\documentclass[border=3mm]{standalone}
\usepackage{luacoolprop}
\pgfplotsset{compat=1.18}
\usetikzlibrary{arrows.meta}
\pgfplotsset{auto node allow outside=true}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
  width=13cm,
  height=8cm,
  lcp fluid=R134a,
  xlabel={$h/{\rm kJ\,kg^{-1}}$},
  ylabel={$p/{\rm bar}$},
  ymode=log,
  grid=both,
  auto node placement,
  auto node algorithm=repair,
  auto node bbox mode=oriented,
  auto node failure mode=allow-minimal-overlap
]
\LCPAddPHQuality[
  fluid=R134a,
  quality values={0,0.5,1},
  labels=true,
  label placement=autonode,
  sloped labels=true
]
\LCPAddPHIsotherms[
  fluid=R134a,
  temperature values={0,40,80},
  labels=true,
  label placement=autonode,
  sloped labels=true,
  autonode candidates=31
]
\LCPAddPHProcess[
  fluid=R134a,
  type=isentropic,
  from={pressure=1bar,quality=1},
  to={pressure=10bar},
  style={very thick,-Latex},
  color=black,
  label={$1\to2$},
  mark endpoints=true
]
\end{axis}
\end{tikzpicture}
\end{document}