Fifty heat flux sensors made of nickel foil are mounted on the walls of the expansion space of a Stirling engine. Only one of the heat flux sensors is heated by CTA. In this measurement, the rotational speed and the width of an annular slit through which the working gas enter the expansion space are changed. For slit widths 0.65mm or wider, the heat flux is small and changed little with phase. When the slit is narrow and the rotational speed is high, there is a significant enhancement of heat transfer in the phases between the transfer process from the compression space and the expansion process. The averaged heat flux for phases between 120° and 180° (the phase origin corresponds to the top dead center of the displacer) and for all sensors simply shows that the heat flux increases rapidly with increasing rotational speed. Comparing the experimental and theoretical heat flux values during the expansion process, the engine working at atmospheric pressure on average and 8Hz can generally transfer the required heat.

A heat and power supply system is constructed by connecting a 1kW class Stirling engine generator and a wood-fired boiler. First, a performance evaluation test of the wood boiler was conducted to determine the amount of wood input. It was found that combustion gas temperature required to drive the Stirling engine generator was more than 600°C, and that 19 kg of firewood per hour was needed to meet this requirement. Based on this result, a power supply system test was conducted, but no power output could be obtained. Therefore, the chimney was installed in an L-shaped position on the back of the wood boiler to improve the combustion gas flow. The improved wood boiler was tested again, so that the power output of 151 W and the heat output of 36.5 kW were obtained, and the energy utilization efficiency of this system was approximately 60%.

In recent years, global warming and the depletion of fossil fuels have become more serious, and the efficient use of available energy sources has become an issue. In addition, in the domestic energy supply process, the majority of primary energy is not effectively utilized and is discarded as waste heat (unused heat). Therefore, to realize a sustainable society, it is essential to develop technologies to effectively utilize these waste heats and implement them in society. Therefore, waste heat recovery systems are attracting attention. In this study, a flash steam engine waste heat recovery system using flash steam and heat transfer from the wall surface was proposed as a new waste heat recovery system. This report describes the results of visualization and heat flux measurements of flash spraying of a low-temperature boiling working fluid and discussion of the results as a first step in the development of a flash steam engine for waste heat recovery from a low-temperature heat source.

A recent experimental study has demonstrated the looped tube acoustic engine's operation when connected to a piston-crank-flywheel assembly. The key parameter is the real part of the input acoustic impedance of the loop. In this study, we investigated the acoustic impedance using the equivalent circuit model and discussed the modification of the geometrical parameters of the loop to increase the thermoacoustic energy conversion efficiency and output power. The results are confirmed by a numerical simulation based on the thermoacoustic theory.

Conventional heat exchangers for thermoacoustic engines have limited heat transfer area and may not utilize heat effectively. A self-circulating heat exchanger proposed by Backhaus and Swift is a looped tube that connects a heat source and a high-temperature heat exchanger, a steady flow is generated in the looped tube due to a thermoacoustic spontaneous acoustic oscillation taking place in a thermoacoustic engine and heat is transported from the heat source to the high-temperature heat exchanger by the steady flow. The purpose of this study is to confirm the heat transport by the acoustically generated steady flow. A standing-wave thermoacoustic engine was constructed with a looped tube connected to the high-temperature side heat exchanger. The relationship between the ratio of the lengths of the thermoacoustic engine and the loop tube and the pressure amplitude was measured. The pressure amplitude became zero when the length of the loop tube was about one times the length of the thermoacoustic engine. Furthermore, the streaming flow was confirmed indirectly by measuring the temperature inside the loop tube. The temperature field of the loop tube implied to the generation of the acoustically generated steady flow.