Heat transfer enhancement in Minichannel heat sinks using fully and partially filled coiled wire inserts

Enhanced heat transfer through minichannel heat sink is beneficial for engineering uses such as air conditioning, cooling system, and heat retrieval processes. In the current study, the heat transfer and friction factor were experimentally measured in a rectangular minichannel heat sink with coiled wire inserts. These coiled wires exhibited two wire diameters (0.4, 0.6 mm) and three pitches (1.2, 2.4 and 3.6 mm). The air was used as the working fluid and the Reynolds number ranged from 3000 to 10,000 in the experiments. The minichannel was either fully or partially filled with coiled wires (upstream or downstream portion). Results indicated that the coiled wire inserts tended to increase heat transfer and friction factor in the channel. The Nusselt number and friction factor increased with wire diameter, but decreased with an increase in the pitch-to-diameter ratio. The partially filled design was proposed to reduce the pressure drop caused by the wire inserts. Compared to the fully filled design, the friction factors were lower and the heat transfer enhancement was still noticeable. The partially filled inserts was particularly useful for reducing pressure losses from the thicker wires. Consequently, the minichannel with partially-filled coiled wires lead to the highest thermal performance.