Commercially available compact heat exchangers are currently fabricated in several steps by joining multiple tubes, or by independently fabricting and joining fluid channels. Friction stir channeling (FSC) is a simple and innovative technique of manufacturing heat exchangers in a single step in a monolithic workpiece. During friction stir welding (FSW), a defect referred to as 'wormhole', is created if the processing parameters (tool traverse speed, tool rotation speed, and tool plunge depth) are not correct. FSC is based on converting this defect formation during FSW into a manufacturing technique for heat exchanger applications. If used to produce a cooling system or heat exchanger, FSC can provide many benefits over standard industrial practices in terms of simplicity in manufacturing. Experiments have shown that a continuous hole in a single plate can be created by selecting the optimum process parameters. The channel is characterized by roughness features on the inside, which can be analyzed using optical microscopy techniques. In this paper, five such channels with different hydraulic diameters are tested for the pressure drop and heat transfer. The thermal behavior of a friction stirred channel is simulated using the commercial CFD code FLUENT. Pressure drop along the channel is studied for different surface roughness heights. Temperature difference of water between the inlet and the outlet of the channel is also measured for the channels.