 Straight channel heat sinks are commonly used to cool electronic devices and lithium batteries. This study aimed to improve their thermal performance by reducing the height of the inner channels without affecting the overall size of the heat sink. Experimental and numerical analyses were performed to compare the effects of four different channel heights, 12.7, 10, 7, and 4 mm, on the temperature distribution, local Nusselt number, velocity, and flow characteristics. It was found that decreasing the height from 12.7 to 10 or 7 mm increased the maximum temperature of the heat sink, while increasing it from 12.7 to 10 mm improved the Nusselt number. Additionally, increasing the flow rate had a greater effect on improving the Nusselt number when the channel height was 10 mm. Overall, the performance evaluation criterion was higher than 1 for all flow rates when the channel height was decreased from 12.7 to 10 mm. This article was authored by Masa Hadjilababey, Mohamed Ziyad Sagar, and Yusuf Bizer.