Investigating condensation heat transfer and flow pattern of R1233zd(E) in hyper-, micro- and normal gravity conditions

The increasing duration and complexity of space missions for extra-terrestrial exploration have raised the need for developing more reliable and efficient thermal control systems (TCS). In fact, TCS are aimed at supporting life in shuttles and planetary bases and ensuring the proper operation of instrumentation for experiments. Consequently, their study is of high interest, particularly as TCS are required to reduce their weight and volume. This latter requirement has led to the introduction of two-phase heat transfer systems in place of traditional single-phase ones. As a result, two-phase heat transfer processes need to be thoroughly studied under reduced gravity conditions to ensure the adequate design of thermal control systems for space applications.

In this work, the condensation heat transfer of R1233zd(E) was studied during the 84^th ESA Parabolic Flight Campaign using a 3.38 mm inner diameter channel. Experiments were conducted under hyper-, micro- and normal gravity conditions at saturation temperature equal to 40 °C and mass fluxes equal to 30 kg m⁻² s⁻¹ and 40 kg m⁻² s⁻¹. The results reveal a significant reduction in heat transfer coefficients under microgravity conditions, with annular flow patterns being predominantly observed. Notably, this study presents experimental condensation data under hyper-gravity conditions for the first time. Comparisons with HFE-7000 data (tested during a previous Parabolic Flight Campaign) and evaluations against existing correlations are presented, highlighting the need for accurate predictive models for condensation heat transfer in microgravity and hyper-gravity.