modelPackedBedControlVolume_L4

Information

1. Purpose of model

The model describes an axial-flow packed bed used for thermal energy storage. Gaseous heat transfer fluid and solid media storage material are generally assumed. It has been validated with air as heat transfer fluid and natural rock as storage material. Main focus is the

• transient behavior of the temperature field and
• fluid pressure loss.

2. Level of detail, physical effects considered, and physical insight

• The packed bed is discretized in one dimension, which is the main fluid flow direction
• A single energy equation is used for each finite volume, meaning particle and fluid temperature are not distinct, but a mean packed-bed temperature is used. This generally holds for ideal heat transfer between the storage material and heat transfer fluid. Neverthess, the effect of a limited heat transfer between both can be still taken into account by adoption of the effective packed bed thermal conductivity correlation for example using the approach of Vortmeyer (1974).
• An additional heat port is added at the sides. It can be used to account for other means of heat transport such as conduction, radiation or natural convection besides the advective energy transport into and out of the packed bed.
• An additional body force according to the Darcy-Forchheimer equation is added to the dynamic momentum balance to account for the packed bed flow resistance.
• A storage material medium model is required, which has an additional state variable for the specific internal energy in order to account for a temperature variant specific heat capacity.

3. Limits of validity

• The one-dimensional spatial representation leads to the plug-flow assumption, meaning no lateral temperature and velocity variations are taken into account
• A horizontal air flow direction is assumed, thus no gravitational force is taken into account in the dynamic momentum balance
• Natural convection is not taken into account

4. Interfaces

1. Hot Air Inlet/Outlet
2. Cold Air Inlet/Outlet

5. Nomenclature

(no remarks)

6. Governing Equations

(no remarks)

7. Remarks for Usage

• Packed bed correlations are replaceable
• The momentum balance is dynamic to allow very small mass flows
• The mean sphericity describes the ratio of the surface of a set of monodisperse spheres with the same number and overall volume as the particle set to the particles set surface. It thus is not solely depended on the particles shape, but also on the particle size distribution.

8. Validation

The model is validated with two experimental setup of Siemens Gamesa Renewable Energy in Hamburg-Altenwerder (6 MWh_th) and -Bergedorf (130 MWh_th), Germany.

9. References

Abschlussbericht zum Teilprojekt der TUHH im Verbundforschungsprojekt Future Energy Solution (FES) (BMWI 03ET6072C) (2021)

Electric Thermal Energy Storage based on Packed Beds for Renewable Energy Integration, Dissertation, Hamburg University of Technology, Michael von der Heyde (2021)

10. Version History

First Version in 04.2020 for the research project Future Energy Solution (FES) by Michael von der Heyde (heyde@tuhh.de)

Parameters

Connectors

Components

Contents

Name	Description
Summary
medium_rock
PressureLoss
HeatTransferPB2Wall
HeatTransferPB2Air
ThermalConductivity
Geometry