Unterschiede

Hier werden die Unterschiede zwischen zwei Versionen angezeigt.

--- en:berechnungen:durchsatz [2024/04/12 13:38] – angelegt admin
+++ en:berechnungen:durchsatz [2025/07/03 13:33] (aktuell) – cschall
@@ Zeile 1: / Zeile 1: @@
 ======Throughput======
+===== Throughput Calculation=====
+If the throughput or dosing time (optional) is specified together with the dosing volume (mandatory) in the process parameters, then the throughput is not calculated. Instead, all subsequent calculations are performed using the specified throughput.
+The following section describes the melt-dominated throughput calculation. If a grooved bushing is used in the process, it determines the throughput (see [[en:berechnungen:einfache_berechnung|]] and [[en:berechnungen:nutbuchsenberechnung|]]). \\ The [[en:berechnungen:feststofffoerderung|]] is carried out in conjunction with the melt-dominated throughput calculation.
+Two melt-dominated throughput models are distinguished: the equivalent zone model and the interval-based model, which will be introduced with REX 19.0 / PSI 17.0.
+Initial temperature and pressure profiles are assumed prior to the throughput calculation. This is necessary to determine the viscosities required for throughput estimation. For more information, see [[prozess_iterieren|]].
+For both models, degassing screws form a special case: the throughput is calculated solely based on the geometry of the first screw stage (before degassing), with the backpressure at the degassing location physically set to 1 bar. Consequently, the backpressure at the screw tip has no effect on the mass throughput.
+Additionally, for both models, pressure losses across shearing and mixing elements are calculated analytically. This also applies to all sections computed using network theory/matrix model (node method for barrier screws, always for wave screws). See also [[druckverlauf|Pressure Calculation]].
+==== Melt-Dominated Equivalent Section Model  ====
+First, a reference section is determined—this is the screw section (excluding shearing and mixing elements) with the smallest channel depth. For degassing screws, the reference section must be located before the first degassing section. This reference section is used to determine the average shear rate, which in turn is used to determine the viscosity using the given melt temperature at the end of the screw.
+Based on the screw geometry and the temperature profile, factors for throughput calculation are determined. The throughput is then calculated using these geometry-dependent factors only for the reference section and the associated pressure drop.
+In the first step, the entire pressure difference (specified backpressure minus hopper pressure) is assumed to apply across the entire screw (excluding shearing and mixing elements), and an initial mass throughput is calculated.
+This value is then used to calculate pressure losses across all shear and mixing sections and, in the case of //PSI//, the non-return valve. These pressure losses are subtracted from the pressure difference to yield a simplified linear pressure gradient across the feeding, compression, metering, and barrier sections.
+With this pressure gradient, an iterative process is used to determine the throughput, which in turn affects the pressure losses across the shearing and mixing elements.
+Additionally, this iterative process can take into account a throughput-dependent backpressure (see [[en:eingabe_eines_werkzeugs:eingabe_eines_werkzeugs_mit_geometriedaten|]] or [[en:eingabe_eines_werkzeugs:eingabe_einer_werkzeugkennlinie|]]).
+==== Melt-Dominated Interval-Based Model  ====
+The interval-based model does not require a reference section.
+Unlike the equivalent Section model, no global geometry-based factors are used. Instead, local screw geometry, temperature, pressure, and—if applicable—the calculated degradation level of the plastic are considered in each calculation interval.
+This is done using a generalized regression equation, which calculates the pressure loss for a given throughput based on local screw geometry and viscosity.
+Because the throughput remains constant along the entire screw, a specific throughput is assumed, and the pressure loss across each calculation interval is computed to determine the overall pressure drop across the screw.
+The calculated total pressure difference is compared with the target pressure difference, and an iterative solution is performed to find the throughput at which both the inlet and outlet pressures match their target values.
+===Further topics===
+  * [[en:berechnungen:einfache_berechnung|]]
+  * [[en:berechnungen:prozess_iterieren]]
+  * [[en:berechnungen:durchsatz|]]
+  * [[en:berechnungen:druckverlauf|]]
+  * [[en:berechnungen:aufschmelzverlauf|]]
+  * [[en:berechnungen:temperaturverlauf|]]
+  * [[en:berechnungen:leistung_und_schubspannungen|]]
+  * [[en:berechnungen:schergeschwindigkeit]]
+  * [[en:berechnungen:verweilzeit|]]
+  * [[en:berechnungen:verweilzeitverteilung|]]
+  * [[en:berechnungen:materialabbau|]]
+  * [[en:berechnungen:faserlaengenabbau|]]
+  * [[en:berechnungen:entgasungskennzahlen|]]
+  * [[en:berechnungen:festigkeitsberechnung|]]
+  * [[en:berechnungen:schlepp-druckstroemung|]]
+  * [[en:berechnungen:feststofffoerderung|]]
+  * [[en:berechnungen:verarbeitung_von_mischungen|]]
+  * [[en:berechnungen:wandgleitende_materialien|]]
+  * [[en:berechnungen:nutbuchsenberechnung|]]
+  * [[en:berechnungen:kompressionsverhaeltnisse|]]