Steam condensation in packed beds - An experimental study

The performance of passive safety systems, in particular, passive heat removal systems is critical for advancing safe nuclear energy in the world. The upcoming light water reactors in design or deployment stage have passive heat removal systems, and steady steam condensation is one of the critical technical requirements to ensure that in most of the designs. A new design of packed bed steam condenser is proposed to ensure steady state heat condensation process for passive heat removal. In order to examine the basic physics associated with this design, the condensation on a randomly packed bed of spherical alumina particles was experimentally studied. This experimental setup ensures controlled condensation process without introducing significant changes in the thermal state or material characteristics of heat sink. The additional benefit of this experimental data would be to validate thermal-hydraulic codes. This data will have reduced spatial inhomogeneities as compared to steam condensation on walls and tubes, thus uncertainties will be reduced. Steam fronts at different flow rates were introduced in a cylindrical packed bed and thermal response of the media was observed. The temperature profile in the bed was monitored using a multi-point thermocouple assembly. Simultaneously, the wall temperature of the bed was measured with an infra-red camera. The obtained high-resolution temperature data was used to create polynomial- regression based supervised learning models for predicting the wall surface temperatures at unknown locations in different experiments. This process helped to understand and model thermal resistance from the packed bed to the container walls. The governing heat transfer modes in the media are completely dependent upon the rate of steam injection into the system. A distinct differentiation between the effects of heat conduction and advection in the bed were observed with slower steam injection rates.