How does Marine refrigeration work? The key elements of a DC refrigeration system embrace the refrigerant, a compressor, and a condenser, a cooling system for condenser, and a plate or plates contained in the refrigeration box.
The compressor is a part of a closed loop pumping refrigerant by the system and thru the evaporator plate within the ice box. The compressor has two sides the Excessive aspect or discharge aspect. The discharge aspect pumps refrigerant below pressure to the condenser. The suction aspect or low aspect and sucks refrigerant after it passes by the evaporator plate again to the compressor. The chilly plates within the fridge area have both growth valves or capillary tube that separate the high and low pressure sides of the refrigeration system.
The refrigerant within the compressor begins as a gasoline. The compressor compresses the refrigerant gasoline, from low pressure to excessive pressure between 100-150 psi. When the pressure is elevated like this its temperature rises dramatically. This sizzling excessive pressure refrigerant is then fed to a condenser, the place it’s cooled and became a liquid. The condenser is cooled by both air or water. The refrigerant is now a cool excessive pressure liquid and is fed to an evaporator plate contained in the boats fridge box.
The evaporator plate takes the refrigerant from the condenser and right here it boils quickly & evaporates again to a gasoline, at a really low temperature. This modification of state absorbs huge quantities of wise warmth from the evaporator which in flip removes warmth from the insulated refrigeration box, thereby decreasing its temperature. The BTU is the measurement of warmth eliminated. From the evaporator plate the refrigerant is returned to the low aspect of the compressor, to begin the method once more.
Evaporator or Holding Plates
Marine refrigeration techniques use both an evaporator plate or a holding plate within the boats refrigeration area or freezer area. Every sort of plate works in a different way in drawing warmth from the boats fridge and ice box area.
Marine Evaporator
Marine evaporator are similar to those present in family fridges. They will get fairly chilly (thermostat setting) and plenty of evaporators have the flexibility to make ice subsequent to the evaporator plate or contained in the evaporator box. Evaporators are available in a number of styles and sizes; they are often horizontal plate’s, vertical plates and rolled plates. Evaporators are fixed biking, or short cycle. Most use a Danfoss marine compressor with H134 refrigerant.
Thermostat managed evaporator temperature. Flip to decrease ice box temperature. Evaporator plates are cheaper, however want Fixed power supply.
Marine Holding plates
Marine Fridge Holding Plates act like massive blocks of ice and the chilly temperature of the holding plate sucks warmth out of the boats refrigeration box. Holding plates can preserve ice boxes chilly for lengthy durations.
The primary benefit of a holding plate over an evaporator is that they solely have to be recharged 1 or 2 instances per day. This charging can coincide with attaching to shore power, working the engine and so the fridge doesn’t depend on the battery bank. When included right into a correctly designed system, holdover plates can considerably scale back vitality consumption. Nonetheless DC holding plates are additionally attainable. The holding plate is crammed with an answer that has a freezing level beneath 23 levels F. Because the compressor runs, the refrigerant passes by the holding Plates coil, freezing the holding plate resolution. The compressor turns of and because the holding plate thaws out, warmth is faraway from the box.
Powering the Compressor
The power supply to the compressor is without doubt one of the key parts of the boats refrigeration system. Refrigeration is without doubt one of the largest vitality shoppers onboard, so the power supply is a crucial aspect of the system. Power supplies to marine refrigeration techniques embrace AC, DC, Shore Power, Engine power, and hybrid techniques. Hybrids are combos of say 12 volt and engine drive, or engine and shore power. The entire level in taking a look at power supply to your boats fridge is to couple it into onboard power necessities for all of your boats marine techniques. In case you run a generator a lot of the time then including on an AC refrigeration unit might make sense, however until you do, you’ll be higher at taking a look at 12 V, engine or shore power.
Power will be selected how you utilize your boat. Are you tied up at a dock for a lot of the time and take days journeys. Or do you cruise and spend massive quantities of time at anchor. Lastly are you Power boating or Crusing may even affect power supply. Crusing means no charging of batteries or power from the engine. Right here a solar panel or wind or towed generator may also help replenish batteries. In case you spend time on the dock, a DC system has loads of time to recharge on shore power. In case you spend time motoring and on the dock and engine drive with shore help works effectively.
