Tag: <span>refrigeration</span>

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There are many commercial industries that rely on refrigeration equipment to keep products or supplies in optimum condition. For instance companies working within the food industry need to store perishable products at set temperatures.

The pharmaceutical industries also have a need for refrigerated containers, in order to keep certain vaccines and medicines at their required temperature. This temperature needs to be accurately monitored and maintained using specialist equipment.

There are many different types of commercial refrigeration on the market. This cold storage equipment can be bought or hired; depending on how long it will be needed for and whether the customer wants to own their equipment.

New commercial refrigeration equipment may be the right solution for many. However, leased cold storage containers are kept to the highest standard and often come with the added benefit of a maintenance contract, so the customer can rest assured their equipment remains in good working order.

Temperature controlled containers come in all shapes and sizes. There are containers that are designed to stay in one place, as well as portable cold storage that can be transported to wherever needed.

For example there are mobile bar units available that are designed for short-term hire at events or launches and can be used to facilitate the promotion of a new chilled drink for instance. At the other end of the scale there are mega cold storage units that are often designed to stay in one place.

Mega cold storage equipment is commonly required for suppliers of large amounts of produce, such as the meat industry. With mega cold storage units the temperature can vary between -35c to + 35c. This large-scale equipment is most often used for chilling and freezing food items.

Commerical refrigeration units can contain remote temperature monitoring, in order to ensure that products being stored remain at the right temperature. This can be installed in both static and portable containers.

With Remote Euroscan Temperature monitoring you can access data through any internet connection. The technology also enables reporting functionality and centralised data archiving. Reports can be customised to specific requirements.

As well as refrigerated equipment, blast freezers can also be supplied for commercial refrigeration. These are available in a range of different sizes and capacities. They are sometimes housed in shipping containers, so can be transported if needed.

Container refrigeration units can also be stored outside, next to a building. They are ideal for blast freezing of fish, meat and pastry products or complete ready meals.

So if you are looking for commercial refrigeration on a mega or more portable scale, there are lots of options to choose from to ensure your supplies and produce are kept at the optimum temperature.

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Source by Tom Bisman

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How does Marine refrigeration work? The major parts of a DC refrigeration system include the refrigerant, a compressor, and a condenser, a cooling system for condenser, and a plate or plates inside the refrigeration box.

The compressor is part of a closed loop pumping refrigerant through the system and through the evaporator plate in the ice box. The compressor has two sides the High side or discharge side. The discharge side pumps refrigerant under pressure to the condenser. The suction side or low side and sucks refrigerant after it passes through the evaporator plate back to the compressor. The cold plates in the fridge space have either expansion valves or capillary tube that separate the low and high pressure sides of the refrigeration system.

The refrigerant in the compressor starts as a gas. The compressor compresses the refrigerant gas, from low pressure to high pressure between 100-150 psi. When the pressure is increased like this its temperature rises dramatically. This hot high pressure refrigerant is then fed to a condenser, where it is cooled and turned into a liquid. The condenser is cooled by either air or water. The refrigerant is now a cool high pressure liquid and is fed to an evaporator plate inside the boats refrigerator box.

The evaporator plate takes the refrigerant from the condenser and here it boils rapidly & evaporates back to a gas, at a very low temperature. This change of state absorbs vast amounts of sensible heat from the evaporator which in turn removes heat from the insulated refrigeration box, thereby lowering its temperature. The BTU is the measurement of heat removed. From the evaporator plate the refrigerant is returned to the low side of the compressor, to start the process again.

Evaporator or Holding Plates

Marine refrigeration systems use either an evaporator plate or a holding plate in the boats refrigeration space or freezer space. Each type of plate works differently in drawing heat from the boats refrigerator and ice box space.

Marine Evaporator

Marine evaporator are just like the ones found in household refrigerators. They can get quite cold (thermostat setting) and many evaporators have the ability to make ice next to the evaporator plate or inside the evaporator box. Evaporators come in several shapes and sizes; they can be horizontal plate’s, vertical plates and rolled plates. Evaporators are constant cycling, or short cycle. Most use a Danfoss marine compressor with H134 refrigerant.

Thermostat controlled evaporator temperature. Turn to lower ice box temperature. Evaporator plates are less expensive, but need Constant power supply.

Marine Holding plates

Marine Refrigerator Holding Plates act like large blocks of ice and the cold temperature of the holding plate sucks heat out of the boats refrigeration box. Holding plates can keep ice boxes cold for long periods.

