Experimental study on thermophysical and porous properties of silica gels

Abstract

Porous silica gel (SG) has been extensively used as an adsorbent in adsorption cooling, dehumidification, and desalination applications. Specific heat capacity (Cp) of SG with temperature variation is not experimentally investigated yet. Therefore, this study focuses on the experimental investigation of Cp along with the porous properties of six types of different particle size silica gels. Adsorbed phase Cp of SG is also determined with 10% and 20% water uptake. The experimental Cp is measured within 30 to 100 °C, and the Cp values vary from 0.8 to 1.10 kJ kg–1 K–1 in the measurement temperature range. RD silica gel of the smallest particle size shows the highest Cp values, whereas indicator type silica gel shows the lowest Cp. The Green-Perry model fits well with the experimental Cp data. The porosity analysis shows that RD silica gels of large particle size (D > 0.7 mm) possess the highest surface area (≈ 770 m2/g), and type B silica gels have the largest pore volume (≈ 0.8 cm3/g) along with larger mesopores. A relationship between pore volume and Cp is also reported. The measured data are novel and essential for rigorous performance prediction of adsorption cooling, dehumidification, and desalination systems.