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The Heat Exchange tab is where the user sets
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the Surface Heat Exchange model and Bed Heat Exchange
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parameters as shown in Figure 1.
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Settings that are relevant to surface heat exchange are provided in
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the Surface Heat Exchange frame with sub-divisional parameter settings that are additional depending on which model is selected. There are five models for the simulation of Surface Heat Exchange process as below.
- No Atmospheric Linkage
- Full Heat Balance (Legacy)
- External Equilibrium Temperature
- Constant Equilibrium Temperature Coefficient
- Equilibrium Temperature
- COARE3.6
- Equilibrium Temp (CE-QUAL-W2 Method)
- External Equilibrium Temperature
If the Full Heat Balance
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These options are described further below.
The ASER.INP file must be used for all of the thermal sub-models to compute the surface and bottom heat exchange processes. Also, depending on whether the current model is EFDC_GVC or EFDC+, the EFDC+ Explorer form will have different options shown in the tab.
Figure 1 Surface Heat Exchange Options.
The Full Heat Balance with Variable Extinction Coefficient option provides the user with the option of allowing light extinction to be dependent on the total suspended solids in the water column, thereby making light extinction temporally and spatially varying. The extinction factors are determined on a cell-by-cell basis for each time step based on TSS, and if the water quality model is active, based on particulate organic matter, dissolved organic matter, and chlorophyll-a as well.
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or COARE3.6 model is used, the user needs to specify the Heat Transfer Coefficients (Figure 2) and COARE parameters (Figure 3), respectively, while other models require no further specifications. A technical blog analyzing the performance of COARE 3.6 in comparison with the equivalent models has been published by DSI.
Anchor Figure 1 Figure 1
Figure 1. Temperature Parameters - Heat Exchange tab.
The bed heat exchange configuration can be assessed under the Bed Heat Exchange option. The user can set to allow temporal variation of bed temperatures by checking the box. The Heat Transfer Coefficient larger than 0 enables the heat flux between water and the sediment bed. Attention should be given to the unit conversion of this coefficient from W/m2/°C to m/s. If the entry is larger than 1E-05 m/s, which is outside the conventional range, EE checks and corrects by multiplying it with 2.39E-07. The Convective Heat Transfer Coefficient is dimensionless and used to simulate the heat exchange at the sediment bed with the presence of solar radiation.
Anchor Figure 2 Figure 2
Figure 2. Surface Heat Exchange - Full Heat Balance.
Anchor Figure 3 Figure 3
Figure 3. Surface Heat Exchange - COARE 3.6.