Transcript Ice - IYPT Archive

Reporter: Hsieh, Tsung-Lin
Question
 A wire with weights attached to each end is placed
across a block of ice.
 The wire may pass through the ice without cutting
it.
 Investigate the phenomenon.
Outline
 Experimental setup
 Typical results
 Hypothesis
 Pressure effect
 Weight
 Thermal conductivity
 Curvature
 Other effect
 Summary
Experimental Setup
Ice
Camera
Weights
Typical Result
 The wire position is
obtained by MATLAB
program.
Duration: 1 hr
Pressure Effect
 Ice under the wire tends to melt.
Heat
Schematic Phase Diagram
Pressure
Wire pressure
Atmospheric
pressure
Solid
Liquid
Ice
Gas
Temperature
Schematic Phase Diagram
Pressure
Wire pressure
Cutting
Atmospheric
pressure
Ice+Water
Hot
Absorbing
heat
Cold
Liquid
Solid
Gas
Temperature
Schematic Phase Diagram
Pressure
Hot
Cold
Releasing heat
Atmospheric
pressure
Solid
Liquid
Ice
Gas
Temperature
Pressure effect
Weight
Thermal conductivity
Curvature
Hot
Cold
Speed at Center
 Speed of the center of the wire after it sinks into the
ice.
distance
Weight
Stainless steel
wire 0.4mm
 3kg: 0.11
 4kg: 0.18
 5kg: 0.26
 6kg: 0.30
 7kg: 0.39
 8kg: 0.49
(cm/min)
Weight vs. Speed at Center
Stainless steel
wire 0.4mm
Pressure
l
s
g
Temperature
Mathematical Estimation
• Heat conducting rate:
dQ
A
dm
 k T  L
 L( Av )
dt
d
dt
• From Clausius-Clapeyron equation,
T0  T
P  L  ln
T0
A
l
• Center speed upper limit
v  101 cm / min
d
• Pressure effect plays an important role.
Hot
Cold
Material vs. Speed at Center
Thermal Conductivity
(W/m-K)
 Aluminum : 235
 Steel : 16.3
speed: 0.34
cm/min
speed: 0.30
cm/min
 Good thermal
conductor cuts faster.
Water Flow Video
Pressure and Curvature
T
T
θ
F 2T sin  T


A 2r * d rd
1
curvature
r
Cross-section of the Wire
θ
r
θ θ
d
Ice
Cutting Speed
 After the whole wire sinks into the ice:
External heat
input is more
significant
Left side
Pressure effect
dominates
center
External Heat Effect
 Water melts due to
external heat input
 It can solidify again
because the temperature
inside the ice is below
00C (-150C~ -0.60C). External
heat
Summary
 The wire passes through the ice
 Pressure effect
 External heat effect
 The ice regelates (without being cut)
 Pressure releases
 Temperature inside the ice is below 00C
Thank you for your attention.
Ambient Temperature
 The “speed at center”
is almost constant.
 Repeatable in
different temperature
(230C~280C).
 Ambient heat can be
neglected.
Weight
 6kg: 0.12
 4kg: 0.06
 3kg: 0.05
(cm/min)
Temperature inside the Ice
Time interval:
5 min
Time interval:
5 min
Curvature vs. Speed
 At the Beginning of Cutting:
Pressure effect
dominates
Left side
center
Patterns formed on regelated ice
Speed v.s. Curvature –at time 1
 In the middle of the ice, speed
is positively related to the
curvature.
 The speed is faster at both side
because of external heat.
Fig. Speed of the whole wire
Fig. Acceleration
Speed v.s. Curvature –at time 2
 In the middle of the ice, speed
is positively related to the
curvature.
 The speed is faster at both side
because of external heat.
Fig. Speed of the whole wire
Fig. Acceleration