1.1.- Process conditions:
Table 1. Process conditions.
|Fluid Allocation | |Shell Side |Tube Side |
|Fluid Name |Unit |Water Glycol |Natural Gas |
|Fluid Quanty|kg/s |382,46 |461,84 |
|Vapor (in/out) |kg/s | | |461,84 |461,84 |
|Liquid |kg/s |382,46 |382,46 | | |
|Temperature (in/out) |°C |5|50 |95 |50 |
|Specific Gravity | |1,0288 |1,0075 | | |
|Viscocity |mN-s/m2 |3,4616 |0,8807 |0,019 |0,018 |
|Molecilar Weight, Vapor |kg/kgmol | | |16 |16 |
|Density |kg/m3 | | |81 |92 |
|Specific Heat |KJ/kg°C |4,0502 |4,0905 |3,3682 |3,3682 |
|Thermal Conductivity |W/m*C |0,4771 |0,5187 |0,0349 |0,0349|
|Inlet Pressure |Kpa |1101,35 | |15401,5 | |
|Pressure Drop Allow |Kpa |100,002 | |70,001 | |
|Fouling Resistance (min) |m2-K/W |0,000172 | |0,000086 | |
|Heat Exchanged|W |69999949 | | | |
Based on this process conditions the heat exchanger to be designed must handle high pressure in the tube side, higher temperature in the tube-side compared to the shell side, work with clean services in tube and shell side (Natural gas y Water glycol), high mass flow on both side and limited thepressure drop to 100 Kpa in the Shell-side and 70 Kpa on the tube-side.
1.2.- Geometric constraints.
Maximum shell diameter: 1,5 m.
Maximum tube length: 7,32 m
Preferred tube length: 4,88m, 6,096m, 6,7 m, 7,32m
In functions of the process conditions and the limitations specific in the exercise the heat exchanger was selection according to the following criterions:
2.1- Type ofshell and tube heat exchanger selected.
2.1.1- Fluid side location.
The exercise required that the Natural gas was located in the tube-side and the water glycol in the shell-side. These fluid locations are correct due to the high pressure in the tubeside (Natural Gas to 152 Bars),the tubes are higher resisting to high internal pressure than to external pressure. Additionally, foreconomic reasons is more feasible to increase the thickness (e) of the front end and rear end heads than to the shell that it is longer.
The fluid located in the tube-side is a higher temperature than the fluid located in the shell-side (inlet temperature 90°C and outlet 50°C) taken in account this the thermal losses are limited, also the thickness of the shell will be minimum due to the factthat the maximum stress will decrease because the colder fluid is in the shell-side.
The tube-side fluid and the shell fluid are clean (fouling factor 0,000086 vs. 0,000172 m2-K/W). Even thought the design criterion is located the services with a fouling factor higher in the tube-side due to the mechanical cleaning of the tubes is easier than the one of the shell, in this case the cleaner services...