Liquids such as water, glycol solutions and high-temperature heat-transfer fluids are coming into wider use as heating media in coils. Some of the reasons for the popularity of water and glycol systems are:
- Heat-recovery systems are becoming more popular, and hot water or glycol solutions are ideal for such duty.
- Hot water may be readily available from such sources as condensate systems or other processes, and it makes sense to use this available heat.
- Users prefer liquids.
The use of high-temperature heat-transfer fluids has a number of practical advantages over water and steam when process air has to be heated to high temperatures. These fluids can operate in the 500˚F to 750˚F (260 to 399˚C) range at or near atmospheric pressure. Steam would have to be more than 1,500 psig (103 bar) to achieve a saturation temperature of 600˚F (315˚C).
Systems capable of operating at high temperatures are expensive to build and maintain. Corrosion caused by steam and water, and the need for water treatment to minimize scale formation, mean high maintenance costs. Systems using heat-transfer fluids do not require supervisory staff to be constantly on duty, which is another advantage.
As with all of Armstrong’s heavy-duty coils, liquid coils are built to withstand the rigors of tough industrial applications. Custom coils are available from Armstrong to fit existing installations and in materials to fit particular applications.