Date of Award

Fall 12-5-2024

Access Type

Thesis - Open Access

Degree Name

Master of Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

Mark Ricklick

First Committee Member

L.L. Narayanaswami

Second Committee Member

R.R. Mankbadi

College Dean

James W. Gregory

Abstract

Cylindrical arrays with a cross flow are commonly used for heat transfer augmentation within an internal channel. In most applications, the cylinders have a spacing of over 2 diameters (2D) between their center points in both the lateral and downstream directions. One option for battery thermal management in hybrid/electric aviation is to use cylindrical batteries packed in arrays with an applied cross flow. In the context of aviation, it is important to maximize space and weight savings. Tightly packing these cylinder arrays with a spacing of under 2D in both directions would save on both of these yet have not been specifically studied before. A variety of cases, ranging from Reynolds number of 1k to 30k and Prandtl numbers of 0.7 and 10, are computationally modeled to develop a relationship between changing spacings and their influence on the heat transfer on the cylinders. The used model consists of a crossflow through 10 staggered rows of 2/3 cylinders with a periodic boundary on either side of the flow direction to represent a much larger array. The cylinder geometry is based off of a lithium-ion 18650 battery. Results show that when looking at tightly packed spacings between between 2D and 1.25D and matching the defined Reynolds numbers, heat transfer effectiveness stays roughly the same until extremely tightly packed cases. Since the spacings get tighter and the flow area gets smaller, this means the amount of heat transfer per a given area increases, by 5-10 times that of a non-tightly packed spacing of 2.5D, thus there is a heat transfer benefit to packing the batteries tighter in addition to the weight and spacing savings. This trend peaks at a spacing of 1.25D or 1.5D before dropping off, a trend that is found to be slightly dependent of Reynolds number but independent of Prandtl number. Even with heat transfer remaining roughly constant as spacing decreases, pumping power required to move the fluid through the test section is found to also decrease with spacing, by over 10 times in some cases, for a set Reynolds number since flows speeds increase more drastically when a smaller spacing creates a smaller contraction thus lower inlet velocities are necessary.

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