Application of phase-change material (PCM)-based compact heat exchanger for periodic cooling of electronic devices is widely employed due to its ability to store high thermal energy with isothermal operating characteristics and insignificant change in the volume while changing phase. The effect of change in refrigerant tube diameter on solidification phenomena in an ice freezing–type PCM-based heat exchanger was evaluated. A transient study for the effect of varying tube diameter on heat transfer characteristics was conducted using Ansys Fluent. The variation in tube diameter was considered for two cases, the first case where the total surface area has been kept constant and the second case in which the number of tubes remained constant. A parametric study to analyze the variation of heat flux and heat transfer coefficient was performed. Increasing the tube diameter reduced the time required for solidifying the ice. However, it would decrease the storage capacity of PCM in the heat exchanger with a significant increment in the refrigerant volume, which ultimately made the system bulkier and unfit for portable electronic equipment and also demanded more inventory. An optimum configuration that balances the solidification time along with the required capacity of PCM inside the system was obtained through the present numerical study.