Summary Commercial photovoltaic (PV) solar panels convert the solar energy directly to electricity but their efficiency is low. The rest of the energy is mostly converted to heat. Although the conversion efficiency of PV panels is low, getting hot causes increase in the temperature of the PV cells which results in further dramatic decrease of their efficiency and the technical lifetime. In the present study, a PV panel with cooling system was made in which a polymer minichannel heat exchanger was fully integrated with the PV cells during the fabrication of the panel. Heat exchangers containing minichannels and microchannels have higher heat transfer capability than pipes and channels as they have a higher ratio of area to volume. Besides, since the heat exchanger is adhered to the solar cells during the panel fabrication, the thermal contact resistance drops to minimum. Circulated coolant dissipates the extracted heat from the panel to the ground by buried long life and low‐price plastic tubes. Since the earth temperature beyond a depth of 4 m is relatively constant, 10°C to 16°C, the earth acts as a cooling medium for free. The experimental results show that the cooling system is capable to dispose of 570 W heat from the PV panel in the ground. The daily electricity generation rises about 10%. The levelized cost of energy (LCOE) is minimum compared to the available PV panels with active cooling techniques in the literature.
The frictional brake system is the most safety critical equipment to decelerate or stop a vehicle. Thermal performance of the frictional region parts, disc and pads, necessitates to evaluate precisely in the design and test steps. In this study, a brake test setup was designed and fabricated with exactly the same braking components used in a common passenger vehicle as disc, pads, rim, tire, and dust shield to simulate the sequential braking. The local temperature on the disc and pads and the brake fluid pressure were measured. In addition, a three dimensional numerical model was designed to simulate the aerodynamics and thermal performance of the braking in detail. Finite element method was employed to simulate the frictional heat between the brake disc and the pads. The results showed that although the velocity of mainstream airflow reduces significantly into the rim, turbulent flow develops in the form of eddies of swirling airflow. Additionally, transient temperature distribution on the braking components was predicted. The cooling vanes in the brake disc have considerably enhanced the convection heat transfer. The amount of convective heat transfer on the inner radial vanes was more than 58% of the total amount of convective heat transfer.
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