بررسي تجربي تاثير قطر كپسول بر عملكرد سيستم ذخيره‌ساز حرارتي حاوي مواد تغيير فاز دهنده در آبگرمكن خورشيدي تخت

Experimental investigation of capsule’s diameter size effect on the performance of energy storage system of a solar water heater using PCM

با توجه به متناوب بودن تابش انرژي خورشيدي، وجود سيستمي براي ذخيره‌ي انرژي ضروري به نظر مي‌رسد. ذخيره‌ي انرژي به‌صورت نهان در يك آبگرمكن خورشيدي، در مواد تغيير فاز دهنده انجام مي‌گيرد. اين مواد اغلب درون يك ظرف كپسوله شده و به‌صورت غير مستقيم درون مخزن آب قرار مي‌گيرند. شكل، جنس و اندازه‌ي اين ظرف در عملكرد سيستم ذخيره تاثير خواهد داشت. در اين نوشتار تاثير قطر كپسول بر عملكرد سيستم ذخيره‌ي حرارت به‌صورت تجربي بررسي شده است. بدين‌منظور پارافين به‌عنوان ماده‌ي تغيير فاز دهنده در لوله‌هايي از جنس آلومينيوم با قطر‌هاي 12، 10 و 6 ميلي‌متر كپسوله شده و مورد آزمايش قرار گرفته است. نتايج حاصله حاكي از آن است كه ميزان ذخيره‌ي انرژي نسبت به حالت بدون مواد تغيير فاز دهنده، با كپسول آلومينيومي به‌قطر‌هاي 12، 10 و 6 ميلي‌متر، به‌ترتيب 2/11%، 3/15% و 4/4% افزايش داشته است.

Regarding the variability nature of the solar ray in a day, application of a thermal storage system seems necessary to accompany the solar system. Latent heat energy storage in a solar water heater can occur in a phase-change material. These materials are generally encapsulated in a container and positioned in the water container. Shape, material type, and size of the encapsulating container have direct effect on the efficiency of the storage system. In this paper, effort has been made to investigate experimentally the encapsulation diameter effect on the storage system efficiency. Industrial paraffin with 5-7% fat was used as a phase-change material. They were encapsulated in aluminum tubes of 6, 10, and 12 mm diameter. The thicknesses of the capsules in all diameters are 1mm. For each tube size, a set of tests was carried out. For each test, 88 capsules with 280 mm height containing the paraffin were used. As a result, for capsules with 6, 10, and 12mm diameter, 281.6gr, 1126.4gr, and 1760gr of paraffin were used, respectively. The results show that the rate of energy storage using aluminum tubes of 6, 10, and 12 mm with phase-change material in comparison to when using no phase-change material, improved energy storage efficiency by 4.4, 15.3, and 11.2%, respectively. With regard to the fact that by reduction of capsule diameter, the rate of surface area to the volume increases; hence, heat transferring surface area increases. Therefore, it is expected that by reducing the capsule diameter, density of energy storage will increase. Consequently, by reducing the capsule diameter, total paraffin mass will decrease. Hence, by considering these two factors, maximum rate of energy storage occurs when the capsule diameter is 10mm.