Billel MEBARKİ, Rabah GOMRİ, İsmail SOLMUŞ

THE PERFORMANCE ANALYSIS OF A SILICA GEL/WATER ADSORPTION CHILLER AND DYNAMIC HEAT AND MASS TRANSFER CHARACTERISTICS OF ITS ADSORBENT BED: A PARAMETRIC STUDY

İki adsorban yataklı silika jel/su çalışma çiftini kullanan adsorpsiyonlu soğutma sisteminin performansı ve sistemin adsorban yatak boyutlarının, ısı değiştirici akışkan hızının ve adsorban tanecik çapının zamana bağlı olarak katı fazın sıcaklık dağılımı, adsorplanan konsantrasyonu ve basınç dağılımı üzerine etkileri sayısal olarak bu çalışmada incelenmiştir. Zamana bağlı iki boyutlu ve lokal olarak ısıl dengenin olmadığı iç ve dış kütle transfer dirençlerini dikkate alan sayısal bir model söz konusu sistemi incelemek için geliştirilmiştir. İç ve dış kütle transfer dirençleri sırasıyla doğrusal itici güç modeli ve Darcy denklemi vasıtasıyla hesaplanmıştır. Parametrik çalışma neticesinde artan adsorban tanecik çapının sistemin performans katsayısı ve özgül soğutma gücü üzerinde bir düşüşe yol açtığı bulunmuştur. Diğer taraftan, sistem performansının ısı değiştirici akışkan hızının değişiminden neredeyse bağımsız olduğu elde edilmiştir. Adsorban yatak kalınlığındaki bir artış sistemim performans katsayısında yükselmeye ve özgül soğutma gücünde ise düşüşe yol açmıştır. Adsorban yatak uzunluğunun sistem performansı üzerine olan etkisi ihmal edilebilecek düzeydedir. Parametrik çalışmamızın sonuçları bu tip adsorpsiyonlu soğutma sistemlerinin tasarımı için faydalı öneriler ortaya koymaktadır.

ADSORPSİYONLU SİLİKA JEL/SU SOĞUTMA SİSTEMİNİN PERFORMANS ANALİZİ VE ADSORBAN YATAĞININ DİNAMİK ISI VE KÜTLE TRANSFERİ DAVRANIŞI: PARAMETRİK ÇALIŞMA

The performance of two adsorbent bed silica gel-water adsorption chiller and the influences of its adsorbent bed dimensions, the velocity of heat exchange fluid and the adsorbent particle diameter on the transient distributions of the solid phase temperature, adsorbate concentration and the pressure are numerically examined in this study. A transient two-dimensional local thermal non-equilibrium model that takes into account both internal and external mass transfer resistances is developed to simulate the adsorption chiller considered herein. The internal and external mass transfers are predicted by the linear driving force (LDF) model and Darcy's equation, respectively. It is found that an increase in the adsorbent particle diameter results in the decrease in both the coefficient of performance (COP) and specific cooling power (SCP) of the adsorption chiller. On the other hand, the system performance is nearly independent from the variation of velocity of heat exchange fluid. An increase in the bed thickness leads to an increase in COP and a decrease in the SCP. The influence of adsorbent bed length on the performances of system can be neglected. The results of our simulations provide useful guidelines for the design of this type of adsorption chillers.

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