AC 110 volt marine refrigeration
These drop in fridges are just like the one in your home and are generally seen on bigger boats with an abundance of AC power and area. The AC powers the marine compressor, and the condenser is usually air cooled. A dependable AC supply is required within the type of a generator.
DC marine refrigeration with Evaporator plate
One of many least expensive marine refrigeration system and best to put in is the 12 v or DC system. Air cooling is the only. The DC system mixed with an evaporator plate that’s thermostatically managed provides flexibility over cooling necessities. Many 12 volt techniques use the Danfoss compressor. With the elevated effectivity of the Danfoss compressor, DC refrigeration onboard is getting extra environment friendly, however remains to be power hungry.
For many boats with a small box, a single 12V compressor, air-cooled condenser, with evaporator sort plate will probably be in regards to the least expensive possibility. The Adler Barbour Chilly Machine has been round for round 25 years and gives nice refrigeration for small to medium measurement ice boxes.
Shore powered marine refrigeration
Shore powered techniques are made to take care of the boat’s ice box at set temperature when the boat is on the dock. They provide much less power than direct from an engine drive however since you’ll be on the dock for some time that’s not a problem.
In case you use a holding plate and shore powered system you may preserve the plate cool whereas away from the dock for 12 hours or so.
Engine powered marine refrigeration
The thought behind an engine pushed compressor system is that the engine will get used anyway for at lest an hour or so. If you’re Power boating this is sensible, in case you are crusing calculate how a lot time you utilize the engine.
If so an engine drive with a holding plate can draw down the ice box in a short interval and after that it may be left for 12 plus hours.
The compressor is run instantly off the engine. Belt pushed or direct compressor, There are two plates and you may add extra, plus add a separate freezer unit. This creates power and quick cooling of the holding plate. Extra power than a 110 volt system. Bigger techniques and a number of plates are attainable. Engine pushed techniques value extra and likewise contain a labor greater value
Condenser Cooling
The marine refrigeration techniques condenser wants cooling. That is how the refrigerant will get cooled and became a liquid. There are 3 methods to chill the condenser;
Air Cooled
Air cooling simplifies set up plus it doesn’t depend on water or including by hulls. It’s subsequently the most affordable set up. For smaller models air cooling is OK, say 4 cu ft or below 6 cu ft you’ll get ample efficiency. The air cooling unit wants a ample supply of re-circulated air for it to work. Ducting and area across the unit will assist this.
Once you cool by air circulate you take away warmth from the condenser and add it to the ambient temperature. The temperature within the cabin solely has sufficient capability to disperse this warmth.
Water cooled Condenser
Water cooled compressors will work higher in greater ambient temperatures and are extra environment friendly and will be 30% extra environment friendly. Water cooling could also be greatest and is healthier for bigger installs particularly if freezer is anxious. Water cooling wants a by hull and a pump to get the water to the condenser. Probably the most environment friendly option to cool the condenser
Keel cooler Condenser
The keel cooler or keel condenser requires no by hull becoming and won’t be topic to clogging. The keel cooler is a 3″ x 7″ bronze plate that mounts on the skin of the hull and it’s the condenser warmth exchanger. The bronze plates are linked direct to the compressor which is the one shifting half within the system. The Keel Cooler is for a box as much as a 15 cu ft fridge or 5 cu ft freezer. Since all the warmth is handed into the water exterior the boat it can doesn’t warmth up the inside. Since it really works with out a water pump there may be by no means a pump or strainer to take care of and better of all it’s almost silent in operation.
Refrigeration Compressor & plate Mixture
Earlier than we decide a measurement of marine fridge we have to perceive what elements are concerned in holding the refrigeration box cool. They’re primarily box measurement, insulation and cooling water temperature, variety of individuals aboard and the temperature you’re setting the plates for.
