THERMAL SIMULATION OF POWER LED DIODE IN COMSOL ENVIRONMENT
The aim of this paper is to build a dynamic thermal model of power LED for simulation environment COMSOL. The dynamic thermal model was based on technical and application manufacturer's data of power light emitting diode. In this way the assembled electrical and thermal model of power LED was simulated in a dynamic process of load within Comsol simulation program. The simulation results have been subjected to verification in the real environment. Measurements of the real LED showed good agreement with the simulation results. 1 Principle of power LED Technical solutions of advanced power LEDs make them suitable for their widespread use in lighting techniques. The reason is their high efficiency of conversion of electrical energy to optical as well as their long life. Despite these positive properties, power LEDs have quite large electrical losses that are transformed into heat. It is necessary to take thermal energy of electrical losses from the LED chip into the environment through effective heat sink. The contribution offers an opportunity to obtain the basic information about a thermal field of specific power LED HUEY JANN ELECTRONIC HPB8C49KYWHB [8] simulated in the COMSOL Multiphysics program [1]. Fig. 1 shows a construction of a power LED (right) and the same diode with the addition of sink (left). Power dissipation heats the LED chip and the diode housing. It is needed to dissipate a heat outside the LED chip so as not to damage components (maximum junction temperature Tj must not exceed 150 ° C). LED power dissipation is related to the specific output of LED, which has a value of 125 Lm / W at an ambient temperature Ta = 25 ° C. 2 Heat dissipation Power dissipation, which is released into the environment in the form of thermal energy, occurs in a volume of semiconductor device by the action of flowing current. It is primarily the loss in a permeable state (voltage drop at the part and forward current). For the power LED, it is necessary to set the dissipation. The common formula is used to calculate active power in integral form [4]:     0 1 t P v t i t dt T    (1) where v(t), i (t) are the instantaneous values of relevant electrical quantities, and T is their period. The product of v(t). i(t) represents the so-called instantaneous power, which is an important indicator of
Optimization procedure for selection of active components of DC-DC converter's thermal simulation model
The power electronic system which contains printed circuit board is comprised from set of passive and active components. Active electronic components are represented as source of thermal energy which arises from power loss of given device. By capturing the surface's temperature of whole electronic system through thermo vision measurement, and by consequent picture analysis of thermo frames, it is possible to identify active components. The aim of this article is development of methodology for optimal selection of mentioned active components for thermal simulation model of given electronic system. The main reason of component minimization is optimization of model's thermal analysis. That means, the computation of thermal field of investigated system may be accelerated due to lower interactions between active and non active components, whereby pre-defined accuracy of heat transfer shall be achieved.
Techno-economic analysis of solar thermal power plants using liquid sodium as heat transfer fluid
Abstract Solar thermal power plants with central receiver and thermal storage are expected to be one key technology in future electricity generation, because they are renewable and due to the thermal storage independent of the current solar radiation. State-of-the-art solar power plants often use molten nitrate salts as heat transfer fluid. The use of liquid sodium instead leads to lower electricity generation costs. Sodium has a high thermal conductivity and thus large heat transfer rates are possible. Hence, a smaller absorber surface is sufficient for the same thermal power. As a result, the sodium receiver achieves a higher efficiency at lower investment cost. Additionally, the aiming strategy, which reduces the peak heat flux on molten salt receivers isn’t necessary for sodium. Even at high heat flux densities, the absorber tubes will be cooled sufficiently due to the high heat transfer coefficients. Therefore, the sodium receiver in this analysis is designed for one single aim point, resulting in a heat flux density of q mean = 1.06 MW / m 2 and q peak = 2.99 MW / m 2 . The state-of-the-art system with molten salt considers q mean = 0.51 MW / m 2 and q peak = 1.0 MW / m 2 . The presented techno-economic analysis of two sodium based concepts compared to a reference system with molten salt results in up to 16% lower electricity generation costs.