rf-accelerating structure: cooling circuit modeling riku raatikainen 16.8.2010

RF-Accelerating Structure:Cooling Circuit Modeling

Riku Raatikainen16.8.2010

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

Content

• 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.


General

• 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


Introduction to improved cooling circuit modeling


First test models

Implementation to SAS cooling and comparing the efficiency to the model done by using 3D CFD

Applying the method to up- to- date model

Process

Methodology

• 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

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

Methods

Fluid elements connected to the copper body via

surface elements (APDL)


Structural Thermal

Young's Modulus

(Pa)

Poisson's Ratio Density

(kg/m^3)

Thermal Expansion

(1/°C)

Thermal Conductivity

(W/m·°C)Specific Heat

(J/kg·°C)

Copper Alloy 110E9 0.34 8300 1.80E-05 401 385

Water 1000 4.20E-02 0.645 4187

• 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)

Materials

• 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


Improved cooling circuit model


Mesh, loads & boundary conditions

simply supported

simply supported

fixed

nonlinear heat flux(EDMS 964717 v.1)

standard earth’s gravity

Beam


Results

Temperature distribution (unloaded)

Max. 35.37 °C, ≈ 1.6 % off from heat balance

Twater in = 25 °C Twater out = 35.37 °C


Temperature distribution (loaded)

Max. 33.49 °C, ≈ 1.6 % off from heat balance


Results


Temperature distribution in the copper body (unloaded)

Temperature distribution in the copper body (loaded)

Results


Axial displacement (unloaded)

Axial displacement (loaded)

Maximum vertical displacement ≈ 2.8 μmunloaded -> loaded

Results

• 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


Conclusions


Extra

The method is already being applied to module level cooling by Risto


Case StudyLab Test Module

• 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


Introduction

mass flow out

mass flow in at 25 °C environment at 30°C


fixed

simply supported

standard earth’s gravity

nonlinear heat flux(EDMS 964717 v.1)

Mesh, loads & boundary conditions


Results

Temperature distribution (unloaded)

Max. 35.19 °C ≈ - 0.1% off from heat balance



Temperature distribution (loaded)

Max. 33,37 °C ≈ 0.2 % off from heat balance

Results



Temperature distribution in the copper body (unloaded)

Temperature distribution in the copper body (loaded)

Results


Beam

Illustration of the vertical displacement field of the iris (the most critical) from unloaded to loaded case

Max ≈ 2.8 μm

Results


- 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.

Pressure loss

Total pressure drop ≈ 101,34 mbars (ansys)≈ 100,53 mbars (hand calc.)

• 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


Conclusions

Thank you

rf-accelerating structure: cooling circuit modeling riku raatikainen 16.8.2010

Documents

improved cooling modeling

sas cooling

thermalstructural modeling

d thermal fluid elements

d fluid flow

methods fluid elements

efficient modeling method

surface elements apdl