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Vapor compression cycle component models

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13 Sep 2011 (Updated )

Modeling of vapor compression cycle components

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The following m files are written as part of my master's thesis at Masdar Instiute of Science and Technology.

The compressor model is a semi-empirical and designed to be used for a positive displacement compressor. The constants in Tchparm.m for compressor model are obtained from experimental data of a hermetic rotary compressor.

The HX's are modeled using discretization approach. The two-phase heat transfer and pressure drop in the fin-tube condenser and evaporator models are modeled using flow-pattern based models presented by wojtan, thome et. al. Correlations for two-phase heat transfer and pressure drop presented by Hsieh and Lin which are developed for R-410a fluid are used in brazed-plate evaporator model.

I have tried to provide a lot of comments in the files. However, kindly refer to documentation.docx
for modeling details and program flow charts.

Refprop is required for running the component model files. Optimization and global optimization toolbox is needed for running compressor model or if you want to solve for min. air or water flow rate for a given set of parameters in case of HX models. Tchparm.m file is necessary to run the component model files. The model testing file and data sets are given to ease the user in testing the component models.

The zip file contains the following:
1. positive displacement compressor model
2. fin-tube condenser model
3. fin-tube evaporator model
4. brazed-plate evaporator model
5. miscelleneaous models parameters file (Tchparm.m) such as their physical description, fluid type, oil concentration etc.
6. Documentation consisting of component model details, assumptions, parameters considered etc.
7. model testing file
8. model testing data sets

The experimental data set consists of the data obtained from the test stand built at Masdar Institute and the test stands used in [1], [2]. Their data sets are represented by “MIT DX” and “MIT Chiller” while the data sets obtained from the test stand at MI are represented by “MI DX” and “MI Chiller” depending on mode of operation.

It is to be noted that a constant heat load was maintained for data sets “MIT DX” and “MI Chiller” by using a resistive heater. However, the heat load on the evaporator varied in the case of “MIT Chiller” and “MI DX” data sets depending on simulated or real outdoor conditions. The steady state was assumed to be attained by observing the temperatures and pressures of the system over a period of 30 minutes after any change in compressor or condenser fan speed in the case of “MI Chiller” data set while a duration of 15-20 minutes was used in the case of “MI DX” data set.
[1] N. T. Gayeski, “Predictive pre-cooling control for low lift radiant cooling using building thermal mass,” 2010.
[2] N. T. Gayeski, T. Zakula, P. R. Armstrong, and L. K. Norford, “Empirical Modeling of a Rolling-Piston Compressor Heat Pump for Predictive Control in Low Lift Cooling,” ASHRAE Transactions, vol. 116, no. 1, 2010.

The person interested in the experimental setup and model validation results can e-mail me at mali@masdar.ac.ae
or tauha15@hotmail.com.

i may try to write simple R410a property routines in MATLAB which will eliminate the need for Refprop and also increase the speed of the code significantly. if anybody has already written R410a property routines in MATLAB then kindly plz let me know.

Required Products Global Optimization Toolbox
Optimization Toolbox
MATLAB release MATLAB 7.11 (R2010b)
Other requirements REFPROP (Nist fluid properties software) http://www.boulder.nist.gov/div838/theory/refprop/Frequently_asked_questions.htm
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26 Mar 2013 zhang  
Updates
13 Sep 2011

description formatting update

26 Jul 2012

correction in file description.

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