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

\begin{document}
\LCPTSDiagram[
  fluid=R134a,
  temperature axis unit=celsius,
  isenthalp=true,
  quality step=0.2,
  enthalpy values={200,250,300,350,400,450},
  labels=true,
  axis options={title={R134a temperature--entropy diagram}}
]
\end{document}