$0$:$31$:$25$ remaining

The inner and outer diameters of the tube are equal to $12$ mm and $13$ mm $,$ respectively.

The inner and outer convection heat transfer coefficients on the tube surfaces are known to be: $h_i=400W*m^{-2}*K^{-1}$ and $h_o=750W*m^{-2}*K^{-1}$ respectively.

The inner and outer surfaces of the tube are subjected to fouling with associated conductances as follows: $h_{fi}=500W*m^{-2}*K^{-1}$ and $h_{fo}=500W*m^{-2}*K^{-1},$ respectively.

Determine the overall $$ value for the heat exchanger referred to the inner surface on a per unit length basis.

Specify your answer in $W*m^{-2}*K^{-1},$ to one decimal place, where applicable.

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