A method for evaluating the heat rejection efficiency in a Lunar power plant consisting of a free-piston Stirling engine (FPSE)

Sergey Smirnov,Mikhail Sinkevich,Hassan Khalife,Yuri Antipov

doi:10.1051/e3sconf/202131307001

Abstract

A method for evaluating the heat rejection efficiency in a Lunar power plant consisting of a free-piston Stirling engine FPSE is proposed. The waste heat from the FPSE is absorbed by the refrigerant circulating in a closed pumped loop and then rejected through a radiator into space. The magnitude of the heat flux rejected through the radiator is determined by the temperature difference between the radiator fins and surrounding environment, as well as the surface areas of the radiator and the emissivity coefficient. The method developed is used to qualitatively evaluate the refrigerant efficiency based on calculating the average temperature of the radiator fin which is established during the heat exchange process in the radiator. The method allowed us to determine the most efficient refrigerant in terms of maximum heat rejection at a given operating temperature range without the need of detailed calculations like in the previous works of the authors. Computational studies in a two-dimensional formulation of the radiator, using helium or liquid ammonia as a refrigerant, to determine the quantitative characteristics of the heat rejection process and overall dimensions of the radiator were performed, and a comparative analysis of the results is presented.

Highlights

Humans are closer than ever from building outposts on the surface of the Moon
The FPSE model considered in this work, is the same on considered in our previous work, and is one of the models that NASA is planning to use in their KRUSTY project.[9]
Differences in the calculation results using the developed method in this work and the more detailed method developed in our previous work were 7.2 - 17.8% for liquid ammonia, and 3.9 - 8.2% for helium

Summary

Introduction

The future habitants of the moon will require power generation systems to fulfill their energy needs and support their activities, such as scientific experimentation, in situ mining and processing, astronomical observation, and surface exploration. Power generation systems will be located in vacuum, and since waste heat rejection is considered a vital aspect of their nominal operation and convection is not possible for heat rejection, the only mechanism of rejecting heat in space is through radiation. The power generation system considered in this paper is the free-piston Stirling engine FPSE, which has proven its effectiveness in space conditions, and is planned to be used in future space exploration missions.[2] One of the important aspects for the efficient and reliable operation of the FPSE, is maintaining the minimum temperature of the working gas in the engine at a given level. Designing a highly efficient heat rejection system and investigating capabilities of the FPSE heat rejection system are crucial for the nominal performance and maximum efficiency of the power generation system.[3]

Objectives

Results

Conclusion