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--- en:berechnungen:kompressionsverhaeltnisse [2024/07/29 18:04] – neelest
+++ en:berechnungen:kompressionsverhaeltnisse [2026/09/17 09:42] (aktuell) – gelöscht - Externe Bearbeitung (Unbekanntes Datum) 127.0.0.1
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-====== Compression ratios ======
-FIXME
-In REX, the following ratios are differentiated between different screw zones:
-===== Compression ratio of a (de)compression zone (CR) =====
-The compression ratio of a compression or decompression zone is calculated from the channel depths at the beginning and end of the zone:
-$CR = \frac{h_{E}}{h_{M}}$
-with the channel depth of the feed zone $h_E$ and the channel depth of the metre zone $h_M$
-===== Volume compression ratio (VCR) =====
-As the ratio of the channel depths does not allow a meaningful comparison between two screw concepts, the volume compression ratio is used for a more precise description. It relates the channel cross-section of the feed zone to the channel cross-section of the metering zone. In REX, the screw clearance is also taken into account. \\
-$VCR=\frac{[(h_E+s)*(t_E-i_E*e_E)]*(D-(h_E+s))}{[(h_M+s)*(t_M-i_M*e_M)]*(D-(h_M+s))}$
-with the channel depth $h$, the side clearance $s$, the pitch $t$, the number of webs $i$, the web width $e$ and the diameter $D$. With the indices $E$ for the feed zone and $M$ for the metering zone.
-===== Volume-compression ratio for barrier screws (VCR) =====
-For barrier screws, the volume-compression ratio is also calculated from the ratio of the channel cross-section of the feed zone to the added channel cross-section of the solids and melt channel at the end of the barrier zone:
-$VCR = \frac{B_E*h_E}{B_S*h_S+B_F*h_F}$
-With the channel width $B$ and the channel height $h$ for the indices $E$ for the feed zone, $S$ for the melt channel and $F$ for the solid channel of the barrier zone.
-===== Pump ratio for degassing screws (PR) =====
-The //Pump Ratio// indicates the ratio of the channel depth of the metering zone after degassing $h_{M,2}$ in relation to the channel depth of the metering zone before degassing $h_{M,1}$.
-$PR = \frac{h_{M,2}}{h_{M,1}}$
-Typically, a value of 1.5 to 1.6 is realised.
-There is also a typical ratio for the channel depth of the degassing zone. This is typically 2.0 to 2.5 times the channel depth of the metering zone **after** degassing. In most cases, this successfully prevents the degassing opening from flooding.
-<details><summary>Source</summary>
-  * Womer, T. W.: Basic Screw Geometry. Things Your Screw Designer Never Told You About Screws. Lecture, ANTEC, Orlando (USA), 2000
-</details>