and return air fans is developed and studied. To validate this procedure, the in-situ fan head versus, airflow and efficiency versus airflow curves for both the supply and return fans of a test AHU are calibrated and compared with the manufacturer's fan curves. The investigation shows that the longer sampling time for velocity measurements can compensate for accuracy losses when the spatial traverse coverage is sacrificed. For example, for the 30 by 30 in. (0.76 by 0.76 m) duct in this study, the velocity mean by 25 sampling points on a traverse plane using a 3-second sampling time has an accuracy equivalent to that measured by three sampling points using a 60-secondsampling time. A coefficient of 1.276 is identified to correct the supply fan airflow measurements based on the return side through synchronized calibrations due to a less ideal traverse plane location in the supply duct. The large discrepancy between the calibrated and manufacturer curves suggests that in-situ fan curve calibration is necessary for the implementation of virtual fan airflow sensors.

UR - http://www.scopus.com/inward/record.url?scp=85020955050&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85020955050&partnerID=8YFLogxK

M3 - Conference contribution

VL - 123

SP - 215

EP - 229

BT - ASHRAE Transactions - ASHRAE Winter Conference

PB - Amer. Soc. Heating, Ref. Air-Conditoning Eng. Inc.

ER -