Small Water Saving Initiative from my company

Dear All,
I just wanted to share a small initiative of my new company towards saving of water. This can be presented by you to your management for implementation which will help us to keep our globe safe and provide sufficient water savings for many families to upkeep their daily life.

The water is very important for all living things and currently it is of utmost importance for any coroporate house, individual, and governments to conserve water & promote conservation fo water.

In our present company the management has implemented waterless urinals in the corporate building. This is saving around 2 Litres of water / day / person. We have around 400 people working in this office which is therefore, saving around 2 x 400 x 300 = 240000 Litre / Year.

Now see the importance of this number. Each family (4 persons) need around 100 litre of water / day for hygeine & drinking. Therefore, it can serve for 2400 families for 1 year OR 40 families for 60 years of average life.

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Steam Properties - II

In the previous post I discussed about P & T correlation for saturated steam. I also mentioned that its better to use Excel add-in than using these formulae in Excel sheet. However, these are essentially required if you are using some non worksheet based computer program for the evaluation / simulation of your project.

So here I will cover the other major property that is enthalpy & latent heat for steam.

2. Enthalpy of Saturated Steam at Given Temperature

Enthalpy Hv = alphat + gamma

alphat = 0.99615 t + 1.8239 x 10^-6 * t^2 -0.13468 x 10^ (-0.036 t) + 0.13468

gamma = 597.34 - 0.555 t - 0.2389 x 10^alpha

alpha = 5.1463 - 1540 / T

Where t = temperature in °C
T = temperature in K

So if you need to find out the enthalpy at a given P, you first need to calculate saturation temperature based on methods given earlier.

3. Enthalpy of Saturated Water at Given Temperature

Hl = 0.001 t2 + 0.8663 x t

Where Hl = enthalpy of Saturated liquid at t temperature in Kcal/Kg
t = temperaure in °C

4. Latent heat of Vaporization at Given Temperature

Lambda = Hv - Hl

Hv & Hl are calculated above.


5. Saturation temperature from Pressure
This part is also required frequently, so I developed an equation based on data from steam tables.

t = A x y^5 + B x y^4 + C x y^3 + D x y^2 + E x y + F
Where
y = Log10 (Pv)

A = 0.03878244
B = 0.5246778
C = 2.7767678
D = 12.6450237
E = 63.9525883
F = 99.082168

Pv is in Kgf/cm2.

List of other property estimation methods on this Blog.

• Calculate Diffusion Coefficient in Gases


• Calculate Diffusion Coefficient in Liquids


• Heat Capacities of dissolved solids & organic solutions - Quickest methods


• Heat capacities with dissolved solids


• Kinematic viscosity of air Vs Temperature


• Thermal Conductivity of air Vs Temperature


• How to calculate viscosity of liquid mixtures


• Surface Tension


• Viscosities of Pure Gases at Low Pressure - 1


• Viscosities of Pure Gases at Low Pressure - 2


• Viscosities of Pure Gases at High Pressure


• Viscosity of Gaseous Mixture


• Steam Properties - I


• Vapor Pressure Vs Temperature


• Latent Heat Calculations

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Ammonia Vapor Pressure & Temperature Equations

In the series of physical properties calculation methods, I am now covering Ammonia P & T correlations which are frequently used in refrigeration system design calculations. Or they may be used for designing of heat pumps - yes may be I don't know at this stage if one can use ammonia for heat pump service or not.

Saturation Pressure vs Temperature.

This equation is valid for t = -75 to 70°C. I have limited this equation to this range for better accuracy of calculated data vis a vis comparison with published data.

Pv = A x T^5 + B x T^4 + C x T^3 + D x T^2 + E x T + F

where Pv = vapor pressure in Kg/cm2
T is temperature in Kelvin.

A = -4.5864778 x 10^-11
B = 9.85099347 x 10^-8
C = - 5.7526544 x 10^-5
D = 1.4773233 x 10^-2
E = -1.7847943
F = 83.3895705

Saturation Pressure vs Temperature for t > 70°C.

