pmagowan
Well-Known Member
Because you require controlled ventilation. If you just use an open hatch then it doesn't work. Then you only dry through ventilation. I am talking about controlling the internal humidity.
Last edited:
Evaporative air conditioning
- Thread starter pmagowan
- Start date
Because you require controlled ventilation. If you just use an open hatch then it doesn't work. Then you only dry through ventilation. I am talking about controlling the internal humidity.
pmagowan
Well-Known Member
It uses less energy and gives a controlled internal environment with better ventilation rates and no risk of mildew etc. Currently we just heat internal environments, get a 'fugg' up and then quietly steam with hatches open letting cold air cause condensation etc.
I admit the air conditioning adds significant complication but then that is air con for you. It would be the most energy efficient type. The mvhr is only an exchanger
Last edited:
pvb
Well-Known Member
I only have hatches and washboards, and a Webasto heater. But I don't have condensation and certainly don't have mildew. I think you're over-complicating things.
duncan99210
Well-Known Member
OK. We lived on board year round for six years in the eastern and western Med. We have a Ebersbacher heater, drawing air in from the outside for heating. Uses about half a litre of diesel per hour. We never had any problems with condensation on board, even with cooking. The fresh air being drawn into the boat by the heater was enough to defeat that particular problem. Whilst I can see the benefit of the heat exchanger ventilation system the OP is suggesting, it is an overly complex solution to a problem that forced air heating will solve.
I've already had my say on the air con bit: it really is a case of not sitting inside a boat during the heat but of getting out into the shaded cockpit and letting whatever wind there is keep things pleasant. A simple fan by th bedside is enough to keep you comfortable for sleeping.
I've already had my say on the air con bit: it really is a case of not sitting inside a boat during the heat but of getting out into the shaded cockpit and letting whatever wind there is keep things pleasant. A simple fan by th bedside is enough to keep you comfortable for sleeping.
geem
Well-Known Member
Evaporative coolers work very well where RH is low. They dont work in the UK where RH in summer is typically 70-80 %. A few were imported from Australia a few years ago. You had to fill them up with water. They just didnt work in thr Uk. Chocolate fire guard...
Great in deserts where there is no moisture but not here.
We met a Aussie couple on a cat a few years ago in the Caribbean. There solution was to have vents in the bridge deck that brought cool air from just above the water into the cabin. Seem to work well.
Great in deserts where there is no moisture but not here.
We met a Aussie couple on a cat a few years ago in the Caribbean. There solution was to have vents in the bridge deck that brought cool air from just above the water into the cabin. Seem to work well.
superheat6k
Well-Known Member
Don't overlook the potential of a massive pool of free chilled water surrounding the boat (UK not Med).
Comfort in warm weather is achieved with just a 5oC drop in temperature, and no need to go below 22oC.
The seawater in the UK will be ~ 8oC in Spring and rises to ~ 16oC by September. An effective heat exchange will require a Delta T Air off to Water off of ~ 4- 6oC, so with 16oC seawater an air off temp of 22oC is just possible.
Thus the cooling becomes a finned coil vessel say 3 rows deep by say 300 mm sq with on a common 1" pitch will be ~ 12 tube rows high.
All that is then needed is a small seawater circulating pump and a fan.
Comfort in warm weather is achieved with just a 5oC drop in temperature, and no need to go below 22oC.
The seawater in the UK will be ~ 8oC in Spring and rises to ~ 16oC by September. An effective heat exchange will require a Delta T Air off to Water off of ~ 4- 6oC, so with 16oC seawater an air off temp of 22oC is just possible.
Thus the cooling becomes a finned coil vessel say 3 rows deep by say 300 mm sq with on a common 1" pitch will be ~ 12 tube rows high.
All that is then needed is a small seawater circulating pump and a fan.
Heckler
Well-Known Member
Nail on head, I thought he was joking at first! How big is his boat?
Stu
Heckler
Well-Known Member
Why?
Ive had my Bene for 8 years, most in N Wales but fir the last two years in Portugal and now Gib. Hot and sticky but no probs with mildew or anything like that, keep the hatches open if its hot, closed if its cold!
