Title:  Condition Monitoring of High Efficiency Heating, Ventilation and Air Conditioning System

Committee: 

Dr. Habetler, Advisor   

Dr. Saeedifard, Chair

Dr. Harley

Abstract:

The objective of the proposed research is to increase energy efficiency in HVAC (Heating, Ventilation and Air conditioning) systems. Energy consumption has increased rapidly in recent decades. This has elevated concerns regarding an energy crisis and heavy environmental impacts. An air handler, or air handling unit (AHU), is a device used to condition and circulate air as part of a HVAC system. The operation of AHUs account, on average, for 40% of an industrial site’s total energy consumption. The air handler unit in the HVAC system has electrical and mechanical components that can experience problems from time to time. Airflow blockage and a failure of a blower motor are two most common problems with air handlers. Airflow blockage is detected utilizing a current based condition monitoring method focusing on the mechanical oscillation of the AHU system. The frequency components of mechanical oscillation of AHUs act as the major index for airflow fault detection. For most AHUs, the unbalanced load of the blower wheel is created by the unevenly distributed contaminants on the blades. The traditional current based condition monitoring method is conducted to a BLDC (Brushless DC) fan motor followed by a stray flux spectrum analysis which increase the reliability in detecting an unbalanced load condition. Static eccentricity and dynamic eccentricity are two of the main faults in the rotor of BLDC motor. An improved method in detecting static eccentricity is proposed based on the comparison between the positive sequence current and negative sequence current. Finally, a current based nonintrusive condition monitoring method is established for refrigerant level detection. A thermal model of compressor is analyzed under insufficient refrigerant level conditions to explore the mathematical relationship between refrigerant level and stator winding resistance.