Thermal characterization of spray impingement heat transfer over a High-Power LED module

Abstract

• Thermal management of single nozzle spray for a high-power LED module is explored. • Maximum experimental heat transfer coefficient ∼12 kW/m 2 K is obtained for Re of 12000. • LED substrate temperature is maintained well below safe limits for Re = 8000 and above. • Spatial and temporal thermal fields over the LED module is computationally estimated. • The experimental results are complemented with 3D numerical heat transfer simulations. The cooling demand for a nominal 300 W power LEDs is around 200 W/cm 2 at the chip-scale, and the junction temperature must be maintained below 120 °C for reliable operation. Special thermal management packaging is required to maintain LEDs below this reliability temperature limit. The present study investigates the thermal characteristics of single-nozzle spray cooling over a high-power LED module. The detailed thermal characterization within the LED assembly is explored using both, experimental and numerical approaches. The LED substrate temperature is experimentally obtained for various input power supplies, water flow rate, inlet water temperature, nozzle height, and offset from the LED center. Heat transfer coefficient at two radial locations ( R = 0 mm and 12.5 mm) is estimated to evaluate the heat removal capacity of the spray for these operating conditions. Numerical study is performed to visualize temperature and heat flux distribution within the LED module, and to investigate the appearance of thermally critical locations. Junction temperature is the critical parameter for thermal characterization of the LED module, and is numerically investigated for various operating conditions. The junction temperature is maintained below 95 °C at the nominal electrical input power for a Re ≥ 8,000 using the proposed spray cooling design. The present study establishes the efficacy of spray cooling for high-power LED modules, even when the supply power exceeds 112% of the nominal power range.