Refrigerant in hvac

Single and mixed refrigerant





Refrigerant

Refrigerant is a fluid that is used as a medium for transferring heat transfer from a conditioned room to the outside of the room or vice versa.

•There are 2 groups of refrigerants when viewed from their composition

•Refrigerant with a single substance saturation point is a refrigerant that only consists of similar molecules.

•Refrigerant with several temperature saturation points is a refrigerant consisting of several different molecules. This type of refrigerant is a mixture of several single refrigerants. So that from mixing with this particular composition another type of refrigerant is formed which has different properties from the constituent refrigerant.

What is the difference between these two groups of refrigerants? 

Single refrigerant has one temperature saturation point, so apart from the difference in properties with its constituent refrigerant, this mixed refrigerant has several temperature saturation points.

What is the effect of temperature saturation in the cooling system? 

Temperature saturation will affect the performance of the engine coolant, namely during the evaporation of refrigerant in the Evaporator and the condensation process  in the Condenser.

•What does temperature saturation mean?

Temperature saturation is the point at which the temperature conditions, a fluid  will change its form from liquid to gas or from gas to liquid depending on the heat flow. Does the refrigerant receive heat or release heat?

•If in the saturation condition, the refrigerant receives heat. Then the refrigerant will change into a form of gas / steam. Vice versa if the refrigerant is releasing heat. Then the refrigerant will change into liquid form.

What affects the temperature saturation point? 

Pressure will affect the temperature saturation point. The increase in pressure is proportional to the increase in temperature saturation.

Can you give an example, to make it clearer?

Water, in the HVACR system better known as R-718. In general you will know or explain in school that water will boil at 100 ° C. Not wrong, but it must be clarified again by the pressure acting on the water. Water will boil at 100 ° C if the pressure is 1 atmosphere. If the water has a temperature of 100 ° C and the pressurized 1 atm is heated then its form will change to gas / vapor (Water evaporates, changes form from liquid to gas). But if it is cooled, then the water will change to liquid (condensed water or change form from gas to liquid). So, 1 ° C is the saturation point of water temperature at 1 atm pressure. The saturation point is the transition period between liquid and gas.

What is latent heat?

Latent heat is heat used for the process of changing the form of a substance / fluid without changing its temperature. So this change of form takes place at a constant temperature.

•What does temperature saturation have to do with refrigerant with a single composition and mixed refrigerant? 

Refrigerants with a single composition have one saturation point, whereas mixed refrigerants have more than 2 points of saturation temperature.

R-404A refrigerant is composed of three types of single refrigerant, namely: R-125 (44%) + R-143a (52%) + R-134a (4%). Each of the refrigerant constituents of the R-404A has a different saturation point. At a pressure of 1 atm, the boiling point is: R-125 = -48.45 ° C R-143a = -47.6 ° C R-134a = -26.3 ° C. If the heat is added to the R-404A refrigerant, the R-125 boils first and then evaporates accompanied by R-143a and finally R-134a. Conversely, if the refrigerant releases heat, then R-134a will first melt.

Under what conditions does the mixed refrigerant mix well, so that the composition is stable? 

In liquid form, the three types of refrigerant will mix well, so that the composition will be maintained.

What refrigerants are included in a single refrigerant group? 

The following are some types of refrigerants that are categorized as refrigerants with a single temperature saturation point: R-11, R-113, R-114, R-12, R-123, R-134a, R-143a, R-14, R-152 , R-21, R-22, R-23, R-C318, R-1150, R-1270, R-170, R-290, R-50, R-600, R-600a, R-717, R -718, R-728, R-732, R-740, R-744, R-32, R-1234yf, etc.

What refrigerants are included in the mixture refrigerant group? 

Here are some types of refrigerants that are included in the mixture refrigerant category: R-401A, R-401B, R-401C, R-402A, R-402B, R-404A, R-406A, R-407A, R-407B, R-407C , R-408A, R-409A, R-410A, R-410B, R-500, R-502, R-507, R-508A, R-729, etc.

•How is the technical filling of refrigerant into the cooling system? 

Basically charging refrigerant to the cooling system is done from the liquid line area, which is the area between the condenser and the expansion inlet. In the case of the system being turned off / off, the refrigerant (either single substance or mixture) is entered into the system in liquid form and weighed according to its needs (see the name plate and rules for adding refrigerants according to manufacturing recommendations).

•Is not filling refrigerant to the system can be done in the form of gas from the suction area? 

For large capacity units it is not recommended to fill from the suction line because during a slow filling process it can damage the compressor (the motor is overheating or the compressor lacks lubrication because the lubricant pressure becomes very low), especially for the Hermetic and Semi-Hermetic Compressors. Whereas for small capacity units under 3hp it can still be filled from the suction line in the form of gas.

What is the technical difference between filling a single refrigerant with a mixture? 

In terms of filling or addition, single substance refrigerant is not too problematic with the entry of refrigerant in liquid or gas form. The important thing to note is only where to fill the liquid refrigerant and where to fill the refrigerant in the form of gas. In contrast to mixed refrigerants, both filling and adding must be done in liquid form so that the composition of the refrigerant mixture does not change. The addition of the refrigerant mixture in liquid form must be done carefully from the suction line, otherwise the process of adding refrigerant can damage the compressor.

What if filling the mixture refrigerant is done in the form of gas?

For example R-404A is a mixture of R-125 (44%) + R-143a (52%) + R-134a (4%). The three types of refrigerants have different saturation points. At atmospheric pressure, the boiling point is: R-125 = -48.45 ° C R-143a = -47.6 ° C R-134a = -26.3 ° C. In the form of liquid the three types of R-404A refrigerant making up mix perfectly. So that the composition of the refrigerant does not change when it comes out in liquid form. But if the refrigerant comes out in the form of gas, the refrigerant that has the lowest saturation point will come out first, then end with the refrigerant that has the highest boiling point, in the case of R-404A, the R-125 refrigerant will come out first, followed by R-143a then R-134a, thus the refrigerant composition will change. In a system filled with R-404A in the form of gas, the composition of the R-125 will be greater (more than 44%) and in the remaining tubes, the composition of the R-134a will be greater (more than 4%). As a result, the temperature-pressure relationship or its thermal properties will change. This results in a decrease in the performance of the engine coolant. In addition, we will also find it difficult to determine the work point / working pressure in the system concerned, due to a shift in the relationship between temperature and pressure.

•When filling, so that the liquid refrigerant that comes out must by reversing the position of the tube? 

Note in the refrigerant tube, usually there is an arrow written "THIS END UP FOR GAS" meaning if the part marked in the direction of the arrow is in the upper position then the refrigerant that comes out in the form of gas. And in the opposite direction written "THIS END UP FOR LIQUID" means if the part marked in the direction of the arrow is in the upper position then the refrigerant that comes out in liquid form.

If the tube does not use a dip stick (the valve connecting the tube to the bottom of the tube), the tube must be turned over to remove the refrigerant in liquid form. Whereas equipped with a dip stick, the tube does not need to be turned over.
So always pay attention to the marking in the tube.

What if there is a leak in a system that uses mixed refrigerant? Wouldn't there be a change in composition because there was a difference in saturation temperature? 

If there is a leak in the liquid area, then after repairs (if the remaining refrigerant can be isolated during repair) then just add the lack of refrigerant in liquid form, because if there is a leak in the liquid area it will not change the composition of the refrigerant.
If there is a leak in the evaporator / gas line area then the remaining refrigerant should be recovered and replaced with a new one, because if there is a leak in this area the composition of the refrigerant will change, refrigerants that have a lower boiling point will come out first in the leaked area .

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