The main advantage of a holding plate over an evaporator is that they only need to be recharged 1 or 2 times per day. This charging can coincide with attaching to shore power, running the engine and so the refrigerator does not rely on the battery bank. When incorporated into a properly designed system, holdover plates can significantly reduce energy consumption. However DC holding plates are also possible. The holding plate is filled with a solution that has a freezing point below 23 degrees F. As the compressor runs, the refrigerant passes through the holding Plates coil, freezing the holding plate solution. The compressor turns of and as the holding plate thaws out, heat is removed from the box.

Powering the Compressor

The power supply to the compressor is one of the key elements of the boats refrigeration system. Refrigeration is one of the largest energy consumers onboard, so the power supply is an important element of the system. Power supplies to marine refrigeration systems include AC, DC, Shore Power, Engine power, and hybrid systems. Hybrids are combinations of say 12 volt and engine drive, or engine and shore power. The whole point in looking at power supply to your boats refrigerator is to couple it into onboard power requirements for all your boats marine systems. If you run a generator much of the time then adding on an AC refrigeration unit may make sense, but unless you do, you would be better at looking at 12 V, engine or shore power.

Power can be decided on how you use your boat. Are you tied up at a dock for much of the time and take days trips. Or do you cruise and spend large amounts of time at anchor. Finally are you Power boating or Sailing will also influence power supply. Sailing means no charging of batteries or power from the engine. Here a solar panel or wind or towed generator can help replenish batteries. If you spend time at the dock, a DC system has plenty of time to recharge on shore power. If you spend time motoring and at the dock and engine drive with shore assist works well.

AC 110 volt marine refrigeration

These drop in refrigerators are like the one in your home and are commonly seen on larger boats with an abundance of AC power and space. The AC powers the marine compressor, and the condenser is typically air cooled. A reliable AC supply is needed in the form of a generator.

DC marine refrigeration with Evaporator plate

One of the cheapest marine refrigeration system and easiest to install is the 12 v or DC system. Air cooling is the simplest. The DC system combined with an evaporator plate that is thermostatically controlled gives flexibility over cooling requirements. Many 12 volt systems use the Danfoss compressor. With the increased efficiency of the Danfoss compressor, DC refrigeration onboard is getting more efficient, but is still power hungry.

For most boats with a small box, a single 12V compressor, air-cooled condenser, with evaporator type plate will be about the cheapest option. The Adler Barbour Cold Machine has been around for around 25 years and provides great refrigeration for small to medium size ice boxes.

Shore powered marine refrigeration

Shore powered systems are made to maintain the boat’s ice box at set temperature when the boat is at the dock. They offer less power than direct from an engine drive but since you will be at the dock for a while that is not an issue.

If you use a holding plate and shore powered system you can keep the plate cool while away from the dock for 12 hours or so.

Engine powered marine refrigeration

The idea behind an engine driven compressor system is that the engine gets used anyway for at lest an hour or so. If you are Power boating this makes sense, if you are sailing calculate how much time you use the engine.

If this is the case an engine drive with a holding plate can draw down the ice box in a short period and after that it can be left for 12 plus hours.

The compressor is run directly off the engine. Belt driven or direct compressor, There are two plates and you can add more, plus add a separate freezer unit. This creates power and fast cooling of the holding plate. More power than a 110 volt system. Larger systems and multiple plates are possible. Engine driven systems cost more and also involve a labor higher cost

Condenser Cooling

The marine refrigeration systems condenser needs cooling. This is how the refrigerant gets cooled and turned into a liquid. There are 3 ways to cool the condenser;

Air Cooled

Air cooling simplifies installation plus it does not rely on water or adding through hulls. It is therefore the cheapest installation. For smaller units air cooling is OK, say 4 cu ft or under 6 cu ft you will get adequate performance. The air cooling unit needs a sufficient supply of re-circulated air for it to work. Ducting and space around the unit will help this.

When you cool by air flow you remove heat from the condenser and add it to the ambient temperature. The temperature inside of the cabin only has enough capacity to disperse this heat.

Water cooled Condenser

Water cooled compressors will work better in higher ambient temperatures and are more efficient and can be 30% more efficient. Water cooling may be best and is better for larger installs especially if freezer is concerned. Water cooling needs a through hull and a pump to get the water to the condenser. The most efficient way to cool the condenser

Keel cooler Condenser

The keel cooler or keel condenser requires no through hull fitting and will not be subject to clogging. The keel cooler is a 3″ x 7″ bronze plate that mounts on the outside of the hull and it is the condenser heat exchanger. The bronze plates are connected direct to the compressor which is the only moving part in the system. The Keel Cooler is for a box up to a 15 cu ft refrigerator or 5 cu ft freezer. Since all the heat is passed into the water outside the boat it will does not heat up the interior. Since it works without a water pump there is never a pump or strainer to maintain and best of all it is nearly silent in operation.

