BlogNCERTImportant Topic of Physics: Refrigerators

Important Topic of Physics: Refrigerators

Introduction:

Open systems, such as a refrigerator, move heat from a closed environment to a warmer one – for example, the kitchen. Because the heat is dispelled from this space, the temperature drops, allowing food and other goods to stay cool. Refrigerators appear to defy the Second Law of Thermodynamics, however, this is due to the amount of effort required as a system input. A heat pump is similar to one of these, but instead of heating a space, it cools it.

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    In this segment, we learned about Refrigeration which is defined as the process of extracting heat from an enclosed space or a substance in order to reduce its temperature. Refrigeration is mostly used to store products at low temperatures in industrialized countries and affluent sections of developing countries, preventing bacteria, yeast, and mold from destroying them. We also learnt about the refrigerator, History of Refrigeration, and the components of refrigerators. We are quite positive that you will find this article as knowledgeable and user-friendly to read, as we have tried to explain things in quite a simple way. Stay tuned for more such content ahead!

    History of Refrigeration:

    Refrigeration is a process that involves moving heat from one medium to the other. Refrigerators are equipment or household appliances that are used for this purpose and are designed to keep food fresh for longer periods of time. They are a relatively new innovation, although people have tried to keep food fresh for thousands of years by keeping it at lower temperatures.

    Refrigeration has a lengthy history, and it has evolved from rather rudimentary yet ingenious technology to current technology that allows people to have refrigerators in their homes and not rely on nature.

    As early as 1.000 BC, the Chinese were harvesting ice from rivers and lakes. For filling and draining ice cellars, religious ceremonies were held. Large volumes of snow were dumped into storage pits by the Hebrews, Greeks, and Romans, who covered it with insulating material such as grass, chaff, or tree branches. These holes, as well as snow, were utilized to keep liquids chilled. Egyptians and ancient Indians would moisten the outside of the jars, allowing the water inside to cool as a result of the evaporation. Persians were the first people to adopt cold storage to preserve food. They created Yakhchal, which is a form of ice pit.

    For generations, ice harvesting was the only way to keep food cool. In 18th century England, servants collected ice and stored it in ice houses during the winter. Ice Houses were underground storage facilities where sheets of ice were packed in salt, wrapped in flannel, and kept frozen till summer.

    The first ice boxes appeared in England in the nineteenth century. With the spread of ice-storehouses and iceboxes, the first commercial ice began to appear at that time. In New England, Frederic Tudor began harvesting ice and shipping it to the Caribbean islands and southern states. He had a 66 percent ice waste rate initially, but with better-insulated ships, he was able to lower it to only 8%. By the early 1830s, he had extended the ice business, and ice had become a mass-market item.

    Because ice harvesting was laborious and risky, individuals tried to come up with artificial cooling methods. Scottish academic William Cullen, who invented the modest refrigerating machine in 1755, was the first to make a breakthrough. He created a partial vacuum over a container of diethyl ether with a pump. Ether boiled, absorbing the heat from the atmosphere. This produced a little amount of ice, but the equipment was inconvenient at the time. In 1758, Benjamin Franklin and John Hadley tried out refrigeration.

    They tested the bulb of a mercury thermometer and discovered that evaporation of liquids like alcohol and ether could be used to drop an object’s temperature below the freezing point of water. In 1805, American Oliver Evans created a refrigerator based on a closed cycle of compressed ether. The design remained in the prototype stage. In 1844, John Gorrie created a mechanism that employed compressed air.

    In 1856, Alexander Twinning began marketing a refrigeration machine based on this idea, while Australian James Harrison expanded and adapted the system for the meat-packing and beer-making industries. In 1859, Ferdinand Carre introduced ammonia as a coolant, but it had a foul odor and was toxic if it leaked, so it was only used for a short time. During the 1920s, synthetic replacements were created, one of which being Freon.

    It is a suitable refrigerant because of its low boiling point, surface tension, and viscosity. Freon was discovered to be harmful to the environment in the 1970s. Refrigeration becomes more inexpensive to the general public over time. It enabled new settlement patterns to evolve, and food began to last longer, become healthier, and pose fewer health risks.

    The Components of Refrigerators:

    • Compressor:

    A refrigerator’s “heart” is the compressor. During this step, the refrigerant circulates throughout the system, increasing the pressure in the warm circuit, and heating the refrigerant. It’s akin to pumping air into a bicycle tube: as you compress the air, you can feel a heat increase in the pump.

    Types of Compressor:

    • Reciprocating compressors
    • Rotary compressors
    • Scroll compressors

    The Condenser:

    The condenser, which is located on the back of a refrigerator, is most likely dirty. Condensation occurs on the inside of a refrigeration unit when the refrigerant condenses from a gas into a liquid.

    Evaporator:

    The evaporator is the component of a refrigerator that keeps the contents cool. The refrigerant cools the area around it as it evaporates from a liquid to a gas, creating the ideal atmosphere for preserving food.

    Capillary tube:

    The capillary tube is a narrow tube that functions as an expansion device. The liquid refrigerant is injected into the evaporator’s low-pressure environment through the capillary tube.

    Thermostat:

    The thermostat regulates the cooling process by monitoring temperature and turning on and off the compressor. When the sensor detects that the refrigerator is cold enough, the compressor is turned off. If it detects excessive heat, it activates the compressor and restarts the cooling process.

    Working of the Refrigerator:

    Refrigerators function by converting the liquid refrigerant circulating inside them to gas. In this process, known as evaporation, the surrounding space is cooled to create the desired effect. It is possible to test the effect of alcohol on your skin by putting a drop or two of it on. You should feel a chill when it evaporates; the same basic mechanism allows us to store food safely.

    The pressure on the refrigerant must be decreased through an exit called the capillary tube to begin the evaporation process and turn the refrigerant from liquid to gas. The impact is comparable to that of using an aerosol product such as hair spray. The pressure/liquid side of an aerosol can is the contents, the capillary tube is the outlet, and the free space is the evaporator. The contents change from a liquid to a gas when released into a lower-pressure open space.

    To keep a refrigerator functioning, you must be able to return the gaseous refrigerant to its liquid state, which necessitates compressing the gas to a greater pressure and temperature. The compressor enters the picture at this point. The compressor, as previously stated, has a similar effect as a bicycle pump. While pumping and compressing the air, you can feel the heat rise in the pump.

    The gas should be under high pressure and heated when the compressor has completed its task. It must be cooled in the refrigerator’s condenser, which is positioned on the rear so that the contents can be cooled by the ambient air. When the gas inside the condenser cools down (while still under high pressure), it transforms back into a liquid.

    The liquid refrigerant then circulates back to the evaporator, where the cycle begins again.

    Also read: Temperature

    Frequently Asked Questions FAQs:

    Question 1: What is refrigeration’s fundamental principle?

    Answer: The primary principles of the refrigeration process, or cycle, are the absorption of the amount of heat required for the change of state from a liquid to a vapor by evaporation, and the release of that amount of heat required for the change of state from a vapor back to a liquid by condensation.

    Question 2: What law does the refrigerator operate under?

    Answer: Thermodynamics’ second law.

    Question 3: According to which of the two laws of thermodynamics?

    Answer: Heat will always flow spontaneously from hot to cold, and never the other way around, according to the Second Law of Thermodynamics. By inputting effort, a refrigerator causes heat to transfer from cold to hot, cooling the space inside the refrigerator.

    Question 4: In a refrigerator, what gas is used as a coolant?

    Answer: Tetrafluoroethane.

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