S-SS-3-13 Re-evaluation of the HTRI Delta Factor for Incremental Calculations
The HTRI Delta Factor Method corrects the mean temperature driving force in a heat exchanger for the effects of leakage and bypassing. HTRI originally formulated this factor for our earlier shell-and-tube software as an empirical way to improve overall predictions of data with large leakage streams and small temperature approaches. Later theoretical developments resulted in improvements that were based on overall heat balances and stream mixing factors. Because our earlier software performed only overall heat exchanger calculations, the original Delta Factor Method was also applied to the overall exchanger performance as a multiplier to the LMTD, as was the tubepass correction (F factor). Therefore, the methods could not be directly applied to IST’s incremental structure. HTRI has adjusted the Delta Factor Method to produce reasonable results in an incremental method. This report documents the incrementation adjustments and suggests some improvements for the future.