Mechanical & Materials Engineering, Department of


Date of this Version

Fall 9-2012


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: Mechanical Engineering, Under the Supervision of Professor C. W. Solomon To. Lincoln, Nebraska: September, 2012

Copyright (c) 2012 Keyhan Rafiee


The Nebraska Center for Energy Sciences Research (NCER) at the University of Nebraska-Lincoln (UNL) strives to be energy efficient through Green Energy. Of course, in meeting some of the requirements for different types of Leadership in Energy and Environmental Design (LEED) certification, certain minimum levels of energy efficiency practices must be met. One such level of energy efficiency, in particular, is reduction in the consumption of electrical energy in buildings. This thesis is a study of methods of reducing the consumption of electrical energy (measured in kW of electrical power) in the UNL Jorgensen Hall (JH) air handling unit 2 (AHU2) ‘fan wall’ of supply air AC motors/fans.

An analysis of the experimental results showed that the numerical values obtained for the total head loss (and the consequential power loss) from the equations employed in each energy method were sufficiently close to each other. This led to the conclusion that the equations employed in the energy methods were properly constructed. A comparison was made between the magnitudes of the head losses (and consequential power losses) associated with the work done by different motor combinations. Furthermore, this comparison was made while, in every combination, the AC motors were operating at a specific speed to move a mass of air through the AHU2 intake air duct system. The

optimal performance of the AHU2 supply air AC motors was achieved through this comparison. The specific power consumption, for every different AHU2 supply air AC motor combination tested, was also taken into consideration in order to determine the combined optimum level of performance for these motors in every setting.

The effects of friction factor on major and minor head losses and consequently on total head loss were considered. A scheme was constructed for the linear optimization of the curve for the total head loss against major head loss. It was also concluded that a particular function developed to describe the relationship between friction factor and Reynolds number is not the only relationship through which friction factor can be determined. Friction factor can be determined independent of Reynolds number.

Finally, recommendations were made so as to bring about the transitioning from one motor combination to another as smoothly as practical in order to meet the specific air supply requirements in different seasonal weather conditions. This can be achieved by way of modifying the appropriate segments of an energy management system software program in constant communication with (field) controllers at all times in order to command these AC motors (operating in different combinations) to run as closely as possible to their peak efficiencies only within a rather narrow range of speed and switching them on and off as needed at all times.

Advisor: C. W. Solomon To