TWL: FW: Gas Dryers? (fwd) (fwd)
Subject: TWL: FW: Gas Dryers? (fwd) (fwd)
From: Keyway (schooley@XXX.XXX)
Date: Tue Nov 13 2001 - 13:25:40 EST
----- Forwarded message: -----
>This message is being typed at work and forwarded through my CDPC phone
>(don't tell my boss:-).
>
>Sorry it took me soooo long to reply, but everything is more difficult when
>you are homeless.
>
>First I would suggest that you have the washer looked at, if you haven't
>already. It could be that adjusting or replacing some work belts could
>improve the effectiveness of the spin cycle (extractor).
>
>As I am sure you all know, dryers work by adjusting the relative humidity of
>air before passing it through the clothes. They do this by taking ambient
>air and heating it to a higher temperature. If the dryers is ineffective,
>then the cause if probably one of two things. 1- not enough heat is
>available and 2 it is temperature limited.
>
>Not having enough heat could be caused by the power supply, i.e. the voltage
>or current is less than required (the marinas power system is overloaded),
>or the heating element is undersized. In either of these case the dryer's
>effectiveness would be a function of the ambient relative humidity and
>independent of the ambient temperature. In other words the power limited
>dryer is always going to provide the same delta temperature. If the inlet
>air has high relative humidity, it will take a long time to dry clothes. If
>the inlet air has low relative humidity it will not take very long. When I
>lived in the high desert, we would run the dryer on air fluff in the summer
>to save propone. When the relative humidity was 23% the clothes would be dry
>in 25 to 30 minutes. In the winter with the gas on a load would take 45
>minutes to an hour.
>
>You might try drying clothes during off peak hours. You might also try
>running the generator to isolate the problem. It could also be that the
>times when the Marine is crowded coincide with the times when the humidity
>is high.
>
>If your dryer is power, you can replace the dryer or augment it. To augment
>the dryer all you need to do is figure out a way to preheat the dryer intake
>air. This could be as simple as ducting the inlet into the engine room and
>only drying clothes while underway or maybe you could rig up a system to
>draw air from your heater. You could also put a heat exchanger in the dryer
>inlet duct and use hot water from the water jacket or hot water tank.
>
>The temperature limit case is a little more difficult to understand. Every
>(quality) dryer has a temperature limit which is set to avoid overheating
>and damaging your clothes (i.e. melting the plastics). If the air starts out
>hot and with high relative humidity, then the relative humidity will still
>be fairly high when the temperature limit is reached. For example if it is
>110 degrees F and 90% humidity at the inlet, when the dryer heats the air to
>say 200 degree F the humidity will still be about 55% (I know it isn't
>linear but my air tables are currently inaccessible and this is just an
>example;-). If the problem is the temperature limit the dryer will work fine
>in cool and/or dry conditions, but not in hot and humid conditions.
>
>The fix for a temperature limited dryer problem isn't replacing it with a
>gas dryer. Both the gas and electric dryers will have the same temperature
>limit. However, since the gas dryer is adding combustion products to the air
>which consist of CO2 and H2O (steam), I think the relative humidity inside
>the gas dryer could actually be higher than the electric dryer (but I could
>be wrong, this requires a lot of analysis to confirm which I haven't done).
>
>The easiest solution for the temperature limited situation is to monitor a
>hygrometer and do laundry on dry days. Unfortunately, in the PNW this might
>be a long wait :-). Another solution is to dehumidify the air before the
>dryer heats it up. The most common method is to do this is to cool the inlet
>air below the dew point so that some moisture condenses out. If the water
>temperature is significantly lower than the air temperature (as is normally
>the case in the PNW), you would use a raw water to air heat exchanger in the
>dryer inlet duct. Following this the dryer should work better, unless it is
>also power limited, in which case you could also use the preheat methods
>discussed above.
>
>I recommend that you try and isolate the problem and make sure that the fix
>is actually going to fix the problem before you spend money. My preference
>would be to pre-treat the dryer inlet air to augment the existing dryer
>rather than replace it. I would also prefer the electric dryer over the gas
>dryer because of the problems with gas on boats and filling the propane
>tanks. With good preheating of the inlet air you could reduce the electric
>load to minimal level.
>
>Relatively yours;
>Mike Schooley
>Trailerable Trawler wannabe
>
>
