\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,
  isochore=true,
  quality step=0.1,
  temperature preset=sparse,
  specific volume preset=sparse,
  labels=true,
  sloped labels=true,
  label placement=autonode,
  label pos for={lcp-ph-T-0C}{0.72},
  label style for={lcp-ph-T-0C}{fill=yellow!20,xshift=2mm},
  label show for={lcp-ph-v-0p005m3kg}{true},
  curve style for={lcp-ph-v-0p005m3kg}{very thick,orange!90!black},
  label pos for={lcp-ph-v-0p005m3kg}{0.83},
  label style for={lcp-ph-v-0p005m3kg}{fill=yellow!20,yshift=1mm}
]
\end{document}