How Ships Convert Sea Water to Fresh Water | Chief MAKOi Study Call Ep 04
Summary
TLDRIn this episode of Study Hall, Chief McCoy explains how ships produce fresh water from seawater using distillation, a process of evaporation and condensation. Ships on coastal voyages can get fresh water from suppliers, but ocean-going vessels must generate their own. Distillation plants aboard ships can produce 15 to 50 tons of fresh water daily. The process involves heating seawater to create steam, which then condenses into fresh water when cooled, leaving behind salt and minerals. Key components of the distillation plant include the evaporator, condenser, ejector pump, and Solano meter, which ensures the purity of the fresh water produced.
Takeaways
- 🚢 Ships require fresh water for various purposes, which cannot be met by seawater alone.
- 🌊 For coastal voyages, ships can easily obtain fresh water from suppliers, but ocean-going vessels must produce their own.
- 💧 Fresh water generators on ships use either distillation or reverse osmosis, with distillation being more common in commercial shipping.
- 🔥 Distillation involves purifying liquid through evaporation and condensation, leaving behind heavier minerals like salt.
- 🌡️ Distillation plants on ships are designed to operate efficiently when the main engine is running, utilizing waste heat from the engine.
- 🏺 The distillation process on ships involves an airtight casing with separate sections for evaporation and condensation.
- 💧 Seawater is heated in the evaporator, turning into steam, which then condenses into fresh water in the condenser.
- 🔬 The purity of the fresh water is checked using a Solano meter, which measures electrical conductivity to determine salt content.
- 🔄 If the fresh water's salinity is above 10 ppm, it is recycled back into the evaporator; if below, it's stored for use.
- 🔧 Distillation plants can be of two types: tube type or plate type, both operating on the same principle of heat exchange and vacuum creation.
Q & A
How does a ship obtain fresh water for use during coastal voyages?
-For ships doing exclusively coastal voyages, fresh water is usually supplied when they are in port. They place an order, and a supplier comes to connect a hose and fill up the water tanks.
What is the primary method used by ocean-going vessels to produce fresh water during long voyages?
-Ocean-going vessels produce fresh water using a freshwater generator, which typically operates on the principle of distillation or, less commonly, reverse osmosis.
What is the basic principle behind the distillation process used to produce fresh water on ships?
-Distillation is the process of purifying a liquid through evaporation and condensation. Seawater is heated to create steam, which leaves behind heavier minerals like salt. The steam is then cooled and condenses back into liquid form, now free of salt, to produce fresh water.
What is the typical daily fresh water production capacity of a distillation plant on a ship?
-Distillation plants on board ships are typically designed to produce between 15 to 50 tons of fresh water per day, depending on the ship type and fresh water requirements.
What are the two main types of distillation plant designs used on ships?
-Distillation plants on ships are either of the tube type or plate type designs, with the principle of operation being the same for both.
Why are distillation plants used when the ship is underway, and how does this relate to the seawater quality?
-Distillation plants are used when the ship is underway because seawater is cleaner in the deep and open sea compared to near land where it might contain mud and other contaminants. Additionally, the heating medium for the evaporator comes from the main engine jacket water, which is more readily available when the ship is in motion.
How does the ejector pump contribute to the distillation process on a ship?
-The ejector pump creates a vacuum inside the distillation plant's shell by using the venturi effect. This vacuum lowers the atmospheric pressure inside the shell, allowing seawater to boil at temperatures lower than 100 degrees Celsius.
What is the role of the condenser in the distillation process aboard a ship?
-The condenser in the distillation process cools the steam produced by the evaporator, causing it to condense back into liquid form, now as fresh water, which is collected in the liquid receiver.
How is the purity of the fresh water produced by the distillation plant measured?
-The purity of the fresh water is measured using a Solano meter, which determines water purity in terms of salt content by measuring electrical conductivity. Pure water has high resistance to electrical flow, while salt water conducts electricity well.
What happens to the fresh water if the salinity measured by the Solano meter is above 10 ppm?
-If the salinity of the fresh water is above 10 ppm, a magnetic valve activates, diverting the flow of fresh water back into the evaporator for further processing.
Outlines
🚢 Freshwater Production on Ships
This paragraph introduces the topic of how ships produce fresh water from seawater, a necessity for long ocean voyages. It explains that while coastal ships can easily replenish their fresh water supply, ocean-going vessels must generate it onboard. The freshwater generator, which can be of two types - distillation or reverse osmosis - is the focus of this episode. Distillation is the more common method in commercial shipping and involves the process of evaporation and condensation to separate fresh water from salt and other minerals. The paragraph also outlines the basic principles of distillation and mentions that the process is typically carried out on a large scale, with distillation plants on ships designed to produce up to 50 tons of fresh water per day.
