It is shown that an indirect cooling system based on the venturi principle enhances the convective heat transfer many-folds as compared to a simple pipe-flow. Such enhancement results from the acceleration of the coolant in a variable cross-section annulus, created by a concentrically placed bi-conical obstruction inside a circular pipe. The heat-source is placed on the outer-wall of the pipe, at a location corresponding to the venturi-throat. The effect of different pipe materials on the thermal performance of the new cooling system are explored. Numerical results are presented for six Reynolds numbers (based on the pipe diameter) covering the range of about 3200 to 32000, and for a single, circular, ring-type heat-load of 273.5 W / cm2. The coolant used is water, at an inlet temperature of 20 °C. The materials considered are copper, aluminium and stainless-steel (AISI 304). It has been found that even though stainless-steel gives heat transfer rates better than copper and aluminium, that gain is outweighed by the undesirably high temperatures at the heat-sources, thereby making it an unsuitable wall-material for indirect cooling of high heat-flux electronics using the venturi system.