I A question about dehumidifiers and condensation

[YoshiBeans]

Hi guys!

My question is about the heat sinks (cold side) used in some dehumidifiers. It appears that thick, well spaced fins are used, as opposed to a larger number of thin fins, which I would expect to provide better heat transfer.

Am I right in assuming that this is to allow space for water droplets to form and fall without bridging the gap between fins?

Or is it because the extra surface area would be conterproductive as it would mean a larger quantity of air would need to be reduced to the dew point before the heat transfer becomes useful? If so, would the multiple thin fins be more efficient in the hyperthetical case of 100% humidity?

Any insight would be appreciated.

Thanks in advance.

Johann

 

[sophiecentaur]

A small cold sink will reach a lower temperature for a given rate of heat transfer. I would imagine that would make for more effective condensation because you want to be well below the dew point.

 

[YoshiBeans]

A small cold sink will reach a lower temperature for a given rate of heat transfer. I would imagine that would make for more effective condensation because you want to be well below the dew point.

So you would agree with the hypothetical about the 100% humidity?

 

[sophiecentaur]

So you would agree with the hypothetical about the 100% humidity?

I guess so. But the point of a dehumidifier is to reduce humidity, is it not? Otoh, if it is used as a condenser, the design could be different (?).

 

[YoshiBeans]

I guess so. But the point of a dehumidifier is to reduce humidity, is it not? Otoh, if it is used as a condenser, the design could be different (?).

True, but unfortunately I can't find much on condenser heat sink design as they are normally larger and use finned pipes with gas or fluid refrigerant instead.

 

[sophiecentaur]

So what do you actually want to achieve?
I still think that the cold sink temperature needs to be as low as possible and that is why it's relative small. There is a problem in getting rid of the condensate fast enough because it tends to act as an insulator, increasing the equilibrium temperature of the surface in contact with the air. The hot sink needs to work with radiation or convection whereas the cold sink works by contact with the damp air and should avoid heat gain by radiation as that would reduce the condensation rate. (I just thought of that but I think it must be relevant)