FIREWALKING

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FIREWALKING

• Brian Casaday
• Cody Heslington

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Introduction

• Firewalking has been practiced for thousands of
  years by people from all parts of the world. It
  is observed as an organized event in many
  different cultures and religions. It is by some,
  thought to be a paranormal phenomena accomplished
  only by those of high spiritual faith or of those
  who claim total mind over body control.
• The objective of our project is to scientifically
  explain why firewalking is possible. We will do
  this through the use of heat transfer principles
  and equations

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Why the Foot Doesnt Burn

• The thermal conductivity of coarse charcoal is
  very small and that of skin or flesh is only
  about four times more (the thermal conductivity
  of most metals is several thousand times larger)
• Charcoal has a very low heat capacity
• Because of the coarseness of the charcoal and how
  the foot is placed when walking, not all of the
  foot is in contact with the charcoal the whole
  time.
• Layer of cooler ash on top of coals acts as
  insulation (low conductivity)
• Body has high heat capacity

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The Problem

• Calculate the change in temperature of the bottom
  of the foot after being in contact with hot
  charcoal for a 3 second period.
• Assumptions
• Values obtained online for skin density and heat
  capacity are correct.
• Equations used in the calculations are legitimate
  for the application.
• Preface This is a fairly complex heat transfer
  problem to model accurately. The methods used
  may not be exact but will provide a good
  approximation

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The Set-up

• Use thermal resistance method to determine heat
  transfer into the foot and ultimately change in
  bottom of foot temperature
• Find all values necessary for calculation (i.e.
  thermal conductivities of charcoal and human
  tissue)
• Calculate resistance values for both skin and
  thin fat layer beneath skin
• Calculate increase in foot surface temperature.
  Evaluate value for significance

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The Set-up
Calculations
q
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Results

• Our calculations show that after 3 seconds of
  contact with the coals the temperature change is
  only 8 degrees Kelvin. This is not a large enough
  increase to cause a significant amount of pain.

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Conclusion

• Firewalking of a short length is something any
  physically fit person could do and does not
  require a particular state of mind.
• It is the short time of contact and the low
  thermal capacity and conductivity of the coals
  that is important.

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Appendix A

• References
• -Howstuffworks.com, Marshall Brain
• http//people.howstuffworks.com/firewalking.h
  tm
• -Firewalking Myth vs. Physics, David Willey
• http//www.howstuffworks.com/framed.htm?par
  entfirewalking.
• htmurlhttp//www.pitt.edu/dwilley/Fire/FireTxt/
  fire.html

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Appendix B

• Detailed Solution

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Appendix C

• List of Values Used in Calculations
• THERMAL CONDUCTIVITY (W/m K ) TEMPERATURES OF
  MATERIALS ( C)
• kskin .37 Tcoal 538 C (1000 F,
  811 K)
• kcoal .1 Tash 205 C (400 F,
  478 K)
• kash .08 Tfoot,i 32.2C (90 F,
  305.2 K)
• kfat .2
• Kair .044 SURFACE AREA OF FOOT .02
  m2
• LENGTH OF MATERIAL (meters) DENSITY OF
  MATERIALS (kg/m3)
• Lskin .001 ?fat 920
• Lcoal .01 ?skin 1010
• Lash .02 ?avg 965
• Lfat layer .002
• Lair .01 HEAT CAPACITY OF MATERIALS
  (J/kg K) cp,fat 2973
• cp,skin 3662
• cp,avg 3318