Let's look at a simple example of the temperature from the enthalpy and work from there to understand, pressure-enthalpy relationship shown in P-H schema. Here is the T-x diagrams for R-22 69 psi, what about normal for evaporator comfort air conditioning systems. The saturation temperature or boiling point, 40F 69 pounds per square inch.
If the pressure is changed, T-H plot will look different, because the boiling point of the liquid is determined pressure. For example, here is the T-x diagrams, actually three T-x diagrams in one. We built saturation of the graph here. He shows T H a relationship for an R-22 refrigerant 102 psi, 69 pounds per square inch, and 43 pounds per square inch. The higher the pressure, the higher the boiling point (saturation) temperature; the lower the pressure, the lower the saturation temperature. In 102 square inch of the saturation temperature 60F; 69 pounds per square inch, 40F, and in 43 PSIG, 20F.
We could continue to add a line for R-22 at some pressure, as we have done here.
In fact, if we wanted to, we could draw a certain saturation line for each pound of pressure. This allows you to quickly and easily compare the pressure, the saturation temperature.
In this diagram, we have shown, pressure in PSI instead PSIG. PSIA is always used on the P-H charts.
When all of saturated liquid points are connected, they form a saturated liquid line. The same is true for other vapour. The space between these lines is a mixture of liquid and vapor. With this scheme, we have identified many T-x diagrams on the same scheme, as we did for three pressures in the previous scheme. This is inconvenient, and not to use that T-H-scheme is designed...