Mollier enthalpy-entropy diagram

Figure 2-38. Mollier (enthalpy-entropy) diagram for steam.

Figure 4.4 shows the thermodynamic processes in a jet pump in a Mollier enthalpy-entropy diagram. The inlet conditions of motive flow and suction flow are assumed to be saturated steam. This is also a common situation in real processes. Besides this, it is also assumed that the expansion in the motive nozzles ends just with the suction pressure p. In the case of a non-dissipative expansion in the motive nozzle, the change of state would be described by the perpendicular from point 1 to point 2. While a real expansion with losses leads to point 2. ... 

Mollier diagram A chart relating enthalpy, entropy, temperature, and pressure of steam. 

Enthalpy/concentration diagram, 440-447 for sodium hydroxide/water, 444 for sulfuric acid/water, 441 Enthalpy/entropy (Mollier diagram), 183, 185 for steam (see back endpapers)... 

On an enthalpy versus entropy diagram (Mollier diagram), the above equation shows the slopes of chords to the constant pressure curve between input and output conditions. The constant pressure curves are convex (d2h/ds2). If the input conditions are the same for both exchangers, inequality (5.120) and Figure 5.5 show that... 

MOLLIER DIAGRAM - An enthalpy-entropy or enthalpy-pressure chart showing the thermodynamic properties of a fluid. 

The PVand ZP diagrams are examples of such charts that we encountered already. There is no limitation as to the properties that can be chosen to represent the axes and this freedom leads to various possible combinations. Three charts that find widespread use the pressure-enthalpy chart, the temperature-entropy chart, and the enthalpy-entropy chart, also known as Mollier chart. These are explained below. 

The data on hydrogen presented by Kubin and Presley include results in the form of tables and of Mollier diagrams. Properties treated include energy, enthalpy, entropy, heat capacities, equilibrium constants for dissociation and ionization, chemical composition of equilibrium gas, density, compressibility, and speed of sound. 

Mollier diagram for potassium. Basis enthalpy = 0.0 oal/g atom at 298 K entropy = 15.8 oal/(g atom-K) at 298 K. (Aerojet-General Rep. AGN8194, vol Reproduced hy permission.)... 

At given inlet conditions, determine inlet entropy (s) and enthalpy (h) from Mollier Diagram ... 

A Mollier Diagram is useful for the expansion of a specific gas/vapor or multicomponent vapor fluid. See Figure 12-91 for comparison of (1) constant enthalpy (Joule-Thompson effect), isenthalpic, and (2) isentropic (constant entropy), which provides the colder temperature. Note that the expander indicated on the figure is somewhere between isenthalpic and isentropic or polytropic. See Figure 12-92. ... 

If a Mollier diagram (enthalpy-pressure-temperature-entropy) is available for the working fluid the isentropic work can be easily calculated. 

The amount of energy that the steam turbine extracts from the steam depends on the enthalpy drop across the machine. The enthalpy of the steam is a function of its temperature and pressure. One can use a Mollier diagram as a graphic tool to determine the amount of energy available under a particular set of conditions. If in Figure 2.131 the inlet conditions correspond to point and the outlet conditions to point P2, a line drawn between these two points is called the "expansion line" and represents the operation of the turbine as it is extracting energy from the steam. In an ideal turbine, the steam would expand at a constant entropy (isentropically) and the condition of the exhaust steam, from an ideal machine (which has no losses), would correspond to point 3. 

Example. The normal boiling point of saturated NaCl brine is 108.7°C. If we are to provide a temperature differential of 10°C, the steam must condense at 118.7°C, or at 190.3 kPa. Taking compression to be a constant-entropy process, we can follow its course on a Mollier diagram or in the steam tables. Increasing the pressure of the cogenerated steam from atmospheric requires an increase in enthalpy of 118 kJ kg and produces a vapor temperature of 196.5°C (78° superheat). We can perform similar calculations for... 

Mollier diagram A plot of enthalpy versus entropy of a fluid, which includes lines of constant pressure and temperature. 

The properties of steam are well documented in steam tables. These tables, or associated numerical formulations, are useful in the calculation of detailed steam turbine cycle performance. A familiar graphical representation of steam properties is the MoUier diagram, which is a plot of enthalpy h) versus entropy (i). An ideal turbine expansion is represented by a vertical path on the Mollier diagram. 

Flashing. The flash from a superheated liquid released to atmospheric pressure can be estimated in a number of ways. If the initial and final state of the release is quiescent, then the initial and final enthalpies are the same (this does not imply a constant enthalpy process). For pure materials, such as steam, a Mollier entropy-enthalpy diagram or a thermodynamic data table can be used. 

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