AVERAGE CONVECTIVE-PORE VELOCITY OF CARBON-DIOXIDE GAS THROUGH GRAIN BULKS

Experiments were conducted to observe the movement of carbon dioxide ( CO2) gas through a variety of grain bulks subjected to controlled temp erature differences. The CO2 concentration, as it varied with time, wa s used in a finite difference, diffusion-convection model to determine an average convective-pore velocity of CO2 through grain bulks. The a verage convective-pore velocity increased as the temperature differenc e increased when the CO2 was introduced into the grain bulk from the b ottom surface (P<0.05). The average convective pore-velocity was not a ffected by the temperature difference when the CO2 was introduced into the grain bulk from the top surface (P>0.05). The average convective- pore velocity was smaller for canola than for two cereal grains (barle y and wheat) and lentils when the CO2 was introduced into the grain bu lk from the top and bottom surfaces (P<0.05). The lowest average conve ctive-pore velocity was 4.30 x 10(-6) m/s for canola at a temperature difference of 20 degrees C when CO2 was introduced into the grain bulk from the bottom surface. The largest average convective-pore velocity was 2.42 x 10(-3) m/s for wheat at a temperature difference of 40 deg rees C when CO2 was introduced into the grain bulk from the top surfac e.