Date of Award

Spring 2021

Project Type

Thesis

Program or Major

Mechanical Engineering

Degree Name

Master of Science

First Advisor

Chris White

Abstract

The objective of this work is to conduct physical experiments to validate and optimize a steady state moving boundary model of a vapor compression refrigeration cycle (VCRC). The experimental facility includes a controlled heat source and a VCRC system for heat rejection. Pressure, temperature, and flow measurements of the VCRC are acquired at specific points in the flow loop from which thermodynamic cycles are created and cycle integrated variables are computed.

Nine sets of experiments were conducted to train the steady state moving boundary model with respect to empirical formulations for the volumetric, isentropic, and combined efficiencies of the compressor. Next, experiments were conducted at different conditions relative to the training data, and the measured thermodynamic cycles and cycle integrated variables were compared to the steady state moving boundary model for validation purposes. Lastly, the now validated model was used to investigate methods to optimize the VCRC. The optimization metric used was the coefficient of system performance (COSP), where COSP is the ratio of heat transfer rate of the evaporator to the power input of the compressor and heat exchanger fans.

The study found that up to 65\% COSP improvement could be achieved for the continuously running range of the compressor by optimizing the system's compressor RPM and heat exchanger fan RPM. In addition, the continuously running range of the VCRC was significantly extended. The findings suggest that VCRCs can be controlled exclusively by their actuating devices removing the need for choke valves.

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