Heat-Exchangers

1. Basic understanding of process engineering
2. Aspen Plus Software installed on your computer
3. Have a Computer
4. Have a Desire

In this part the trainer aims to design a shell and tube heat exchanger for a actual process condition. At first, he uses simple form of heat exchanger so that the duty of the heat exchanger is calculated. Then by knowing the inlet and outlet temperature of cooling water and by using Design Spect, he determines tha exact flowrate of cooling water needed for that duty.

Overview
Heater performs these types of single phase or multiphase calculations:
•Bubble or dew point calculations
•Add or remove any amount of user specified heat duty
•Match degrees of superheating or subcooling
•Determine heating or cooling duty required to achieve a certain vapor fraction
Heater produces one outlet stream, with an optional water decant stream. The heat duty specification may be provided by a heat stream from another block.
You can use Heater to model:
•Heaters or coolers (one side of a heat exchanger)
•Valves when you know the pressure drop
•Pumps and compressors whenever you do not need work related results
You can also use Heater to set or change the thermodynamic condition of a stream.

Now he uses the rigorous model in Aspen Plus to gain detailed insight about shell and tube heat exchanger charachteristics such surface required, heat transfer coefficients. At last, he explains how a part of cooling table could be created using the results of Aspen Plus.

Overview

HeatX can perform these types of calculations:
•Shortcut design or simulation
•Detailed rating or simulation for most types of two stream heat exchangers (only supported for compatibility with older files; new exchangers should use Rigorous instead).
•Rigorous design, rating, or simulation by interfacing with the Aspen Exchanger Design and Rating (EDR) programs: Shell&Tube, AirCooled, or Plate. Kettle Reboiler and Thermosyphon reboilers use the same rigorous calculations using Shell&Tube while interfacing with a column.
The main difference among the calculation methods is the procedure for the calculation of the overall heat transfer coefficient.
The shortcut method always uses a user specified (or default) value for the overall heat transfer coefficient.
The Rigorous methods use EDR models for film coefficients and combines the resistances due to films on each side of the wall with the wall resistance, to calculate the overall heat transfer coefficient. There are several different methods for different EDR programs. You need to specify the name of the input file for this program.

You must specify the hot and cold inlet streams and one of these performance specifications for your heat exchanger:
•Outlet temperature or temperature change of the hot or cold stream
•Molar vapor fraction of the hot or cold stream
•Degree of superheating (subcooling) of cold (hot) stream
•Heat exchanger duty
•Surface heat transfer area
•UA as an optional if heat transfer area is missing
•Temperature approach at the hot or cold stream outlet

For the shortcut method you may specify a pressure drop for each side of the heat exchanger. The HeatX model determines the outlet stream conditions based on heat and material balances and uses a constant value for the heat transfer coefficient to estimate the surface area requirement. You may also provide phase specific heat transfer coefficients.
HeatX can also perform detailed design, rating, or simulation calculations by using an Aspen Shell&Tube model, which has a large variety of shell and tube heat exchanger types available, including:
•TEMA E, F, G, H, I/J, K, X shells, and double pipe and hairpin multi-tube exchangers
•Bare, low-finned, and longitudinal-finned tubes
•Single and double segmental baffles, rod baffles, and unbaffled exchangers
•HeatX will perform the required calculations (all combinations of single phase, boiling or condensing heat transfer, with associated pressure drop calculations), returning key calculation results to be viewed within Aspen Plus. For more detailed views of results and access to utilities such as the setting plan, the standalone version of Shell&Tube must be used.

HeatX can:
•Perform design, rating, or simulation calculations
•Perform mechanical vibration and Rhov2 analysis
•Estimate maximum fouling
•Display setting plan and tubesheet layout drawing
To use this rigorous method:
1.Specify the appropriate program as the Calculation method.
2.Specify the name of the input file for that exchanger.
3.Specify optional parameters on the EDR Options form.
Information related to the heat exchanger configuration and geometry are entered through the EDR Browser form. The exchanger specification is then saved in the input file.
HeatX can also perform detailed design, rating, or simulation calculations by using an Aspen AirCooled model, which has more variety of cross flow heat exchanger types than the detailed method, including:
•Air-cooled heat exchangers
•Hot gas heat recuperators
•Fired heater convection sections
•Gas-cooled heat exchangers

HeatX can:
•Perform design, rating, or simulation calculations
•Estimate maximum fouling
•Display setting plan and tubesheet layout drawing
To use this rigorous method:
1.Specify the appropriate program as the Calculation method.
2.Specify the name of the input file for that exchanger.
3.Specify optional parameters on the EDR Options form.
Information related to the heat exchanger configuration and geometry for AirCooled are entered through the EDR Browser form. The exchanger specification is then saved in the input file.