RF-Accelerating Structure: Cooling Circuit Modeling Riku Raatikainen

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, 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. Cooling Circuit Modeling, Riku Raatikainen, 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 Cooling Circuit Modeling, Riku Raatikainen, Introduction to improved cooling circuit modeling

Cooling Circuit Modeling, Riku Raatikainen, 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,, ! Mass flow definition esel, s, type,,5000 sfe, all,, conv,, 3737 ! Heat transfer coefficient alls fini /solu ******************************************* Cooling Circuit Modeling, Riku Raatikainen, Methods Fluid elements connected to the copper body via surface elements (APDL)

Cooling Circuit Modeling, Riku Raatikainen, Structural Thermal Young's Modulus (Pa) Poisson's RatioDensity (kg/m^3) Thermal Expansion (1/°C) Thermal Conductivity (W/m·°C) Specific Heat (J/kg·°C) Copper Alloy110E E Water E The heat transfer coefficient used between the water and copper is 3737 W/m²·°C (EDMS v.1) The mass flow rate is 276.7/4 l/hr for one SAS (EDMS 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 Cooling Circuit Modeling, Riku Raatikainen, Improved cooling circuit model

Cooling Circuit Modeling, Riku Raatikainen, Mesh, loads & boundary conditions simply supported fixed nonlinear heat flux (EDMS v.1) standard earth’s gravity Beam

Cooling Circuit Modeling, Riku Raatikainen, Results Temperature distribution (unloaded) Max °C, ≈ 1.6 % off from heat balance T water in = 25 °C T water out = °C

Cooling Circuit Modeling, Riku Raatikainen, Temperature distribution (loaded) Max °C, ≈ 1.6 % off from heat balance T water in = 25 °C T water out = °C Results

Cooling Circuit Modeling, Riku Raatikainen, Temperature distribution in the copper body (unloaded) Temperature distribution in the copper body (loaded) Results

Cooling Circuit Modeling, Riku Raatikainen, Axial displacement (unloaded) Axial displacement (loaded) Maximum vertical displacement ≈ 2.8 μm unloaded -> 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 Cooling Circuit Modeling, Riku Raatikainen, Conclusions

Cooling Circuit Modeling, Riku Raatikainen, Extra The method is already being applied to module level cooling by Risto

Cooling Circuit Modeling, Riku Raatikainen, Case Study Lab 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 Cooling Circuit Modeling, Riku Raatikainen, Introduction mass flow out mass flow in at 25 °Cenvironment at 30°C

Cooling Circuit Modeling, Riku Raatikainen, fixed simply supported standard earth’s gravity nonlinear heat flux (EDMS v.1) Mesh, loads & boundary conditions

Cooling Circuit Modeling, Riku Raatikainen, Results Temperature distribution (unloaded) Max °C ≈ - 0.1% off from heat balance T water in = 25 °C T water out = °C

Cooling Circuit Modeling, Riku Raatikainen, Temperature distribution (loaded) Max. 33,37 °C ≈ 0.2 % off from heat balance Results T water in = 25 °C T water out = °C

Cooling Circuit Modeling, Riku Raatikainen, Temperature distribution in the copper body (unloaded) Temperature distribution in the copper body (loaded) Results

Cooling Circuit Modeling, Riku Raatikainen, Beam Illustration of the vertical displacement field of the iris (the most critical) from unloaded to loaded case Max ≈ 2.8 μm Results

Cooling Circuit Modeling, Riku Raatikainen, 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 ≈ 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 Cooling Circuit Modeling, Riku Raatikainen, Conclusions

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