g new ideas for keeping things like foodcold. Up until the early 20th century ice was the best method for cooling perishable items, butthen we figured out a more efficient and affective way of keeping items cold. It was called therefrigerator. Soon after the introduction of the refrigerator we developed something calledcryogenic freeing, which is freezing with very low temperatures.
Cryogenic freezing is the study mater that is colder than temperatures that occur naturallyon earth. The air in the cryogenic temperature range becomes a liquid or even a solid.
Thelowest possible temperature is -459.69 degrees F, and the highest temperature in the cryogenicrange is somewhere around -100 degrees F. The most common matter in cryogenic freezing isliquid nitrogen. Liquid nitrogen is most commonly used at temperatures from -100 degrees F to-320 degrees F. Cryogenic freezing is mostly used in food processing plants to freeze small itemslike patties, prepared meals, pizza, pasta, baked goods, appetizers, and confectioneries. Althoughthere are some systems that are designed to freeze large items like turkey breast, pork, and beef,but because the cost of liquid nitrogen and the amount of liquid nitrogen it takes to freeze largeitems it is not economically feasible.
However for freezing small items cryogenic freezing is areasonable choice since a cryogenic freezing unit is two thirds less than a conventional system, butyou still have to add the cost of the nitrogen which will put you at over one and a half as much asac conventional unit.
Under natural conditions a substance is cooled by placing something cooler next to it. Incryogenic freezing a substance is made cooler by a substance that is colder than anything innature. For this to happen work must be done to remove heat and then insulation must beprovided to maintain temperature. First you must compress the gas in a system so that it releasesall of its heat and then insulate the system so that it has to allow the gas to expand by using up theremaining heat energy and cooling the system below the temperature of its surroundings. Now toreach even colder temperatures you have to the second law of thermodynamics which states thatdisorderly atoms within a system may be made more orderly only if outside energy is applied tothe system. This is accomplished by demagnetization. In demagnetization you apply a strongmagnetic field to the system which causes the molecules of paramagnetic to line up. Then removethe magnetic field and the system will use up more energy inside the system to move back into adisorderly arrangement. By using the demagnetization process you can achieve temperatures of-459.69 degrees F. Conventional freezing is cheaper and is used in almost every house, restaurant, grocerystore, and food plants. Most places use a compression system which is composed of fourdifferent elements: a compressor, a evaporator, a compressor, and a expansion valve. Therefrigerant is vaporized in the evaporator then the vapor goes to the compressor and ispressurized and heated. After that it goes on to a water cooled condenser were it is condensedinto liquid. Now the refrigerant moves on to the expansion valve, in which its temperature andpressure are maintained. The same system is used in refrigerators and freezers only the freezershave bigger tubes and more insulation. In a compression system the refrigerant never has to bereplaced unless the system fails. The most common refrigerant is called R-12.
If only cryogenic freezers werent so expensive we could have frozen food in just seconds. Instead of waiting on those slow conventional freezers. We will just have to wait until the priceof nitrogen goes down.
EXPERMENTThe first thing that I for my experiment is take two pieces of turkey breast meat andmade them weigh the same weight.(5lbs.) After that I took one piece of meat and put it in afreezer. Then I took the other piece of meat and soaked it in liquid nitrogen until it was frozenand then put it in a conventional freezer over night. Next I took both pieces of meat and thawedthem out by putting them in a tub of water. When the two pieces were thawed out I weighedthem and the piece that was froze by liquid nitrogen weighed more than the one that was frozeconventionally. Now I gave the pieces of meat to our inspector and he took them and ran a sometest to check the bacteria count. Again the one froze with liquid nitrogen had less bacteria thanthe piece that was froze conventionally. After that I ran the two pieces of meat through amachine that injects the meat with all the ingredients. The piece frozen with liquid nitrogenpicked up more solution and held it longer than the meat that was froze in a conventional freezer. Also the physical appearance of the two pieces was dramatically different. For instance the piecefroze with liquid nitrogen had a more brighter and fresher look, while the piece that was frozeconventionally looked paler and not quite as plump. So as you can very well see cryogenicfreezing is much more efficient but not quite as economical.
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