Characteristics of thermal plume from an array of rectangular straight fins with openings on the base in natural convection

Abstract

Straight rectangular fins with openings in the base surface in natural convection exhibit greater heat transfer than rectangular fins without openings in the base. In this paper, thermal plume arising from such fin configuration used as a heat sink for natural convection cooling of light-emitting diode (LED) grow lights is investigated using three-dimensional conjugate laminar flow simulations. Understanding of plume characteristics is crucial in optimizing the cooling performance as well as optimal placement of grow lights from ceilings and walls in proximity. A prototype LED grow light was designed and experimentally measured to assess the cooling performance, and numerical simulations were conducted to investigate the plume structure. The results showed that openings in the base enhanced vertical draft of air, mixing, and overall heat transfer rate. It was found that local pressure gradient is proportional to the degree of mixing of ambient air into the plume. Low pressure regions around the fins and channels showed upward convection of plume mass and a high pressure region below the fins indicated higher concentration of denser air mass. High pressure gradients were observed in the openings, which further justifies the significance of openings in improving mixing of ambient air with the plume to enhance heat transfer.