(249b) Comparison Between Traditional and Dynamic Heat Exchangers through Experimental Verification and Aspen HYSYS Simulation

Authors: 
Fazlollahi, F., Brigham Young University
Baxter, L. L., Brigham Young University
Smith, H., Brigham young university

The purpose of this experiment was to develop a heat exchanger (HX) network using dynamic HXs, devices that can decrease or eliminate HX efficiency and performance losses related to transient changes in flow rates. Dynamic HXs can accommodate varying flow rates of ethanol while maintaining constant outlet temperatures throughout the HX network. The main temperature that needs to remain constant is the temperature of the outlet ethanol. Traditional heat exchangers often represent the slowest part of the process to adjust to load changes. Through the dynamic heat exchanger developed in this experiment, the heat exchanger was able to adjust to load change significantly faster. This was accomplished by using  pumps,  tank system and proportional-integral-derivative controllers (PID controller) to change the flow rate of ethanol. As the flow rate of feed ethanol increased, the flow rate of return ethanol increased, thus maintaining constant outlet temperatures. The scope of this experiment includes using various inlet ethanol flow rates whilst observing transient responses for all units specifically heat exchangers. Aspen HYSYS dyanmics was used to simulate both traditional and dynamic designs. The results of this experiment are verified with simulation’s results to indicate that a dynamic heat exchanger is a novel way of decreasing the time needed for a heat exchanger to adjust to load change.