Session: 16-01: Poster Presentations

Paper Number: 140777

140777 - Flow Network Modeling and Controls Implementation for Efficient Adsorption-Based Air Conditioning Systems 

Abstract: 

Traditional vapor compression air conditioning systems for residential applications contain two problems: the most common refrigerants contain a high global warming potential, and vapor compression systems can strain the electric grid during periods of intense heat, occasionally resulting in blackouts. These issues are only going to be exacerbated as climate change produces more intense heat waves. An alternative approach to air conditioning that does not have these two issues is explored here that uses the cyclical adsorption and desorption of water molecules from a molecular sieve. As the adsorbent bed is charged with water vapor, thermal energy is removed from an airspace via a downstream cooling unit. Then, the heating of the adsorbent bed desorbs water molecules, enabling the system to run without the requirement for high-GWP refrigerants nor electricity. System performance is currently limited by factors such as a high generation temperature and a long desorption cycle time. Therefore, models are developed in this study to enable design modifications to address these issues. These models, developed using flow network models featuring established adsorption physics libraries in the Modelica language and implemented via the commercial software package Dymola, enable calculation of key performance metrics for adsorption-based refrigeration systems and identify limiting behavior. The presentation will focus on describing the various types of models developed for adsorption-based air conditioners, such as single-bed with thermal storage and oscillating dual-bed models. The models will furthermore explore the extension of current models towards new designs with improved performance metrics. These extended designs feature optimized features to maximize efficiency by first performing a sensitivity analysis on model parameters, with a primary focus on the adsorption bed characteristics including bed dimensions, geometry (planar versus cylindrical), the implementation of heat sinks of various geometries, bed pellet diameters, along with flow channels between the adsorption bed(s) and the downstream cooling units. New models are also developed that include novel control algorithms to maximize air conditioning efficiency, examining such control algorithms such as proportional-integral-derivative (PID) schemes and supervisory control and data acquisition (SCADA). The presentation describes (1) the development of the flow network models for analysis of specific systems of interest, (2) the implementation of a sensitivity analysis to determine and optimize the performance of various implementations of adsorption refrigeration designs, (3) the development of nonstandard alternative adsorption refrigeration designs, and (4) the development and implementation of control algorithms, with their resultant effect on adsorption refrigeration system energy efficiency metrics. Conclusions are drawn based on the relative effectiveness of these strategies (parts 2-4 above), providing recommendations for further investigation into making adsorption refrigeration systems more viable for residential air conditioning applications.

Presenting Author: Schuyler Sices Villanova University

Presenting Author Biography: Schuyler Sices is an MSME student at Villanova University. He graduated with his BSME from Villanova in 2023.

Authors:

Schuyler Sices Villanova University
Aaron Wemhoff Villanova University