1 / 71

# Procedure - PowerPoint PPT Presentation

Tables of Thermodynamic Properties by Dr. M. A. Habib Professor, Mechanical Engineering Department, KFUPM. Procedure. The procedure of calculating the thermodynamic property is as follows: Define the state by two independent properties. Choose SI units tables.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about ' Procedure' - leo-huffman

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### Tables of Thermodynamic PropertiesbyDr. M. A. HabibProfessor,Mechanical Engineering Department, KFUPM

The procedure of calculating the thermodynamic property is as follows:

• Define the state by two independent properties.

• Choose SI units tables.

• Choose the table of the concerned substance.

• Define the region being compressed liquid, saturation or superheated.

• Determine the required property from the table.

• The state is defined by two independent properties. It should be noted that, in the saturation region, P and T are two dependent properties.

3. Calculation of the thermodynamic properties3.1 Saturation region

• Given T and x

• Example:

• Saturation water at T=100 oC and x=0.4. Find P and v.

• Solution:

• From saturation table at T=100oC, read P= 101.3 kPa, vf = 0.001044 m3/kg and vfg= 1.67185 m3/kg, then:

• v= vf + x (vfg) = 0.6698 m3/kg

3.1 Saturation region_ Given P,x

• Given P,x

• Example

• Saturated water at P= 100 kPa and x=0.6. Find T and v.

• Solution

• From saturation table at P=100 kParead T= 99.62 oC, vf =0.001043 m3/kgand and vfg= 1.67185 m3/kg . Then

3.1 Saturation region_ Given P,x

• v= vf + x (vfg)

• = 1.01682 m3/kg

3.1 Saturation region_ Given T,v

• Given T,vExample

• Saturated R134a at T=10 oC and v=0.02 m3/kg. Find x and P

• Solution

• From saturation table at T=10oC read P= Psat = 415.8 kPa, vf = 0.000794 m3/kg and vfg= 0.04866 m3/kg, then

3.1 Saturation region_ Given T,v

= 0.3947

3.1 Saturation region_ Given P,v

• Given P,v

Example.

• Saturated water at P=100 kPa and v=0.1m3/kg. Determine T and x.

• Solution

• From saturation table at P=100 kPa read vf = 0.001043 m3/kg and vfg= 1.69296 m3/kg and T= Tsat =99.62 oC. Then:

• Given P, T

Since the pressure and temperature are two dependent properties inside the saturation region, therefore, this state is not inside the saturation region

• Given T,v and T > Tc

The state is not inside the saturation region

• Interpolation is required when the given property is not found, but instead it lies between two given values in the tables

• Example

• Given saturated water at T= 102 oC, x=0.4. Determine P and v.

T, oC P, kPa vf, m3/kgvfg, m3/kg

100 101.3 0.001044 1.67185

105 120.8 0.001047 1.41831

• Solution

• The available table provides only T=100 oC and T= 105oC as shown. Therefore, the student has to create another table having T = 102 oC as shown in the table below. The values P, vf and vfg at 102 oC can be obtained by interpolation. As an example, P102 can be obtained from the following equation:

Thus, P102 =109.1 kPa

Superheated region

• Given P, T

Example

• Water vapor at

• P=1 MPa,

• T=300 oC.

• Calculate v.

• Solution

v=0.25794 m3/kg

• Given T, v

• Example

• Water vapor at T=300 oC, v=0.3 m3/kg. Determine P.

• Solution

Interpolation gives:

• Given P, v

• Example:

• R134a vapor at P=0.8 MPa, v=0.035 m3/kg. Determine T.

• Solution

Thus T= 98.55oC

• Double interpolation

• Example

• Given water at P= 1.1 MPa, T= 220 oC.

• Solution

• First, interpolate between v1a and v1b to get v1

• Then, interpolate between v2a and v2b to get v2

• Then, interpolate between v1 and v2 to get v.

• Given P,T

• Example:

• Compressed-liquid water at P=10 MPa and T=100 oC. Find v.

• Solution:

• From compressed-liquid table, at P = 10 MPa and T= 100 oC read:

• v= 0.001039 m3/kg

• Case of compressed liquid water at low pressure

• Example:

• Compressed liquid water at P=100 kPa, T=20 oC. Calculate the specific volume.

• Solution:

• The first available pressure in the compressed liquid table is 5000 kPa. Thus P<< 5000 kPa, therefore, the following approximation will be performed:

• Using the saturation table, read:

• v=vf at T= 20 oC, thus v= 0.001002 m3/kg.

• Case of state in the compressed liquid region and the compressed liquid table is not available.

• Example:

• Compressed liquid R134a at P=1.0 MPa and T=10 oC. Determine v.

• Solution

• The compressed-liquid table is not available, therefore, the following approximation will be performed:

• Using the saturation table, read:

• v= vf at T=10 oC, thus, v= 0.000794 m3/kg.

• A state in the superheated region and close to saturated vapor.

• Example

• Water vapor at P= 800 kPa and T=180 oC. Determine v.

• Solution:

• Interpolation between Saturation temperature and T= 200 oC, thus:

Thus v= 0.247 m3/kg

• Defining the region

• The region in which the state lies is determined by its two independent properties. The following are examples. This section is only concerned with defining the region.

Given (T, x) OR (P, x) procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Given (T, x) OR (P, x)

• The state has to be inside saturation region because x (having a value between 0 and1) indicates a mixture of liquid and vapor.

