Single-phase heat transfer and pressure drop in the micro-fin tubes with coiled wire insert

The heat transfer characteristics and the pressure drop of the horizontal double pipes with and without coiled wire insert are investigated. The inner and outer diameters of the micro-fin tube are 8.92 and 9.52 mm, respectively. The coiled wire is fabricated by bending a 1-mm-diameter iron wire into the coil wire with coil diameter of 7.80 mm. Cold and hot water are used as working fluids in shell side and tube side, respectively. The test runs are performed at the cold and hot water mass flow rates ranging between 0.01 and 0.07 kg/s and between 0.04 and 0.08 kg/s, respectively. The inlet cold and hot water temperatures are between 15 and 20 °C and between 40 and 45 °C, respectively. The results obtained from the micro-fin tube with coiled wire insert are compared with those obtained from the smooth and micro-fin tubes.