Since the invention of a steam pump by Thomas Savery in 1698 steam has been used for multiple processes. Application have included pulling trains, creating electricity from nuclear plants, cooling with an absorption exchanger or simply heating liquid or air with a heat exchanger. Steam design has been done the same ways for hundreds of years.
Nothing new came out except for boilers, steam traps, pumps or valves but the way of designing a steam network didn’t change.
Until a new advance steam technology came out that is revolutionizing the steam design. The concept is using high pressure steam and instead of using just the latent heat in each pound of steam, it is using the total heat (latent + sensible) which creates energy savings up to 15%.
The way to do it is by using a vertical flooded heat exchanger. By being vertical and oversize by 20%, that allows the steam heat exchanger to keep a condensate level at the bottom of the same steam heat exchanger on a full demand. Than the concept consist to put the control valve on the condensate. When the steam control valve modulates it plays with the heat surface area in the steam heat exchanger and extract more heat in each pound of steam.
A steam heating system with low maintenance
When you use this advance steam technology on high steam pressure, you avoid different components like the need of pressure reducing valves, the need of 1/3-2/3 control valves, no more condensate return pump with no flash tank and if all the other components (steam heat exchanger, insulation valves, control valve, steam trap, etc.) are rated for high pressure you won’t need a safety valve pipe to the roof on steam because the manufacturer will provide an ASME (CRN for Canada) stamp on the steam heat exchanger or on the all package.
Straight tube versus u-tube design on the vertical heat exchanger
Many steam heat exchanger manufacturer are providing a vertical heat exchanger especially on domestic hot water application whether you control on the steam side or on the condensate side. Because by using a straight tube design you expose the higher tube sheet to more thermal shock especially on a flooding steam heat exchanger by using high pressure steam. The stress on the tube sheet is cause by the fact that the upper tube sheet always sees high pressure steam inside the tube and sees different level of condensate also in the tubes plus it sees colder liquid on the other side of the tubes.
By using a u-tube design on a flooding heat exchanger, the tube sheet which is at the bottom of the heat exchanger, always sees liquid on both side, so very low stress on the tube sheet. Normally with a straight tube design on high pressure steam application, the tube will start to be remove from the tube sheet in less than 3 years.
Be aware that some of straight tube heat exchanger manufacturer will blame those failures on water hammer which is never the case. Also, keep in mind, that with a u-tube steam heat exchanger you can always replace just the bundle compare with a straight tube design you will have to replace the all heat exchanger. And if your ceiling is high enough you can replace the bundle of the u-tube design for a flooded vertical steam heat exchanger without touching the water connexions.
Once you choose the right steam heat exchanger design for flooding it, you will not only save on energy cost and maintenance cost but this advance steam technology will provide you savings on the installation by using less big and complicated components to install but also you will need more than 40% less room for the same process on steam in a traditional way.
Plus by using high pressure steam every components is smaller; piping, valves, union, condensate return lines… means less welding, less insulation and all components are easier to manipulate.Just by avoiding the use of low pressure steam for heating we gain a lot in the 3 major aspects; energy, maintenance and installation costs.