modelHeatExchanger
Base class for heat exchanger fluid - gas
Information
This is the model of a very simple heat exchanger. The modelling assumptions are as follows:
- The boiler contains Nr rows of tubes, connected in series; each one is made of Nt identical tubes in parallel.
- Each tube has a length L, internal and external diameters Dint and Dext, and is made of a metal having density rhom and a specific heat capacity of cm.
- The series connection of the tubes is discretised with Nr+1 nodes, so that each cell between two nodes corresponds to a single row.
- The gas flow is also discretised with Nr+1 nodes, so that each gas cell interacts with a single tube row.
- The gas flows through a volume having a (net) cross-section Sb and a (net) length Lb.
- Mass and energy dynamic balances are assumed for the water side.
- The mass and energy balances for the gas side are either static or dynamic, depending on the value of the StaticGasBalances parameter.
- The fluid in the water side remains liquid throughout the boiler.
- The heat transfer coefficient on the water side is computed by Dittus-Boelter's correlation.
- The external heat transfer coefficient is computed according to the simple law declared Flow1DGasHT. To change that correlation, it is only necessary to change equations in that model.
Parameters
| Type | Name | Default | Description |
|---|
| Real | pi | Modelica.Constants.pi | |
| Boolean | StaticGasBalances | false | |
| Integer | Nr | 2 | Number of tube rows |
| Integer | Nt | 2 | Number of parallel tubes in each row |
| SI.Length | Lt | | Length of a tube in a row |
| SI.Length | Dint | | Internal diameter of each tube |
| SI.Length | Dext | | External diameter of each tube |
| SI.Density | rhom | | Density of the tube metal walls |
| SI.SpecificHeatCapacity | cm | | Specific heat capacity of the tube metal walls |
| SI.Area | Sb | | Cross-section of the boiler (including tubes) |
| SI.Area | Sb_net | Sb - Nr*Nt*Dext*pi*Lt | Net cross-section of the boiler |
| SI.Length | Lb | | Length of the boiler |
| SI.Area | St | Dext*pi*Lt*Nt*Nr | Total area of the heat exchange surface |
| SI.CoefficientOfHeatTransfer | gamma_nom | 150 | Nominal heat transfer coefficient - gas side |
Components
| Type | Name | Default | Description |
|---|
| Gas.FlangeA | gasIn | | |
| Gas.FlangeB | gasOut | | |
| Water.FlangeA | waterIn | | |
| Water.FlangeB | waterOut | | |
| Water.Flow1DFV | WaterSide | | |
| Thermal.MetalTubeFV | TubeWalls | | Tube |
| Gas.Flow1DFV | GasSide | | |
| Thermal.CounterCurrentFV | CounterCurrent1 | | |
GasMedium