Session: 12-16-01: Decarbonization and Renewable Energy

Paper Number: 165521

Optimizing Heat Transfer in a Modular Concentric Tube Heat Exchanger for Renewable Energy Applications 

This study presents the design, optimization, and theoretical evaluation of a modular concentric tube heat exchanger for renewable energy applications. Unlike conventional research that often focuses on fixed-geometry designs, this work investigates how modifications to the inner copper tube influence heat transfer. Three configurations are proposed: (1) a baseline system with smooth copper tubing, (2) a moderately turbulent design incorporating soldered fins angled at 45 degrees to disrupt the boundary layer, and (3) a fully turbulent system that integrates external fins with an internally brazed 3/8-inch helical spring running the entire length of the inner copper pipe to enhance convective mixing.

 

The system will be integrated into a facility which aims to capture and store thermal energy in liquid water using the three different modes of heat transfer for heating. Upon transport, the heated water will flow through a ½-inch type M copper inner pipe, transferring thermal energy to counterflowing air within an annular air gap formed by a 1-inch type L copper outer pipe. The pipe is further enclosed within a secondary air gap and surrounded by a 2-inch PVC outer shell. Additionally, to minimize heat loss, the outer air gap is completely sealed with spray foam insulation, maximizing thermal retention before a final outer layer of foam insulation tubing is attached to the PVC. A major innovation of this design is using copper caps sealed with hot glue to separate the inner and outer copper pipes while maintaining uniform spacing and allowing for modular adaptability when altering the geometric configurations. The 1-inch copper was selected instead of PVC due to its superior thermal conductivity, which ensures even heat distribution and prevention of localized hot or cold spots. Furthermore, a 30-degree angled air inlet was included to enhance velocity distribution, minimize stagnation zones, and improve convective efficiency by directing airflow along the exchanger’s length to optimize heat transfer.

 

Forced convection systems often struggle with uneven heat transfer due to poor flow distribution. This design addresses that issue by improving flow uniformity and reducing thermal inefficiencies. The total length of the heat exchanger is approximately 5 feet due to spatial constraints within the room where it will be installed. The study is grounded in heat transfer principles, evaluating parameters such as the Reynolds number, Nusselt number, heat exchanger effectiveness, and heat transfer rates. The modular design has made the system more scalable and adaptable for potential applications in sustainable HVAC systems, waste heat recovery, and solar-assisted heating units. Experimental validation will provide insights into turbulence-induced heat transfer enhancements and system-wide efficiency improvements. Ultimately, this research aims to contribute to the development of more efficient and adaptable heat exchangers for renewable energy applications, improving energy efficiency and expanding sustainable heating alternatives. By coupling theoretical analysis with experimental testing, this study merges conceptual heat exchanger designs with hands-on experimental applications, showcasing potential advancements in thermal management for residential, commercial, and industrial settings.

Presenting Author: David Steel Missouri State University

Presenting Author Biography: David Steel studies mechanical engineering in the cooperative engineering program with Missouri University of Science and Technology and Missouri State University. Since his freshman year, he has been involved with the American Society of Mechanical Engineers and currently serves as president, leading officer meetings, design projects, and community outreach. In January 2025, he began research at Missouri State University on a concentric tube heat exchanger while mentoring a high school student weekly. He also works as a resident assistant on campus and has recent job experience in manufacturing and HVAC. In his free time, he plays the Highland bagpipes, fences, and experiments with circuit designs. In the future, he hopes to develop and optimize CSP-powered heating systems as a viable replacement for traditional furnaces and boilers.

Authors:

David Steel Missouri State University
Daniel Moreno Missouri State University