Marine Refrigeration

How does Marine refrigeration work? The most important components of a DC refrigeration system embody the refrigerant, a compressor, and a condenser, a cooling system for condenser, and a plate or plates contained in the refrigeration field. The compressor is a part of a closed loop pumping refrigerant by way of the system and thru the evaporator plate within the ice field. The compressor has two sides the Excessive facet or discharge facet. The discharge facet pumps refrigerant below strain to the condenser. The suction facet or low facet and sucks refrigerant after it passes by way of the evaporator plate again to the compressor. The chilly plates within the fridge house have both growth valves or capillary tube that separate the high and low strain sides of the refrigeration system. The refrigerant within the compressor begins as a gasoline. The compressor compresses the refrigerant gasoline, from low strain to excessive strain between 100-150 psi. When the strain is elevated like this its temperature rises dramatically. This sizzling excessive strain refrigerant is then fed to a condenser, the place it's cooled and was a liquid. The condenser is cooled by both air or water. The refrigerant is now a cool excessive strain liquid and is fed to an evaporator plate contained in the boats fridge field. 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 alteration of state absorbs huge quantities of wise warmth from the evaporator which in flip removes warmth from the insulated refrigeration field, thereby decreasing its temperature. The BTU is the measurement of warmth eliminated. From the evaporator plate the refrigerant is returned to the low facet of the compressor, to begin the method once more. Evaporator or Holding Plates Marine refrigeration programs use both an evaporator plate or a holding plate within the boats refrigeration house or freezer house. Every kind of plate works in another way in drawing warmth from the boats fridge and ice field house. Marine Evaporator Marine evaporator are similar to those present in family fridges. They will get fairly chilly (thermostat setting) and lots of evaporators have the flexibility to make ice subsequent to the evaporator plate or contained in the evaporator field. 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 brief cycle. Most use a Danfoss marine compressor with H134 refrigerant. Thermostat managed evaporator temperature. Flip to decrease ice field temperature. Evaporator plates are cheaper, however want Fixed energy provide. Marine Holding plates Marine Fridge Holding Plates act like giant blocks of ice and the chilly temperature of the holding plate sucks warmth out of the boats refrigeration field. Holding plates can preserve ice containers chilly for lengthy durations. The primary benefit of a holding plate over an evaporator is that they solely should be recharged 1 or 2 instances per day. This charging can coincide with attaching to shore energy, operating the engine and so the fridge doesn't depend on the battery financial institution. When integrated right into a correctly designed system, holdover plates can considerably scale back power consumption. Nonetheless DC holding plates are additionally doable. The holding plate is full of an answer that has a freezing level under 23 levels F. Because the compressor runs, the refrigerant passes by way of 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 field. Powering the Compressor The facility provide to the compressor is without doubt one of the key components of the boats refrigeration system. Refrigeration is without doubt one of the largest power customers onboard, so the facility provide is a vital aspect of the system. Energy provides to marine refrigeration programs embody AC, DC, Shore Energy, Engine energy, and hybrid programs. Hybrids are combos of say 12 volt and engine drive, or engine and shore energy. The entire level in energy provide to your boats fridge is to couple it into onboard energy necessities for all of your boats marine programs. In case you run a generator a lot of the time then including on an AC refrigeration unit could make sense, however except you do, you'd be higher at 12 V, engine or shore energy. Energy might 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 giant quantities of time at anchor. Lastly are you Energy boating or Crusing can even affect energy provide. Crusing means no charging of batteries or energy from the engine. Right here a photo voltaic panel or wind or towed generator will help replenish batteries. In case you spend time on the dock, a DC system has loads of time to recharge on shore energy. In case you spend time motoring and on the dock and engine drive with shore help works properly. AC 110 volt marine refrigeration These drop in fridges are just like the one in your house and are generally seen on bigger boats with an abundance of AC energy and house. The AC powers the marine compressor, and the condenser is often air cooled. A dependable AC provide 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 programs use the Danfoss compressor. With the elevated effectivity of the Danfoss compressor, DC refrigeration onboard is getting extra environment friendly, however continues to be energy hungry. For many boats with a small field, a single 12V compressor, air-cooled condenser, with evaporator kind plate might be concerning the least expensive choice. The Adler Barbour Chilly Machine has been round for round 25 years and gives nice refrigeration for small to medium measurement ice containers. Shore powered marine refrigeration Shore powered programs are made to take care of the boat's ice field at set temperature when the boat is on the dock. They provide much less energy than direct from an engine drive however since you may be on the dock for some time that's not a difficulty. In case you use a holding plate and shore powered system you'll be able to preserve