8. Questions for Practice

  • Hot water at 2.5 kg/s and 100oC enters a concentric tube heat exchanger having a total area of 23 m\(^2\). Cold water at 20oC enters at 5 kg/s and the overall heat transfer coefficient is 1000 W/m\(^2\).K. Find the heat transfer rate and the outlet temperature of hot and cold fluids. (AU-May-2017)

    Assume:

    • Counter flow in heat exchanger.

    • Hot and cold water \(C_P\) is 4200 J/kg.K.

  • A heat exchanger has a mean overall heat transfer coefficient of 420 W/m\(^2\).K based on the side whose surface area is 100 m\(^2\). Find the outelet temperatures of hot and cold fluids for both counter and parallel flow operations from the data given below: (AU-Nov-2007)

    Hot fluid Cold fluid
    Inlet temperature oC 700 100
    Mass flow rate (kg/min) 1000 1200
    Heat capacity (kJ/kg.K) 3.6 4.2