Last Updated: 6/18/2018



Free Excel/VBA Spreadsheets for Thermodynamics:

Rankine, Brayton, Otto, Diesel and Humphrey Power Cycles, Vapor Compression Refrigeration Cycle

 

Usage, Disclaimer, Notes


 

Brayton Cycle (Cold Air Standard) Template including Regeneration (Updated 3/22/2018)

 

This spreadsheet provides a template for analysis of the Brayton Cycle using the Cold Air Standard (constant specific heats).  The user must fill in the data in the top grid.  From that data, the cells in the second grid are updated, and Pressure-volume and Temperature-entropy diagrams are generated.  Make sure your volume is set up high when you open it!   A second sheet in the same workbook (not seen below but operating in a similar fashion) is set up to include Regeneration.  For photos of aircraft powered by the Brayton cycle (Turbofans and Turboprops) as well as some powered by the Otto cycle, click here.

 

BraytonColdTemplate

 

 


Rankine Cycle Template (Updated 6/18/2018)

 

This spreadsheet provides a template for analysis of the Rankine (steam) Cycle.  The user must fill in the data in the top grid (from other software or table lookup).  From that data, the cells in the second grid are updated, and Pressure-volume and Temperature-entropy diagrams are generated.   For best results download the handy Excel “add-in” from Coolprop.  That easy-to-implement add-in provides functions for all the properties of water you’ll need in completing this spreadsheet (and those of 150+ other fluids as well).   The logic is not much different that manual table look-up and interpolation – provide two independent properties, e.g., P and Q (quality) and the function returns any of the others (U, T, H, S, etc.)   Once you have implemented these functions properly, then the whole spreadsheet will update whenever any input parameter (those having the green background in the screen grab below) is changed.   This spreadsheet includes a VBA function that (assuming you’ve automated the property evaluations using Coolprop or something similar) allows you to run a sequence of cases automatically to assess the sensitivity of one variable, e.g., the cycle efficiency, to another parameter, e.g., the turbine inlet pressure.

 

RankineCycleProps

 

 

 


Otto Cycle Template (Updated 3/27/2018)

 

This spreadsheet provides a template for analysis of the Otto (spark-ignition, internal combustion) Cycle.  The user must fill in the data in the top grid (from other software or table lookup).  From that data, the cells in the second grid are updated, and Pressure-volume and Temperature-entropy diagrams are generated.   If you use the thermal properties Excel add-in from CoolProp, then you can have the whole spreadsheet update whenever any input parameter is changed.  This updated spreadsheet includes the capability of doing a sensitivity analysis.  Turn up your volume before opening!    For more on large aircraft engines using the Otto cycle, click here. 

 

OttoCycleTemplate

 

 


Diesel Cycle Template (Updated 3/15/2018)

 

This spreadsheet provides a template for analysis of the Diesel (compression-ignition, internal combustion) Cycle.  The user must fill in the data in the top grid.  From that data, the cells in the second grid are updated, and Pressure-volume and Temperature-entropy diagrams are generated.   This workbook includes the capability of doing a sensitivity analysis.   

 

DieselCycleTemplate

 


Humphrey Cycle (New 5/3/2018)

 

        You won’t find the Humphrey cycle in your thermo book.   It involves a slight (in theory) modification to the Brayton cycle.     The heat is added at constant volume instead of constant pressure.  Thus the temperature rise in the combustion step is a factor of the ratio of specific heats higher than in the Brayton cycle.  You will find that the increase in entropy is lower than that in the Brayton cycle and the cycle efficiency is correspondingly higher.   If the practicalities can be worked out, the Humphrey cycle will be a “game changer.”

 

 

 


Vapor-Compression Refrigeration Cycle (New 5/2/2018)

 

          The vapor-compression refrigeration cycle is analogous to the Rankine cycle, but runs in the opposite direction (counter-clockwise on the TS diagram vs. clockwise for the Rankine power cycle).   This template uses R-134a as the working fluid, but can be readily changed to another refrigerant.

 

 


Mollier Diagram (New 6/5/2018)

 

          The Mollier Diagram provides a useful way of depicting states and processes in a graphical format.  This workbook for water allows you to plot points (obtained using the CoolProp Excel add-in directly) on a Mollier-Diagram found online at engineeringtoolbox.com.  In theory you could use the CoolProp functions to create your own Mollier diagram from scratch, but Excel won’t allow you to plot that complicated a data set.

 

 

 

 

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