“Discovering how to make cold would change the way we eat—and live—almost as profoundly as discovering how to cook.” — George Dyson
Refrigeration – the process of decreasing the temperature of some thing (my definition). Air conditioning (AC) can be a form of refrigeration.
- chlorofluorocarbons (CFCs) – At the time of its invention, CFCs (used in Freon) led to safer and mass market refrigeration methods.
What’s the problem?
Mechanical refrigeration is accomplished by continuously circulating, evaporating, and condensing a fixed supply of refrigerant in a closed system. Evaporation occurs at a low temperature and low pressure while condensation occurs at a high temperature and high pressure. Thus, it is possible to transfer heat from an area of low temperature (i.e., refrigerator cabinet) to an area of high temperature (i.e., kitchen).
- Ask – Before there were refrigerators, people kept food cool in an “icebox” – a small cabinet with a space for a block of ice, and another space for storing food. Ice was a problem. It melted so the melted ice (water) needed to be drained away and a fresh block of ice added. How could the ice be replaced and the food still stay cold?
- Imagine – What makes hot air cold? Could an electrical device be used to produce cold air? How can heat be transferred out of the icebox cabinet?
- Design, Build – By removing the heat from the special liquid refrigerant and transferring it outside with a fan, the remaining cooler refrigerant could be pumped back through the coils of pipes inside the icebox to lower the temperature of the air inside.
- Improve – One of the problems with early home refrigerator was ice build-up. When the door was opened, moist air from the kitchen comes into the refrigerator. The moisture condenses on the cold surface of the cooling unit to form ice. Over time the ice would accumulate preventing proper operation of the refrigerator. How could this ice build-up be prevented? What changes were made to make refrigerators “frost-free”?
- evaporation, circulation, refrigerant, condensation, temperature, presssue
Here are some challenges for you to work on…
- Make an icebox with foam cups, ice, water and straws. Demonstrate the cooling effect of the cold water passing through the “icebox”