Cross-Flow Heat Exchanger

Air at 300 °C at the rate of 1.5 kg/s is used to heat pressurized water at 35 °C and a flow rate of 1 kg/s. If a cross-flow heat exchanger (both fluids unmixed) with a gas side heat transfer coefficient and area of 100 W/m2.C and 40 m2 is used for this process, determine:

  • The rate of heat transfer by the exchanger
  • Air and water outlet temperatures

image

 

Start ThermoFlo by double-clicking its icon.

Create new model:

  • Click on Create Model in “Create New” section of home screen.
  • Type filename “Cross_Flow_HX” and click Save

 

Model the Components and Connectors:

  • Click on Thermodynamic folder in “Library Components Window”
  • Drag and Drop “HX_Cross Flow” on to the canvas.
  • Drag and Drop “EndPoint TC”s near every inlet and outlet.
  • Connect each inlet and outlet to the corresponding “EndPoint”

 

Set Working Fluid and Loop Properties:

  • Right-click on the top Inlet-1 node and choose “Set Loop Fluid” from the options.
  • Leave Water as the default fluid.
  • Right-click on the top Inlet-2 node and choose “Set Loop Fluid” from the options.
  • Double Click on the Fluid icon to open its properties form; choose “Library Fluids”/”All Fluid”/”Air”.
  • Double Click on the Inlet-1 EndPoint and set:
    • Mass Flow Rate = 1 kg/s
    • Pressure = 1 atmosphere
    • Temperature = 35 °C
    • Click Apply to set properties and close the form.
  • Double Click on the Inlet-2 EndPoint and set:
    • Mass Flow Rate = 1.5 kg/s
    • Pressure = 1 atmosphere
    • Temperature = 250 °C
    • Click Apply to set properties and close the form.

 

Set Heat Exchanger Properties:

  • Set UA = 4000 W/C
  • Keep all properties unchanged. Note that this will assume zero pressure loss in both flow paths.  This is acceptable since the focus of this exercise is on thermal calculations.
  • Click Apply to set properties and close the form.

Run Model and View Results by right clicking on the HX icon and selecting results. 

image

    Comments are closed.