Investigation of effect of heat exchanger size on power output in low-temperature difference Stirling engines

David Nobes,Linda Hasanovich

doi:10.1051/e3sconf/202131303002

Abstract

The Stirling engine is capable of converting any source of thermal energy into kinetic energy, which makes it an attractive option for utilizing low-temperature sources such as geothermal or waste heat below 100 °C. However, at these low temperatures, the effects of losses are proportionally higher due to the lower thermal potential available. One such significant loss is excess dead volume, wherein a significant contributor is the heat exchangers. The heat exchangers must be selected to optimize power output by minimizing the dead volume loss while maximizing the heat transfer to and from the engine. To better understand what the optimal geometry of the heat exchanger components is, a Stirling engine is modelled using a third-order commercial modelling software (Sage) and trends of engine properties of power, temperature, and pressure for different heat exchanger geometries are observed. The results indicate that there is an optimum heat exchanger volume and geometry for low temperature Stirling engines. This optimum is also affected by other engine properties, such as regenerator size and engine speed. These results provide insight into the optimal geometry of these components for low-temperature Stirling engines, as well as providing design guidance for future engines to be built.

Highlights

IntroductionNamely those below 100 °C, are a possible energy source for generating electricity that could lower carbon emissions
Low temperature heat sources, namely those below 100 °C, are a possible energy source for generating electricity that could lower carbon emissions
From the investigation of a low-temperature Stirling engine using a 3rd order model it was determined that an optimum heat exchanger size and geometry exists which balances good heat transfer with dead volume penalties

Summary

Introduction

Namely those below 100 °C, are a possible energy source for generating electricity that could lower carbon emissions. One possible technology solution is the Stirling engine as these have been proven to run at temperature differences as low as 0.5 °C and source temperatures below 100 °C [3] For these low temperature Stirling engines there are proportionally higher losses present than in a high temperature Stirling engine due to the lower thermal potential available, and less energy available to overcome losses. This presents the need to optimize the heat exchanger volume to maximize the heat transfer into and out of the engine while minimizing the associated losses due to the heat exchanger dead volume Determining this optimum size is of particular importance for low temperature Stirling engines due to the low thermal potential available

Methods

Results

Conclusion