2022 Horizons Symposium

Thomas G. Lestina
Senior Vice President, Engineering
Heat Transfer Research, Inc.

Thomas G. Lestina, Senior Vice President, Engineering, has more than 30 years of engineering project management experience. He directs HTRI's contract and consulting services, as well as oversees research and technical support. Lestina also assists in developing and customizing training and teaches courses. He earned a BS in Mechanical Engineering from Union College, Schenectady, New York, USA, and an MS in Mechanical Engineering from Rensselaer Polytechnic Institute, Troy, NY. Prior to joining HTRI, he worked as a Lead Engineer for MPR Associates, Inc., Alexandria, Virginia, USA. Besides being a member of ASME, he serves on the technical committee for the ASME Performance Test Code 12.5, Single Phase Heat Exchangers. He is a licensed Professional Engineer (PE) in Texas.

ABSTRACT

Environmental technologies put a premium on the heat transfer design to minimize the thermal pollution and reduce carbon footprint. Designs of high temperature effectiveness are often specified where the temperature change of a flow stream, ΔT, is a large fraction of the maximum possible temperature change (hot inlet temperature minus cold inlet temperature, T_hi – T_ci). This attribute along with low pressure drop requirements and compact sizing push the limits of commercial design practices. Process heat exchangers have traditionally been designed with large thermal margins due to application of conservative rules-of-thumb. Large engineering margins and traditional rules-of-thumb result in low effectiveness and promote fouling.

HTRI has experience in troubleshooting heat exchangers where the performance is inadequate for desalination, geothermal, thermal solar, and waste heat recovery applications. Problems include fouling, flow maldistribution, tube vibration, and acoustic vibration. This presentation highlights the challenges of implementing effective thermal design and will question the practical limits to the effectiveness of TEMA shell-and-tube exchangers and other designs such as plate heat exchangers and pure counterflow tubular designs. A discussion on the future of heat exchanger design for environmental technologies will include minimizing flow maldistribution, using precise manufacturing, and developing accurate thermal methods.