# How to find the entropy for a given temperature using P-H chart for a refrigerant?

How do I find the entropies for T1 = -10 deg C and T2 = 30 deg C, respectively using the R-134a refrigerant chart (SI):

Instead of giving you fish I will teach you how to catch it.

There isn't a particular entropy at a given temperature. Considering the wet region there should be given a dryness fraction value for the entropy. With dryness fraction value and temperature combined, you can calculate the entropy of the refrigerant:

$$entropy (s) = sf + x * sfg$$

Where:
$\text{sf = the entropy of saturated liquid R-134a}$ $\text{x = the dryness fraction (between 0 and 1)}$ $\text{sfg = the entropy change during the evaporation process}$