Smart Solar Tanks with Variable Auxiliary Volume
Jianhua Fan
Associate Prof., Ph.D.
Department of Civil Engineering, DTU
Tele: 45251889
DTU Byg, Danmarks Tekniske Universitet 2
Content
• Why smart solar tank?
• How does a smart solar tank work?
PIV (Particle Image Velocimetry) measurement CFD (Computational Fluid Dynamics) simulation
• Preliminary conclusion and future plans
15.06.2011
Smart Solar Tanks with Variable Auxiliary Volume
auxiliary volume: the (upper) part of tank which is heated to a temperature between 50-60ºC by auxiliary energy (for example oil/gas/electricity)
Why smart solar tank?
A traditional tank with fixed auxiliary volume
Advantages of a solar tank with a variable auxiliary volume
• lower heat loss from the tank
• higher system thermal performance
Smart solar tanks with a variable auxiliary volume fitted to expected energy demand
DTU Byg, Danmarks Tekniske Universitet
How to achieve a variable auxiliary volume?
15.06.2011 4
A variable tank volume is charged by the heating element in the side arm by means of thermosyphoning.
A tank with internal heating elements at different levels
A tank with a side arm with a built- in heating element
heating element
A variable tank volume is charged by the heating elements at different levels.
View A Electric heating
element
For the purpose of model validation
Tank design
Does it work and how it works?
CFD model of the tank with an internal heating
element
DTU Byg, Danmarks Tekniske Universitet
Does it work and how it works?
CFD model of the tank with a side arm
6
View A and B View C
Electric heating element
For the purpose of model validation
15.06.2011
Tank design
Does it work and how it works?
Fluid flow and temperature measurement
PIV=Particle Image Velocimetry
DTU Byg, Danmarks Tekniske Universitet
Thermal stratification in the smart solar tanks during charging
8
0.0 0.2 0.4 0.6 0.8 1.0
19 20 21 22 23 24 25 26
Height, m
Temperature, °C
Measurement: 10 min Measurement: 30 min Measurement: 58 min CFD: 10 min
CFD: 30 min CFD: 58 min
0.0 0.2 0.4 0.6 0.8 1.0
19 24 29 34 39 44 49
Height, m
Temperature, °C
Measurement 10 min Measurement 30 min Measurement 60 min CFD: 10 min
CFD: 30 min CFD: 60 min
A tank with an internal heating element Charging power: 0.5 kW
A tank with a side arm Charging power: 3 kW
15.06.2011 VIP Presentation
temperature sensor
Flow field comparison between PIV and CFD
vel 0.15 0.1 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.001
0.04 m/s
velocity-magnitude 0.15 0.1 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.001
0.04 m/s
PIV CFD
DTU Byg, Danmarks Tekniske Universitet
Influence of charging power on thermal stratification in the tank
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Charging power 1 kW
Duration: 30 min Charging power 3 kW
Duration: 30 min
Influence of charging power on flow
circulation in the tank
DTU Byg, Danmarks Tekniske Universitet 12
Preliminary conclusions
• CFD models have been created and validated for smart solar tank with an internal heating element and tank with a side arm.
• The validated CFD models will be used to investigate the influences of the following parameters:
charging power, diameter & location of the side arm, design and location of the heating element.
• The validated CFD models will be used to determine the optimal design of smart solar tank.
15.06.2011
Fabric
stratifier Fabric
stratifier
3 kW 3 kW
3 kW
Fabric stratifier
9 kW
PEX-pipe PEX-pipe
Auxiliary energy – different ways of charging System sketch
Cold water/hot water
DTU Byg, Danmarks Tekniske Universitet
Three solar combisystems with differently designed smart tanks will be tested in PTF.
