Experimental research of fluid flow and effective thermal parameters in micro-particle packed bed as a thermal biosensor reactor under constant wall temperature conditions

In this work, fluid flow and effective thermal parameters were investigated experimentally in a column (with a length of 70 mm, an inner diameter of 10 mm) filled with different diameter micro-particles as a reactor of thermal biosensor. The axial and radial temperature distribution inside the packed bed and the pressure drop between inlet and outlet were measured under constant wall temperature condition (i.e. 60 °C). The effects of particle diameter, particle thermal conductivity and fluid velocity were examined for three different non-metal filling material (resin, activated carbon, glass), for three particle sizes (0.4–0.5 mm, 0.7–0.8 mm and 0.9–1.0 mm) and for three low flow rates (1 mL/min, 3 mL/min and 5 mL/min). The pressure drop greatly increased with increasing flow rate and decreasing particle diameter, and Ergun equation cannot be used to accurately predict the pressure drop in this work. The effective thermal conductivities as well as wall heat transfer coefficients become larger with increasing flow rate due to enhanced heat and mass transfer, but those decrease with smaller particle size, and the main reason is the poor thermal conductivity of the filling materials which together leads to a larger thermal resistance. So it is very important to select a good thermal conducting filling material for optimization design of thermal biosensor reactor. Comparing the correlations of both this work with those published in the literatures, there are considerable discrepancies among them due to different experimental conditions such as test procedures, filling materials, working fluid medium and flow rates.