🔬 Detailed Operation of Distillation Plants
This paragraph delves into the specifics of how distillation plants operate on ships. It explains that the process is most efficient when the ship is underway, utilizing cleaner seawater from the deep sea and waste heat from the main engine. The paragraph describes the components of the distillation plant, including the shell, evaporator, condenser, ejector pump, inductor nozzle, distillate pump, and Solano meter. It outlines the process of seawater being sucked into the evaporator, heated, and evaporated, leaving behind heavier minerals. The steam then condenses back into fresh water in the condenser, which is collected and checked for purity before being stored. The paragraph also discusses the creation of a vacuum inside the shell to lower the boiling point of water, allowing it to evaporate at temperatures below 100 degrees Celsius.
📚 Conclusion and Future Topics
In the final paragraph, the narrator wraps up the discussion on distillation plants used for fresh water production on ships. It summarizes the key points covered in the episode and hints at future episodes that will explore other methods of fresh water production, such as reverse osmosis. The paragraph serves as a conclusion, reinforcing the educational value of the video and setting the stage for further exploration of related topics.
Mindmap
Keywords
💡Distillation
💡Seawater
💡Freshwater
💡Evaporation
💡Condensation
💡Heat Exchangers
💡Ejector Pump
💡Salinity
💡Solano Meter
💡Vacuum
💡Reverse Osmosis
Highlights
Ships require fresh water for various purposes, which cannot be met by seawater alone.
For coastal voyages, ships can easily obtain fresh water from suppliers.
Ocean-going vessels produce their own fresh water using a freshwater generator.
There are two types of freshwater generators: distillation and reverse osmosis.
Distillation is the more common method used in commercial shipping.
Distillation purifies liquid through evaporation and condensation.
Seawater is a mixture of fresh water, salt, and minerals.
Heating seawater causes it to evaporate, leaving behind heavier minerals like salt.
Cooling the steam condenses it into distilled water, which is theoretically pure H2O.
Distillation plants on ships are designed to produce 15 to 50 tons of fresh water per day.
The distillation plant consists of an evaporator, condenser, and other components.
The shell of the distillation plant is an airtight casing divided into an evaporator and condenser.
The ejector pump creates a vacuum inside the shell, lowering the boiling point of water.
Seawater is heated by the main engine's jacket water, which is around 80 to 85 degrees Celsius.
The adductor pump uses the venturi effect to create suction and draw in seawater.
The steam produced in the evaporator is filtered and condensed in the condenser tubes.
The condensate is collected and analyzed for salt content using a Solano meter.
If salt content is below 10 ppm, the fresh water is stored; otherwise, it's redirected to the evaporator.
Distillation plants are used when the ship is underway to ensure cleaner seawater and efficient heat recovery.
The distillation process involves complex interactions between the plant's components.
The distillation plant's design allows for the recovery of waste heat from the main engine.
Transcripts
hello everyone welcome to another
episode of study hall with chief McCoy
in today's video we will discuss how
ships transform seawater into fresh
water in the previous episodes I've
shown you the fresh water cooling system
and how heat exchangers work we know
that ships utilize sea water s it is
very abundant at sea but apparently
ships still require fresh water for a
lot of things wherein sea water will be
unsuitable for use so where do ships get
their fresh water for ships doing
exclusively coastal voyages it's quite
easy as fresh water is usually supplied
when they are important they simply
place an order then the supplier comes
connects the host and fill us up the
water tanks but for ocean-going vessels
which go on voyages for weeks or even
months without calling into port the
only option is to produce their own
fresh water they do this by using what
we call a freshwater generator
there are two popular types of fresh
water generators
the first type utilizes the process of
distillation and the other is by reverse
osmosis now for this episode we will
only discuss distillation as it is by
far more commonly used in commercial
shipping we will touch on reverse
osmosis in another episode let's go back
to basics for a bit distillation is the
action of purifying a liquid through the
process of evaporation and condensation
on that note evaporation is when liquid
turns into gas and condensation is when
gas turns into liquid to put things
simply sea water is basically a mixture
of fresh water and salt and a few other
minerals like calcium and other stuff
now if we apply heat to sea water it
will eventually boil and evaporate and
turn into steam when it does the heavier
minerals like salt will be left behind
now if we cool down steam it will
condense and turn into distilled water
which theoretically should be pure h2o
otherwise known as fresh water obviously
ships need to do this on a large scale
and distillation plants on board carbon
ships are typically designed to produce
somewhere between 15 to 50 tons of fresh
water per day sometimes more depending
on the ship type and fresh water
requirements distillation plans are
basically heat exchangers and similar to
other types of heat exchangers they come