Stu
William_H
Well-Known Member
Whole of house evaporative air con is common here in Perth. The box about 1 metre cubed sits on the roof.4 sides have a matrix of like straw. The bottom is a container of water about 5cms deep fed from the mains water via a ball valve. A pump lifts the water up to flow down through the straw. A big fan sits in the middle sucking in air and so blowing down into the ceiling via ducts to each room. (bungalow to you of course). Works very well mostly and requires doors or windows open to let the air out. Fails miserably on humid days. Not to many though. Some people have compressor refrigerated air con as a stand by for bedroom.
Anyway for the boat Yes I think much could be done with heat exchanger from sea water which is almost always cooler.
I wonder why we don't use the bilges as a giant heat exchanger. The skin particularly of an ali boat (but surely with GRP too) would be cool from the sea and would have a large area to transfer heat into air sucked through the bilges.
I can't help thinking the OP with his heat recovery system with have to have a very bulky heat exchanger taking up room.
Perhaps then a cooler system where cabin air goes through a duct or heat exchanger where the duct is cooled by sea water running over it. With evaporation as a part of the cooling. Great ugly thing on the cabin top but it might work.
All sorts of crazy ideas. good luck olewill
Anyway for the boat Yes I think much could be done with heat exchanger from sea water which is almost always cooler.
I wonder why we don't use the bilges as a giant heat exchanger. The skin particularly of an ali boat (but surely with GRP too) would be cool from the sea and would have a large area to transfer heat into air sucked through the bilges.
I can't help thinking the OP with his heat recovery system with have to have a very bulky heat exchanger taking up room.
Perhaps then a cooler system where cabin air goes through a duct or heat exchanger where the duct is cooled by sea water running over it. With evaporation as a part of the cooling. Great ugly thing on the cabin top but it might work.
All sorts of crazy ideas. good luck olewill
vyv_cox
Well-Known Member
We have a Transcool on board, bought this year. Its design could hardly be more simple: a trough of water with a sponge placed vertically so the water comes half way up it. A fan blows air through the top half of the sponge, it then exits the box via two directional nozzles. We first saw one at the Manchester Motorcaravan Show in February, hardly a desert climate, and were most impressed. On board we don't use it all the time but it is a great help to the chef when cooking and sometimes if we eat below for some reason. Electricity consumption is quite low on medium fan speed. We add a few drops of tea tree oil
to every second batch of water to deter mildew.
Sorry Charles, the beer came from our water-cooled conventional fridge.
to every second batch of water to deter mildew.
Sorry Charles, the beer came from our water-cooled conventional fridge.
geem
Well-Known Member
These evaporative solutions will only work with air that is fundementally dry. With high humidity air there is no room for evaporation as the air already carry a large quantity of moisture. If you are fortunate enough to be in a region where the air is relatively dry then evaporative coolers will work.
We tried some evaporative coolers in Manchester many years ago in our office. Somebody got them on hire as it was one of those rare hot summers! They were a joke. You filled a trough with water and a fan blew across a wet matrix. The humidty went through the roof and we were all hot and sweaty. We got rid of them and purchased some conventional compressor portable coolers.
charles_reed
Well-Known Member
Sorry Charles, the beer came from our water-cooled conventional fridge.
Read more at http://www.ybw.com/forums/showthrea...ve-air-conditioning/page3#1SU9D0lASUqtcxpW.99
Well it was pleasantly cool - I'm now suffering 40C temperatures in Rethymno - a change after the breezy conditions in Ag Nikoloas. I got pinned down for an extra 24 hrs in Spinalongga, until a 10' freak break in the 4/5 allowed me to break out my anchor @23:10 on Saturday 23 July.
Read more at http://www.ybw.com/forums/showthrea...ve-air-conditioning/page3#1SU9D0lASUqtcxpW.99
Well it was pleasantly cool - I'm now suffering 40C temperatures in Rethymno - a change after the breezy conditions in Ag Nikoloas. I got pinned down for an extra 24 hrs in Spinalongga, until a 10' freak break in the 4/5 allowed me to break out my anchor @23:10 on Saturday 23 July.
