Session: 09-05-01: Sustainable Energy Systems for Heating and Cooling I

Paper Number: 164910

Analyzing Energy Efficiency of Rooftop Units Utilizing Different Refrigerant Types - An Uncertainty and Game Theory Analysis 

One of the most energy consuming industries in US is the Heating, ventilation and air conditioning (HVAC) industry.  This industry consumes a significant amount of energy (between 40 to 60 percent)  in US residential and commercial buildings. Based on department of energy produced information, in 2020, electricity consumption for air conditioning accounted for about 19% (254 billion kilowatt-hours [kWh] of the total electricity consumption in U.S. homes. Also, according to the department of energy information, in 2018, electricity consumption for cooling accounted for about 14% (170 billion kWh) of total electricity consumption in U.S. commercial buildings, with additional 18% (213 billion kWh) of electricity consumed for ventilation in commercial buildings. Different types of HVAC systems can be utilized for air conditioning purpose. According to some report close to 60 percent of the commercial building floors in the US are served by rooftop units. Rooftop units are one of the most popular HVAC equipment in HVAC industry due to its self-containing characteristics and lack of need for additional equipment such as water pumps, piping and cooling towers that are typical equipment utilized for the main competitor system that is a chilled water systems. Rooftop units also known as direct expansion (DX) systems, generally are machines that use a cooling system where the refrigerant directly expands inside the evaporator section of the refrigeration cycle to help cooling the air passing through the evaporator. The main components of the vapor compression refrigeration cycle are, compressor, evaporator, condenser and expansion valve. Rooftop units are used throughout the industry for the air conditioning purpose (both cooling and heating) and utilize different types of refrigerants as the operating agent within its vapor compression cycles. Two commonly used refrigerants in most rooftop units are R-410A and R-134A.  Each of these refrigerants operate under different high and low pressure and temperature levels. The higher pressure and temperature levels occurs at the discharge from the compressor and at the condenser, while lower pressure and temperature level happens in evaporator. In addition temperature and pressure sensors that are utilized throughout the sections of any vapor compression cycles are produced with their associated allowable tolerances. The authors will use an uncertainty analysis approach for a typical range of cooling capacities for rooftop units in order to compare and recognize which type of generally utilized refrigerants can offer higher overall system energy efficiency and therefore produce higher benefit for the same size rooftop units.

Presenting Author: Hugh Allen-Magande Kennesaw State University

Presenting Author Biography: Hugh Allen-Magande is a PhD candidate in Kennesaw State University.

Authors:

Hugh Allen-Magande Kennesaw State University
Javad Khazaii Kennesaw State University
Amin Esmaeili Kennesaw State University
Ali Khazaei Kennesaw State University