Follow us on Call us for support at 952-935-2345. After hours messages are monitored 24/7.


Test Your Knowledge: How much more efficient is steam compared to hot air?

Air, water and steam are three media commonly used to distribute heat to process loads. However, steam has several advantages compared to hot air and hot water. These advantages include.

  • the heat carrying capacity of steam is much greater than air or water
  • steam provides its own locomotive force.
  • steam provides heat at a constant temperature

How much more efficient is steam compared to hot air? If 100 psig steam were condensed in a heat exchanger, the mass flow rate of steam required to transfer 1,000,000Btu/hr of heat would be about 1,135 lb/hr.

If the temperature of hot air dropped by 100 F as it passed through a heat exchanger, the mass flow rate of air to transfer the same amount of heat with the same temperature difference would be about ________?

4,800 lb/hr
10,000 lb/hr
23,200 lb/hr
38,500 lb/hr

And the answer is…

38,500 lb/hr or about 34 times as much as steam. Here are the calculations to see for yourself:

  • Msteam = Q / hfg = 1,000,000 Btu/hr / 881 Btu/lb = 1,135 lb/hr
  • Mwater = Q / (cp x dt) = 1,000,000 Btu/hr / (1 Btu/lb-F x 100 F) = 10,000 lb/hr
  • Mair = Q / (cp x dt) = 1,000,000 Btu/hr / (0.26 Btu/lb-F x 100 F) = 38,500 lb/hr

The higher flow rates required by water and air require pipes and ducts with larger diameters than steam pipes, which increases first cost and heat loss. In addition, air and water do not propel themselves. Thus, hot air and water distribution systems require fans or pumps, whereas a steam distribution system does not require any additional propulsion for outgoing steam and a very small pumping system for returning the condensate to the boiler.

Finally, because steam condenses at a constant temperature, 100-psig steam could heat a process stream to a maximum temperature of 338 F which is the temperature of the steam. On the other hand, the temperature of water and air decrease as heat is transferred; thus, if the heat in these examples was delivered by a cross-flow heat exchanger, the maximum temperature of the process stream would be 100 F less than the incoming temperature of the air or water.

Because of these advantages, steam is the most widely used heat-carrying medium in the world.

<< Go Back
Subscribe to our CS Update Newsletter: Send Me The Latest News

952-935-2345  address15350 Minnetonka Blvd., Minnetonka, MN 55345

Products We Carry

  • Hot Water Boilers
  • Watertube Steam Boilers
  • Firetube Steam Boilers
  • Deaerators
  • Heat Recovery Steam Generators (HRSG’s)
  • Automatic Recirculation Valves
  • Economizers
  • Gas-Fired Water Heaters
  • Gas-Fired Humidifiers
  • Boiler/Generator Flue Stacks
  • Continuous Emissions Monitors (CEMS)
  • Pressure Reducing Valves
  • Safety and Relief Valves
  • Control Valves
  • Pressure Independent Control Valves
  • Expansion Joints, Guides, Anchors
  • Flash Tanks
  • Flow Meters
  • Balancing Valves
  • Check Valves
  • Separators
  • Pumps
  • Pressure Booster Systems
  • Piston Valves
  • Heating/Cooling Coils
  • Plate and Frame Heat Exchangers
  • Shell and Tube Exchangers
  • Water Heaters
  • Steam Humidifiers
  • Vacuum Systems
  • Condensers
  • Steam Traps
  • Wireless Steam Trap Monitors
  • Tube Bundles
  • Direct Gas-Fired Space Heaters
  • Direct Gas-Fired Make-Up Air Units
  • Unit Heaters
  • Strainers
  • Air Vents
  • Liquid Drainers
  • Heat Transfer Packages
  • Digital Water Mixing Valves
  • Air Cooled Condensers/Dry Coolers
  • Steam Filters
  • Electric Condensate Pumps
  • Steam/Air-Powered Condensate Pumps
  • Packaged Condensate Pump Skids