\documentclass[border=3mm]{standalone}
\usepackage{luacoolprop}
\pgfplotsset{compat=1.18}
\pgfplotsset{auto node allow outside=true,
  auto node failure mode=hide-low-priority}
\begin{document}
\LCPPHDiagram[
  fluid=R134a,
  isotherm=true,
  quality step=0.1,
  quality color=blue!55!black,
  quality boundary color=blue!80!black,
  isotherm color=red!65!black,
  temperature mode=linear,
  temperature min=-40,
  temperature max=120,
  temperature step=20,
  labels=true,
  sloped labels=true,
  quality label every=2,
  isotherm label every=2,
  quality label pos=0.45,
  isotherm label pos=0.16
]
\end{document}

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