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The liquid droplet radiator (LDR) as a frameless heat removal system is considered as a promising solution for the waste heat dissipation of megawatt aerospace applications. The radiation heat transfer and evaporation characteristics of the LDR working fluid are tightly coupled with the operational performance of the liquid droplet generator. In this paper, the effects of operational parameters of droplet generator on the radiative heat transfer and evaporation loss rate are clarified, including the pressure disturbance frequency, pressure difference between the inside and outside of the droplet generator. It is observed that higher coolant mass flow rate does not assure higher heat transfer power for the LDR. For cases with higher pressure difference, where the coolant flow rate is higher consequently, the evaporation loss rate increases continually with pressure difference while the heat transfer power does not increase any more. The disturbance frequency has inconspicuous impact on the evaporation characteristics. Besides, cases with higher pressure differences have wider suitable frequency ranges according to the droplet formation restriction. Generally, a relatively higher pressure difference coupled with a higher disturbance frequency (such as 0.3 MPa and 12 kHz) is suggested to achieve a higher heat transfer power and low evaporation loss rate. This paper may provide favorable reference for determining the operational parameters of the droplet generator in consideration of radiation heat transfer and evaporation characteristics. [ABSTRACT FROM AUTHOR]

Liquid droplet radiator is promised to be used for waste heat dissipation of the large power space nuclear reactor. This paper analyzes the radiative heat transfer and evaporative characteristics by treating the droplet layer as a participating medium. The silicon oil is adopted as the working fluid. The mathematical models are established. The effects of the optical thickness κ D , initial temperature, and flight time on the droplet radiation and evaporation are investigated. The main works are listed as follows: Firstly, the grid independence analysis of the temperature calculation is conducted, and the grid number on the thickness direction is suggested to be 100 times of κ D. Secondly, the calculation results obtained from the one dimensional (1-D) simplified formula and the two dimensional (2-D) simulation have been compared, proving that it is acceptable to obtain the average temperature by 1-D simulation for droplet layers with any κ D. Thirdly, detailed temperature distribution is calculated for both thin and thick droplet layers, and higher initial temperature and longer flight time can enhance the radiative heat transfer. Finally, the evaporative loss rate of the working fluid is found to be nearly constant with κ D larger than 4. This paper may contribute to the thermal design and optimization of the liquid droplet radiator for space applications. [ABSTRACT FROM AUTHOR]