Lecture 4: Thermal Analysis Flashcards

1
Q

What is the aim of reactor cooling?

A

To remove heat generated by the fuel. and keep the reactor at a safe temperature.

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2
Q

How is heat transferred?

A

Convection

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3
Q

What is the greatest constraint on how much electricity can be generated?

A

The amount of heat that can be safely extracted.

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4
Q

How do spacer fuel rod supports aid heat extraction?

A

Cause flow turbulence for the coolant to improve heat transfer performance by convection.

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5
Q

What is the general strategy for thermal analysis?

A

Use knowledge of pipe flow.
Convert to flow in an anti-pipe via use of hydraulic/equivalent diameter.

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6
Q

Name five dimensionless numbers:

A

Reynolds Number
Stanton Number
Nusselt Number
Fanning Friction Factor
Prandtl Number

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7
Q

Define Reynolds Number:

A

Ratio between momentum and viscous forces

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8
Q

Define Stanton Number:

A

Relative importance of heat convection through a boundary layer and convection with the flow

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9
Q

Define Nusselt Number:

A

Relative importance of surface convection and conduction

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10
Q

Define Fanning Friction Factor:

A

Ratio of wall shear stress and dynamic pressure

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11
Q

Define Prandtl Number:

A

Ratio of momentum diffusivity and thermal diffusivity

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12
Q

What are the three flow types?

A

Laminar
Turbulent
Transition

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13
Q

Which dimensionless number can indicate flow type?

A

Reynolds number

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14
Q

Which flow type is more effective at extracting energy?

A

Turbulent

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15
Q

Which dimensionless numbers can be used to find the heat transfer coefficient (h)?

A

Nusselt Number
Stanton Number

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16
Q

What is the purpose of the hydraulic diameter?

A

To approximate behaviour in non-circular passages from measurement s in circular ones.

17
Q

What is the importance of preventing boiling?

A

Must ensure water does not convert to steam as it is an extremely poor coolant.

18
Q

True or false: Nucleate boiling is poor at heat transfer?

A

False

19
Q

Which flow type is fastest?

A

Turbulent

20
Q

What Reynolds number is the transition phase of flow?

A

10^3 to 10^4

21
Q

What is the Darcy-Weisbach Friction Factor for laminar flow?

A

= 64/Re

22
Q

What is the Darcy-Weisbach Friction Factor for turbulent flow?

A

= 0.184Re^-0.2

23
Q

What type of convection is used for heat extraction?

A

Forced

24
Q

How is the hydraulic diameter calculated?

A

= 4 (flow area) / wetted perimeter