Basic guide to homeowners appliance repair

When trouble shooting a home appliance, it helps to understand the basics of the technology behind our major home appliances. What follows is a description of how some of them work:

How a refrigerator cools or freezes your food?

The cold temperature of the refrigerator is produced by passing a colder liquid around objects within an enclosed area to draw heat from the air and food. What is needed is a continuous way of producing a cold liquid to achieve continuous refrigeration. Fortunately, for us, some of our brilliant forerunners discovered useful entropy changes during phase shifts of a gas to liquid, and back again. Specifically, restriction of the flow of a high-pressure liquid produces a big temperature shift to cold liquid. This cold liquid will then absorb heat as it is released to a larger space, and as it becomes hotter it returns to a gas form. These Pioneers in refrigeration were:

  • William Cullen, a Scotsman who in the early 1700s worked with the evaporation of liquids in a vacuum. In 1755, Cullen used a pump to create a partial vacuum over a container of Diethyl ether which then boiled while absorbing heat from the surrounding air. The experiment even created a small amount of ice, but had no practical application at that time.
  • Michael Farady, a Londoner who in the early 1800s used liquefied ammonia in a series of experiments using high pressures and low temperatures to produce cooling.
  • John Goorie, an American who in 1834 built a machine to make ice to cool the air for malaria patients in Apalachicola, Florida. He was convinced that the cure for malaria was cold because outbreaks did not happen in winter.
    Today’s refrigerators operate upon principles developed from observations from Farady’s experiments. When a high-pressure liquid is, restricted or forced through a smaller aperture it becomes cold. Then, when that high pressure cold liquid absorbs heat from its surroundings its boiling point is lowered- transforming it into a gas.

There are 4 main components of a refrigerator, Throttling device, Evaporator, Condenser, and compressor. These mechanical components work in tandem to produce the very wonderful invention of Refrigeration. A short explanation of the process follows:

 

Throttling Device is what produces the cold liquid.

 

 

  • The Throttling Device is what produces the cold liquid. It is a coiled capillary tube of about 6.5 ft. with an inside diameter of .0236, like a small capillary tube. The inlet takes in the refrigerant, Freon, in the state of a high-pressure liquid, pushes it through a much smaller space. Restricting the flow of Freon causes a tremendous pressure drop. This drop-in pressure reduces the boiling point of Freon, making it very cold as it loses heat. This large change of temperature is what’s needed for next phase of evaporation through the Evaporator.
  • Evaporator is a much larger metal coil space then the Throttling Device, and it is placed to surround the interior of the Refrigerator. This is where the cold liquid is sent to absorb heat from the food within the Refrigerator.
  • This can be likened to when a mother will place her children’s cold hands on their stomach, under their shirt, in order to warm them quickly- the same principle of Entropy is at work. When heat is absorbed from the food within the Refrigerator by the cold liquid inside the Evaporator coil it causes the cold liquid, to boil changing its phase to that of a low-pressure vapor.
  • The Compressor will raise the pressure back to its initial high level by compressing the gas or constricting it. Now the refrigerant is a high-pressure vapor, but it must be changed to a high-pressure liquid state in order to continue the recycling. The next device, the Condenser, takes the hot high pressure vapor and changes it to a high-pressure liquid.
  • The Condenser is a heat exchanger, large metal coil, fitted to the outside of the Refrigerator.  Since the temperature of the air outside the Refrigerator is lower than the refrigerant temperature, the heat will dissipate to the surroundings. The high-pressure vapor will return to a high-pressure liquid with the surrounding ambient temperature. The high-pressure liquid is then taken up by the Throttling Device to run a never-ending cycle through the four main components.

 

 

 

 

 

 

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