A device for processing hydrocarbon resources in a subterranean formation may include a radio frequency (RF) source, a dielectric cooling liquid source, and an RF applicator in the subterranean formation and coupled to the RF source to supply RF power to the hydrocarbon resources. The RF applicator may include concentric tubular conductors defining cooling passageways therebetween coupled to the dielectric cooling fluid source. At least one property of the dielectric cooling liquid, a flow rate of the dielectric cooling liquid, and a configuration of the cooling passageways may be operable together to generate a turbulent flow of the dielectric cooling liquid adjacent surfaces of the plurality of concentric tubular conductors to enhance thermal transfer.