How to use a-two-Line Tension-Temperatures Chart

How to use a-two-Line Tension-Temperatures Chart

Functions of one’s brand new zeotropic refrigerant mixes are very different than simply traditional refrigerants, it is beneficial to learn how to read a two-line PT chart.

Antique PT maps listing the over loaded refrigerant tension, into the psig, having a line to have temperature along the left front side. Single-role refrigerants and you can azeotropes boil and you will condense in the one heat getting confirmed tension. For this reason, just one column is required to tell you to show pressure-heat dating for all the phase-change techniques when you look at the a network. (find Fig. 1)

The services of the zeotropic mixes was slightly unique of the standard refrigerants. Zeotropic combines change in the composition from inside the boiling hot otherwise condensing techniques (find Fig. 2) While the blend change stage, a lot more of one to role tend to move into one other phase quicker compared to the people.

This house is named fractionation. The latest changing constitution of liquid reasons the fresh new boiling point temperature in order to change as well. The entire move out-of heat from a single region of the temperature exchanger to another is called the warmth slides. Zeotropic mixes can’t be discussed of the a single tension-temperatures matchmaking. The heat glide will cause additional philosophy getting temperature during the an excellent offered stress, based on how much refrigerant is h2o and how much try vapor. The first opinions having checking superheat and you may subcooling are definitely the avoid points of slides or the tension-heat matchmaking having saturated liquid and you will soaked steam.

New soaked water standing is frequently also known as the newest ripple section. Visualize a container out of liquid sitting on a stove; as it begins to cook it variations bubbles about drinking water. The fresh soaked steam reputation is called this new dew point. Photo a bedroom laden with steam and you will dew drops developing with the the furniture. PT charts toward zeotropic blends list two columns close to for every temperatures: one to into the over loaded liquids (bubble point) together with other on the over loaded vapor (dew-point).

A number of the zeotropic blends have quite lowest slides (from one?F in order to 2.5?F). Of these blends, new steam and you will liquid demands are merely separated because of the step 1 otherwise 2 psi. Once the huge difference is pretty short between the two philosophy some manufacturers’ PT charts simply checklist one line of these blends. Mixes having large glide (greater than 5?F will normally enjoys each other articles indexed.

When examining the fresh subcool condition, the new specialist will gauge the heat of liquid range, the pressure at that point and you will subtract brand new counted temperatures regarding brand new soaked heat at the end of the newest condenser. Towards the merge you browse the saturated temperature near the pressure on liquids (bubble area) column of one’s graph.

Getting a single-part otherwise azeotropic refrigerant, this new functioning pressure to your reduced side of a system is be found because of the mix referencing the desired coil temperatures for the PT graph. To have higher-slides blends, however, the mandatory coil weather is the common (otherwise midpoint) temperatures of coil.

The issue with several-column PT maps is the fact that the requirements from the endpoints off the warmth slides was indexed, maybe not the fresh midpoint. In this situation, you must put 1 / 2 of the temperature glide for the desired midpoint temperature, next investigate soaked steam line to determine the working tension. (look for Fig 3)

Should your steam column was read physically during the desired temperatures, then your prevent of the evaporator could be the proper temperature, nevertheless remaining coil might be as well cool. If your water column can be used personally, then your beginning of the coil could be the correct temperature, nevertheless the rest of the coil would-be as well warm.

Pressure Temperatures Graph

Two-column PT charts try just as of good use since the antique ones. Brand new charging and you will service actions have become similar both for single-part refrigerants and you may zeotropic combines, and the formal drinking water and steam data proper with the consequences of one’s blends’ temperatures slides.

Just remember observe the fresh new phase of the blend from the area you have an interest: over loaded steam uses the newest vapor (dew point) line and you may over loaded water uses the h2o (bubble point) column.


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