Download Coupled thermal-structural modeling

RF-Accelerating Structure:
Cooling Circuit Modeling
Riku Raatikainen
16.8.2010
Content
Part I
Improved cooling circuit modeling
- About me and my work at CERN
- Introduction to improved cooling circuit modeling
- Coupled thermal-structural modeling
- Used engineering data
- Improved cooling circuit model
- Results for the SAS solved earlier by using CFD
(computational fluid dynamics)
- Conclusion
Part II
Case study: Test Lab Module
- Introduction
- Results
- Conclusion
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
General
• Summer trainee of HIP (3 months)
• Student in Master’s Degree Programme of Mechanical Engineering majoring in
Applied Mechanics
• Main task and motivation
- Improved cooling circuit modeling for TMM accelerating structures
- The aim was to gain more efficient modeling method in order to solve
current and future coupled thermal-structural models.
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Introduction to improved
cooling circuit modeling
• Coupling CFD and structural analysis problems usually leads to complicated and
computationally quite heavy models
•This is due to coupling of the equations of continuum mechanics and fluid
dynamics which especially in 3D cases occur to be very complex
• The improved cooling modeling that is to be presented here reduces this 3D
fluid flow into 1D flow which is still capable of acting in a 3D environment
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Methodology
Implementation to SAS cooling and comparing
the efficiency to the model done by using 3D CFD
First test models
Process
Applying the method to up- to- date model
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Methods
• Problem was solved by using 1D Thermal Fluid elements (FLUID 116) which have both temperature and
pressure degree of freedom
• The element has a ability to conduct heat and transmit fluid between its two primary nodes
• The solid copper body was connected to the fluid elements via convection surface elements
• If the pressure is a degree of freedom the element is always nonlinear
! Convec is named component of nodes on convection surfaces.
! Piping is the named component of fluid elements
! NDSURF - Generates surface elements and connects them to the fluids
ndsur f,'Convec','Piping', 3
! Surface elements in 3D environment
! Specification of mass flows - Note direction lines
Fluid elements connected
to the copper body via
surface elements (APDL)
cmsel, s, Piping
sfe, all,, hflux,,0.01922
! Mass flow definition
esel, s, type,,5000
sfe, all,, conv,, 3737
! Heat transfer coefficient
alls
fini
/solu
*******************************************
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Materials
• The heat transfer coefficient used between the water and copper is 3737 W/m²·°C (EDMS 964717 v.1)
• The mass flow rate is 276.7/4 l/hr for one SAS (EDMS 964717 v.1)
• The error estimation for the absorbed heat by the water is done by using the heat conservation
• Unit system in (N, m, s, kg, °C)
Structural
Copper
Alloy
Young's
Modulus
(Pa)
Poisson's
Ratio
110E9
0.34
Water
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Thermal
Density
(kg/m^3)
Thermal
Expansion
(1/°C)
Thermal
Conductivity
(W/m·°C)
Specific Heat
(J/kg·°C)
8300
1.80E-05
401
385
1000
4.20E-02
0.645
4187
Improved cooling circuit
model
• In this case calculations were done to one of the SAS which was analyzed earlier by using 3D CFD
• Instead of applying a 3D fluid flow directly into the cooling channel, a separate wiring model was
created which transports the fluid inside the structure
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Mesh, loads & boundary
conditions
standard earth’s gravity
nonlinear heat flux
(EDMS 964717 v.1)
simply supported
fixed
Beam
simply supported
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Results
Twater in = 25 °C
Twater out = 35.37 °C
Temperature distribution (unloaded)
Max. 35.37 °C, ≈ 1.6 % off from heat balance
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Results
Twater in = 25 °C
Twater out = 33.49 °C
Temperature distribution (loaded)
Max. 33.49 °C, ≈ 1.6 % off from heat balance
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Results
Temperature distribution in
the copper body (unloaded)
Temperature distribution in
the copper body (loaded)
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Results
Axial displacement
(unloaded)
Axial displacement
(loaded)
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Maximum vertical displacement ≈ 2.8 μm
unloaded -> loaded
Conclusions
• 1D thermal fluid elements gives excellent results and they are in agreement
with the previous ones
• Computational time collapsed to only a fractions compared to the results
obtained by using 3D-CFD
• New and more efficient method of solving coupled thermal-structural problems
was achieved.
• Moreover, the method provides an efficient tool to design optimisation
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Extra
The method is already being applied
to module level cooling by Risto
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Case Study
Lab Test Module
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Introduction
• The design parameters are the same as above but the diameter of the channel is now 6 mm instead
of 7 mm. Hence, the flow is more turbulent.
• Both thermal and structural analysis is performed. Moreover, the pressure loss is obtained
• The geometrical model with the cooling routing is presented below
mass flow out
mass flow in at 25 °C
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
environment at 30°C
Mesh, loads & boundary
conditions
standard earth’s gravity
nonlinear heat flux
(EDMS 964717 v.1)
fixed
simply supported
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Results
Twater in = 25 °C
Twater out = 35.19 °C
Temperature distribution (unloaded)
Max. 35.19 °C ≈ - 0.1% off from heat balance
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Results
Twater in = 25 °C
Twater out = 33.37 °C
Temperature distribution (loaded)
Max. 33,37 °C ≈ 0.2 % off from heat balance
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Results
Temperature distribution in
the copper body
(unloaded)
Temperature distribution
in the copper body
(loaded)
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Results
Beam
Illustration of the vertical displacement field of the iris (the most critical)
from unloaded to loaded case
Max ≈ 2.8 μm
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Pressure loss
- Flow was considered to be continuous, fully developed and turbulent. Friction factor was calculated by using the
implicit Colebrook-White equation for smooth pipes, f ≈ 0.037
- Element reduces the pipe into a straight pipe. Minor losses in the elbows was taken into account as a equivalent
length.
Total pressure drop
≈ 101,34 mbars (ansys)
≈ 100,53 mbars (hand calc.)
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Conclusions
• The 1D fluid elements are capable of working efficiently also in more complex
geometries
• For more even thermal distribution, a smaller mass flow rate can be used for
loaded case
• Moreover, different kinds of support boundary conditions can be used to adjust
the displacement field
• Pressure loss can minimized by using larger radius tubes and bendings, if
needed
Cooling Circuit Modeling, Riku Raatikainen, 16.8.2010
Thank you