Heating Water by Injecting Steam
Water can be heated by injecting steam.
For some applications a direct heating of water by injecting steam may be convenient. A direct heating system is very simple since it don't require heat exchangers. Fouling of surfaces, which may be a major problem in certain processes, is also avoided.
The required steam flow rate in an steam injection process can be calculated as
m_{s} = P / (h_{g}  (t c_{p})) (1)
where
m_{s} = steam flow rate (kg/s)
P = heat transfer rate or power from the steam (kW)
h_{g} = specific total enthalpy of the steam before the control valve (kJ/kg)
t = final temperature of the water after the heating (^{o}C)
c_{p} = specific heat water (kJ/kg)
The specific heat of evaporated steam is related to zero degrees Celsius.
Example  Heating a Water Volume by Injecting Steam
100 liter (kg) of water is heated from 20 ^{o}C to 80 ^{o}C in 5 minutes (300 s). The specific heat of water is 4.2 kJ/kg^{o}C and the power required to heat the water can be calculated as
P = (100 kg) (4.2 kJ/kg^{o}C) ((80 ^{o}C)  (20 ^{o}C)) / (300 s)
= 84 kW
The absolute steam pressure is 220 kPa and the total enthalpy of the steam is 2711 kJ/kg. The required steam flow rate can be calculated as
m_{s} = (84 kW) / ((2711 kJ/kg)  ((80 ^{o}C) (4.2 kJ/kg^{o}C)))
= 0.035 kg/s
= 127 kg/h
The total steam consumption for the heating process can be calculated as
q = (0.035 kg/s) (300 s)
= 10.5 kg
Related Topics

Thermodynamics
Thermodynamics of steam and condensate systems.
Related Documents

Condensation of Steam  Heat Transfer
Heat transfer when steam condensates. 
Pipes Submerged in Water  Heat Emission
Heat emision from steam or water heating pipes submerged in water  assisted (forced) or natural circulation. 
Saturated Steam  Properties  Imperial Units
Steam table with sensible, latent and total heat, and specific volume at different gauge pressures and temperatures. 
Saturated Steam  Properties for Pressure in Bar
Saturated Steam Table with properties like boiling point, specific volume, density, specific enthalpy, specific heat and latent heat of vaporization. 
Steam and Vapor Enthalpy
Vapor and steam enthalpy, specific enthalpy of saturated liquid, saturated vapor and superheated vapor. 
Steam Heating Processes  Load Calculating
Calculating the amount of steam in nonflow batch and continuous flow heating processes. 
Steam Heating Systems  Design
An introduction to the basic design of steam heating systems. 
Water  Thermophysical Properties
Thermal properties of water at different temperatures like density, freezing temperature, boiling temperature, latent heat of melting, latent heat of evaporation, critical temperature and more.