Thermal simulation of a pellet boiler and a heat storage tank for future control strategies

Transcription

1 Thermal simulation of a pellet boiler and a heat storage tank for future control strategies Rosemarie Schnetzinger MSc

2 Content Motivation Model Concept Pellet Boiler Model Concept Heat Storage Tank Simulation Results Conclusion and Outlook Acknowledgement Slide 2

3 Motivation: Efficiency Enhancement of Heating Systems Influences on efficiency: Heat generator Distribution system Collaboration of heating system control strategy Determination of efficiency: Measurement Simulation Slide 3 Simulation model for development of efficient control strategies

4 Content Motivation Model concept pellet boiler Model concept heat storage tank Simulation Results Conclusion and Outlook Acknowledgement Slide 4

5 Model Concept Pellet Boiler I Simulating the physical layer of a boiler: Thermodynamic relationships and heat balances Heat transfer through conduction, convection and radiation Heat storage in material and water Assumption: complete combustion or no combustion Empirically determined parameters (e.g. fitting parameter in the heat exchanger ) Adjustable for different boiler types by changing parameters (e.g. size, water volume, material properties ) Slide 5

6 Model Concept Pellet Boiler II System Boundary Slide 6

7 Content Motivation Model concept pellet boiler Model concept heat storage tank Simulation Results Conclusion and Outlook Acknowledgement Slide 7

8 Model Concept Storage Tank I One-dimensional mulit-node model Conductional heat transfer and fluid dynamics Each node represents a cylinder Number of nodes is free but at least 3 nodes (top, middle, bottom) Heat exchange only in top and bottom node implemented Node 1 Node 2 Node 3 Node 4 Node 5 Node n-1 Node n Slide 8

9 Model Concept Storage Tank II Operation modes Charging: Heat at the top into the tank Temperature at the bottom as return temperature into the boiler Discharging: Heat at the top out of the tank to the consumer Tank temperature decreases Storing No heat into or out of the tank Tank temperature decreases due to losses to the ambient Node 1 Node 2 Node 3 Node 4 Node 5 Node n-1 Node n Slide 9

10 Content Motivation Model concept pellet boiler Model concept heat storage tank Simulation Results Conclusion and Outlook Acknowledgement Slide 10

11 Simulated Cycle of Operation I Pellet boiler with 25 kw nominal power Thermal storage tank with 1,500 litres Load cycle representing heat demand for heating and hot water production over one day Connection modes: Boiler ON, tank in charging mode Boiler OFF, tank in discharging mode Consumer Consumer Storage Storage Pellet Tank Pellet Tank Boiler Boiler Slide 11

12 Simulated cycle of Operation II Slide 12

13 Simulation Results I Heating Energy: Measurement: 304 kwh Simulation: 296 kwh Difference 8 kwh (2,6%) Slide 13

14 Simulation Results II Slide 14

15 Simulation Results III Slide 15

16 Conclusions & Outlook Simulation results correspond quite well to the measurement data Thermal behaviour of real devices can be estimated Further simulations and adaption of empirical parameters will minimize differences For simulating heating systems models for pipes, valves and pumps are necessary Development of control algorithms by simulation will be possible soon Slide 16

17 Acknowledgement The work funded in the frame of the Kplus- & COMET-programme of the Austrian Federal Government. The funding by the Austrian Research Promotion Agency (FFG) and the Federal Governments of the Provinces Styria and Lower Austria shall be highly acknowledged. Industrial project partners: Slide 17

18 Thank you for your attention! Rosemarie Schnetzinger MSc Junior Researcher Bioenergy GmbH, Location Wieselburg, Austria