Two-phase flow pressure drop — a TI-84 Plus CE program

By E-Code · updated 2026-09-26

TWOPHASE is a TI-BASIC program for the TI-84 Plus CE. Frictional pressure gradient of a gas-liquid flow in a pipe by the homogeneous model and by Lockhart-Martinelli with Chisholm's C (chosen from the phases' laminar/turbulent regimes), plus the homogeneous void fraction.

What it asks for and what it shows

It asks for 7 values at its prompts. In the example below it shows RHO H, DP HOM, VOID, X LM, C, PHI L², DP LM.

Example run

One of its oracle test cases: “steam-water 7 MPa, x .2, both turbulent”. The inputs are typed in order, and the results are the values the case expects on the screen.

Step	Value
You enter
Input 1	1000
Input 2	0.2
Input 3	0.02
Input 4	740
Input 5	36.5
Input 6	0.092
Input 7	0.019
The screen shows
`RHO H=`	152.4266366
`DP HOM=`	2081.417796
`VOID=`	0.835214447
`X LM=`	0.909834379
`C=`	20
`PHI L²=`	24.19004604
`DP LM=`	8093.362664

How it's checked

4 test cases, each checked against the textbook formula it uses. Replayed key by key on a virtual TI-84 Plus CE, they make 30 checks.

How E-Code checks every program

Run it or put it on your calculator

Open the library in the TI-84 Plus CE calculator and pick “Two-phase flow pressure drop” (TWOPHASE).
Put it on your own calculator with a computer and a USB cable, or type it in by hand.

Related programs

All TI-84 Plus CE engineering programs · All TI-84 Plus CE programs