## 1 Introduction
An increase in the surface-area-to-volume ratio increases the heat transfer surface area. However, the channels of the tortuous flow path relatively decrease with increasing surface-area-to-volume ratio, and thus, increase heat sink flow resistance. Therefore, determining an appropriate fluid flow channel, ventilation holes, and height for heat sinks is essential. The limited installation space of the LED lamp results in optimized dimensions and geometries of PTFHS and MFLHS heat sinks fabricated using AlSi10 Mg alloy are shown in Figure 1.  
Figure 1: The geometry designs for TTFHS (**a1**)–(**a3**), PTFHS (**b1**)–(**b3**), and MFLHS (**c1**)–(**c3**). The performance of impingement heat sink designs and the heat transfer capabilities of the designed heat sinks under jet impingement cooling with different Reynolds numbers was examined in this study. Heat sinks with larger surface areas for heat transfer and perforated heat sinks with ventilation holes were studied through simulations and experiments. In the experiments, the perforated-finned heat sinks (PTFHS), metal-foam-like heat sinks (MFLHS), and traditional finned heat sink (TTFHS) were individually mounted to a 10 W compact LED recessed downlight (CLRDL) at an ambient temperature of 25 \({}^{\circ}\)C. A cooling fan was installed on the top of each heat sink, and two cooling fans with higher and lower velocities of 6.13 and 2.71 m s\({}^{-1}\) were individually installed to perform air jet impingement cooling evaluations. This ensures that the CLRDL had a very low \(T_{\rm j}\), which satisfied the long lifetime requirement. The previous studies ([PERSON] and [PERSON] 2016; [PERSON] and [PERSON] 2018) [9; 10] have validated that the use of PTFHS, MFLHS, and TTFHS for cooling a CLRDL under natural convection complied with Energy Star lifetime requirements. High-power heat dissipation of LED lighting for state-of-the-art heat sinks is one of the foremost requirements in the recent emerging era. The high heat dissipation capability using fans enables superior cooling performance for the high-power LED module, in which high luminous flux indoor lighting or extremely high intensity light source for automated optical inspection equipment are requisites. Therefore, investigation of the SLM heat sink heat transfer performance when the additional fan is introduced should be conducted. Figure 2 illustrates the flowchart of the numerical simulations and experiments on designing the PTFHS, MFLHS, and TTFHS heat sinks under jet impingement cooling for (CLRDLs. Due to the created forced convection turbulence flow, increasing surface area through mixed cooling convection and the ensemble interactive effect between perforated holes of heat sinks should prevail and dominate the CLRDL market. These applications require extremely high light output in a limited space. In the following sections, we include the research procedure, numerical simulation, followed by experiments. Results demonstrate the advantages of heat transfer of the PTFHS and MFLHS SLM heat sinks over conventional TTFHS under air jet impingement cooling. Enhanced heat transfer techniques result in lower LED junction temperature and increase the CLRDL lifetime and reliability.