\documentclass[border=3mm]{standalone}
\usepackage{luacoolprop}
\pgfplotsset{compat=1.18}
\begin{document}
\LCPDeclareFluid{R134a}
\begin{tikzpicture}
\begin{axis}[
  width=13cm,
  height=8cm,
  xlabel={$h/{\rm kJ\,kg^{-1}}$},
  ylabel={$p/{\rm bar}$},
  ymode=log,
  grid=both,
  auto node placement,
  lcp fluid=R134a,
  ymax=\LCPFluidPcritBar,
  title={R134a : $p_c=\LCPFluidPcritBar$ bar},
]
\LCPAddPHIsotherms[
  temperature values={-20,0,20,40,60,80,100},
  labels=true,
  isotherm label every=2
]
\LCPAddPHQuality[
  quality step=0.2,
  labels=true,
  quality label every=1
]
\end{axis}
\end{tikzpicture}
\end{document}

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