either as to type or plate type designs
either way the principle of operation is
basically the same the most prominent
feature of the distillation plant is the
shell which is an airtight casing
the inside of the shell is divided
between the evaporator and the condenser
other important components include the
ejector pump the inductor nozzle the
distillate pump and the Solano meter so
how does the distillation plant work
let's go through the simple explanation
first the flow operation begins when the
sea water enters the evaporator from
there it absorbs heat and evaporates
passes through a baffle screen to filter
out remaining impurities and then comes
into contact with the condenser tubes
where it is cooled down and eventually
condenses back into liquid but this time
without the salt content
now this condensate is collected in the
liquid receiver which is directly below
the condenser tubes where it is then
suctioned by the condensate pump the
condensate pumps function is to deliver
the fresh water into the freshwater
tanks but before it could go there it is
sampled and analyzed by the salon owner
if the remaining salt content is below
10 parts per million the fresh water is
delivered into the tanks if it's higher
than 10 ppm it is diverted to go back to
the evaporator sounds simple right well
not exactly
for us to fully understand how the
distillation plant works we need to dive
in to a few more details and learn the
function of each major component and see
how the fluid reacts when passing
through each of them now let's dive into
the detailed explanation first of all
for optimal performance distillation
plants are used when the ship is
underway that is to say when the main
engine is running at navigation speed
this is mainly because the seawater is
cleaner in the deep and open sea as
compared to near land where the water is
shallow and might contain mud and other
contaminants and also the heating medium
used by the evaporator to boil the
seawater comes from the main engine
jacket water which has a temperature of
around 80 to 85 degrees Celsius weight
the boiling point of water is 100
degrees Celsius right so how could we
boil it at 80 degrees well it's true
water boils at 100 degrees Celsius at
sea level atmospheric pressure which is
around one bar but if we apply the
combined gas law which is the
combination of Boyle's Charles and gay
lussac's law the boiling point will
decrease if the atmospheric pressure
will also decrease but how exactly will
we be able to decrease the atmospheric
pressure earlier I mentioned that the
shell is an airtight casing which gives
us the potential to create a vacuum
inside the shell now just for clarity's
sake when we say vacuum it means that
the gas pressure inside the shell is
much lower than the atmospheric pressure
at sea level
so basically much lower than one bar so
during operation the ejector pump
suctions water from the main seawater
line and from there it will pass through
the adductor an adductor is a type of
pump which utilizes the venturi effect
which in simple terms only requires a
fluid moving at high velocity as the
driving medium going past a nozzle to
generate suction now the adductor
suction line is tapped into the shell so
when the fast-moving seawater goes
through the adaptor it will generate a
drop in pressure which will suction the
air and other fluid particles and create
a vacuum effectively lowering the
atmospheric pressure inside
so the shell vacuum eventually becomes
slow enough to allow the seawater to
boil at temperatures lower than 80
degrees Celsius on a side note as you
can see the distillation plant is
designed to allow the ship's power plant
to recover waste heat from the main
engine jacket water and utilize that
heat energy instead of just throwing it
out at sea now from the adductor the
seawater will pass through the
condensers cooling tubes as the cooling
medium in there it absorbs the heat from
the steam produced by the evaporator
upon leaving the condenser some of the
sea water goes into the evaporator area
as feed water now inside the evaporator
it will pass through the tubes heated by
the jacket water until it evaporates and
leaves behind the salt and other heavier
particles which will be discarded by the
adductor now the steam will arise and
will pass through a wire mesh baffle for
filtration and comes into contact with
the condenser tubes the cooling effect
will cause the steam to condense and the
resulting liquid will be collected in
the liquid receiver and then suction by
the distillate pump from there the fresh
water will be sampled and analyzed by
the solano meter the Celaeno meter is a
device which determines water purity in
terms of absence of salt by measuring
electrical conductivity the concept is
basically pure water has a high
resistance to electrical flow as
compared to salt water which has a high
electrical conductivity therefore the
higher the current flow means more salt
content so if the measured salinity is
above 10 ppm a magnetic valve activates
and diverts the flow of fresh water back
into the evaporator but if the water
salinity is below 10 ppm it is then
delivered into the ship's fresh water
storage tanks
as I mentioned earlier this relation
plants are either to type or plate type
designs I showed the to type in my
visual aids but the principle of
operation is exactly the same I hope you
enjoyed and learned something from this
episode we will have more topics to
discuss in the future but for now class
dismissed
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