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These devices require non-linear transient thermal simulations, in which there is a lack of information. In this study, we introduce an innovative 1D thermo-hydraulic lumped parameter model to simulate loop heat pipes as heat switches by regulating the temperature difference between the evaporator and the compensation chamber. The developed thermo-hydraulic model uses the continuity, energy, and momentum equations to represent the behaviour of loop heat pipes as heat switches. The model also highlights the importance of some thermal conductance parameters and correction coefficients for accurately simulating the different operational states of a loop heat pipe. The simulations are conducted using the proposed 1D model, solved through the application of the Mathcad block function. The numerical model presented is successfully validated by comparing the temperatures of the evaporator and condenser inlet nodes with those of a referenced loop heat pipe from the literature. In conclusion, in this research, the mathematical modelling of loop heat pipes as heat switches is presented. This is achieved by incorporating correction coefficients with Boolean logic that results in non-linear transient simulations. The presented 1D thermo-hydraulic lumped parameter model serves as a valuable tool for thermal system design, particularly for systems with non-linear operational modes like sorption compressors. The graphical and nodal representation of this proposed 1D thermo-hydraulic model further enhances its utility in understanding and optimising loop heat pipes as heat switches across various thermal management scenarios.<\/jats:p>","DOI":"10.3390\/app132312547","type":"journal-article","created":{"date-parts":[[2023,11,21]],"date-time":"2023-11-21T10:24:13Z","timestamp":1700562253000},"page":"12547","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Modelling a Loop Heat Pipe as Heat Switch for Transient Application in Space Systems"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4117-3621","authenticated-orcid":false,"given":"Jo\u00e3o P.","family":"Castanheira","sequence":"first","affiliation":[{"name":"Centro de Astrof\u00edsica e Gravita\u00e7\u00e3o (CENTRA), Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"},{"name":"Synopsis Planet, Advance Engineering Unipessoal LDA, 2810-174 Almada, Portugal"},{"name":"Associate Laboratory of Energy, Transports and Aerospace (LAETA)\/Aeronautics and Astronautics Research Cente (AEROG), Universidade da Beira Interior, 6201-001 Covilh\u00e3, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1064-3205","authenticated-orcid":false,"given":"Nicole G.","family":"Dias","sequence":"additional","affiliation":[{"name":"Centro de Astrof\u00edsica e Gravita\u00e7\u00e3o (CENTRA), Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"},{"name":"Synopsis Planet, Advance Engineering Unipessoal LDA, 2810-174 Almada, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1081-2729","authenticated-orcid":false,"given":"Rui","family":"Melicio","sequence":"additional","affiliation":[{"name":"Associate Laboratory of Energy, Transports and Aerospace (LAETA)\/Aeronautics and Astronautics Research Cente (AEROG), Universidade da Beira Interior, 6201-001 Covilh\u00e3, Portugal"},{"name":"Associate Laboratory of Energy, Transports and Aerospace (LAETA)\/Institute of Mechanical Engineering (IDMEC), Instituto Superior T\u00e9cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6861-8446","authenticated-orcid":false,"given":"Paulo","family":"Gordo","sequence":"additional","affiliation":[{"name":"Centro de Astrof\u00edsica e Gravita\u00e7\u00e3o (CENTRA), Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"},{"name":"Synopsis Planet, Advance Engineering Unipessoal LDA, 2810-174 Almada, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4901-7140","authenticated-orcid":false,"given":"Andr\u00e9 R. R.","family":"Silva","sequence":"additional","affiliation":[{"name":"Associate Laboratory of Energy, Transports and Aerospace (LAETA)\/Aeronautics and Astronautics Research Cente (AEROG), Universidade da Beira Interior, 6201-001 Covilh\u00e3, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-6912-8464","authenticated-orcid":false,"given":"Roger M.","family":"Pereira","sequence":"additional","affiliation":[{"name":"Synopsis Planet, Advance Engineering Unipessoal LDA, 2810-174 Almada, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2023,11,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1","DOI":"10.4236\/jectc.2015.51001","article-title":"Heat Pipe for Aerospace Applications\u2014An Overview","volume":"5","author":"Shukla","year":"2015","journal-title":"J. Electron. Cool. Therm. Control."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Bao, K., Zhuang, Y., Gao, X., Xu, Y., Wu, X., and Han, X. (2021). 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