Post on 05-Jan-2016
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