Development of advanced high porosity wicks for the high temperature heat pipes of concentrating solar power

Abstract

Sandia National Laboratories and Heat Pipes Laboratory of National Technical University of Ukraine «KPI» developed several methods of improving robustness of the high-temperature heat pipe wick for their application to concentrating solar power (CSP) systems with stirling engine. In this case the wick structures must retain high heat pipe performance with robustness for long term operation. Recent modeling indicates that wicks based on various fiber combinations could provide the robustness combined with sufficient performance. Results of the development, characterization, modeling, and testing of an advanced felt metal wicks that addresses durability issues while maintaining sufficient performance are showed in the paper. The project resulted in an ongoing durability bench-scale heat pipe that simulates wick load conditions required for an 80kWth throughput solar receiver, including periodic non-destructive evaluation of the wick durability. Two mock-ups of high-temperature heat pipes were made for long life and performance tests: the first sample with wick based on 12 μm felt; and second with hybrid wick based on 30 μm felt and 6.5 μm felt. Second heat pipe operation has continued unattended at 775°C vapor temperature for nearly 11,700 hours, with no observable loss of performance or change in startup characteristics.