PERPINDAHAN PANAS DAN MASSA PADA PROSES KRISTALISASI GULA SEMUT MENGGUNAKAN KRISTALISATOR BERPEMANAS UAP

SHIAMMITA ROSMINDARI, Sri Rahayoe, STP., MP.

2014 | Skripsi | TEKNIK PERTANIAN

Gula semut merupakan salah satu hasil pengolahan dari nira kelapa. Keunggulan gula semut dibandingkan gula adalah lebih tahan lama, mudah disimpan, praktis, mudah larut, memiliki aroma khas, dan lebih higienis.Pada penelitian ini, kristalisator berpemanas air digunakan dalam proses kristalisasi gula semut. Penelitian ini bertujuan untuk mengkaji perpindahan panas dan massa pada proses kristalisasi gula semut, dengan parameter yang dicari adalah koefisien perpindahan panas gabungan (U), konstanta penurunan kadar air selama evaporasi (k), konstanta penurunan kadar air selama pertumbuhan kristal (kM), dan konstanta penurunan suhu (kT), serta efisiensi pemanasan. Penelitian ini menggunakan variasi 5 kg dan 8 kg gula kelapa, serta masing-masing kapasitas diberi perlakuan tanpa dan dengan penambahan bibit kristal. Proses kristalisasi gula semut dibagi menjadi dua yaitu evaporasi dan pertumbuhan kristal. Proses evaporasi dilakukan hingga larutan mencapai titik jenuh dengan pengadukan kontinyu. Kemudian, pemanasan dihentikan dan larutan siap untuk mengalami proses pertumbuhan kristal. Pengukuran suhu dilakukan pada bahan (T1), wajan (T2), uap air (T3), air pemanas (T4), dan knalpot kompor (T5). Kadar brix diukur menggunakan refraktometer dan kadar air diukur menggunakan pendekatan terhadap kadar brix. Koefisien perpindahan panas gabungan (U) selama proses evaporasi untuk perlakuan 5 kg dan 8 kg tanpa dan dengan bibit kristal adalah 8,4168 W/m2K; 8,3506 W/m2K; 7,9070 W/m2K; dan 7,6137 W/m2K. Konstanta penurunan kadar air (k) selama proses evaporasi perlakuan 5 kg dan 8 kg tanpa dan dengan bibit kristal adalah 0,0176/menit; 0,0209/menit; 0,0108/menit; dan 0,0121/menit. Konstanta laju penurunan suhu (kT) selama proses pertumbuhan kristal perlakuan 5 kg dan 8 kg tanpa dan dengan bibit kristal adalah 0,1273/menit; 0,1058/menit; 0,4490/menit; dan 0,0657/menit. Konstanta laju penurunan kadar air (kM) selama proses pertumbuhan kristal perlakuan 5 kg dan 8 kg tanpa dan dengan bibit kristal adalah 12,4450/menit; 7,2973/menit; 8,0133/menit; dan 7,2283/menit. Efisiensi pemanasan bahan selama proses evaporasi untuk perlakuan 5 kg dan 8 kg tanpa dan dengan bibit kristal adalah 41,2374%; 52,5175%; 46,1726%; dan 49,5294%. Kata kunci : Perpindahan panas, perpindahan massa, proses kristalisasi, efisiensi pemanasan.

Palm sugar is one of coconut sap product. The advantages of palm sugar than coconut sugar are easy to be stored, easy to be transported, more soluble, has a special aroma, and more hygienic. In this research, water heater crystallizer was used in palm sugar crystallization process. This research had objectives to study heat and mass transfer in palm sugar crystallization process, with some parameters should be determined e.g. overall heat transfer coefficient (U), constant of decreasing moisture content during evaporation (k), constant of decreasing moisture content during crystal growth (kM), and constant of decreasing temperature during crystal growth (kT), also the calculation of heating efficiency. This research used two variations of capacity, 5 kg and 8 kg of coconut sugar and each capacity used two treatments of without and with addition of crystal seeds. This palm sugar crystallization process was divided into two processes called evaporation and crystal growth. Evaporation process was done until the solution of coconut sugar turned into saturated point with the continuous of stirring. Then, the heating process is stopped and the saturated solution was ready to be turned to the next stage called crystal growth. Measuring temperature also needed in this research on the solution (T1), wok (T2), water vapor (T3), water (T4), and exhaust stove tube (T5). Brix content measured using refractometer and moisture content of the material measured by an approach to brix content. Overall heat transfer coefficients (U) during evaporation on 5 kg and 8 kg without and with addition of crystal seed are respectively 8.4168 W/m2K; 8.3506 W/m2K; 7.9070 W/m2K; and 7.6137 W/m2K. Constants of moisture content (k) during evaporation on 5 kg and 8 kg without and with addition of crystal seeds are respectively 0.0176/minute; 0.0209/minute; 0.0108/minute; and 0.0121/minute. Constants of decreasing temperature (kT) during crystal growth on 5 kg and 8 kg without and with addition of crystal seeds are respectively 0.1273/minute; 0.1058/minute; 0.4490/minute; and 0.0657/minute. Constants of decreasing moisture content (kM) during crystal growth on 5 kg and 8 kg without and with addition of crystal seeds are respectively 12.4450/minute; 7.2973/minute; 8.0133/minute; and 7.2283/minute. Meanwhile, heating efficiency through evaporation on 5 kg and 8 kg without and with addition of crystal seeds are respectively 41.2374%; 52.5175%; 46.1726%; and 49.5294%. Keywords : Heat transfer, mass transfer, crystallization process, heating efficiency

Kata Kunci : Perpindahan panas, perpindahan massa, proses kristalisasi, efisiensi pemanasan, Heat transfer, mass transfer, crystallization process, heating efficiency