Refrigeration Compressor & plate Combination

Before we pick a size of marine refrigerator we need to understand what factors are involved in keeping the refrigeration box cool. They are mainly box size, insulation and cooling water temperature, number of people aboard and the temperature you are setting the plates for.

Refrigerator Box Volume

This is obvious, the larger the box the more heat removal is necessary. A larger box will need more BTUs of heat removal. After this basic size issue we have things like, Front opening or top opening. Front opening lets cold air out quickly but does allow you to get to the bottom of the box. Drains, if you had a drain for you ice box plug it. You will not need to drain water out of the ice box and this will only let cold air out and heat in. Gaskets, are a must. A trick to identify if there are gaps in the gasket is to put a piece of paper in between the lid or door and the cabinet and close it. Pull on the paper and you should feel some drag if the gaskets are sealing properly. It comes out easily there is a gap. Get new or better gasket material.

Insulation

Typical insulation to a fridge or freezer is foam insulation like Dow Blue board. The recommendation is for 3-4 inches for refrigeration and 4-6 inches for freezer for medium sized boxes. Foam has an R value of 5 per inch thickness, R being a thermal unit. This means in terms of thermal units 3-4 inches represents 15-20R value for the refrigeration unit, and 20-30 for the freezer.

There are manufacturers of vacuum panel thermal insulation. The Glacier bay Barrier Ultra-R super-insulation at R-50 per inch provides lots of insulation without taking up valuable volume. These panels are vacuum panels and are sealed to work. It is very important that you do not drill through or puncture these panels. These panels are custom made, so you would need to provide the manufacturer, exact sizes with locations for copper plate tubes to enter the box. These are built into the panels.

Water temperature

In the tropics water temperature is a lot warmer than northern climates. For every degree water temperature increases a corresponding 2 % increase in required BTU. If you are in the Atlantic portions of the east coast US, you have some cool sea water temps, but of you then cruise down to the Caribbean you may strain your refrigeration system.

Plate Thermostat

The evaporator plate temperature is set by the thermostat. Dial the box temperature down and the system will have to work harder.

Number of people aboard

More people means the box gets opened more and the heat build up from more people adds to the ambient temperature.

How big a Refrigeration System?

To calculate how big a refrigeration or marine freezing unit required, you will need to start with an estimation of the BTU requirements of the box. A simple rule of thumb for estimating the BTUs is based on the box volume.

These BTU estimations are based on these assumptions;

– Insulation has an R value of 30 no leaks.

– Water temperatures are tropical in the mid 80s F.

– 2 people aboard, for each extra person add an additional 1,000 daily BTU

– Top opening box, for a front opening door add 15 BTU/inch of door

BTU estimate on refrigeration volume;

Refrigerator daily heat load; 600 BTU per cu. ft.

Freezer daily heat load; 1200 BTU per cu. ft

Lets look at how this works for the 4 cu ft refrigeration system, using the above formula

4 cu. ft. times 600 = 2,400 BTU.

Two additional people on board = 2,000 BTU.

Total required per day = 4,400 BTU

Choosing 12 volt unit with Evaporator

Match this number to the compressor capabilities, and then calculate amps needed to power the system, and then work on the battery bank capability. Start by using the 4,400 BTU form the above example. The Adler Barbour Cold Machine uses the Danfoss BD50 Compressor is rated at 650BTU / hr based on 25F evaporator temp.

This is well above the 4,400/day we need for the 4 cu ft fridge, using only about 1/3 of the power. We could easily go down the Danfoss DB35.

Amps

To calculate how many amps the system will draw we start by converting BTUs to amps with this formula, using an assumption of 5 BTUs per watt hr of energy used. BTU/5/volts. so say we have 4400 BTUS and 12 volts, 4,400/5/12=74 amp hours/day.

Battery Bank

The Amps needed to power the compressor should be 1/4 of the capacity of the house bank. So for the above 74 amp hours needed multiply by 4 to get recommended house battery capacity = 296 amp hrs.

Conclusion

These days being on the water means keeping food and drinks cold. 12 volt refrigeration units are becoming more popular with technological advances. Greater compressor efficiency and evaporator technology brings 12 volt cooling to the smallest of boats.

