Water Heater Package Design

[pedrajuan]

Hi dear all,

I am writing up the data sheet for a hot water generation package that will feed continuously a gas scrubber heat exchanger (to speed up the reaction kinetics) at 80°C.
The water heater package will heat up the hot water coming from the scrubber heat exchanger from 70 °C to 80 °C. We plan to use a steam to water heating system.
Most water heater fabricators use a vessel with a top outlet and small recirculation pump. This configuration seems is a standard.
What we need is a vessel with heating control that feeds the pumps to get the water to the scrubber heat exchanger. The line going to the pump would come from the bottom of the vessel. It seems though this configuration is not used by hot water generators companies, that is, one in which the water heater feeds a pump.

How do i reconcile my system needs with the apparent standard configuration of hot water heater manufacturers?
Do you have any experience of a hot water generator?

Any insight would be greatly appreciated.

Juan.

 

[EdStainless]

If you are using steam to heat then this is a custom designed heat exchange.
This will look a lot like a power plant low pressure feedwater heater.
If you want the reaction to be at 80C then you will need water hotter than this.
there are commercial gas fired heaters that would do this:

https://www.htproducts.com/phoenix-sanitizer.html

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P.E. Metallurgy, Plymouth Tube

 

[georgeverghese]

You are missing a key component of this closed loop hot water circuit - an expansion drum. You need this for 2 reasons
a) to handle thermal expansion volume as the fixed volume of water in this circuit changes in temperature
b) to enable degassing of the feed to the hot water recirc pump - gas may be trapped in the piping circuit for one of many reasons, and small amounts of gas may also be leaking from the scrubber HX to the hot water, through leaky tube to tubesheet joints - this gas would be separated in this expansion drum.
For gas to leak from the scrubber HX to the closed loop hot water, gas pressure would have to be higher than HW pressure - check if this is the case in your system.
In this preferred scheme with the expansion drum, the recirc pump takes degassed feed from the expansion drum and sends "cold" HW to the hot water heater.
An expansion drum is typically inert gas blanketed to minimise corrosion that would occur otherwise due to dissolved oxygen.

 

[pedrajuan]

Ok, so my vessel would be a storage and provide expansion volume for the system.
i will throw some numbers to estimate a volume capacity.

i have been looking brochures from manufacturers like this:

http://www.hubbellheaters.com/model/stx/#formulas

but still find it odd to foresee a top water outlet for my system.

Thanks for the answers.