\documentclass[tikz,border=6pt]{standalone}
\usepackage{luacoolprop}
\pgfplotsset{compat=1.18}

\begin{document}
\LCPPVDiagram[
  fluid=R134a,
  specific volume axis unit=lkg,
  isotherm=true,
  isentrope=true,
  quality step=0.2,
  temperature values={-20,0,20,40,60,80},
  entropy values={1.6,1.8,2.0},
  labels=true,
  axis options={title={R134a pressure--specific-volume diagram}}
]
\end{document}

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