3 replies to this topic

[Sureshbhad]

Hello.

I am working on Thermal design of Liquid to Liquid heater for Intermediate Fuel Oil (IFO 380). Below is the data:

 

1. Hex type: Shell and tube

2. Heat Load : 6200 kW 

3. Shellside fluid: Heat transfer oil @ 600 m3/h(Density@105 deg. C=834.47 kg/m3, Cp=1992 J/kg.k, Th. Cond.=0.148 W/m.k, Kine. viscosity@105 deg. C=11.04 mm2/s)

 

4. Tubeside fluid: IFO 380 @ 750 m3/h (Density@15 deg. C=991 kg/m3, Cp=2000 J/kg.k, Th. Cond.=0.150 W/m.k, Kine. viscosity@50 deg. C=380 mm2/s)

 

My assumptions:

1. Tube: 31.75 OD x 2 thk x 4800 mm Long

2. Tubeside passes: 4

3. Tube layout: Square type with 39.69 pitch

4. Tube material: CS SA 178 ERW

5. Baffles: Segmental, transeverse

6. Overall U assumed : 300 W/m2.C

7. Calculated U : 308 W/m2.C

8. Area calculated: ~387 m2

 

But the problem is Pressure drops through shell and tubes:

Shellside Pressure drop with above configuration: 1.51 bar (This is too high, which should be below 0.7 bar)

Tubeside Pressure drop with above configuration: 2.4 bar (This is too high, which should be below 0.5 bar)

 

I have tried many combinations to deal with/ to olwer the pressure drops, But could not succeed.

 

I am a Mechanical Engineer with exp. of Pressure vessel and Heat exchanger design,

Since I am not an experienced process designer/Chemical engineer, I expect help on this forum.

 

an advice or suggestion to minimize the pressure drops are much appreciated.

 

Have attached excel sheet for thermal calculations.

 

I have referred: Chemical Engineering. Vol. 6, Chemical Engineering Design, 4th Ed by Coulson & Richardson

 

-Suresh Bhad

 

 

 

Attached Files

•  Thermal design-HFO.xls   484.5KB   22 downloads

[Sureshbhad]

Sorry.

Forgot mention: It's an U tube heat exchanger.

 

-Thanks.

[srfish]

To cure the excess pressure through the tubes, drop back to 2 tube passes.

 

To cure excess pressure drop through the shell  side, use wider baffle spacing and a larger baffle cut.

[Pilesar]

Try these if you haven't already:

Use J Shell

Use double segmented baffles

Switch shell side and tube side.

Use 2 passes instead of 4.

Vary the tube length.

Consider if you can use larger diameter tubes.

Use multiple shells.

Ask for more allowable pressure drop from the process engineer - it may be available.