Fouling Focus
Heat exchanger fouling in practice – understand & mitigate
Part 7 – heat exchanger monitoring
In this series of articles we will look at how heat exchangers foul , how to understand the root causes of fouling , and how to mitigate the impact of fouling . The material presented is based entirely on the author ’ s experience and analysis of operating situations in the Oil & Gas industry . However , many theories and varied experiences exist across the industry and amongst researchers .
About the author
Himanshu Joshi retired from Shell in 2021 after 34 combined years with ExxonMobil and Shell , during which he specialized in heat exchangers and fouling . He was part of a team that was granted a patent related to fouling deposit analysis at ExxonMobil , and led applied fouling R & D projects at both companies . He has made several presentations about the field aspects of fouling and fouling mitigation , and deployed many mitigation technologies in the field . He can be reached by email at alph . hmj @ gmail . com .
By Himanshu Joshi , Heat Exchanger Specialist
Monitoring heat exchanger performance is a very common practice , especially when fouling is a concern . It can be done very simply using a single calculation in a spreadsheet , or one can use software tools which can handle heat exchanger networks , work on large amounts of historical data , simulate different types of heat exchangers , model the fouling process for future predictions , and perform these tasks automatically on a time frequency of choice ( such as daily ). Intermediate approaches using a combination of software and manual calculations and approximations can also be used . Regardless of the sophistication of the calculation , the one requirement of monitoring should be that it can quantify the impact ( or the loss ) due to fouling , which should be done using the heat duty . Quantification of the loss ( heat duty converted to money ) should be used to make decisions – what actions to take and the cost vs benefit implications of those actions . This article is a basic introduction to monitoring and its requirements . It is written with the assumption that the purpose of monitoring is to make decisions for taking actions and base those decisions on quantification using data , and not simply to know that performance is decreasing .
Data requirements and definitions Availability : Calculation of heat duty ( Q ) requires values of flow rates , inlet / outlet temperatures , and the specific heats or enthalpies corresponding to those temperatures . If data is available on at least one side ( hot or cold ), the operating heat duty can be calculated . Accuracy : Flow and temperature instruments need to be functional so the heat duty can be calculated with decent accuracy , say within ± 15 %. Heat Balance : It is desirable that the heat duties on the two sides ( hot and cold ) match , at least within a practical range of ± 15 %. Larger discrepancies will introduce errors depending on which side you choose to treat as correct . Frequency : Daily average readings of flows and temperatures are sufficient to provide good quantification and basis for actions . Only in rare cases would a higher frequency , such as hourly , might be required . www . heat-exchanger-world . com