Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Rooftop Air-Conditioning Unit Performance Improvement using Refrigerant Circuitry Optimization



David A. Yashar, Sunil Lee, Piotr A. Domanski


This study demonstrates the performance improvement of an air-to-air 7.5 Ton (26.4 kW) rooftop unit (RTU) achieved by optimizing an evaporator’s refrigerant circuitry using evolutionary algorithms. We measured its cooling capacity and Coefficient of Performance (COP) in an environmental chamber where we also measured the in-situ air velocity profile using Particle Image Velocimetry (PIV). We used a detailed heat exchanger model to simulate the performance of the original evaporator operating with the measured air distribution, and then we used an evolutionary algorithm-based optimization module embedded in the simulation tool to optimize the refrigerant circuitry for the measured inlet air distribution. The optimized refrigerant circuitry design was implemented in a new prototype evaporator, which replaced the original evaporator in the tested RTU system. Laboratory tests of the new system showed an improvement of 2.2 % in capacity and 2.9 % in COP over the performance of the original system.
Applied Thermal Engineering


Yashar, D. , Lee, S. and Domanski, P. (2015), Rooftop Air-Conditioning Unit Performance Improvement using Refrigerant Circuitry Optimization, Applied Thermal Engineering, [online], (Accessed June 12, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created March 20, 2015, Updated February 19, 2017