• Design and execution of experiment (data generation).
•Develop simulation to model
experiment.
•Run simulation and generate
results.
•Compare actual data versus
simulation.
• Repeat above steps until data and
simulation agree within desired
tolerance.
Thermocouple Location Table
Brick
316F
1 in. from Left Bottom
Edge
A
0103
Location
Absolute Geometric
Center
B
0102
VALIDATION OF REFRIGERANT
PHASE CHANGE
Phase Change Experiment. A
robust modeling process needs accurate
simulations of phase changes in thermal
shippers. The phase change validation
process began by designing a simple,
controlled experiment to model the
phase change process in a similar way
to what actually occurs during shipping. In one experiment, two CCT
water-based foam bricks (CCT 316F,
7 × 5 × 1 in.) were placed back-to-back, with three thermocouples
(TCs) in between them, and secured
together. This approach eliminates
the need to insert the TCs directly
into the frozen bricks, and makes
exact TC geometric location easy
Midpoint of Absolute
Center and Top
C
0105
Table 1: The location of each thermocoupling shown in Figure 1 can be referenced here.
to control. The taped brick assembly was placed into an environmental chamber at –20ºC, and once all
three TCs verified that the bricks
were completely frozen, the assembly was suspended in a temperature-controlled (ambient, 22ºC) chamber
with the configuration and direction
of gravity as shown in Figure 1.
The thermal response of the brick
assembly, including phase change,
26
24
22
20
18
16
14
12
Temperature (ºC)
10
8
6
4
2
0
- 2
- 4
- 6
- 8
- 10
- 12
- 14
- 16
- 18
- 20
-22
012345
Location A Data: TC 01 03
Location A Data: Node 49537
Ambient Temperature
6 7 8 9 10 11 12 13
Time (hrs.)
78.8
75.2
71.6
68.0
64.4
60.8
57.2
53.6
50.0
46.4
42.8
39.2
35.6
32.0
28.4
24.8
21.2
Temperature (ºF)
17. 6
14.0
10. 4
6. 8
3. 2
-0.4
- 4.0
- 7. 6
14
Figure 2a: Foam Brick Phase Change Data vs. Simulation for TC location “A.” The agreement between
the actual TC data and the simulation shows the phase change time for each TC location are close to
actual data.
was measured via TC, at the locations
shown in Figure 1, namely: a) 1 in.
from the bottom left corner, b) the
absolute geometric center, and c) the
midpoint between the geometric center and the top edge. The data were
collected, and temperature versus time
graphs were constructed for each of the
three TCs and the chamber (ambient).
Phase Change Simulation and
Comparison of Results. The brick
geometry was generated via solid modeling software and input into the analysis program, along with the thermal
properties—density, specific heat, and
thermal conductivity—of solid ice.
To account for phase change from
solid ice to liquid water, thermal
conductivity and specific heat variation were input into the program,
along with the corresponding latent
heat of fusion. The brick geometry was meshed using solid elements.
The air surrounding the brick was
assigned room temperature properties and meshed using fluid elements
(perfect thermal contact was assumed
between the two bricks).
A 3-D transient thermal model,
including both conduction and free
convection was then executed. To
replicate the above testing conditions, an initial condition of –20ºC
was assigned to the entire solid brick