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Source by Mike Hobson

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From large multi-deck chillers and patisserie display cabinets to upright and under-counter fridges, specialist refrigeration equipment is essential to the running of a restaurant.

Commercial refrigerators are designed to keep temperatures between 34°F and 40°F. The ability to preserve food at the specified temperature, a compressor ventilation component and stainless steel finishes are typical of restaurant refrigeration equipment.

Choosing the right refrigeration for your restaurant will make your kitchen run smoothly, as well as providing optimum food safety for your customers.

HOW TO CHOOSE THE RIGHT REFRIGERATION EQUIPMENT

Before you commit to purchasing any restaurant refrigeration equipment, you must first determine exactly what types of chillers and fridges you need.

The size of your restaurant and the type of food you serve will be the biggest deciding factors in choosing the right commercial refrigeration.

If your kitchen space is small, you are not likely to have space – or the need – for a large walk-in fridge, so a spacious upright fridge should suffice. If you serve a variety of patisserie items or chilled drinks, you should consider choosing a specialist patisserie display fridge or upright display fridge.

The frequency of your fresh produce deliveries will also determine which type of refrigeration equipment you need for your restaurant. For example, if you receive daily deliveries of fresh or chilled produce, you will need less refrigeration space than those who get a delivery once or twice per week.

WHAT ARE THE DIFFERENT TYPES OF RESTAURANT REFRIGERATION?

With many types of restaurant refrigeration available, it’s important to choose the right kind of chiller or fridge to best fit your commercial kitchen:

Upright storage fridges & Freezers – with less storage capacity than a walk-in fridge, an upright fridge is suitable for most restaurant kitchens. Available in a choice of sizes depending on your chilling requirements, an upright Gastronorm fridge requires less floor space than a walk in or chest fridge, with the suitability to store all fresh and perishable produce. Ideal for use in a hotel, restaurant, school or hospital canteen or any location which requires the unit to work under the high temperatures of a busy kitchen whilst providing ample storage capacity, Gastronorm upright chillers are designed to operate to 43ºC ambient, making them suitable for chilling meat.

Under counter fridges – also known as refrigeration drawers, these large capacity chiller cabinets are ideal for kitchens where space is at a premium. Depending on the size of your kitchen and your chilling needs, choose a two, three or four door under counter chiller cabinet to store seafood, poultry or meat

Reach in fridges – easy to access and with a with a large storage capacity, a reach-in fridge is the ideal refrigeration equipment for many restaurant kitchens. Suitable for all perishable and chilled produce, a reach in fridge should be situated away from the heat of the restaurant ovens

Refrigerated preparation tables – available for either pizza preparation or salad/sandwich preparation, this type of commercial refrigeration equipment should be situated in the food preparation area of the restaurant kitchen. They typically include additional drawers beneath the table top for additional chilled storage

Display fridges – specially designed to keep chilled produce at an ambient temperature whilst on display in your restaurant, a display fridge is ideal for patisserie and desserts, as well as drinks. The glass counter protects the fresh produce, whilst retaining an appealing display for your customers.

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Source by Blaise Lester

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With few exceptions, all compressors that are lubricated with oil will discharge oil into the gas stream. The rate of discharge can be as small as parts of oil per million parts of refrigerant for direct drive hermetic centrifugal compressors and as much as several percent for screw compressors. Oil discharge rates are usually expressed in terms of lbm of oil discharged per lbm of refrigerant compressed or in mass percent of oil in the discharge gas.

Oil in compressor discharge gas is in two forms: fine oil droplets (mist) in the gas stream; and liquid oil driven by the gas velocity, crawling along the tube walls. Oil flows from the compressor with the discharge gas through the oil separator (if equipped and always less than 100% efficient), and into the condenser. The liquid leaving the condenser consists mostly of refrigerant with some amount of dissolved oil (assuming that the oil is miscible in the refrigerant). The oil content in the liquid refrigerant at this point is the same as the oil discharge rate of the compressor/separator.

The liquid oil-containing refrigerant flows through the expansion valve and into the evaporator. In the evaporator, the refrigerant boils off delivering its refrigerating effect. The oil, however, does not evaporate as its boiling temperature is very high relative to the temperatures existing in the evaporator. In the absence of an oil return system, oil will continue to collect and concentrate in the evaporator which will lead to two negative consequences: heat transfer in the evaporator will be progressively degraded and the compressor will eventually run out of oil shutting it down. Hence, an effective oil return system is essential.