• Given T, v procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Given T, v

From saturation tables, determine vf and vg at T. The region is determined based on the following conditional table:

Given T,v procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

Given T,v procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Example:

• R134a at T= 0 oC, v= 0.3 m3/kg. Define the region.

• Solution:

• At T= 0 oC, vf = 0.000773 m3/kg and vg=0.06919 m3/kg, thus v > vg, then, the state is in superheated region.

Given P, v procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

Given P, v

• From saturation tables determine vf and vg at Psat = P then:

Given P, v procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Example:

• Water at P= 150 kPa, v= 1.0 m3/kg. Define the region.

• Solution:

• At P= 150 kPa, read vf=0.001053 m3/kg and vg= 1.15933 m3/kg , Thus vf < v < vg , then the state is in the saturation region.

Given P, T procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Given P, T

• One of two alternative methods can be used as follows:

• a. Method 1: Starting with temperature:

• From saturation tables determine Psat at T, then, according to the following table the region can be determined:

• Given P, T procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

Example:

Water given at 100kPa and 40 oC

Given P, T procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Solution:

• Psat (at T= 40 oC) = 7.384 kPa. Thus, P > Psat, therefore, the state is in the compressed liquid region.

• Property diagrams for case of P > Psat (The state is in the compressed-liquid region).

Given P, T procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

Given P, T procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Example

• R134a at 1.0 MPa and T=50 oC. Define the region.

• Solution:

• From saturation tables, determine Psat (at T= 50 oC). Thus Psat = 1318.1 kPa. Therefore, P< Psat. Then, the state is in the superheated region.

• Property diagrams for case of P < P procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.sat (The state is in the superheated region).

Method 2: Starting with temperature procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• b. Method 2: Starting with temperature:

• From saturation tables determine Tsat at P, then, according to the following table, the region can be determined:

Method 2: Starting with temperature procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Example:

• Water at 300 oC and P=1 MPa. Define the region.

• Solution:

• From saturation table at P=1 MPa, read Tsat = 179.91oC, thus, T > Tsat . The state is in the superheated region.

Method 2: Starting with temperature procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Property diagrams for case of T > Tsat (The state is in the superheated region).

Method 2: Starting with temperature procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Example

• Water at 200 oC and P=3 MPa. Define the region.

• Solution

• From saturation table at P= 3MPa get Tsat = 233.9. Thus, T< Tsat. Therefore, the state is in the compressed-liquid region.

Method 2: Starting with temperature procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Property diagrams for case of T < Tsat (The state is in the compressed-liquid region.

Thermodynamic processes for a system procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• The following are examples of constant property processes of a system.

• Constant-pressure process

Constant-volume process procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Work = = zero

Process following the relation Pv = constant procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

Isothermal process (T=constant) procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

Spring-controlled Process p=cv procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

Isentropic Process procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

Defining the region for u, h, or s procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Given T, h

• From saturation tables, determine vf and vg at Tsat=T. Then use the following table to determine the region.

• Given P, h procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Given P, h

• From saturation tables determine hf and hg at Psat = P. Then use the following table to determine the region.

• Calculation of properties for given u, h, s procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Saturation region

• Given T, h

• Example.

• Water T=200 oC, h=1500 kJ/kg. Calculate P and x (if the state is in the saturation region).

• Saturation region procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Solution

• From saturation table it can be found that hf < h < hg, thus the state is in the saturation region. At T=100oC read P= Psat, hf= 852.43 kJ/kg and hfg= 1940.75 kJ/kg. Thus,

• P= Psat =1.5538 MPa

= 0.3337

Given P, h procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Given P, h

• Example.

• R134a at P=120 kPa , h=200 kJ/kg. Calculate T and x (if the state is in the saturation region).

• Solution

• From saturation table it can be found that hf < h < hg, thus the state is in the saturation region. From saturation table at P=120 kPa try to read T= Tsat, hf and hfg

Given P, h procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• In this case, because P=120 kPa is not given in the table, interpolation has to be performed between P=107.2 kPa and P=133.7 kPa to create a row of data at P=120 kPa as shown in the following table:

Given P, h procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

Thus, from this table, T= Tsat = -22.58 oC and

Superheated region procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Given T, h

• R134a at T=100 oC, h= 467 kJ/kg

Given T, h procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

Substituting for h=467 kJ/kg gives P=2259.1 kPa.

Given P, h procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Given P, h

• Water P=1 MPa, h=3000 kJ/kg. Calculate T

Given P, h procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

Substituting for h=3000 kJ/kg gives T=276.4 oC

Compressed liquid region procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Given P, T

• Example

• Compressed-liquid water at P=10 MPa, T=100 oC. Calculate h

• Solution

• From the compressed-liquid table, get h= 426.48 kJ/kg.

pressure is very low procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Given P, T and the pressure is very low or the compressed liquid tables are not available

• The following approximation can be done:

• u= uf

• h= hf + vf (P2-Psat at T)

pressure is very low procedures given in Section 3 based on the region being compressed liquid, saturation or superheated.

• Example

• R 134a at P= 1MPa, T=10oC. Calculate h.

• Solution

• h= hf + vf (P2-Psat at T), thus,

• h= 213.58+ 0.000794(1000-415.8)= 214.04 kJ/kg.