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      For the introductory class to mechanical engineering at Seattle University students have the opportunity to collaborate in teams to prototype an invention. I had the pleasure of working with Sam Simon, and Mark Toma. Together we designed and built a cup that could cool a drink from 70° F to 40° F in less than 4 minutes. The cup used generic computer duster cans to provide the refrigerant and a cooling rod up the center of the fluid to remove heat and thus cool the drink.

First cryostein drawing      This was one of the original designs as seen on paper. Instead of using the larger air duster cans that are filled with refrigerant, the original model used CO2 cartridges like those used for paintballing. During the prototyping phase CO2 cartridges were determined to be too small and thus we switched to the large air duster can. The CO2 cartridges had been used because they were small and could be more easily integrated into the cup.
     In this design, the cooling rods run through the fluid parallel to the ground in tubes. This was also ditched for a single cooling rod that ran perpendicular to the ground as seen in the red and green cup prototypes below. This was to greatly simplify the manufacturability of the cup.

 

Cryostien drinking cup first prototype      This is the first prototype. To be sure our idea would work we wanted to test the idea in as cheap of a manner as possible. This prototype cost us less than five dollars and proved to us that it was possible to semi-efficiently cool down a liquid using computer duster cans.
     The prototype is composed of a blue tin cup sitting in an old Britta filter plastic pitcher with a thin tube bent up to squirt the bottom of the tin cup with air duster fluid.
Cryostien drinking cup first prototype diagram Here is a list of features as seen in the diagram:
 A - Air duster can containing refrigerant
 B - Tin cup
 C - Brita filter cup
 D - Incoming coolant spray
 E - Water

 

Cryostien drinking cup second prototype      This is the second prototype. For this prototype a coffee mug was used for the cup and the Seattle University machinist made a copper cooling rod that would mount in the center of the cup. The coffee mug has a metal inner cup and a plastic shell. This configuration was ideal because of its good insulation properties.
     This prototype was okay. The cooling rod was too thick and short so it would only cool the small amount of fluid at the bottom of the cup. The coolant delivery tube was also made out of plastic and had only one outlet. This means that the coolant spray was concentrated in one area of the cooling rods inner surface area as shown in the diagram below.

     The red straw poking out at the bottom of the cup is where  the air duster fluid is injected. There are also extra holes near the bottom that allow the coolant to expand and cool the rod. This also prevents pressure build up which could be unsafe and cause the cooling rod break and leak.
Cryostien drinking cup second prototype diagram
Here is a list of features as seen in the diagram:
 A - Air duster can containing refrigerant
 B - Cooling rod
 C - Inner metal cup
 D - Outer plastic cup
 E - Excess settled liquid coolant
 F - Incoming coolant spray
 G - Bolts and watertight gasket

 

Cryostien drinking cup third prototype      Unsatisfied with the results of the previous prototype and with a lot of ideas on how to improve it, the third and final prototype was created.  
     There were four major improvements from prototype two. First the cooling rod was made skinnier and taller so that more fluid is closer to the rod. The second improvement is the stir rod. This allowed us to create convection as the fluid cooled. The stir rod is sticking up out of the lid in the picture. It worked by rotating around the center cooling rod when the cup was fully assembled.
     Another improvement that is evident in the diagram below is that the coolant delivery rod was made out of copper with slits throughout the length of the tube. This allowed for a more even distribution of coolant over the inside of the cooling rod. The fourth improvement is the sponge at the bottom of the cup that soaks up excess coolant.
Cryostien drinking cup second prototype diagram Here is a list of features as seen in the diagram:
 A - Air duster can containing refrigerant
 B - Stirring rod
 C - Cooling rod
 D - Bolts and rubber gasket
 E - Outer plastic cup
 F - Yellow sponge
 G - Inner metal cup
 H - Incoming coolant spray
 I - Copper coolant delivery tube

 

 

Copyright, Brian De Vitis, 2013       Contact Me at bdevitis@live.com