Fridge Box Quantity
That is apparent, the bigger the box the extra warmth elimination is critical. A bigger box will want extra BTUs of warmth elimination. After this fundamental measurement problem we’ve issues like, Entrance opening or high opening. Entrance opening lets chilly air out shortly however does let you resolve the box. Drains, should you had a drain for you ice box plug it. You’ll not want to empty water out of the ice box and this can solely let chilly air out and warmth in. Gaskets, are a should. A trick to establish if there are gaps within the gasket is to place a chunk of paper in between the lid or door and the cupboard and shut it. Pull on the paper and you must really feel some drag if the gaskets are sealing correctly. It comes out simply there’s a hole. Get new or higher gasket materials.
Insulation
Typical insulation to a fridge or freezer is foam insulation like Dow Blue board. The advice is for 3-4 inches for refrigeration and 4-6 inches for freezer for medium sized boxes. Foam has an R worth of 5 per inch thickness, R being a thermal unit. This implies when it comes to thermal models 3-4 inches represents 15-20R worth for the refrigeration unit, and 20-30 for the freezer.
There are producers of vacuum panel thermal insulation. The Glacier bay Barrier Extremely-R super-insulation at R-50 per inch gives plenty of insulation with out taking over helpful quantity. These panels are vacuum panels and are sealed to work. It is vitally necessary that you don’t drill by or puncture these panels. These panels are customized made, so that you would wish to supply the producer, actual sizes with places for copper plate tubes to enter the box. These are constructed into the panels.
Water temperature
Within the tropics water temperature is lots hotter than northern climates. For each diploma water temperature will increase a corresponding 2 % improve in required BTU. If you’re within the Atlantic parts of the east coast US, you’ve some cool sea water temps, however of you then cruise right down to the Caribbean it’s possible you’ll pressure your refrigeration system.
Plate Thermostat
The evaporator plate temperature is ready by the thermostat. Dial the box temperature down and the system must work tougher.
Variety of individuals aboard
Extra individuals means the box will get opened extra and the warmth construct up from extra individuals provides to the ambient temperature 냉장고.
How huge a Refrigeration System?
To calculate how huge a refrigeration or marine freezing unit required, you’ll need to begin with an estimation of the BTU necessities of the box. A easy rule of thumb for estimating the BTUs relies on the box quantity.
These BTU estimations are primarily based on these assumptions;
– Insulation has an R worth of 30 no leaks.
– Water temperatures are tropical within the mid 80s F.
– 2 individuals aboard, for every further individual add an extra 1,000 each day BTU
– High opening box, for a entrance opening door add 15 BTU/inch of door
BTU estimate on refrigeration quantity;
Fridge each day warmth load; 600 BTU per cu. ft.
Freezer each day warmth load; 1200 BTU per cu. ft
Lets take a look at how this works for the 4 cu ft refrigeration system, utilizing the above method
4 cu. ft. instances 600 = 2,400 BTU.
Two extra individuals on board = 2,000 BTU.
Complete required per day = 4,400 BTU
Selecting 12 volt unit with Evaporator
Match this quantity to the compressor capabilities, after which calculate amps wanted to power the system, after which work on the battery bank functionality. Begin through the use of the 4,400 BTU kind the above instance. The Adler Barbour Chilly Machine makes use of the Danfoss BD50 Compressor is rated at 650BTU / hr primarily based on 25F evaporator temp.
That is effectively above the 4,400/day we’d like for the 4 cu ft fridge, utilizing solely about 1/3 of the power. We might simply go down the Danfoss DB35.
Amps
To calculate what number of amps the system will draw we begin by changing BTUs to amps with this method, utilizing an assumption of 5 BTUs per watt hr of vitality used. BTU/5/volts. so say we’ve 4400 BTUS and 12 volts, 4,400/5/12=74 amp hours/day.
Battery Bank
The Amps wanted to power the compressor must be 1/4 of the capability of the home bank. So for the above 74 amp hours wanted multiply by 4 to get really helpful home battery capability = 296 amp hrs.
Conclusion
Nowadays being on the water means holding meals and drinks chilly. 12 volt refrigeration models are rising in popularity with technological advances. Larger compressor effectivity and evaporator know-how brings 12 volt cooling to the smallest of boats.