Transient Thermal Analysis of a Hybrid Energy Harvester

The seasonal nature of solar panels and windmills has been a major challenge towards realizing sustainable energy. Over the years, several attempts have been made to perfect a device capable of harnessing the energy of wind and rain, titled as triboelectric and piezoelectric nano generators. Although such technologies yield promising results, a superior energy device can be achieved by addition of solar cells to wind and rain energy harvesting devices. Hybrid Nano generators are expected to be the future of commercially sustainable energy generation which are used to simultaneously harvest wind, rain, and solar energy. Though a substantial amount of work has been done with regard to such energy harvesting modules, studies that test their environmental capabilities are limited. In this study, a hybridized power panel comprising of dual-mode triboelectric nano generator and a solar cell have been tested under majorly solar, majorly windy, majorly rainy, and normal tropical conditions. Average temperature attained by the panel in such conditions have been studied through a transient thermal analysis done using Ansys Fluent. The results obtained are used to calculate thermal strain in the panel for different cases. The proposed model is an innovative way to make use of energy.

Thermal Analysis of IC Engine

Calculating the heat transfer rate of the engine is very difficult due to the complex geometry design of the engine and the periodic flow of air and fuel during engine operation for full cycles. Various theories hypothesize that about 25% of the energy contained in the fuel is converted into useful work and the remaining 75% is released into the environment by the engine. The main objective of the present work is to improve the heat transfer rate of existing constructions of the engine cylinder block by modifying its construction and also with new materials. To this end, two CAD models were created using CATIA software, then a transient thermal analysis with ANSYS at ambient temperature for the summer season of 45oC for the real one and the proposed internal combustion engine design was performed one after the other. Other to optimize the geometric parameters and improve the heat transfer rate. From the results of the transient thermal analysis, it was found that the proposed engine cylinder block design has better performance and heat transfer rates than the actual engine cylinder block design.

Transient Thermal Analysis of a Magnetorheological Knee for Prostheses and Exoskeletons during Over-Ground Walking

Proper knee movement is essential for accomplishing the mobility daily tasks such as walking, get up from a chair and going up and down stairs. Although the technological advances in active knee actuators for prostheses and exoskeletons to help impaired people in the last decade, they still present several usage limitations such as overweight or limited mechanical power and torque. To address such limitations, we developed the Active Magnetorheological Knee (AMRK) that comprises a Motor Unit (MU), which is a motor-reducer (EC motor and Harmonic Drive) and a MR clutch, that works in parallel to a magnetorheological (MR) brake. Magnetorheological fluids, employed in the MR clutch and brake, are smart materials that have their rheological properties controlled by an induced magnetic field and have been used for different purposes. With this configuration the actuator can work as a motor, clutch or brake and can perform similar movements than a healthy knee. However, the stability, control, and life of magnetorheological fluids critically depend on the working temperature. By reaching a certain temperature limit, the fluid additives quickly deteriorate, leading to irreversible changes of the MR fluid. In this study, we perform a transient thermal analysis of the AMRK, when it is used for walking over-ground, to access possible fluid degradation and user’s discomfort due overheating. The resulting shear stress in the MR clutch and brake generates heat, increasing the fluid temperature during the operation. However, to avoid overheating, we proposed a mode of operation for over-ground walking aiming to minimize the heat generation on the MR clutch and brake. Other heat sources inside the actuator are the coils, which generate the magnetic fields for the MR fluid, bearings, EC motor and harmonic drive. Results show that the MR fluid of the brake can reach up to 31°C after a 6.0 km walk, so the AMRK can be used for the proposed function without risks of fluid degradation or discomfort for the user.