Chapter 8H

8H. Pressure-enthalpy diagram of Propane, R-22 or Ammonia Back to Main

This page is used to determine the enthalpy and the entropy for pure substances using a Pressure-Enthalpy diagram. Figures 8.5 and 8.5a are examples of a Pressure-Enthalpy diagram for propane. These figures' values are based on a computer program developed for use with refrigeration processes. Other P - H diagrams may show different absolute values for h, however, the Dh will still be correct so long as these relative numbers are consistent.

At any combination of pressure and enthalpy inside the phase curve the propane system is two - phase. At a P and h along the saturated liquid cure it is a saturated liquid, and it is a saturated vapor along the saturated vapor curve. The region to the left of the saturated liquid line is a subcooled liquid and the region to the right of the saturated vapor curve is the superheated vapor region.

To calculate the vapor and liquid enthalpy and entropy of a pure substance the type of refrigerant and method of calculation must be decided. Choose either Propane, Chlorodifluoromethane R - 22, or Ammonia R - 717 by clicking and shading the circle provided for that selection. Under Calculation Option choose a method of calculation by clicking on and shading the circle provided for that selection. For super heated properties, if the temperature and pressure conditions are known, select this method by clicking and shading the circle provided.

Once a selection for refrigerant and calculation option has been made the Temperature and/or Pressure must be entered into the entry space. To do so use the mouse to click the courser in the entry space and input the data. Once this has been done, select Run to execute the solution.

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