lbs/hr of steam 1

[joecontrol]

Gents,

I am looking to control Rh in 5000 cu/ft of air with air replacement changes every 4 hours(low air flow).
The temperature range is 85 F(98%Rh) to 120 F(20%Rh)

The High Rh(95%-90%) at lower temps 85 F to 100 F and lower Rh(75% -20%) at higher temps 100F to 120F.
I am using dry heat (fin tubes)to heat and was going to use steam sprays to add Rh. I need to know what to expect in lbs/hr use of steam to size steam boiler for jets.

I figure there is a formula for volume of steam to increase Rh by 1% per cu/ft of air at various temps.

Is there such a beast??

With the volume of air I think the heat added by the steam will be small enough not to affect the temp wildly.Also if I place many small jets along the lenght of the space the Rh will be somewhat uniform.

space is 7'X 7'X 98'==4802 cu/ft(5000)

Air will enter from floor many small holes (1/2" on 4" centers) and exit out 4 evenly spaced draw fans(5-20 cfm/fan w vfd)
Spray misters above floor plate at floor level spaced at 10'?? along center line. Two temp/Rh sensors (rototronic) at 30' spacing(to avg). Fin coil under floor plate with holes 1/2" plate(to help with uniformity)and walk on. Hot water heated 150F to 200F.

1 small supply air fan 20 cfm to 100 cfm w/vfd control

Space pressure control by slightly faster supply fan then exhaust fan with dp xmitter and controller.
space pressure +.05 to -.05 " H20

Thanks,Joe

 

[tombmech]

Sorry to keep adding to this, but it's one of my primary interests. After all of that above, you might be asking yourself, "So what do I do?" Your case is similar to drying processes that I have tackled before. Your sink process is the most important - maintaining the same temperature and humidity over the 48 hr period. We have demonstrated the easy calculation for steam rates - based on your possible exhaust flows.

To answer your ultimate question: in the past, I have simply kept the humidity ratio at the same value attained during the sink period. The result is not a straight-line process for temperature and relative humidity - the fallacy of which was proven above. Instead, if the humidity ratio is kept constant, a linear reduction in temperature will result in the gentle slope of steadily decreasing relative humidity as shown.

You are still drying the product - not the air. In that case, relative humidity is definitely a measure of how well the air can absorb moisture from the product. As with the original responses, the goal is to keep the introduction of new air from upsetting that balance. Maintaining that balance is a function of maintaining the humidity ratio, not relative humidity. The result will be a gentle process of constant moisture removal from the product, and simple, easily controlled mechanical components.

 

[joecontrol]

Tombmech,

Thank you for the excellent explanation and, your work. It will help me to explain to my customer what the "Process" expects to do to get the clay dry. Not what they think they need to do to get the clay dry.



Thanks Again to everyone,Joe

 

[joecontrol]

Fellas,

One other thing to ask,Are there any good books available on the above topic??

Drying clay or textiles? It would be helpful to have that if i ever run into a similar problem in the future.

Thanks to everyone for their hard work and input.

Joe