Email this pageHeating with Steam
Steam is widely used as a heat source.
An increasingly large number of households now have ovens that use steam for heating. This new twist on a traditional use of steam, namely the “steaming” of food for cooking purposes, has become commonplace in many households.
Both these steaming ovens and normal steaming-cooking are examples of direct heating, in which steam comes into direct contact with the item being heated. In a manner similar to that used in household applications but on a much larger scale, direct heating with steam is also widely used in industrial applications such as sterilizing, sanitizing and in the vulcanizing process for rubber products.
Yet having said that, there is a heating method even more widely used in industrial applications than direct heating. This method is indirect heating.
What is Indirect Heating?
Indirect heating is a method of heating that uses some form of a ‘heat exchanger.’
Steam passes over the wall surface area of the heat exchanger and the heat from the steam is transferred to the substance being heated. In this way, the steam never comes into direct contact with the substance being heated. Some typical examples of heat exchangers used for steam heating are jacketed kettles, coiled-tube types, plate-type heat exchangers and finned-tube types (plate fins, aerofins).
This method of using a heat exchanger for heating is not limited to using steam as the only possible heat medium; other heat mediums such as hot water and oil may also be used.
Advantages of Steam Heating
How does using steam for heating differ from using hot water or oil for heating?
Heating with Steam
Steam is supplied in a gaseous state to the heat exchanger, inside which it changes into liquid form (condensate) and leaves the heat exchanger.
Heating with Hot Water or Oil
Hot water and oil are supplied at very high temperatures to the heat exchanger, and they leave the heat exchanger at a lower temperature.
In other words, in contrast to hot water and oil which heat by lowering their own temperature, steam heats by changing from a gaseous form to a liquid form.
Condensation heat transfer from steam provides a markedly greater heating effect than does convection heat transfer from hot water or oil. It also offers the following advantages:
- If the heat transfer surface areas of the heat exchangers are identical….
- Heating times can be shortened if heating with steam
- If redesigning the heat exchanger to do the same amount of work….
- If using steam for heating, the design can incorporate a smaller heat transfer surface area
These are just two of the important properties of steam—steam offers a number of advantages in addition to this. For this reason, steam has an important position as an industrial heat source.
For further discussion of steam’s superior properties, go to Steam Heat Transfer.
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