Pv = 89875.92511 exp (-2706.64791 / T)

where units are same as above.

Saturation Temperature Vs Pressure for P = 0 to 34 Kg/cm2.


T = A x y^5 + B x y^4 + C x y^3 + D x y^2 + E x y + F

Where
A = 0.13493672
B = 0.380555
C = 2.13810444
D = 10.058439
E = 45.5972648
F = 239.1719874

T is in Kelvin

List of other property estimation methods on this Blog.

• Calculate Diffusion Coefficient in Gases


• Calculate Diffusion Coefficient in Liquids


• Heat Capacities of dissolved solids & organic solutions - Quickest methods


• Heat capacities with dissolved solids


• Kinematic viscosity of air Vs Temperature


• Thermal Conductivity of air Vs Temperature


• How to calculate viscosity of liquid mixtures


• Surface Tension


• Viscosities of Pure Gases at Low Pressure - 1


• Viscosities of Pure Gases at Low Pressure - 2


• Viscosities of Pure Gases at High Pressure


• Viscosity of Gaseous Mixture


• Steam Properties - I


• Vapor Pressure Vs Temperature


• Latent Heat Calculation

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Latent Heat Calculation

The most used & ever needed property is the latent heat of vaporization which is critical also for various calculations. A process engineer must understand it properly.

This is one of the property of a pure fluid or a mixture which is never available to you when you need it most specially when you need it urgently. That time you are never able to recall the source where did you see it last time.

So don't worry now. There are few easy methods available which can give you quick & accurate estimate of this be it for pure fluid or for a liquid mixture.

The first method I am discussing is Riedel's Correlation.
This method is limited to calculating latent heat at normal boiling point only. However, this is a property which can be used for the derivation of other properties also. We will see it in future & coming posts.

Hvb = 1.093 R Tc [ Trb x {Ln(Pc)-1}/{0.930 - Trb}]

Where
Hvb = Latent heat at normal boiling point. (Remember this is an important definition)
Trb = Tb / Tc Reduced Boiling Point Ratio in Kelvin
Pc = Critical Pressure atm

Hvb Unit is Lit-Atm/Gm-mole
R = Gas Constant in Lit-Atm/Gm-mole/K

So change R value in different unit & you will get Hvb in desired unit accordingly, because the value in parantheses is unitless.
Also note that 1 Lit-Atm/Gm-mole is equal to 24.12 Cal/gm-mole

The second method I am discussing is Pitzer's Correlation.
This method is applicable for a wide range from normal boiling point to critical point.

The equation given is as below.

(Hv / R Tc) = 7.08 ( 1 - Tr)^0.354 + 10.95 * omega ( 1 - Tr)^0.456

Hv = Latent heat at t °C.
Tr = (t+273.15)/Tc
omega is accentricity factor - a std property


The third method I am discussing is Watson's Correlation.
This method is most useful for the fluid where you know the latent heat at a given temperature & want to calculate it at another temperature, or using some simulation where accurate estimate is required so instead of using basic equations you can use this escalation equation.


Hv2 = Hv1 [ (1 - Tr2) / (1 - Tr1)]^0.378

Hv1 = latent heat at T1
Hv2 = latent heat at T2

Units are same as described in first method.


List of other property estimation methods on this Blog.

• Calculate Diffusion Coefficient in Gases


• Calculate Diffusion Coefficient in Liquids


• Heat Capacities of dissolved solids & organic solutions - Quickest methods


• Heat capacities with dissolved solids


• Kinematic viscosity of air Vs Temperature


• Thermal Conductivity of air Vs Temperature


• How to calculate viscosity of liquid mixtures


• Surface Tension


• Viscosities of Pure Gases at Low Pressure - 1


• Viscosities of Pure Gases at Low Pressure - 2


• Viscosities of Pure Gases at High Pressure


• Viscosity of Gaseous Mixture


• Steam Properties - I


• Vapor Pressure Vs Temperature

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