A printing fluid delivery system includes a reservoir, a conduit system, and a first heating module. The reservoir may store printing fluid. The conduit system may include a plurality of conduit segments to transport the printing fluid between the reservoir and the printing fluid applicator. The first heating module may selectively heat one conduit segment to increase a temperature of the printing fluid therein to a first temperature which is greater than a second temperature of the printing fluid in an other conduit segment, and to thermally induce recirculation of the printing fluid.