A novel particle-to-fluid direct-contact counter-flow heat exchanger for CSP power generation applications: Design features and experimental testing

A novel particle-to-fluid direct-contact counter-flow heat exchanger (PFDCHX) is introduced and investigated. The proposed heat exchanger offers efficient integration with an air-breathing power cycle. A proposed particle-based power tower integrated system using the PFDCHX is presented. The PFDCHX system comprises two main parts: the particle handling unit (PHU) and the direct-contact heat exchanger (DCHX). The PHU delivers solid particles to the pressurized DCHX, a manifold assembly was deployed to separate particles into several separate streams to be injected at the upper end of the DCHX via several distributor pipes. Several enhancement features were considered to prevent particle carryover, including a tangential inlet for the pressurized air (at the bottom end of the DCHX), particle–air disengagement zone (at the top end of the DCHX), and a tapered-shaped heat exchange chamber. Results showed that, for tests with excessive particle flow rate, more than 80% of the temperature rise was achieved within 0.35 m above the air inlet, attributed to the tangential inlet’s swirl flow pattern. The overall temperature rise along the heat exchanger was not significantly influenced by a change in operating air pressure from one barg to three barg.