## 1 Introduction  
In recent years, light emitting diode (LED) technology has undergone rapid growth. LED technology has become standard for both residential and commercial lighting because of its well-knownadvantages, such as long lifetime, energy saving, ecologically friendly, durable quality, design flexibility, and more controllable, instant lighting, low voltage, high luminous efficacy, high color rendering, operational in cold or hot temperatures. LED downlights are commonly used for indoor lighting. Compact LED recessed downlights (CLRDLs) provide visual comfort and efficiency, as well as being economical and eco-friendly. The shallow recess depth enables them to be used where ceiling space is limited. Insufficient heat dissipation caused by poor ventilation, high ambient temperatures, and the thermal resistance (\(R_{\text{th}}\)) resulting from the long distance from LED junctions to the outside atmosphere prompted this research [1]. Cooling is crucial [2] to ensure LED lighting lifetime and performance. Maintaining a lower LED junction temperature (\(T_{\text{j}}\)) tends to increase light output and slow LED lumen depreciation, ensuring reliability. Junction temperature is used to evaluate LED lighting quality and lifetime expectancy. The US EPA Energy Star(r) Manufacturer's Guide requires an L70 of 25,000 h for indoor lighting fixtures. L70 is defined as 70% of the initial lumen output. Thermal resistance, which is the reciprocal of thermal conductance, describes a material's resistance to heat flow and is measured in degrees Celsius per watt (equivalent to Kelvins per watt). Heat sinks are typically used for cooling electronic devices. Two types of high-performance heat sinks, namely the aluminum finned heat sink (ALFHS) and copper foam heat sink (CUFHS), were used in this study. To determine the appropriate height of the heat sinks, the ALFHS and CUFHS were individually mounted in a CLRDL aluminum housing before and after installation (INST) for simulation and testing. Computational fluid dynamics (CFD) simulation facilitates the optimal design of heat sinks [3; 4]. Regarding cost reduction, a trapezoidal fin profile is considered to be a favorable choice for replacement of the traditional rectangular fin [5]. Traditional trapezoidal fins are widely used for cooling electronic devices, and exhibit the lowest thermal resistance and maximum heat transfer coefficient [6]. Metal foam is already used in LED systems because highly porous materials have physical and mechanical advantages regarding buoyancy driven flow [7; 8]. According to [PERSON]'s law of cooling, the heat transfer rate can be enhanced by either increasing the heat transfer coefficient or the heat transfer area under a specific temperature difference [9]. Fins are used to increase the surface-to-volume ratio of contemporary heat sinks. These fin shapes can be quite complex. A promising material that can be used for three-dimensional surface extensions is a highly porous open-cell metal foam. Open-cell metal foam is a porous medium that has a very high volumetric porosity [10]. CUFHSs achieve heat transfer through their large surface-area-to-volume ratio, tortuous flow path, low specific weight, and relatively high thermal conductivity [11; 12]. The thermal performance of CUFHSs is 35%-40% higher than that of conventional aluminum metal heat sinks under a conventional comparison approach [13]. Compared with the ALFHSs, the area for heat dissipation in CUFHSs is enlarged. The parameters for heat sink design, such as the fluid flow resistance and surface-to-volume ratio, should be considered. In certain cases, some parameters may be interactive. Heuristically, enlarging heat dissipation surfaces can reduce the dissipation capability. Nevertheless, the fluid flow resistance may be affected by the total volume being limited, producing an ineffective heat escape pathway for the heat sink that results in increased heat localization.