NUMERICAL ANALYSIS OF MELTING AND SOLIDIFICATION PROCESSES OF RT35 PARAFIN WAX IN THERMAL ENERGY STORAGE SYSTEM USING EXHAUST GASES

Öz

In this paper, a numerical analysis of the melting and solidification processes of the thermal energy storage (TES) system designed for the exhaust waste heat recovery of a spark-ignition engine was performed. Paraffin wax, which stores thermal energy as latent heat and is commercially identified with the code RT35, is used as phase change material in the thermal energy storage (TES) system. Two closed-loop fluid circulation system was designed consisting, two heat exchangers for the TES system. The first of the heat exchangers were used to the exhaust path of the SI engine for waste heat recovery, and the other was used for charging and discharging waste heat energy in the PCM container. In the PCM container, two serpentine type heat exchangers are positioned one inside the other to be used in the melting and solidification processes of the RT35. In the numerical analyses, the experimental exhaust gas temperature and flow rate values of a single-cylinder SI engine were used. As a result of the numerical analysis, it has been determined that 1136 kJ energy can be stored as latent heat energy in the PCM container at 13375 sec by 98% liquid fraction, while in the heat discharge process, 945 kJ of energy can be released at 49775 sec by 18% liquid fraction.

Anahtar Kelimeler

• Thermal Energy Storage
• Exhaust Waste Heat Recovery
• Paraffin Wax
• Spark Ignition Engine.

EGZOZ GAZLARINI KULLANAN TERMAL ENERJİ DEPOLAMA SİSTEMİNDE RT35 PARAFİN MUMUNUN ERİME VE KATILAŞMA SÜREÇLERİNİN SAYISAL ANALİZİ

Öz

Bu çalışmada buji ateşlemeli bir motorunun egzoz atık ısı enerjisinin geri kazanımı için tasarlanan termal enerji depolama (TED) sisteminin erime ve katılaşma süreçlerinin sayısal analizleri gerçekleştirilmiştir. TED sisteminde termal enerjiyi gizli ısı olarak depolayan ve ticari olarak RT35 koduyla tanımlanan parafin mumu faz değişim malzemesi (FDM) olarak kullanılmıştır. TED sistemi için iki ısı eşanjöründen oluşan iki kapalı devre sıvı sirkülasyon sistemi tasarlanmıştır. Isı eşanjörlerinden ilki, atık ısı geri kazanımı için buji ateşlemeli motorunun egzoz yoluna, diğeri ise FDM kabında atık ısı enerjisinin şarjı ve boşaltılması için kullanıldı. FDM kabı içerisinde, RT35’in erime ve katılaşma süreçlerinde kullanılmak üzere serpantin tipi iki adet ısı eşanjörü iç içe konumlandırılmış. Sayısal analizlerde, tek silindirli ve buji ateşlemeli bir motorda gerçekleştirilen deneysel çalışmadan elde edilen egzoz gazının sıcaklık ve debi değeri kullanılmıştır. Sayısal analizler sonucunda, tasarlanan gizli ısı TED sistemi ve kabul edilen sınır şartları altında RT35’in erime işleminde 13375.sn’de %98 sıvı oranına ulaşılarak 1136 kJ’ün gizli ısı enerjisi olarak depolanabildiği, katılaşma işleminde ise 49775.sn’de %18 sıvı oranı ile 945 kJ’lük enerjisinin geri salınabildiği tespit edilmiştir.

Anahtar Kelimeler

• Termal enerji depolama
• Egzoz atık ısı feri dönüşümü
• Parafin mumu
• Buji Ateşlemeli Motor

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