Download presentation

Presentation is loading. Please wait.

Published byZaria Tanner Modified over 3 years ago

1
**Entropy changes of pure substances: retrieving data from property tables.**

Tds relations relate properties of any pure substance exactly to entropy change. But it is not convenient to use them. Instead tabulated data for s are used, e.g. Table B.1. for water. Table B.5 for refrigerant R134a The tabulated value s actually means the entropy change from chosen reference state which is assigned a value 0 (e.g. entropy of saturated liquid water is assigned a value 0 kJ/kg/K) at the triple point of water where t=0.010 C and P=0.61 kPa) In the superheated vapor region and compressed liquid region (Table B.1.4) s can be calculated given P and T. In the saturated liquid region: s=sf+xsfg When no compressed liquid data is available the saturated liquid table (e.g. Table B.1) can be used to get an approximate value

2
**h-s plot or the Mollier diagram for a pure substance.**

Horizontal line segment entropy change during an isenthalpic process (application: throttling) Vertical line segment enthalpy change during an isentropic process (application: turbine). Constant pressure lines are inclined straight lines in the two-phase region, since temperature is also constant. In the superheated region, isotherms lines become more and more horizontal as pressure is reduced (h=h(T) for an ideal gas.) Concave curves in the superheated region. Diverge from one another as psat up means tsat up

3
**An actual h-s chart (Mollier diagram) for water**

4
**T-s and h-s plots: checklist**

Show critical point, SLL and SVL on T-s plot. Show constant P lines on T-s plot. Show constant v lines on T-s plot. Show constant P lines on h-s plot. Inside the vapor dome, why straight lines; why inclined; why diverging from one another. Show critical point, SLL, SVL on h-s plot. Water 374 degrees C and 22 MPa

Similar presentations

OK

Further Analysis of Reversible Machines P M V Subbarao Professor Mechanical Engineering Department Innovation of A New Property of A System!!!!

Further Analysis of Reversible Machines P M V Subbarao Professor Mechanical Engineering Department Innovation of A New Property of A System!!!!

© 2018 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Quantum dot display ppt online Ppt on minimum wages act 1948 Ppt on power grid failure prep Ppt on review writing examples Perspective view ppt online Ppt on 9/11 terror attack impact on world economy Ppt on bank lending ratio Ppt on limits and derivatives in calculus Ppt on conjunctive use of water Animated ppt on magnetism facts