CLIC Prototype Test Module 0 Super Accelerating Structure Thermal Simulation Introduction Theoretical background on water and air cooling FEA Model Conclusions / Next steps CLIC Test Module Meeting Lauri Kortelainen

INTRODUCTION  Goal of this study is to evaluate the heat dissipation between water and air in steady state conditions  Theoretical background for water and air cooling is provided  The effect of changing cooling parameters is studied  Q rf = Q w + Q a water air rf load

 Heat Transfer coefficient can be calculated in five steps when mass flow is known 1)Calculate speed of water 2)Calculate Reynold’s number 3)Calculate Prandtl’s number 4)Calculate Nusselt’s number (Dittus-Boelter correlation) 5)Calculate Heat transfer coefficient  Total energy carried by the water is WATER COOLING SYSTEM Formulation for heat transfer coefficient

Material properties are evaluated at 30C (bulk temperature of water) Material properties and dimensions of water WATER COOLING SYSTEM

Input to Ansys Heat transfer coefficient calculation Input to Ansys WATER COOLING SYSTEM

AIR COOLING Forced flow over plate  Plate represents the surface of the Super Accelerating Structure  For forced flow over plate (laminar flow) Nusselt number is defined as  Heat flux for air cooling (Newton’s law of cooling)

AIR COOLING  Flow over plate has laminar and turbulent domains  The limit for turbulent behavior is Re > so in this case we can assume fully laminar flow Laminar and turbulent domains u ∞ = 0.5 – 0.8 m/s T ∞ = 20 – 30 °C

Material properties and dimensions AIR COOLING

 The procedure for calculating heat transfer coefficient is similar to that of water cooling system Heat transfer coefficient calculation Input to Ansys

 Super Accelerating Structure  Vacuum manifolds  Waveguides  Cooling channel FEA MODEL Geometry

 Water inlet T in = 25°C  Mass flow m = 0.019kg/s = 0.068m 3 / h  Heat transfer coefficient h w = 4196 W/(m 2 K) FEA MODEL Boundary conditions for water cooling system

 Ambient air temperature T ∞ = 30°C  Heat transfer coefficient to air h a = 3.8 W/(m 2 K) FEA MODEL Boundary conditions for air convection

 Heat dissipation from AS Q rf = 800W FEA MODEL Loads

FEA MODEL Results: Temperature  Maximum temperature 42.6°C in the iris

FEA MODEL Results: Water temperature  Water temperature rises about 9.8°C along the cooling channel

FEA MODEL Results: Heat flow  Heat flow to air Q a = 18.5W (2.3% of the total)  Heat flow to water Q w = 781.5W

Results: The effect of changing mass flow  Increasing the mass flow m leads to more heat going to the cooling system and less to the air  Also the outlet temperature of the water and temperature of the structure T s decrease FEA MODEL CaseMass flow m (m 3 /h) Heat transfer coefficient to water h w (W / m 2 K) Temperature rise in the cooling channel dT w (°C) Maximum temperature of structure T s (°C) Heat flow to water Q w (W) Heat flow to air Q a (W)

Results: The effect of changing mass flow FEA MODEL Case 1 Case 2

Case 3 Results: The effect of changing mass flow Case 3 FEA MODEL

Results: The effect of changing air cooling parameters  Increasing the speed of air u or decreasing ambient temperature T ∞ leads to more heat flow to the air maximum CaseSpeed of air u (m/s) Ambient temperature T ∞ (°C) Heat transfer coefficient to air h a (W / m 2 K) Heat flow to air Q a (W) % of Q rf % % % % % %

CONCLUSIONS  One CLIC prototype TM0 Super Accelerating Structure was modelled in steady state conditions with a heat load, water cooling system and air cooling  The effect of changing cooling parameters was studied  Maximum heat flow to air is 7.0%

NEXT STEPS  Implement air convection to CLIC prototype TM0 thermo-mechanical simulation (ready)  CFD model of lab room provides more accurate results about the behavior of air flow along CLIC modules