A 3-D model is presented for a novel sub-watt packed bed reactor. The reactor uses an annular inlet flow combined with a radial flow packed bed reactor. The baseline reactor is compared to a reactor with multiple outlets and a reactor with 3 internal fins. Increasing the outlets from 1 to 4 may have improved flow distribution, but did not increase the performance. However, inserting fins allowed > 99% methanol conversion with approximately 30 K decrease in temperature with same inlet flow. (C) 2015 Elsevier Ltd. All rights reserved.