STUDI EKSPERIMENTAL PENGINTEGRASIAN PARAFFIN WAX DAN AIR SEBAGAI MEDIA PENYIMPAN KALORPADA SISTEM PEMANAS AIR TENAGA SURYA

Muhammad Nadjib,ST., Dr. Ir. Suhanan, DEA

2014 | Tesis | S2 Teknik Mesin

Air sebagai material penyimpan kalor sensibel (sensible heat storage, SHS) telah umum digunakan dan dapat diandalkan pada sistem pemanas air tenaga surya (PATS). Meskipun begitu, SHS ini cenderung memiliki karakteristik sistem yang berat dan dapat menimbulkan masalah korosi serta kebocoran. Di sisi lain, phase change material (PCM) sebagai penyimpan kalor laten (latent heat storage, LHS) mempunyai keunggulan khas yaitu densitas penyimpanan energinya tinggi dan fluktuasi temperatur operasionalnya rendah. Mengingat kelebihan tersebut maka LHS berpotensi diaplikasikan pada PATS. Salah satu jenis material LHS komersial adalah paraffin wax. Tujuan penelitian ini adalah untuk menyelidiki secara eksperimental unjuk kerja termal pada PATS tipe thermosyphon yang mengintegrasikan air dan paraffin wax sebagai material penyimpan kalor. Tangki penyimpan energi termal (thermal energy storage, TES) yang dipakai berbentuk silinder dengan panjang 1,67 m, diameter luar 0,168 m dan volume 31,27 liter. Tangki TES dihubungkan dengan kolektor matahari sebagai sumber energi dan tangki dipasang horisontal di atas kolektor. Paraffin wax diisikan pada 16 buah kapsul silinder sebanyak 8,95 kg. Kapsul berdiameter luar 2,54 cm dan panjang 1,63 m diletakkan di dalam tangki. Termokopel dipasang di bagian SHS dan LHS, sedangkan piranometer diletakkan di dekat kolektor matahari. Air digunakan sebagai penyimpan kalor dan fluida pemindah kalor (heat transfer fluid, HTF). Setelah sistem PATS terisi air penuh, penelitian dilakukan selama proses charging, discharging kontinyu dan discharging bertahap. Temperatur dan radiasi matahari selama penelitian direkam setiap 30 detik. Data temperatur SHS dan LHS digunakan untuk mengetahui evolusi temperatur HTF dan PCM. Berdasarkan evolusi temperatur HTF dan PCM dapat diketahui perilaku termal dan unjuk kerja sistem PATS. Dari penelitian ini diketahui bahwa air dan paraffin wax pada PATS thermosyphon telah berfungsi menyimpan energi termal dengan baik. Pada kondisi terbaik saat rata-rata radiasi matahari 699,92 W/m2, sistem TES mampu menghasilkan temperatur rata-rata air panas sebesar 66,86°C dan temperatur ratarata PCM adalah 66,14°C selama 250 menit proses charging. Tangki sistem PATS yang berisi 17,3 liter air mampu menghasilkan 60 liter air panas pada temperatur air campuran rata-rata 45,11°C saat dilakukan proses discharging bertahap. Penyimpanan kalor pada kapsul PCM di bagian bawah tangki kurang efektif sehingga sebaiknya dihindari pemasangan kapsul di daerah tersebut. Kata kunci: PATS, SHS, LHS, PCM, TES, paraffin wax, proses charging, proses discharging

Water as sensible heat storage (SHS) medium has commonly been used and reliable in solar water heaters (SWH) system. Nevertheless, SHS tends to heavy system characteristic and also give rise to problems like corrosion and leakage. In another side, phase change material (PCM) as latent heat storage (LHS) possesses some advantages, i.e. higher energy density and narrower operational temperature fluctuation. Considering these, LHS is potential for being applied in SWH. One of the commercial LHS is a paraffin wax. The objective of this research is to experimentally investigate the thermal performance of thermosyphon SWH with integration of water and paraffin wax as heat storage materials. The thermal energy storage (TES) is a cylindrical tank of 1.67 m length, 0.168 m outer diameter, and volume of 31.27 liters. The TES tank being connected to a flat plate solar collector as a source of energy was placed horizontally above the collector. The amount of paraffin wax being filled into 16 cylindrical capsules was 8.95 kg. The capsules possessing outer diameter of 2.54 cm and length of 1.63 m were placed inside the tank. A number of thermocouples were installed at some points of SHS and LHS part, while a pyranometer was placed beside the solar energy collector at the same tilt angle. Water is used as heat storage and heat transfer fluid (HTF). After SWH was full filled by water, the research was performed during charging, continuous discharging, and gradual discharging processes. The temperatures of SHS and LHS as well as solar radiation were recorded every 30 seconds. The data of SHS and LHS temperature is used to determine the temperature evolution of HTF and PCM. Based on these temperature evolutions, the thermal behavior and SWH system performance can be calculated. It was revealed that the integration of water and paraffin wax in thermosyphon SWH is able to store thermal energy well. In a peak condition with average solar intensity of 699.92 W/m2, this TES system was able to produce a highest average temperature of 66.86ºC for the water and of 66.14 ºC for the PCM. The SWH tank with 17.3 liters in it was also able to produce 60 liters of hot water at average mixed water temperature of 45.11°C during gradual discharging process. Furthermore, it was recommended that installing PCM capsules underside the tank should be avoided because its heat storage less effective. Key words: SWH, SHS, LHS, PCM, TES, paraffin wax, charging process, discharging process

Kata Kunci : PATS, SHS, LHS, PCM, TES, paraffin wax, proses charging, proses discharging