met 211 steam-tables

Steam Tables

Chapter 5

Dr.Khaled S. Al-Zahrani

Steam Formation

T°C

H

-20 - a

0 -b c

d e

f

S S+L L L+V V

100 -

S = SolidL = LiquidV = Vapour

Sensib

le

Sensib

le

Sensib

le

Latent

Latent

374 -Critical Point

Saturated Vapour

Saturated Liquid1 Bar

Steam Formation

Mollier Chart

Mollier Chart

Steam TablesSteam tables commonly consist of two sets of tables of the energy transfer properties of water and steam:

1. saturated steam tables

I. Temperature basis

II. Pressure basis

2. superheated steam tables

Both sets of tables are tabulations of pressure (P)temperature (T)specific volume (v)specific internal energy (u)specific enthalpy (h)specific entropy (s)

The following notation is used in steam tables.T : temperature (°C)P : pressure (bar)v : specific volume (m3/kg)u: specific internal energy (kJ/kg)h: specific enthalpy (kJ/kg)s: specific entropy (kJ/kg K)

Steam Tables

Important points

1. Steam tables give values for 1 kg of water and 1 kg of steam.

2. The steam table gives values of properties from the triple point of

water to the critical point of steam.

3. If pressure is known use the table on pressure basis.

4. If temperature is known use the table on temperature basis.

5. At low pressure the volume of saturated (vf) liquid is very small as

compared to the volume of dry steam and usually the specific

volume of liquid is neglected.

Definitions

Sub cooled or compressed: is a fluid under thermodynamic

conditions that force it to be a liquid

Saturated liquid: fully in the liquid state but is about to vaporize

Wet steam: When steam contains water in the form of fine water

particles suspended in steam

Dry steam: When steam contains no moisture.

Saturated steam: is steam at equilibrium with liquid water

Superheated steam: a steam heated above its (boiling point)

saturation point

Qality (x): quantity of dry steam in 1 kg of wet steam

Steam Formation

vspecific volume

uspecific internal energy

hspecific enthalpy

sspecific entropy

v = (1 – x) vf + xvg

vf is neglected

v = x vg

u = (1 – x) uf + x ug

u = uf + x (ug– uf)

u = uf + x ufg

h = (1 – x) hf + x hg

h = hf + x (hg – hf)

h = hf + x hfg

s = (1 – x) sf + x sg

s = sf + x (sg – sf)

s = sf + x sfg

Sub cooled water (A) Saturated liquid (B) (x = 0) Evaporation of saturated liquid (B-C) 10x

Wet steam (F) x Dry Saturated steam (C) ) (x = 1) Superheated steam (D)

masstotal

massvapourx

A

D T

F B

s

C

Group WorkUsing your Thermodynamic Properties of Fluids Tables, determine.

1. The specific enthalpy of: i. Saturated water at a temperature of 130 C⁰ ,

ii. Dry saturated steam at a temperature of 130 C ⁰

2. The saturated water pressure at 130 C. ⁰3. The specific volume of dry saturated steam at a pressure of

2.7bar.

4. The specific enthalpy of steam at a pressure of 2.7 bar and x =0.9.

5. The specific enthalpy of steam at pressure of 20 bar and a temperature of 400 C ⁰

Assignment

Fill in the tables in the given handout