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Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
(a) Valve with wax-loading port full of wax; (b) Penetration of the wax inside the channel by capillarity; (c) Formation of the wax barrier on top of the heater. Bottom drawings are cross-sectional illustrations of the process.