Synergetic Effect between Lighting Efficiency Enhancement and Building Energy Reduction Using Alternative Thermal Operating System of Indoor LED Lighting

Selective Laser Melting Heat Sinks under Jet Impingement Cooling for Heat Dissipation of Higher Light Output LED Lighting in a Limited Space

In this study, we aimed to create heat sinks with higher heat dissipation capabilities for a compact light-emitting diode (LED) recessed downlight (CLRDL) under jet impingement cooling. We desired to use the sinks in limited space to maintain lower junction temperature and allow higher LED power. Perforated-finned heat sinks (PTFHSs) and metal-foam-like heat sinks (MFLHSs) fabricated using selective laser melting (SLM) were compared with a traditional finned heat sink (TTFHS). Two cooling fans with higher and lower velocity at Reynolds numbers of 16916 and 6594 were individually installed on each heat sink. Numerical simulations were performed using COMSOL rotating machinery and nonisothermal flow interface with the standard k-ε turbulence flow model. Validations were performed on this apparatus. The SLM heat sinks exhibited higher Nusselt numbers and lower thermal resistance than traditional heat sinks because of a relatively higher heat transfer coefficient and larger heat transfer area. For the proposed SLM heat sinks with larger surface areas, complex flow channels, and ventilation holes under jet impingement cooling, the PTFHS exhibited the highest heat transfer enhancement followed by MFLHS and TTFHS. The results contribute to solving the problems of heat dissipation of higher light output LED lighting.

Research on Luminance Distributions of Chip-On-Board Light-Emitting Diodes

Chip-On-Board Light-Emitting Diodes (COB LED) are increasingly more common. Their development in recent years has directly contributed to increasing the power of LED sources, whilst simultaneously increasing the luminous flux from the entire COB. Consequently, it has led to new developments in some applications. Information regarding the size of the light source luminous surface and luminance distribution on its surface is critical for a designer whilst designing optical systems. The purpose of this conducted research was to establish to what extent luminance distribution is even on the examined COB LEDs. In order to verify luminance distributions on an LED surface, direct measurements with a matrix luminance measuring device were made. As a result of the research, it has been observed that luminance distribution is not even, and in many cases luminance maximum does not fall in the geometric center of the luminous surface, which was initially expected. So, it has been concluded that while designing optical systems for COB LEDs, irregular luminance distribution on their surface needs to be considered.

Thermal Analysis of the Factors Influencing Junction Temperature of LED Panel Sources

Limiting junction temperature Tj and maintaining its low value is crucial for the lifetime and reliability of semi-conductive light sources. Obtaining the lowest possible temperature of Tj is especially important in the case of LED panels, where in a short distance there are many light sources installed, between which there occurs mutual thermal coupling. The article presents results of simulation studies connected with the influence of construction and ambient factors that influence the value of junction temperature of exemplary LED panel sources. The influence of radiator’s construction, printed circuit boards, as well as the influence of ambient factors, such as ambient temperature Ta and air flow velocity v were subjected to the analysis. Numerical calculations were done in the FloEFD software of the Mentor Graphics company, which is based on computational fluid dynamics (CFD). For construction of the LED thermal panel model the optical efficiency ηo and real thermal resistance Rthj-c were determined in a laboratory for the applied light sources.

Energy Consumption Optimization Measures for Buildings in the Midwest Regions of USA

This paper investigates various building material effects on the cooling load requirements of a typical two-floor house located in the Midwest region in the USA. A survey was done for various building materials along with their prices in the US market. Various building walls, lighting, window glazing, and insulations were used for simulation as single and combined cases. The return on investment from savings in the electrical load consumption against the materials cost was investigated. It was found that the best single case savings and investments were for cases when lights were changed from incandescent lighting with 20 W/m2 to fluorescent bulbs, or when using double skinned walls with 5 cm rock wool or expanded polystyrene insulation. Combined cases, combining more than one single change, offered more reductions in cooling loads but were associated with higher initial costs and, thus, longer returns on investment. The best case recommendation was for buildings with a 20 cm hollow concrete block (HCB) when combined with fluorescent lights and double pane heat-absorbing glazing for windows. Although these recommendations were for a typical house in the Midwest region of the United States, a similar analysis could be adopted by designers and building owners to optimize the energy consumption in their buildings. The final design decision should be based on an optimum correlation of the air-conditioning units’ size and cost, running and maintenance costs, the return on the investment duration, and the available usage area in the building.