CLIC Prototype Test Module 0Super Accelerating Structure

Thermal Simulation

Introduction

Theoretical background on water and air cooling

FEA Model

Conclusions / Next steps

CLIC Test Module Meeting 3.10.2012Lauri 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

Qrf = Qw + Qa

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 > 500 000 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

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 Tin = 25°C

Mass flow m = 0.019kg/s = 0.068m3 / h

Heat transfer coefficient hw = 4196 W/(m2 K)

FEA MODEL

Boundary conditions for water cooling system

Ambient air temperature T∞ = 30°C

Heat transfer coefficient to air ha = 3.8 W/(m2 K)

FEA MODEL

Boundary conditions for air convection

Heat dissipation from AS Qrf = 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 Qa = 18.5W (2.3% of the total) Heat flow to water Qw = 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 Ts decrease

FEA MODEL

Case Mass flow m(m3/h)

Heat transfer coefficient to waterhw

(W / m2 K)

Temperature rise in the cooling channeldTw

(°C)

Maximum temperature of structureTs

(°C)

Heat flow to waterQw

(W)

Heat flow to airQa

(W)

1 0.068 4196 9.842.6

781.5 18.5

2 0.090 5227 7.539.7

788.3 11.7

3 0.108 6047 6.338.1

792 8

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

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

Case Speed of airu

(m/s)

Ambient temperature

T∞ (°C)

Heat transfer coefficient to air

ha

(W / m2 K)

Heat flow to airQa

(W)

% of Qrf

1 0.5 30 3.8 18.5 2.3%

2 0.8 30 4.8 23 2.9%

3 0.5 25 3.8 31.8 4.0%

4 0.8 25 4.8 39.5 4.9%

5 0.5 20 3.8 45.1 5.6%

6 0.8 20 4.8 56.0 7.0%

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