Integrated collector storage solar water heater under partial vacuumIntegrated collector storage solar water heater under partial vacuum Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2018-03-162017enThe work focuses on the experimental study of the heat diode mechanism in an Integrated Collector Storage Solar Water Heater (ICSSWH) for domestic applications. The solar device combines a horizontal cylindrical vessel with an asymmetric reflector trough (Compound Parabolic Concentrator – CPC). The cylindrical storage tank comprises two concentric cylindrical vessels: the outer absorbing vessel and the inner storage vessel. The annulus between the cylindrical vessels is partially depressurized and contains a small amount of water serving as Phase Change Material (PCM), which changes phase (mainly at low temperatures) thus producing vapor and creating a thermal diode transfer mechanism from the outer to the inner surfaces of the vessels. Several experimental results, including uncertainty analysis, are demonstrated through diagrams depicting temperature variations, mean daily efficiency and thermal losses coefficient. Additionally results from the variation of the temperature and the total pressure inside annulus are also presented. The results clearly show that the vapor's pressure plays the most important role regarding the thermal performance of the device.http://creativecommons.org/licenses/by/4.0/Energy139991-1002 Σουλιώτης Μανόλης Souliotis Manolis Papaefthimiou Spiros Παπαευθυμιου Σπυριδων Καούρης Γιάννης Γ. Caouris Yiannis G. Ζαχαρόπουλος Άγγελος Zacharopoulos Aggelos Quinlan Patrick Smyth Mervyn Elsevier CPC Compound parabolic concentrators Heat diode mechanism ICSSWH Integrated collector storage solar water heaters PCM Phase change materials Thermal behavior