Experimental study of the effect of using wavy pipes and pipe with straps fins on the improvement of the ice formation rate in ice-on-coil thermal storage systems

Cold storage is a commonly used form of the energy storage systems. A major drawback in this type of energy storage is its low heat-transfer rate caused by the low thermal conduction of the phase change material and/or inefficiency of the components utilized in the thermal system. In the present experimental research, straps fins are used to improve the solidification rate of an ice storage system equipped with coiled tubes. Furthermore, the effect of employing straps fins in improving the ice-formation process is compared to that of the strorage system equipped with wavy coil tubes. The results indicate that wavy tube demonstrate a superior performance in increasing the ice formation rate. Comparing the ice-thicknesses obtained from using either of these methods approves the better peoformance characterstics of the wavy tubes. Employing wavy tubes is shown to increase to stored ice volume by 21.08% compared to the use of straps fins. The required power consumption per one liter of ice produced in the system equipped with straps finned tube and wavy coil tube is 0.72 kWh and 0.62 kWh, respectively. Also, in the crest area of the wavy tube configuration, the ice formed on the lower tube surface is generally thicker than that on the upper tube surface. The ice formation behaviour is opposite in the troughs where the ice thickness on the upper surface is 25% higher that on the lower surface. Finally, the difference in the ice thicknesses measured in horizontal and vertical directions is less than 1%.