Kelpie
Well-Known Member
The Albin Vega was designed with an interesting passive cooling system. Mushroom vents in the deck led to ducts which lay against the hull, below the waterline, and fed into the saloon. Air from the saloon exited via the mast, which was intended to act as a stack ventilator. Those who have sailed Vegas to warmer climes seem to think it works, a bit.
AntarcticPilot
Well-Known Member
Sound like a potentially good idea. I have some concerns about using salt water as the evaporative medium. Surely salt water will become concentrated brine, and brine concentrated beyond a certain point is hygroscopic - in other words, it attracts water rather than evaporating. And, of course, concentrated brine is very corrosive. I'd imagine that there is a concentration of salt in the water beyond which there is no cooling effect. This could be avoided by using a gentle flow of salt water, ensuring the water was constantly replaced, but that adds complications.
vyv_cox
Well-Known Member
Humidity is currently 71% where we are in Greece, on an unusual cloudy day. The cooler is working well, considerably more effective that a fan alone. Of course full aircon is more effective but in the absence of 230 volt power is a pipe dream.
BrianH
Well-Known Member
I often wondered if an evaporative cooler would alleviate my summer cabin temperatures while marina bound in the Adriatic within a lagoon complex, which is 5nm inland from the open sea. In my berth, late afternoon cabin temperatures from June on can be nudging 40°C, invariably above 35°C. and not much less during the early night hours. This makes it hard to sleep in windless conditions, especially as those are when the mosquitoes are particularly active, needing all ports and companionway to have netting that reduces any incoming air-draught that the fan could induce.
However, when I enquired, local Italian stores told me they did not stock evaporative coolers as they are ineffective in the area and that they are only suitable with low humidity climates such as desert regions, not our lagoon one. I had already known they are popular in the dry, higher altitude US states where they are known as 'Swamp Coolers'.
True air-conditioning in these conditions is the only answer but cost and installation difficulties have prevented that to date. But in 2014 my local Swiss Bauhaus had a special offer for an evaporative cooler that would fit under the table opposite to the companionway, which was cheap enough to take a chance on.
By comparative testing I found the cooling unit would indeed lower the >30°C cabin temperatures .... by an average of 2°C. However, on balance, the extra humidity it generated made the discomfort level more, not less. After a week's trial the unit was placed next to the nearest marina rubbish bin - indicative of free for all - and it disappeared within an hour.
However, when I enquired, local Italian stores told me they did not stock evaporative coolers as they are ineffective in the area and that they are only suitable with low humidity climates such as desert regions, not our lagoon one. I had already known they are popular in the dry, higher altitude US states where they are known as 'Swamp Coolers'.
True air-conditioning in these conditions is the only answer but cost and installation difficulties have prevented that to date. But in 2014 my local Swiss Bauhaus had a special offer for an evaporative cooler that would fit under the table opposite to the companionway, which was cheap enough to take a chance on.
By comparative testing I found the cooling unit would indeed lower the >30°C cabin temperatures .... by an average of 2°C. However, on balance, the extra humidity it generated made the discomfort level more, not less. After a week's trial the unit was placed next to the nearest marina rubbish bin - indicative of free for all - and it disappeared within an hour.
Last edited:
pmagowan
Well-Known Member
The increased humidity is the problem with direct systems. Indirect systems don't have this problem as the evaporating water is not in the ventilated air. The relative humidity of the air obviously affects efficiency as does the design and size of the unit.
Last edited:
BrianH
Well-Known Member
Understood. Guilty of not reading your OP, which on doing so makes all clear. However, some relevance can be gleaned by the somewhat limited temperature difference obtained in my case.
whiteoaks7
Well-Known Member
Lots of background useful stuff here including how much you could expect to lower the temperature of the air passing through an evap cooler: www.ecocool.org Although this is big boys stuff there are no scaling issues in the physics.
