My dishwasher's design is focused on noise, so there is no air vent which would allow noise to escape. When the dishes are done, I always open the dishwasher to fully dry the still-hot dishes.

But, here's the quandary: do I open the door all the way, or just leave it cracked? It seems like the best approach would be to open the door all the way, in order to let as much air as possible flow past the moist dishes, thus quickly taking the water away. However, my instinct suggests that it might be better to only crack the door, so that entering dry air fully reaches equilibrium with the heat and moisture before leaving, thus better using the residual heat of the dishes to dry them.

Is there an analytical approach that would clearly promote either a cracked or a wide-open door?


You could use convection relationships and mass transfer to figure out exactly which scenario is better.

I don't really want to go through all that; because I'm quite sure fully opening will be a better option for several reasons.

Greater surface area between the inside and outside conditions. The greater this surface area, the more the damp air communicates with the dry air, and therefore the more vapour diffuses to the outside.

Better convection. When the dishwasher is only open a crack, the only place that the transfer takes place is at the top. Because the steam is less dense than air the steam will easily escape through that crack; but then air will have to come in to take it's place. This will lead to a limited flow rate of fresh air out, and cool air in. Either they will both only use a portion of the open surface area, or it will be a cyclic pattern of losing some steam, then filling back up (think of trying to empty a bottle too fast, air bubbles have to rush in and interrupt the flow).

If you open it fully, the less dense steam will want to rise to the top, while the cool air will go over the dishes and pick up more moisture and heat, before also rising.

There's also a chance that by leaving it only a crack open, it would increase the pressure in the dishwasher. That would make the vapourization less likely to occur. (I'll admit, this one is unlikely to do much. I assume the dishwasher has mechanisms so that it doesn't build up much pressure, even when fully closed, for safety reasons)

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    $\begingroup$ Of course, if everything's at room temperature then the more air through the system the better. However, the key of my question is the heat energy in the dishes; the more efficiently this is used to evaporate water (rather than just heat the air) the quicker the dishes will dry. Any thoughts on this? $\endgroup$ – Daniel Griscom Sep 28 '17 at 16:35
  • $\begingroup$ @DanielGriscom I don't think it would be more efficient. You aren't really promoting an even transfer of the moist air out by opening it less. You don't just need heat to evaporate water. The amount of water in the air will play a big factor, and even at room temperature you can expect the dishes to eventually dry because of all the evaporation into the air. By limiting the space for moist air to escape, you're really just making it hard for that moist air to evaporate, because the humidity is already too high. By lowering the relative humidity, you also increase the amount evaporated. $\endgroup$ – JMac Sep 28 '17 at 17:29

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