Flow and heat transfer characteristics of droplet-shaped pin-fin channel under rotational conditions

The pin-fin structure is widely used for internal cooling in engines. Studying the performance of different pin-fin structures is meaningful. This investigation conducts experimental research on a straight droplet-shaped pin-fin channel. Furthermore, numerical methods are adopted to assist in the analysis of experimental phenomena. The influence of different dimensionless parameters on distribution and variation of the heat transfer coefficient (HTC) and the thermal performance factor (TPF) within the channel under rotating conditions are the core objective of this study. The dimensionless parameters in this investigation is Re = 10,000–70,000, Ro = 0–1.0, r/D = 25.67–52.33, TR = 0.04–0.22, and Buo = 0–2.55. According to this investigation, rotation weakens heat transfer on the leading surface (LS) while increasing it on the trailing surface (TS) by 10 %-20 %. Rotation can enhance the TPF of the channel under low-Re condition, and causes a decrease of 0–10 % in the TPF of the LS under high-Re condition. The effect of rotation on the TPF of the TS is minor within the channel at X/D ≤ 4, whereas rotation can increase the TPF of the TS by 0–10 % at larger X/D condition. The effect of r/D on heat transfer also be discussed. When Re = 5000, rotational radius ratio of 52.33 leads to a 8.6 % increase in the average Nu compared to the rotational radius ratio of 25.67. Similarly, when Re = 15,000, there is a 1.5 % enhancement observed. The droplet-shaped pin-fin are less affected by TR variations compared to circular pin-fin, and higher TR decreases the TPF of the channel. The study finally explored the impact of Buo on experimental accuracy and found that when Re and Buo are identical, there is an obvious difference in Nu, with a minimum variation of 34.6 %, during variations in Ro, r/D, and TR. To obtain accurate HTC, it is essential to maintain similar ranges for the dimensionless parameters including Re, Ro, r/D, TR, D. These findings enhance the overall comprehension of HTC and TPF within the internal cooling channel, providing valuable insights for optimization endeavors.