A sugar solution is heated from $10\backslash$deg C to $15\backslash$deg C in a double$-$pipe heat exchanger with water flowing countercurrently, which cools from $49\backslash$deg C to $27\backslash$deg C$.$ The sugar solution flows at a flow rate of $14400$ kg$/$hour in a pipe with an outer diameter of $8$ mm and an inner diameter of $5$ mm$.$ Ignore the resistances on the pipe wall and water side. Calculate the length of the pipe.