Pond water for kiln dehumidifying.

[Asima]

Hi, and have a  very good year for all of you. I' m thinking of building a 500 to 1k b/f kiln, having a 1 acre  16 feet deep pond with bottom temp in the mid 50 f degrees. Have already access to pumping water, here' s my question: fane ning moist hot air from the kiln trough a heat exchanger with a steady flow of pond bottom water (and return) could I acheive sufficiant drying capacity? Have not figured out what type of heat will be supplied
Location  Eastern Township Québec

[jueston]

i don't know if 50 degrees would be cool enough to condense the water at the speed you want, if its condensing too slowly then you might waste a lot of time, and give some species like maple the opportunity to mold while the humid air is sitting around. that might just be an issue of sizing your heat exchanger correctly for the job.

someone smarter then me on the topic of dehumidification will comment, if you build this i think many people on the forum will be interested in the outcome...

[GeneWengert-WoodDoc]

Using a cold water coil to dehumidify a kiln is indeed technology that has been used before.  Sometimes, the cold water has been from a cold lake (but 55 F temperature is not very cold), sometimes cold water from a deep well, and sometimes from a cold river.  I saw one in NC that used well water and automobile radiators for the heat exchangers.

A key issue when using cold water instead of an electric compressor, is that you still need a source of energy to evaporate the water.  That is, if you use 50 F water, soon the kiln and its content will be 50 F at 100% RH.  So, you need to heat the air to at least 80 F (30 degrees warmer) assuming that the heat exchanger is very efficient.  You could bring in outside air at 80 F (some days during the afternoon in the summer), but then you would have to dehumidify the air  before it would do any drying, which means you would not have dry warm air, but cool, somewhat drier air.  So, you need a fairly large heater to supply the heat necessary for evaporation.

With a water dehumidifier, the heat goes into warming the water, but 65 F warm water is not useful, so you cannot make this energy efficient.  An electric DH has both hot and cold coils in the kiln, so the heat of evaporation is reused.  This re-use is not possible in a water dehumidifier.

Note that we can cool and dehumidify the air with a water system in a home, but in this case there is no evaporation of water, so there is no need for extra energy.

[Al_Smith]

For what it's worth the older early "Tetco" geothermal units used a water A coil for  cooling and only used a water cooled heat pump for heat .They dehumidified fairly well .

I've never done it but I suppose like any other dehumidification process it would depend on the surface area of the A coil and air flow in addition to water temperature .

[Asima]

Thanks for each of your input, a special  hello! to Doctor Wengert ( being a follower of your science and instructions  on the WoodWeb.)
This pond is used for swimming and for  never more then  +- 200 rainbow trouts. The temperature are at bottom, summer high' s. Closer to surface trough winter and spring probably much chiller. I know that we need extra heathing of the moist air to speed-up dehumidifying process near exchanger. Milling bi-products such as bark slabs,  wood chipping, and sawdust could be used for free energy to solve heat input to kiln. Any solution using or adding free solar heat (without interrupting air flow)?

[submarinesailor]

I have a buddy who use to design refer systems for the Defense Commissary Agency. A long time before he became the General Manager of the Pentagon Heating and Cooling Plant. I can remember several conversations with him about using the river (Rose River) for cooling my house down in Madisn County, VA. He always stated that in order to get good DH, the water needed to be 45 or lower. Now that is for cooling and DH of a people space.  Not sure if it applies to a DH kiln or not.

[Asima]

I do understand one must create a sufficiant temperature differential to alough condensation to happen and to acheive proper rates of dh. I' ve got to figure out how fast it can be done. Might try a small size mock-up of the idea this spring. Please excuse my english writting, not being my first language.

[GeneWengert-WoodDoc]

If you consider the cost, you will find that it is much cheaper to dehumidify the kiln by venting to the outside rather than by using a cold water dehumidifier and the associated pumps, heat exchangers, etc.  a cold water dehumidifier does not save energy, as the heat goes into the lake or pond...cold water comes in and this water is warmed and returned to the pond.  Further, the warm condensate also goes outside the kiln.  An electric dehumidifier does capture and recycle the energy using a heat pump that is within the kiln.