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Selaed System
Chapter 1 Page 5

The Sealed System


The refrigerant/Freon flows through the system with the use of a compressor - The compressor is similar to a pump. The main difference is a compressor in an Appliance can only circulate refrigerant in vapor form not liquid. Passing liquid through the compressor could either bend or damage valves inside the compressor or even damage the piston/crankshaft.

Lets break down the flow of refrigerant as the compressor pumps it around the system.

1.  This Line on the compressor is called the discharge line. The compressor compresses the refrigerant from a Low Pressure Vapor to a High Pressure Vapor. In a system with R134a Refrigerant the pressure leaving the compressor is about 120 psi to 140 psi for a normal operating system an R600 system the high side would be between 60 psi and 80 psi. The discharge line directs the refrigerant into the condenser the term for the refrigerant in this line is called "High Pressure Superheated Vapor"

2.  This is the entrance to the condenser which helps cool down the refrigerant by releasing heat. Although the process of refrigerant cooling down starts as soon as the vapor leaves the compressor, condensers are designed to release as much heat as possible. This is where the vapor is condensed into a liquid. That is how the name of that section of the system is called a condenser. Between step 2 and 3 the vapor refrigerant remains under high pressure but as the vapor is condensed in the condenser it is still a mixture of vapor and liquid refrigerant. This mixture is called saturated and the refrigerant is High Pressure Saturated Refrigerant inside the condenser.

3.  In step 3 the refrigerant is now almost 100% in liquid form. The term for the refrigerant at this point in the system is called High Pressure Subcooled Liquid. The term subcooled is used to describe the refrigerant after it leaves the condenser and releases trapped heat inside the refrigerant. The removal of heat cools down the vapor so it becomes liquid. Once leaving the condenser is goes into the Drier Filter. NOTE: When installing a new Drier some have arrows which indicate direction of refrigerant flow and should be installed with the arrow pointing towards the capillary tube.


Example of dissacants found inside a Drier Filter

Filtration is usually done with a screen, wire mesh, and the desiccant core itself. As small particles accumulate on the screen, wire mesh, or desiccant, they can act as very fine filters that remove even finer particles.

4.  Once the refrigerant leaves the Drier Filter it enters directly into the capillary tube. The inside diameter of the capillary tube is the smallest tube in the refrigerant tubing and is very susceptible to getting a restriction from moisture or oil in the system. The capillary tube is very important to the systam. Its function is to control the flow of refrigerant from the High Side "Condenser" to the Low Side "Evaporator" Its diameter and length is critical to the system maintaining proper pressures on both sides of the system.If the capillary tube is restricted it is possible to cust a few inches off without major changes in the system, but remember anything you do remove will affect the systems efficiency. This means the refrigerator will still cool to desired temperatures but may take longer of use more energy to reach tose temperature. The refrigerant inside the capillary is High Pressure Subcooled Liquid.

5.  The Heat Exchanger is a combination of Capillary Tube and Suction Line. Most of them are Soldered together to exchange heat between the two lines one is High Pressure Subcooled Liquid "Capillary Tube" and other "Suction line" is Low Pressure Superheated Vapor. This helps the refrigerant change from a liquid to a vapor.  On smaller Dorm/Office size refrigerators the capillary tube is run inside the suction line instead of soldered to it.

roll evap heat exchange.png

Mini Fridge above showing the capillary running inside the suction Line.

6.  The refrigerant leaves the capillary tube and enters the evaporator and becomes Low Pressure Subcooled Liquid. The evaporator tubing is larger than the capillary tube, and as it leaves the capillary tube as a liquid, the pressure drops causing the refrigerant to lower the temperature inside the Evaporator. The refrigerant absorbs the heat inside the refrigerator and causes the refrigerant to turn to vapor. Inside the Evaporator it is Saturated which is a mixture of Liquid and Vapor Refrigerant until it leaves the evaporator as 100% Vapor.

7.  The refrigerant inside the Suction Line is leaving the evaporator and returning to the compressor. The refrigerant is 100% Vapor and is called Low Pressure Superheated Vapor.

8.  This is the compressor Suction Line entrance it is important that the refrigerant at this point be 100% vapor so it does not harm the internal components inside the compressor.

Follow the instructions for setting up you account with this site is where you will go to take tests and exams throughout this module. NOTE: you will only be able to take each exam once, Questions include Multiple Choice, Multiple Correct, True False and some short answer questions (Requires multiple sentences to complete). This exam will be graded manually. 

Account setup


Follow the link to take the Chapter 1 exam - TMM Sealed System Chapter 1 Test 

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