History of Refrigeration
Foods such as fruits, vegetables, meats, and dairy products will only remain fresh if kept cool. People used natural ice that was collected during the cold winter months and stored in icehouses, to keep their foods from spoiling. In 1748, a Scottish inventor named William Cullen designed an artificial refrigeration system. He never did anything with his discovery. The Civil War made it difficult for the South to get ice from the North, and at around the same time, there were many warm winters in the North. As they say, necessity is the mother of invention, and the need for artificial refrigeration brought out many inventors trying new designs. Refrigerated railcars were created, along with commercially available refrigeration units. By the 1900’s, companies such as General Electric, Kelvinator, Servel, and Frigidare all began manufacturing home refrigerators.
Have you ever wondered how refrigerators work? An electric motor is used to pump a liquid, called refrigerant, through pipes into a compressor. This causes the refrigerant to pressurize, and move through a valve to the evaporator where it quickly turns from a liquid to a gas, absorbing heat and chilling the compartment. The vapor is then pumped to the condenser where it changes back to liquid, giving up its heat to the outside air. This is why you feel heat coming off the back (or sometimes the bottom) of your fridge. A thermostat regulates this cycle by turning the compressor on and off as needed. How would life today be different without refrigeration? If desired, further research the advancement of refrigerators, learning about the different varieties including natural gas, propane, and kerosene refrigerators.
Long before there were electric or propane freezers, like those of modern days, people used to cut ice blocks to keep their food cold. The ice blocks were cut, in the manner so vividly described in this chapter, and were then packed in sawdust and stored in icehouses. The sawdust acted as an insulator, keeping the cubes cold all through the hot summer months.
Do the following simple experiment. Try wrapping ice in different substances to see which one works as the best insulator. Some ideas: Sawdust, styrofoam, newspaper, plastic bubble wrap, and tin foil. Which one melts the fastest? Which ice cube lasts the longest? What if you use larger pieces of ice? What if you put many ice cubes together?
For a second experiment, you can get a cooler and pack it full of ice, and get a similar size of non-insulated container (with or without a lid) and pack it full of the same amount of ice. How long does it take each to melt? The cooler will take longer because it is insulated. Ice will probably keep in a cooler for many days (depending on the size of the cooler).