Match the correct items in Column 1 with Column 2:
\[\begin{array}{|c|c|} \hline \textbf{Column 1} & \textbf{Column 2} \\ \hline \text{P: Pipe-in-pipe heat exchanger} & \text{1: Cooling of air} \\ \hline \text{Q: Shell and tube heat exchanger} & \text{2: Simultaneous co-current and counter-current heat exchange} \\ \hline \text{R: 1-2 shell and tube heat exchanger} & \text{3: Large flow rate} \\ \hline \text{S: Cross flow heat exchanger} & \text{4: Small heat exchange area} \\ \hline \end{array}\]