Experimental analysis of the effect of helical capillary tubes on cooling a cylindrical lithium battery

• Investigates an indirect liquid cooling approach using helical copper tubes • Revealed that flow rate is the most influential factor in thermal regulation • Increasing NOT raised pressure drop up to 72.73% for DOC=0.07, showing the strongest relative rise. • Each extra turn improved T-BT by about 0.34%, while DOC enlargements of 1.26 and 2.5 showed no effect. • Optimize system performance, a central composite design (CCD) was employed Efficient thermal management is critical for ensuring the safety, reliability, and performance of lithium-ion batteries (LIBs), particularly during high charge/discharge cycles. This study investigates an indirect liquid cooling approach using helical copper tubes (HCT) wrapped around a cylindrical 26650 LIB. The experimental setup examines the effects of parameters: diameter of the copper tubes (DOC), number of turns (NOT), and flow rate (FLR) on the battery temperature (T-BT). Analysis of the empirical data indicated that the T-BT enhancement was invariant with respect to the specific DOC enlargement factors of 1.26 and 2.5 when the NOT was held constant. At a fixed flow rate, increasing the number of turns consistently reduced the average T–BT for all DOC values, with temperature drops reaching about 4–5% across pitches, showing similar relative reductions for DOCs of 0.028, 0.036, and 0.07. Conversely, for a fixed DOC, a linear relationship is observed where each supplementary coil turn contribute a mean T-BT’s heat transfer (HTR) improvement of 0.34%. Upon further investigation, a higher FLR further decreases T-BT but results in a higher pressure drop. Flow rate proved to be the dominant factor in thermal performance, with tube pitch having a secondary effect, as shown by the CCD analysis. At a constant flow rate, increasing the number of turns led to higher pressure drops for all three DOC values, with increases of up to 13.43% and 16.95% for DOCs of 0.028 and 0.036, respectively, while the larger DOC of 0.07 exhibited the highest relative increase, reaching 72.73%.