Troubleshooting Heat Exchangers for Environmental Technologies
Thomas G. Lestina
Senior Vice President, Engineering
Heat Transfer Research, Inc.
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, Thi – Tci). 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.