the plate cool whereas away from the dock for 12 hours or so. Engine powered marine refrigeration The concept behind an engine pushed compressor system is that the engine will get used anyway for at lest an hour or so. If you're Energy 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 field in a brief interval and after that it may be left for 12 plus hours. The compressor is run immediately 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 energy and quick cooling of the holding plate. Extra energy than a 110 volt system. Bigger programs and a number of plates are doable. Engine pushed programs value extra and in addition contain a labor greater value Condenser Cooling The marine refrigeration programs condenser wants cooling. That is how the refrigerant will get cooled and was 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 way of hulls. It's due to this fact the most cost effective set up. For smaller models air cooling is OK, say 4 cu ft or below 6 cu ft you're going to get sufficient efficiency. The air cooling unit wants a enough provide of re-circulated air for it to work. Ducting and house 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 inside 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 might be 30% extra environment friendly. Water cooling could also be finest and is healthier for bigger installs particularly if freezer is worried. Water cooling wants a by way of hull and a pump to get the water to the condenser. Essentially the most environment friendly method to cool the condenser Keel cooler Condenser The keel cooler or keel condenser requires no by way of 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 related direct to the compressor which is the one transferring half within the system. The Keel Cooler is for a field 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 is going to doesn't warmth up the inside. Since it really works with no water pump there's by no means a pump or strainer to take care of and better of all it's practically silent in operation. Refrigeration Compressor & plate Mixture Earlier than we choose a measurement of marine fridge we have to perceive what elements are concerned in retaining the refrigeration field cool. They're primarily field measurement, insulation and cooling water temperature, variety of folks aboard and the temperature you might be setting the plates for. Fridge Field Quantity That is apparent, the bigger the field the extra warmth elimination is critical. A bigger field will want extra BTUs of warmth elimination. After this fundamental measurement difficulty we've issues like, Entrance opening or high opening. Entrance opening lets chilly air out rapidly however does can help you resolve the field. Drains, in the event you had a drain for you ice field plug it. You'll not want to empty water out of the ice field 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 bit 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 containers. Foam has an R worth of 5 per inch thickness, R being a thermal unit. This implies by way of 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 numerous insulation with out taking on worthwhile quantity. These panels are vacuum panels and are sealed to work. It is extremely essential that you don't drill by way of or puncture these panels. These panels are customized made, so that you would want to offer the producer, actual sizes with areas for copper plate tubes to enter the field. These are constructed into the panels. Water temperature Within the tropics water temperature is quite a bit hotter than northern climates. For each diploma water temperature will increase a corresponding 2 % enhance in required BTU. If you're within the Atlantic parts of the east coast US, you might have some cool sea water temps, however of you then cruise right down to the Caribbean you might pressure your refrigeration system. Plate Thermostat The evaporator plate temperature is about by the thermostat. Dial the field temperature down and the system should work tougher. Variety of folks aboard Extra folks means the field will get opened extra and the warmth construct up from extra folks provides to the ambient temperature. How massive a Refrigeration System? To calculate how massive a refrigeration or marine freezing unit required, you will want to begin with an estimation of the BTU necessities of the field. A easy rule of thumb for estimating the BTUs relies on the field 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 folks aboard, for every further individual add a further 1,000 each day BTU

  • High opening field, 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 have a look at how this works for the 4 cu ft refrigeration system, utilizing the above components 4 cu. ft. instances 600 = 2,400 BTU. Two extra folks on board = 2,000 BTU. Whole 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 energy the system, after which work on the battery financial institution functionality. Begin by utilizing the 4,400 BTU type 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 properly above the 4,400/day we want for the 4 cu ft fridge, utilizing solely about 1/3 of the facility. We may 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 components, utilizing an assumption of 5 BTUs per watt hr of power used. BTU/5/volts. so say we've 4400 BTUS and 12 volts, 4,400/5/12=74 amp hours/day. Battery Financial institution The Amps wanted to energy the compressor must be 1/4 of the capability of the home financial institution. So for the above 74 amp hours wanted multiply by 4 to get beneficial home battery capability = 296 amp hrs. Conclusion As of late being on the water means retaining meals and drinks chilly. 12 volt refrigeration models are rising in popularity with technological advances. Better compressor effectivity and evaporator know-how brings 12 volt cooling to the smallest of boats.

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