A urea supply conduit (68) has a wall of good thermal conductivity. Urea solution in liquid phase is sucked out of a tank (24) through conduit (68) and delivered to a point of use (22) in an engine exhaust after-treatment system (18) through which products of combustion are conveyed from engine combustion chambers (16) to atmosphere. Liquid engine coolant is circulated through a coolant conduit (66) that has a wall of good thermal conductivity placed side-by-side and in physical association with the urea supply conduit wall to form a thermal conduction path for heat transfer between coolant in the coolant conduit and urea in the urea supply conduit, more quickly thawing any frozen urea.