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GGSISM (García-Granados Simulation Software for Stirling Machines) has already been described and validated [1], [2], [3]. It has also been presented in this e-journal [4]. The aim of this article is to offer it free of charge as a contribution to the Stirling community and also to show a brief review of the published results and its capabilities.

Review of published results
1-In reference [1] we compare GGSISM simulations for the Solo V160 Stirling engine to experimental values obtained by IK4-Tekniker, and also to those data obtained with Prieto et al. methods [1]. The figures in the paper show good matching.

2-In reference [2], for two Stirling engines: Vølund SM-1 and United Stirling P-40, simulations results are compared with experimental data and with simulations results from three other programs. In general terms, the present program produces lower errors than the others.

3- In reference [3], we analyze a single operating point for the Solo 161 Stirling engine. We conclude that there is uncertainty in the mechanical efficiency because it seems too low: 61.4% assuming 90% for the alternator efficiency.

Later, García et al. [5] analyze this operating point and they estimate a mechanical efficiency of 81%. They attribute this discrepancy to the use of “inadequate assumptions about the geometric characteristics” rather than a malfunction of the program. This is because in the same article [5] they check that some simulations by the author of the present article work well for the Solo 160 engine.

Then, Mesonero [6] provided to the author of the present article some more accurate geometric characteristics (dead volumes mainly). It is not clear if these data are exactly those used in [5], but anyway simulations with GGSISM lead to a mechanical efficiency of around 70-75%, depending on the correlations applied and roughness of the tubes. The conclusion is that differences in the geometric data mainly caused the discrepancies between references [3] and [5].

GGSISM capabilities
The gas circuit is divided in 19 gas control volumes (Figure 1). Mass, pressure, temperature and mass flow rate for each control volume are variable with time. The regenerator matrix is divided in 10 parts. The temperature of each part is time dependent, too. The software provides any of these magnitudes varying with the cycle angle. Figure 2, Figure 3, Figure 4 and Figure 5 are examples. The software also provides energetic magnitudes such as the indicated power or the heat exchangers.

[1] Mesonero I., López S., García-Granados F. J., Jiménez-Espadafor F. J, García D. and Prieto J.I., Characterization and Simulation of a restored V160 Stirling Engine, 2014, 16th International Stirling Engine Conference and Exhibition, Bilbao, Spain.
[2] García-Granados F. J., Silva-Pérez M. A., Prieto J.I. and García D., 2009, Validation of a Stirling engine thermodynamic simulation program, 14th International Stirling Engine Conference and Exhibition, Groningen, The Netherlands.
[3] García-Granados, F. J., Silva-Pérez, M. A., Ruiz-Hernández, V., 2008. Thermal Model of the Eurodish Solar Stirling Engine, Journal of Solar Energy Engineering, 130, pp. 011014-1 – 011014-8.
[4] García-Granados, Francisco J., Presentation of a new software for the analysis of the Stirling cycle: GGSISM, 2013, e-journal, http://www.stirlinginternational.org/
[5] García D., González M.A., Prieto J.I., Herrero S., López S., Mesonero I., Villasante C., Characterization of the power and efficiency of Stirling engine subsystems. Applied Energy 2014; 121:51–63.
[6] Iván Mesonero (IK4-TEKNIKER). Personal communication, 2014.

1- I would like to thank IK4-TEKNIKER and its Stirling crew for sharing their valuable experimental data, which not only led to a joint publication [1], but also to make other issues clear such as the discrepancy between references [3] and [5] as discussed above.
2- I would also like to thank Danila Datti for her collaboration with the English version.

If you were interested in the software or if you had any other questions, do not hesitate to contact the author of this article: Francisco Javier García Granados, e-mail: fjggranados@gmail.com
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