Zeolite Refrigeration: Cooling the Worlds Vaccines
AcknowledgmentsAdvisor: Doug Bradley, Project Coordinator:
Steven LaguetteKurt Van Nugtren, Walter Yuen, Nelson Bednersh, Mary
Dinh
Team Leader: Sarah Morgan, Heidi Attia, Armando Marquez, Austin
Roth, and Alex Williams
ME 189 CAPSTONE Design Project. June 6, 2008
AbstractThe current process of medical supply transport, called
the cold chain, consists of making several stops en route to reload
medical coolers with ice. The availability of ice and the
protection of vaccines against high temperatures become important
factors in keeping vaccines cool.
Our prototype cooler was able to keep our medical storage
container below 10 for 3 hours without input electricity. Our
design utilizes a zeolite/water adsorption system under vacuum, as
well as phase-change material (PCM) heat sinks, and a thin-walled
aluminum medical storage container for optimized conduction.
Figure 1. Thermodynamic Process
Figure 5. Affect of PCM on Zeolite and Water Temperature
Conclusion Overall, immense progress has been made in creating a
zeolite cooler. We have validated a design that optimizes the shelf
distance and zeolite/water ratio, along with exposed surface. We
recommend further research in PCM heat sinks and a more robust
design. We hope to one day see a portable zeolite cooler for
cooling the worlds vaccines.
References1. Boles, Michael, and Ynus A. engel. Thermodynamics:
An Engineering
Approach Fifth Edition. New York: McGraw-Hill, 2006.2. Latent
Heat of Vaporization, The Triple Point of Water.AVS , 22, Jan.
2008 < http://www.avs.org/pdf/triple%20point.pdf >
Introduction & RequirementsThis design uses a low-grade
vacuum to lower the chamber pressure to the saturation pressure of
the contained water, causing the water to vaporize. Zeolites,
naturally occurring molecular sieves, rapidly absorb the water
vapor which forces the water to continue vaporizing. The water
temperature decreases according to the energy lost due to
vaporization(1). Utilizing experimental data and theory from
previous research, in addition to our own data and theory, a
prototype was built using the following requirements: Maintain
effective pressure of 0.61 kPa Maintain temperature between 0-10C
for 3 hours
With the pressure requirement met, the thermodynamic process
between the water and zeolites will successfully occur, lowering
the water temperature inside of the chamber and keeping our medical
storage container below 10 C. Energy BalanceEnergy Balance
QQwaterwater ++ QQconvectionconvection = = EEvaporvapor(1) (1)
mcmcpp T + (hT + (hstag,airstag,airA A T)*t = T)*t =
hhfgfgmmvaporizedvaporized
MethodsA lab prototype of a medical storage container and
cooling chamber (Fig 2b-c) was fabricated to study the transient
temperatures in the chamber during the thermodynamic process. The
lab model consists of three thermocouples and a shelf to hold the
zeolites (Fig. 2a).
ResultsIt was found that the closer the zeolites are to the
water surface, the quicker the water cools (Fig. 3).
Figure 3. Shelf Distance Figure 4. Zeolite/Water Ratio
A 5:1 zeolite ratio formed ice the quickest by reaching 0C in
approximately three minutes (Fig. 4). Even though the 10:1 and 5:1
ratio had similar paths, the 10:1 ratio is less efficient. The 10:1
ratio requires more zeolites to achieve nearly the same path as the
5:1 ratio.
A longevity test was completed over a span of 3 hours using PCM.
As seen in Figure 6, by the end of the 3 hour test period, the
water was still measured to be below 10C, which fulfills our
requirement.
While testing to improve the duration of our cooling process,
the use of PCM heat sinks significantly improved our design. PCM
heat sinks provide a means of absorbing heat from the zeolite bed,
preventing the heat from circulating and affecting the ice created
in the chamber.
Figure 6. Successful 3 hour Test
B
C
D
A
Figure 2. A) Setup of lab model testing B) Lid C) Base of
medical storage container D) Insulated medical container 0 5 10 15
20 25 30 35 40 45
0
10
20
30
40
50
60
70
Compare 2 tests- Control without PCM and W ith PCM
Time(minutes)
Tem
pera
ture
(C)
Control ZeoliteControl W aterZeolite with PCMW ater with PCM
0 20 40 60 80 100 120 140 160 180
0
10
20
30
40
50
60
70
Time (minutes)
Tempe
rature (C
)
Longevity Test-May 19
Zeolite TemperatureWater Temperature
