Efficient cooling of high-temperature synthesis gas produced in underground coal gasification (UCG) systems is critical for ensuring safe gas transportation and improving the overall efficiency of downstream energy conversion processes. Previous computational investigations have demonstrated that membrane helical coil heat exchangers can significantly enhance heat transfer performance compared with conventional serpentine tube configurations due to curvature induced secondary flow structures.

The present study focuses on the experimental validation and multi objective optimization of a membrane helical coil heat exchanger designed for high-pressure syngas cooling applications. A laboratory scale experimental test rig was developed to investigate the thermo-hydraulic behavior of the heat exchanger under simulated syngas flow conditions. Experimental measurements of temperature distribution, heat transfer coefficient, and pressure drop were obtained over a range of Reynolds numbers between 10,000 and 40,000.

The experimental results were compared with previously obtained computational fluid dynamics (CFD) predictions to validate the numerical model. Good agreement between experimental and numerical results was observed, with deviations within ±6%. In addition, a multi objective optimization approach based on response surface methodology was employed to determine the optimal geometric and operating parameters that maximize heat transfer performance while minimizing pressure losses.

The results indicate that coil pitch, tube diameter, and Reynolds number significantly influence the overall thermal performance factor of the heat exchanger. The optimized configuration achieved a heat transfer enhancement of approximately 30% compared with conventional straight tube designs while maintaining acceptable pressure drop levels.

The findings of this study provide valuable insights for the design and practical implementation of advanced heat exchanger systems in underground coal gasification and other high temperature energy conversion processes.