### Quick Reference

**Temperature - °C or °K**

**Pressure**SI unit – Pascal

1 Pa = 1 N/m

^{2}, too small a unit

Common unit = Bar

1 Bar =105 N/m

^{2}= 0.1 Mpa

Atmospheric Pressure = 1 Bar abs at MSL

Vacuum = 0 Bar abs

**Gauge pressure + Atmospheric pressure = Absolute pressure**

barg = kg/cm

^{2}g

**Density**

**in kg/m**

^{3}

Specific Volume = 1 / Density in m

Specific Volume = 1 / Density in m

^{3}

**/kg**

Specific Gravity = Density ratio to water

Specific Gravity = Density ratio to water

**Energy**SI unit = 1 Joule = 1 Nm = 4.186 cal

Common unit = kilocalorie

1 kcal = heat reqd to raise 1 kg water by 1°C

1 kcal = 4186.8 Joules

Cp = sp. heat capacity in kcal/kg °C

**Conversions between SI and other units**

mWC = meters water column

1 Bar = 10 mWC

1 Bar = 14.23 PSI (Lbs/in

^{2})

150 psi = 10.54 Kg/cm

^{2}g

50 psi = 3.5 Kg/cm

^{2}g

**10 bar g = 11 bar a = 10.2 kg/cm**

^{2}

**g = 11.2 kg/cm**

^{2}

**a = 145 psig = 1 MPa = 106 N/m2**

**Where**

ρ= Density(kg/m

ρ= Density(kg/m

^{3}

**)**

m = Mass (kg)

V= Volume (m

m = Mass (kg)

V= Volume (m

^{3)}

vg= Specific volume (m

vg= Specific volume (m

^{3}

**/kg)**

**Enthalpy of saturated steam**

**hg = hf + hfg**

Where:

hg = Total enthalpy or total heat of saturated steam (kJ/kg)

hf = Liquid enthalpy (Sensible heat) (kJ/kg)

hfg = Enthalpy of evaporation (Latent heat) (kJ/kg)

**Heat Balance in Process**

**Primary Q = m x hfg**

Where,

Primary Q = Quantity of heat energy released (in kcals)

m = Mass of steam releasing the heat (in kgs)

hfg = Specific enthalpy of evaporation of steam (in kcals/kg)

**Secondary Q = m x cp x ΔT**

Where,

Secondary Q = Quantity of heat energy absorbed (in kcals)

m = Mass of the substance absorbing the heat (in kgs)

cp = Specific heat capacity of the substance (in kcals / kg °C )

ΔT = Temperature rise of the substance (in °C)

**Primary Q = Secondary Q**

**Heat transfer equation**:

Where:

Q = Heat transferred per unit time (kcals/hr)

U = Overall heat transfer coefficient (kcals/hr / m²°C)

A = Heat transfer area (m²)

ΔT = Temperature difference between the primary and secondary fluid (°C)

**Steam line sizing**

Where,

D = Line size in mm

m = Mass flowrate of steam in kg/h

V = Specific volume in m

^{3}/kg

π = a constant 3.14

c = velocity m/s

**Calculating Savings:**

**Boiler
Heat Input = Qf x GCV**

where,

Qf = Quantity of fuel (in kg/hr)

GCV (Gross Calorific Value) =Energy contained in fuel in kcal/kg

**Boiler
Heat Output = Qs x (Hs – Hw)**

Where,

Qs = Quantity of steam (in kg/hr)

Hs = Heat contained in steam (Enthalpy of Saturated steam hg)

Hw = Heat already present in the water from which steam is raised

where,

Qc = Quantity of condensate (in kg/hr)

Hc = Heat contained in condensate (in kcal/kg)

Hw = Heat already present in the water at ambient temperature (in kcal/kg)

GCV (Gross Calorific Value) =Energy contained in fuel in kcal/kg

η = Boiler efficiency

ρ = Specific gravity of liquid/gas fuel

**% Flash steam calculation**:

Where,

hf1 = Enthalpy of water at the higher pressure kcal/kg

hf2 = Enthalpy of water at the flashing pressure kcal/kg

hfg2 = Enthalpy of evaporation at the flash steam pressure

**Actual rating of a Boiler**

**Actual
Rating = F&A Rating X 540 / ( hg – hf _{FW})**

where,

hg = enthalpy of steam at generation pressure

hfFW = Feed water enthalpy

**Blowdown:**

Where,

F = Feedwater TDS in ppm

B = Boiler water set point in ppm

S = Steam generation in kg/hr.