|Title:||Experimental and Modeling Investigation of Two Evaporator Automotive Air Conditioning Systems
|Author(s):||Peuker, S.; Hrnjak, P.S.
|Abstract:||This document presents results of experimental and model investigations of two evaporator automotive air
conditioning systems using R134a and R744 as refrigerants. The R134a system investigated originated from the
vehicle air conditioning system used in the U.S. Army HMMWV (High Mobility Multi-purpose Wheeled vehicle).
The results from the HMMWV R134a breadboard system investigation are used as a baseline to compare the
experimental results from the investigation of the U.S. Army HMMWV R744 two evaporator prototype system. The
subject of different hardware setups (e. g. choice of expansion devices) for the HMMWV R744 two evaporator
system and their implications on performance is addressed. For the case of two controllable expansion devices, the
iterative process which was used to derive an ambient temperature dependent high side pressure correlation for the
HMMWV R744 two evaporator system is presented. The optimized HMMWV R744 system shows higher cooling
capacity (up to 57%) and higher coefficient of performance (up to 18%) compared to the HMMWV R134a system.
In addition, further general issues related to R744 two evaporator systems are investigated. Different
system configurations are explored to investigate where to split and reunite the two refrigerant streams and how this
affects the system stability. Several expansion device combinations are investigated with the focus on fixed area
versus controlled area expansion devices. The role of an accumulator in an R744 two evaporator system is
explained. A control strategy for an R744 two evaporator system using two controlled area expansion devices is
introduced and validated against transient experimental data. Dymola and the AirConditioning Library are used to
simulate an R744 two evaporator automotive air conditioning system. The model results are validated against
experimental data in steady state and transient conditions. The predicted performance at steady state is within 10%
of the experimental results. For the investigated transient scenario the model prediction shows some discrepancy but
the overall trends are well predicted.
|Publisher:||Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
|Series/Report:||Air Conditioning and Refrigeration Center TR-253
|Sponsor:||Air Conditioning and Refrigeration Project 176
|Date Available in IDEALS:||2009-06-24