In this article, we will explain what is temperature glide of refrigerants: what it depends on, how it is measured. We disassembled the definition of the temperature glide using the example of the refrigerant R-407c. At the end of the page you will find a temperature glide table for refrigerants.
Zeotropic and azeotropic mixtures
All refrigerants are divided into two types – one-component and mixtures. Freons consisting of one substance cannot have a temperature glide. Their boiling point is constant and depends only on pressure. They are azeotropic. Some manufacturers and suppliers refer to such blends as quasi-zeotropic.
Blends (multi-component refrigerants) contain 2 to 5 (eg R410a and R438a) substances. If the components have the same boiling point within a certain range, they are also azeotropic. Belonging to azeotropic or quasi-azeotropic gases, as a rule, is determined in the range of operating temperatures and pressures.
Often, the composition of a multi-component refrigerant includes substances with different boiling points. Such mixtures are called zeotropic or non-azeotropic. They have a temperature glide. For these mixed refrigerants, the dew point (saturation point) plays an important role.
Temperature glide definition:
The total temperature glide of a refrigerant blend is defined as the temperature difference between the saturated vapor temperature and the saturated liquid temperature at a constant pressure.Source
What is temperature glide
It is best to show on the example of refrigerant R407c. At atmospheric pressure, its boiling point is -43.6 °C. With her, he begins to boil. Since it is non-azeotropic, only one component evaporates.
As it evaporates, the composition of the liquid refrigerant changes. Accordingly, its characteristics change. The boiling point rises. At one fine moment, it ceases to pass into the gaseous phase.
In order for R-407c to continue to boil, it must be heated. In order for it to reach the dew point and boil away completely, it must be heated to -36.4 ° C. Then all the freon will go into a state of vapor. The difference between the first and second temperatures is 7.2 degrees Celsius. This is the temperature glide. It is expressed in degrees using the formula:
Tg = Tmax – Tmin
- Tg – temperature glide;
- Tmax – Dew point at a given pressure;
- Tmin – Boiling temperature at a given pressure.
What determines the temperature glide
Temperature glide is the temperature range in which a refrigerant can be both a gas and a liquid. This value varies depending on the composition. The fact is that the difference between the boiling points of refrigerants is not constant.
For example, there is some refrigerant, which contains gases A and B. They have a slight difference in boiling point. But the properties of refrigerants are different. Therefore, at different pressures, the temperature glide will be different.
The higher the pressure, the higher the boiling point of freons. Since their relationship is not direct, the difference between saturation and boiling points is greater. Accordingly, the temperature glide is larger.
What the manufacturers say
Due to the fact that the temperature glide depends on pressure, it is impossible to specify its exact value. Freon manufacturers measure it differently. For example, they can specify a temperature glide:https://acceptable.a-ads.com/1474539
- At atmospheric pressure;
- At 0 degrees;
- Medium in pressure range;
- Medium in the boiling point range.
Therefore, do not blindly trust the numbers. In the specification for the same freon, different values can be indicated. Not everyone indicates under what conditions they measured the freon temperature glide. If you are faced with a new refrigerant, it is best to test it yourself.
Refrigerants temperature glide table
This table summarizes the temperature glide values for zeotropic freons. The data is taken from the official websites of manufacturers and official documentation. Unfortunately, not everywhere is indicated exactly how the glide was measured.
|R408A||less than 0.6|
|R410A||less than 0.3|
|R426A||less than 1|
In this article, we tried to popularly explain what is temperature glide of refrigerants is and what it depends on. We have provided a precise temperature glide definition. Also brought the average glide of the most popular multi-component freons.. Don’t forget to share it with colleagues and friends!
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