cambiare orientazione freccia

salve, ho disegnato due grafici, dando una orientazione alle curve.
Ora dovrei cambiare l’orientazione di una delle due (la seconda nello specifico). come potrei fare?

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\documentclass[a4paper,11pt,oneside]{book}
\usepackage{amssymb}
\usepackage[italian]{babel}
\usepackage{fancyhdr, afterpage}
\usepackage{graphicx}
\usepackage{amsmath}
\usepackage[utf8]{inputenc}
\usepackage{pgfplots}
\usepackage{caption}
\usepackage{bm}
\usepackage{subfig}
\usepackage{tikz}
\usepackage[subnum]{cases}
\usepackage{booktabs}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usetikzlibrary{arrows,decorations,decorations.markings}

\tikzset{insert arrow/.style args={#1 at #2}{
postaction=decorate,
decoration={
markings,
mark= at position #2
with
{
\arrow{#1}
}
}
}
}

\begin{document}
\begin{figure}[h]
\label{fig:calore}
\centering
\subfloat{
\begin{tikzpicture}
\draw [-stealth] (2,4) — (3.5,4) node[above, midway] {Flusso positivo};
\end{tikzpicture}
}\\
\setcounter{subfigure}{0}
\subfloat[\label{fig:calorea}]{
\begin{tikzpicture}[scale=0.9,transform shape]
\draw[-stealth] (0,0) –++(5,0)node[below right]{$x$};
\draw[-stealth] (0,0) –++(0,4.5)node[above left]{$T$};
\draw [-stealth] (3.5,4) — (2,4) node[above, midway] {Flusso};
\draw[insert arrow=stealth at 0.5] (0.7,0.7)arc[start angle=280, end angle=345, radius=4cm];

\node[font=\small] at (2.7,3) {$\dfrac{\partial \, T}{\partial \, x}>0$};
\node[font=\small] at (4.5,3.2) {$\partial \, T>0$};
\node[font=\small] at (4.4,2.8) {$\partial \, x>0$};
\end{tikzpicture}
}\qquad
\subfloat[\label{fig:caloreb}]{
\begin{tikzpicture}[scale=0.9,transform shape]
\draw[-stealth] (0,0) –++(5,0)node[below right]{$x$};
\draw[-stealth] (0,0) –++(0,4.5)node[above left]{$T$};

\draw[insert arrow=stealth at 0.5] (3.5,0.7)arc[start angle=245, end angle=195, radius=4.5cm];
\draw [-stealth] (2,4) — (3.5,4) node[above,midway] (2.7,4.2) {Flusso};
\node[font=\small] at (2.7,3) {$\dfrac{\partial \, T}{\partial \, x}<0$};
\node[font=\small] at (4.5,3.2) {$\partial \, T<0$};
\node[font=\small] at (4.4,2.8) {$\partial \, x>0$};
\end{tikzpicture}
}
\end{figure}
\end{document}
`