Co-current loop thermosyphon with active working fluid management: Application for water recovery in flue gas

This study presents the design and simulation of an active-controlled film closed-loop thermosyphon that uses co-current circulation of working fluids. The liquid and vapor flows in traditional thermosyphons counter-current, which gives rise to several operating limits that restrain the maximum heat flow through the device. In these devices the liquid return is also done exclusively by gravity. In this article, the design and modeling of a co-current thermosyphon with active fluid management is presented. The evaporator and condenser are separated, and both liquid and vapor flow downward together in each section. A small pump is used to return the working fluid from the bottom of the condenser to the top of the evaporator. In addition, the evaporator temperature can be monitored to provide the optimal working fluid flow rate for optimal performance, allowing the device to perform optimally across different heat load requirements. In this work, a model is built based on correlations and models from the literature. Such an approach provides significantly improved overall heat transfer, but at the expense of additional cost and complexity. It is best suited for large, high heat transfer applications, such as condensing water from flue gas in commercial power plants.