What you can expect from method changes in Version 9.0

Revised correlations for bend and tee pressure losses (Xist^®)

The single-phase and two-phase pressure loss correlations for U-bends and piping element bends have been revised to produce lower pressure losses for sharp bends at high Reynolds numbers and to provide a smooth transition from moderate to sharp bends. The two-phase pressure loss correlations for tees have been revised to produce lower pressure losses. The previous methods overpredicted pressure losses.

Modified airside heat transfer coefficient calculation for Air-cooled heat exchanger mode operating at low
Reynolds numbers (Xace^®)

Previously, when modeling low-Reynolds number heat transfer by Air-cooled heat exchanger mode (e.g., forced-draft or induced-draft configuration), the program overpredicted the airside heat transfer coefficient at flows with a Reynolds number less than 2000. We have modified this calculation using a mixed convection method to match research data.

Updated condensation heat transfer coefficient method to follow PHE-19 (Xphe^®)

The program now uses the method described in Report PHE-19 to calculate the condensation heat transfer coefficient for pure components and consolidates the new method with the HTRI Resistance Proration Method (RPM) to calculate the heat transfer coefficient for mixtures. The previous "Literature" condensation method is no longer available. As PHE-19 shows, the results can be significantly different from previous versions.

Updated boiling heat transfer coefficient method to follow PHE-20 (Xphe)

The program now uses the method described in Report PHE-20 to calculate the boiling heat transfer coefficient. The method is based on more experimental data that cover different fluids and geometries. The program now also determines the boiling temperature using the multiple reference pressures when specified, which improves cases with lower effective mean temperature differences. As PHE-20 shows, the results can be significantly different from previous versions.

Added velocity checks at tubes on impingement plate periphery scaled according to STG-13 (Xvib^®)

When a tube adjacent to an impingement plate is exported to Xvib (color-coded red in the velocity state view), the exported velocities in the affected span are scaled to account for impingement plate jetting. The exported velocities use the nozzle velocity, augmented by a scaling factor. The scaling factor is a function of height under nozzle and nozzle diameter.

Method to estimate reduced pressure used in boiling heat transfer calculations (Xist, Xjpe^®, Xhpe^®, and Xace)

This version adds an estimation of reduced pressure from the vapor-to-liquid density ratio that is used when a fluid’s true critical pressure is unknown, as documented in Report BG1-17. This method is always used when a critical pressure is not available. It may also be selected for use on the Control > Methods input panel when critical pressure is available. The new reduced pressure impacts boiling heat transfer calculations.