PERFORMANCE DETERIORATION OF  THERMOSIPHON SOLAR FLAT PLATE WATER HEATER DUE TO SCALING

arunachala umesh chandavar

doi:10.31436/iiumej.v12i3.157

Authors

arunachala umesh chandavar MIT, Manipal

DOI:

https://doi.org/10.31436/iiumej.v12i3.157

Keywords:

Thermosiphon system, scaling, instantaneous efficiency, H-W-B equation.

Abstract

The performance of Flat plate Solar Water Heater deteriorates within five to twelve years of their installation due to factors related to manufacturing, operating conditions, lack of maintenance etc. Especially, problem due to scaling is significant as it is based on quality of water used. The remaining factors are system dependent and could be overcome by quality production. Software is developed by incorporating Hottel Whillier Bliss (H-W-B) equation to ascertain the effect of scaling on system efficiency in case of thermosiphon system. In case of clean thermosiphon system, the instantaneous efficiency calculated at 1000 W/m² radiation is 72 % and it drops to 46 % for 3.7 mm scale thickness. The mass flow rate is reduced by 90 % for 3.7 mm scale thickness. Whereas, the average temperature drop of water in the tank is not critical due to considerable heat content in water under severe scaled condition. But practically in case of major scale growth, some of the risers are likely to get blocked completely which leads to negligible temperature rise in the tank.

ABSTRAK: Prestasi plat rata pemanas air suria merosot selepas lima hingga dua belas tahun pemasangannya disebabkan faktor-faktor yang berkaitan dengan pembuatannya, cara kendaliannya, kurangnya penyelenggaraan dan sebagainya. Terutama sekali, masalah disebabkan scaling (tembunan endapan mineral) perlu diambil berat kerana ianya bergantung kepada kualiti air yang digunakan. Faktor-faktor selebihya bersandarkan sistem dan ia boleh diatasi dengan mempertingkatkan kualiti pembuatannya. Perisian komputer dihasilkan dengan menggunakan persamaan Hottel Whillier Bliss (H-W-B) untuk menentukan kesan scaling terhadap kecekapan sistem dalam termosifon. Dalam sistem termosifon bersih, kecekapan seketika dikira pada 1000 W/m², pada kadar radiasi 72 % dan ianya jatuh kepada 46 % untuk ketebalan skala 3.7 mm. Kadar aliran jisim berkurangan sebanyak 90 % untuk ketebalan skala 3.7 mm. Manakala, penurunan suhu purata air di dalam tangki tidaklah kritikal, disebabkan oleh kandungan haba yang tinggi di dalam air di bawah keadaan kerak yang teruk. Tetapi dalam kes tumbesaran kerak yang genting, sesetengah penaik akan tersumbat sepenuhnya, mengakibatkan peningkatan suhu di dalam tangki boleh diabaikan.

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Author Biography

arunachala umesh chandavar, MIT, Manipal

Prof. Arunachala U. C. has obtained Bachelor degree in Mechanical Engg. and Master degree in Energy systems Engg. from Karnatak University. He has teaching experience of more than 14 years and pursuing Doctoral programme under VTU, Belgaum. He is presently working in the Department of Mechanical Engineering of Manipal Institute of Technology, Manipal. He has presented 6 papers in International and National conferences and 6 national and international publications in his credit.