Distributed Optical Measurement System for Plate Fin Heat Exchanger

Area of Science:

• Thermodynamics and Heat Transfer
• Optical Engineering
• Fluid Mechanics

Background:

• Plate-fin heat exchangers (PFHEs) present challenges in obtaining flow information due to their metallic structure and complex internal conditions.
• Accurate measurement of flow characteristics and boiling intensity is crucial for optimizing PFHE performance and efficiency.
• Existing methods are often limited by the physical constraints and intricate flow dynamics within PFHEs.

Purpose of the Study:

• To develop and validate a novel distributed optical measurement system for acquiring flow information and quantifying boiling intensity in PFHEs.
• To investigate the boiling behavior and identify distinct developmental stages within PFHEs under varying heating fluxes.
• To overcome the limitations of conventional measurement techniques in complex heat exchanger environments.

Main Methods:

• A distributed optical measurement system was designed, incorporating numerous optical fibers installed on the PFHE surface.
• Optical signals detected by the fibers were analyzed for attenuation and fluctuation patterns.
• These signal variations were correlated with gas-liquid interface dynamics to estimate boiling intensity.
• Experimental flow boiling tests were conducted in a PFHE under diverse heating flux conditions.

Main Results:

• The developed optical measurement system successfully acquired flow condition data within the PFHE.
• Experimental results demonstrated the system's capability to monitor variations in gas-liquid interfaces.
• Boiling intensity was effectively estimated by analyzing optical signal attenuation and fluctuation.
• Four distinct stages of boiling development were identified with increasing heating flux: unboiling, initiation, developing, and fully developed.

Conclusions:

• The novel distributed optical measurement system offers a viable solution for non-intrusive monitoring of flow and boiling in PFHEs.
• The system provides valuable insights into the complex thermal-hydraulic phenomena occurring within PFHEs.
• The identification of four boiling stages offers a framework for understanding and controlling boiling processes in PFHE applications.
• This technology enhances the ability to analyze and optimize heat transfer in plate-fin heat exchanger systems.