The project contains MATLAB simulation programs that investigates the thermodynamic performance of a multi-pressure vapor compression cycle (VCC) and a dual ejector-assisted VCC, including energy and exergy analysis.

The goal of the study is to evaluate how incorporating dual ejectors can improve system efficiency compared to a conventional multi-pressure refrigeration cycle.

This repository contains two MATLAB simulation codes:

A baseline refrigeration cycle that includes:

• Flash tank
• Intercooler
• Multi-stage compression

This model is used as the reference system to compare performance improvements when ejectors are introduced.

An enhanced cycle that incorporates two ejectors based on the design methodology proposed by:

Mendoza et al. (2020) – Novel Dual-Ejector Vapor Compression Cycle.

The ejectors are modeled with:

• Nozzle efficiency
• Suction chamber efficiency
• Mixing section efficiency
• Diffuser efficiency

The simulation iteratively solves for:

• Entrainment ratios
• Intermediate pressures
• Mass flow balances
• Thermodynamic state points

The model also performs:

• Energy analysis
• Exergy analysis
• COP calculations (cooling, heating, combined)

This simulation requires NIST REFPROP for thermodynamic property calculations.

MATLAB accesses REFPROP using the refpropm interface.

• MATLAB
• NIST REFPROP

The easiest setup is to place the MATLAB scripts inside your REFPROP directory.

Typical location:

C:\Program Files (x86)\REFPROP\

Inside the code, the path is added using:

addpath('C:\Program Files (x86)\REFPROP\')

Make sure MATLAB can locate:

refpropm.m

You can verify by running:

which refpropm

The simulations currently use:

R1234yf

However, this can be easily changed in the code:

refrigerant = 'R1234yf';

REFPROP will handle the property calculations for any supported refrigerant.

The model calculates:

• Enthalpy
• Entropy
• Pressure
• Vapor quality

• Evaporator cooling capacity
• Condenser heat rejection
• Compressor work
• Coefficient of Performance (COP)

COPcooling
COPheating
COPcombined

Component-level exergy destruction is computed for:

• Compressors
• Condenser
• Evaporator
• Expansion valve
• Ejector 1
• Ejector 2

Overall exergy efficiency is also calculated.

The dual ejector model uses nested iterative loops to solve for:

• Ejector entrainment ratios
• Pressure convergence
• Mixing and diffuser conditions

A secant method is used for solving the entrainment ratio.

The code calculates:

• Refrigeration capacity
• Compressor work
• Total power input
• COP values
• Exergy destruction
• Exergy efficiency

Optional lines are included in the code to export results to CSV for further analysis.

Default conditions in the simulation:

These can be modified directly in the parameter section of the script.

This simulation was developed as part of an undergraduate mechanical engineering thesis investigating advanced refrigeration cycle configurations and their thermodynamic performance.

From the simulation under baseline conditions:

• The dual ejector configuration improved COP compared to the standard multi-pressure cycle.
• Compressor work was reduced due to pressure recovery in the ejectors.
• Exergy destruction was significantly reduced in the expansion process by replacing the throttling valve with ejector expansion.

These results highlight the potential of ejector-assisted refrigeration cycles for improving thermodynamic efficiency in low-temperature applications.

• The code prioritizes thermodynamic modeling clarity over computational speed.
• It is intended for cycle analysis and academic exploration.