Simulation and experimental design of thermoacoustic heat engine

Abstract

Renewable energy is an important field in providing reliable and sustainable energy to the world. Wasted heat is found to be a good source of renewable energy. This wasted energy can be found almost in all types of production processes, including the heat exchanger. The heat energy dissipated from these processes is unutilized leading to inefficiency in the system. The need to harvest the wasted heat is essential in making sure the energy can be further utilized for other applications. Previous research works conducted on harvesting heat into sound in the system is still lacking and there is no specific standard can be employed. This research focused on analysing and developing a reference method of harvesting sound from a thermoacoustic heat engine system. A simulation approach was employed to investigate the performance of heat flow on the heat exchanger and related components. A standard test rig was designed to evaluate the performance of heat transfer experimentally. A comprehensive laboratory work was set-up to collect ample data to obtain the correlation of acoustic sound pressure-volume due to heat transfer performance by the oscillatory flow on the thermoacoustic system. The design of the developed thermoacoustic engine was able to produce waste heat in the range between 200°C and 700°C, and the harvested sound frequency ranged from 20Hz to 2kHz. From the experimental study, the sound level started at 4s to 8s and reaches a steady-state at 10s. The temperature gradient on stack performance was 8.45°C/mm with a temperature difference at the steady-state point of 300°C. The spectrum analysis amplitude reached 133.5dB with the frequency value of 397.5 Hz. The pressure volume analysis has proved the existence of both isochoric and isothermal process through the gas bucket brigade phenomenon as the lead compression and expansion happened at the stack wall between the sound pressures of 12.94Pa and 20.15Pa. The finding confirmed that the sound energy from the heat oscillation can be harvested and a standard method has been developed. This study also confirmed the presence of a thermoacoustic cycle on the stack wall. This finding is significant as it provides a new standard in harvesting sound from the thermoacoustic heat engine. The efficiency of the system was successfully improved by 40% and the wasted energy was successfully harvested for further applications.