Refrigerant and Oil Mass Flow Balance in a Flooded Evaporator

Consider the evaporator of an operating water chiller. Oil is arriving at a certain rate, specifically: the oil discharge rate of the compressor less the removal rate of the oil separator, if equipped. For illustration purposes, assume the mass arrival rate in the evaporator to be 2 lb of oil along with 1000 lb of refrigerant liquid in one hour. The compressor/separator has an oil discharge rate of 0.2%, i.e. mass of oil per mass of refrigerant compressed expressed as a percent. This would be a good discharge rate for a screw compressor/separator.

Oil is also leaving the evaporator via the oil return system. The amount of oil leaving via the oil return system is a function of the liquid removal rate and the concentration of oil in that liquid. Let us assume that the oil return system draws 50 lbs of refrigerant/oil mixture from the evaporator per hour. If the concentration of oil in the evaporator liquid is say 2%, then the oil returned is 1 lb per hour. Since this leaving rate is less than the arrival rate, oil will further accumulate in the evaporator and the oil concentration will rise. Under the conditions stated above the oil concentration in the evaporator will rise to and stabilize at 4%.

Four percent is unacceptably high. There are two things we can do to reduce this concentration. The first is that we can increase the oil return liquid withdrawal rate. If we double the oil return flow rate to 100 lbs/hr and the oil concentration is 2%, the oil arrival and removal rates will be equal at 2 lbs/hr and the concentration will be stable at 2%. Or, we can decrease the concentration of oil in the liquid entering the evaporator (perhaps by installing a more efficient oil separator). These two possibilities also suggest the cause of unacceptably high oil concentrations in evaporators and of chiller shutdowns due to loss of oil. The first is a failure of the compressor (leaking o-rings, missing plugs, etc.) and/or of the oil separator that causes unusually and unacceptably high oil discharge rates. The second is a failure of the oil return system, such as plugged lines, inadequate capacity of a pump, or inadequate driving pressure difference for an eductor. Considering the above, it should be obvious that the more effective improvement to any oil return system is to reduce the oil arrival rate; i.e. reduce the compressor oil discharge rate and/or improve the efficiency of the oil separator.

Oil Inventory in the Evaporator

If you were to do an oil mass balance analysis on an operating flooded evaporator as described above, by measuring liquid line flow and concentration and oil return line flow and concentration, you might yet experimentally find more oil in the evaporator than you expect. The discussion which follows offers a possible explanation. The point of the discussion is that the design of the evaporator itself and the location of the oil return pickup can have a major impact on the success or failure of an oil recovery system. This is relevant because it can mean that replacing a poorly operating oil return system of one kind with another (e.g. pump with eductor) may not fix the problem, the real problem being that the oil return pickup point is poorly located.

Consider a one pass flooded evaporator. Warm water enters tubes at one end and exits as chilled water at the other end. Refrigerant liquid surrounds the tubes and is introduced by a pipe at the cold water end of the shell. Liquid refrigerant is withdrawn from the shell by the oil return system from the middle of the shell (or worse, from the cold end by the liquid inlet). As above, the refrigerant entering the evaporator contains 0.2% oil, and refrigerant is drawn by the oil return system at a rate of 100 lbs/hr and the concentration at the point of withdrawal is 2%. The arrival and removal rates are identical at 2 lbs per hour. If the evaporator refrigerant charge were 100 lbs, one would be tempted to conclude that the evaporator contained 2 lbs of oil. Yet, if you were to measure the oil concentration at the ends of the shell, you might find that the concentration was 10% at the warm end and 0.2% at the cold end. Why would this be? The answer is that most of the evaporation of liquid refrigerant takes place at the warm end of the shell where the temperature difference between water and refrigerant is the greatest. Gravity will see to it that this liquid is replaced with liquid from a higher elevation: liquid at the cold end of the shell which is evaporating, but slowly. Hence, there will be a slow axial flow of liquid refrigerant from the cold end of the shell to the warm end and it will take oil with it that will not return while the chiller operates. But that oil will not evaporate at the warm end nor will it be picked up by the oil return system which draws from the middle of the shell. Hence, oil will tend to concentrate in a place where the oil return system does not pick it up. And where the oil return system does pick up liquid, that liquid will not contain much oil. This will result in a “stored inventory” of oil in the evaporator which can be substantial. So it is important to know where in the evaporator the oil tends to concentrate and to draw return liquid from that point. That location varies by design of the evaporator and any associated internal liquid distribution system.

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Source by Ed Keuper