A model-based feed-forward controller scheme for accurate chilled water temperature control of inlet guide vane centrifugal chillers

Yongzhong Jia, T. Agami Reddy

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

Abstract

Capacity control in most commercial centrifugal chillers is achieved by inlet guide vanes, which are activated by the leaving chilled water temperature sensor. Due to mechanical reasons, vane control is done discretely, and not continuously. The control module compares the value provided by the temperature sensor to pre-set control band values, and if those bands are exceeded, it sends a signal to the vane control motor to adjust the vane position by one step that could be upwards or downwards. The advantage of this type of discrete control method is its simplicity. Normally, the accuracy in the outlet chilled water temperature is of the order of 0.5°C, which is acceptable for normal cooling plants such as used in office buildings. However, there are applications such as in pharmaceutical processes, mechanics labs, or instances in chemical processes where more accurate control is required (sometimes as low as 0.05°C). This paper proposes a simple method to achieve such tight control without any hardware modifications. The basis of this method is a transient physical inverse model of the refrigerant boiling process in the evaporator, in conjunction with a feed-forward control scheme. The model parameters need to be identified from monitored data since they are chiller-specific. This paper describes the model, and applies it to one-minute monitored data from an actual chiller plant of 1580 kW (450 Tons). It is demonstrated that for this specific chiller such a control scheme has the potential to improve control accuracy by about 28% as compared to the traditional control method.

Original languageEnglish (US)
Title of host publicationAdvanced Energy Systems
PublisherAmerican Society of Mechanical Engineers (ASME)
Pages513-522
Number of pages10
ISBN (Print)0791836266, 9780791836262
DOIs
StatePublished - Jan 1 2002
Externally publishedYes

Publication series

NameASME International Mechanical Engineering Congress and Exposition, Proceedings

ASJC Scopus subject areas

  • Mechanical Engineering

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    Jia, Y., & Reddy, T. A. (2002). A model-based feed-forward controller scheme for accurate chilled water temperature control of inlet guide vane centrifugal chillers. In Advanced Energy Systems (pp. 513-522). (ASME International Mechanical Engineering Congress and Exposition, Proceedings). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/IMECE2002-33343