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Strategies for a two-Line Tension-Temperatures Chart

Qualities of the new zeotropic refrigerant combines are different than simply old-fashioned refrigerants, it is useful to learn how to see a-two-line PT chart.

Antique PT charts list the fresh new over loaded refrigerant pressure, into the psig, that have a line for temperature along the remaining side. Single-role refrigerants and you may azeotropes cook and you will condense in the one heat to possess certain pressure. Hence, singular line must let you know to display the stress-heat relationships when it comes to stage-change procedure in the a network. (pick Fig. 1)

Brand new attributes of one’s new zeotropic blends try somewhat distinct from the standard refrigerants. Zeotropic combines shift inside constitution when you look at the boiling hot otherwise condensing procedure (come across Fig. 2) Since the merge change phase, a lot more of you to definitely role usually transfer to others stage reduced compared to the rest.

It home is entitled fractionation. The newest changing composition of one’s liquid factors the boiling-point temperatures so you can change too. The general shift of heat from 1 section of the heat exchanger to the other is named the temperature slides. Zeotropic mixes can’t be discussed by a single stress-temperatures relationships. The heat glide will cause various other viewpoints for temperature at a beneficial given tension, based on how far refrigerant is h2o and just how much is actually vapor. The initial viewpoints to possess checking superheat and subcooling her would be the stop circumstances of your slides and/or pressure-temperature matchmaking to own soaked h2o and you will soaked vapor.

The fresh new over loaded water status is frequently named the latest ripple section. Photo a pot regarding liquids looking at a stove; because actually starts to cook it versions bubbles throughout the drinking water. The new soaked steam condition is referred to as the fresh new dew-point. Photo a-room packed with steam and you may dew drops developing into the item of furniture. PT maps to the zeotropic combines listing one or two columns next to for every single heat: you to definitely on over loaded liquid (bubble point) plus the almost every other to the over loaded vapor (dew-point).

A number of the zeotropic combines have very low slides (from 1?F so you’re able to dos.5?F). Of these combines, the fresh steam and you will liquids demands are only split by 1 or 2 psi. As variation is fairly small between them philosophy particular manufacturers’ PT maps simply list that column for those mixes. Blends having high slides (greater than 5?F will generally features one another articles detailed.

Whenever checking the fresh new subcool position, the new technician often gauge the temperature of your water line, pressure at that point and you can subtract the fresh measured temperatures of the fresh new over loaded temperatures at the conclusion of the brand new condenser. Towards combine you look at the saturated temperature beside the pressure on the h2o (ripple section) column of chart.

Getting a single-parts otherwise azeotropic refrigerant, brand new doing work tension toward lower side of a system can be discovered by the cross referencing the desired coil heat towards PT graph. To own higher-slides mixes, but not, the mandatory coil weather is the average (or midpoint) temperature of the coil.

The issue which have a couple of-line PT maps is the fact that criteria at the endpoints out-of the temperature slides was listed, not the newest midpoint. In cases like this, you ought to put half of heat slides with the need midpoint temperatures, following look at the over loaded vapor line to select the working pressure. (get a hold of Fig 3)

When your vapor column is actually read really at wished temperatures, then your stop of your own evaporator could be the right heat, but the remainder of the coil is too cool. When your liquid column is utilized actually, then start of the coil will be the right temperature, although remaining portion of the coil will be too warm.

Stress Temperatures Chart

Two-column PT maps was every bit as the beneficial because the traditional of those. The recharging and you may service strategies have become comparable for solitary-component refrigerants and zeotropic combines, therefore the official h2o and you will steam analysis best towards outcomes of the blends’ temperatures glide.

Remember to monitor new stage of combine within section you have an interest: saturated vapor uses the latest steam (dew point) line and you can over loaded liquid spends the fresh new water (ripple area) line.