Architectural Engineering and Construction, Durham School of
Durham School of Architectural Engineering and Construction: Dissertations, Theses, and Student Research
First Advisor
David P. Yuill
Date of this Version
12-2019
Document Type
Thesis
Citation
A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science
Major: Architectural Engineering
Under the supervision of Professor David P. Yuill
Lincoln, Nebraska, December 2019
Abstract
Air economizers are widely used in building air conditioning systems. The purpose of using them is to reduce needed mechanical cooling by properly introducing outdoor air to the space when its temperature is low enough without compromising space ventilation. It is common that air economizer experience malfunction and faulty performance, causing energy savings to be lost, furthermore, energy penalty occur.
This thesis discusses the impacts stuck outdoor air dampers have on the value and performance of air economizers used in air handling units (AHU) and rooftop units (RTU). The study used multiple EnergyPlus simulations of a small office building model located in 6 different cities: Phoenix, Arizona, San Francisco, California, Baltimore, Maryland, Chicago, Illinois, Boise, Idaho, and Fairbanks, Alaska. The economic impacts caused by stuck outdoor air damper faults are quantified, and the effect of loss in cost-effectiveness on RTU sizes that justify installing economizers is highlighted. The implication is an increase in minimum RTU size that justifies the addition of an economizer. For fixed dry bulb economizers, the minimum RTU size (in tons) that justifies having an economizer with the probability of faults is 27.5 for Phoenix, 5 for San Francisco, 20 for Baltimore, 10 for Chicago, 7.5 for Boise, and 5 for Fairbanks. For fixed enthalpy economizers, the minimum RTU size is 5 for San Francisco, 20 for Baltimore, 27.5 for Chicago, 17.5 for Boise, and 5 for Fairbanks. Fixed Enthalpy economizers were found to be economically not justified in Phoenix. For differential dry bulb economizers, the minimum RTU size is 25 for Phoenix, 5 for San Francisco, 15 for Baltimore, 12.5 for Chicago, 7.5 for Boise, and 5 for Fairbanks.
The second part of the thesis is to develop a remote tool to detect economizer faults. A cellular data logger (CelLo) was developed and tested in the lab. The tool is assembled and program to detect stuck open and stuck closed damper faults, and send an alarm over the 3G network to the user.
Advisor: David P. Yuill
Comments
Copyright 2019, Moh'd-Eslam Dahdolan. Used by permission