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Natural Convection & Cooling PHY3138 Will Surridge Monday 23rd October 2017

Outline • Introduction – Heating and cooling aluminium shafts

• The Physics – Background theory • Experiment – The setup and method • Preliminary Results – Initial data collected

• Preliminary Findings – What we need to change • What happens next • Summary Monday 23rd October 2017

Introduction • • • •

Set of 9 aluminium shafts Heating and measuring cooling Size should affect convection Finish should affect radiation

• AIM: Calculate emissivity coefficient and heat transfer coefficient for the shafts. Monday 23rd October 2017

The Physics • 3 types of heat transfer: Conduction, Convection, Radiation • Assume effects of conduction negligible

American Journal of Physics 61 , 568 (1993); doi: 10.1119/1.17211

Monday 23rd October 2017

Experiment • Heat in water bath • Cool in a metal containment cylinder • Rise off table • Suspend with wire • Use thermistors and Arduino for data collection Monday 23rd October 2017

Preliminary Results

Direct contact with shaft

Monday 23rd October 2017

Distributed in containment cylinder

Preliminary Findings Need to change: • Separation of thermistors • Fixing of thermistors • Increasing cable lengths to Arduino • Improving efficiency of the Arduino code • Cool shafts down for longer

Monday 23rd October 2017

What happens next • • • • • •

Impliment changes Setup of analysis spreadsheet Measurements of shafts Data collection for the different sizes & finishes Analysis to calculate emissivity & heat transfer coefficient Identify and implement improvements if time permits

Monday 23rd October 2017

Summary • • • •

Heating up and cooling down aluminium shafts Measuring temperature in various places around the shaft Calculating emissivity and heat transfer coefficients Comparing to known values for the different surface finishes

Monday 23rd October 2017...