Johannes Jäschke - Patent
Optimal operation of heat exchanger networks with split
We have developed a surprisingly simple and effective way for optimizing heat exchanger networks with split.
This low-tech approach to optimizing the split is new, as has been confirmed by two rounds of patent applications.
We are looking for partners who would like to implement it. Please contact us (jaschke@ntnu.no, skoge@ntnu.no) for more information!
Here a cold stream with temperature T0 and flowrate m0 is split into two branches, which are heated separately by hot streams with temperature Th1in and Th2in.
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We developed a method for controlling the split ratio u such that the heat transfer is maximized.
This is equivalent to maximizing Tend.
The idea is to calculate a simple function of temperatures for each branch, the “Jäschke Temperature” Tj, and to adjust the split u such that the Jäschke Temperatures of all branches are equal, i.e. Tj1=Tj2.
Here
Tj1=(T1-T0)^2/(Th1in-T0) (Jäschke Temperature for 1. branch)
and
Tj2=(T2-T0)^2/(Th2in-T0) (Jäschke Temperature for 2. branch).
By controlling the Jäschke temperatures of all branches to equal values, we maximize the overall heat transfer.
Controlling the Jäschke temperatures to equal values gives a near-optimal split despite varying flow rates, heat capacities and heat transfer properties (UA-values).
We have also extended the approach to handle larger networks with more lines and more heat exchangers.
Further information
Video preseintation:
A recording from the 2013 AIChE annual meeting is found here
Patent application:
Johannes Jäschke, Sigurd Skogestad. Parallel Heat Exchanger Control. EU/UK Patent PCT/EP2013/059304 and GB1207770.7 Documents and search result on google patents
Refinery application:
Johannes Jäschke, Sigurd Skogestad. A Self-Optimizing Strategy for Optimal Operation of a Preheating Train for a Crude Oil Unit, European Symposium on Computer Aided Process Engineering, ESCAPE 24, Budapest, June 15-18, 2014
Paper describing the method:
Johannes Jäschke, Sigurd Skogestad. Optimal operation of heat exchanger networks with stream split: Only temperature measurements are required. Article in press, Computers & Chemical Engineering, doi: 10.1016/j.compchemeng.2014.03.020. A preprint can be downloaded here