Tag: <span>refrigeration</span>

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HVAC training is offered in a variety of formats, including initial training and continuing education. Programs are available for the training needed to obtain certification or a degree in heating, ventilation and air conditioning or heating and refrigeration. This training will vary depending upon the type of degree or certification desired. This can include an associate’s degree or a bachelor’s degree, which will require from two to four years of education. The length of time for certification programs will differ depending on the program.

General or Specialized Training

HVAC training encompasses the fields of refrigeration, air conditioning, ventilation systems and heating technology. The technologies differ, but due to the close relationship between the systems, many students choose a generalized education in this field while others specialize.

The specific areas of training available for heating and refrigeration will include building codes, refrigeration technology, heating design, ventilation, electronics technology and indoor air standards among others. The heating, ventilation and air conditioning field will include study in electronics, equipment construction, design theory, blueprint reading, installation and maintenance.

There are numerous opportunities for those who wish to enter this high-demand field. From universities to online courses and apprenticeships, those who are interested in a career can find the specific program that meets their needs. The demand for professionals in the field is growing and is expected to continue.

HVAC training includes:

• Knowledge of HVAC equipment and the methods in which they are used
• Environmental issues
• Handling chlorofluorocarbons and refrigerants in a safe and responsible manner
• Health issues on air quality
• Energy efficiency
• Safety issues

Even though apprenticeship is an option for learning the basics in this field, a school is the best option to obtain a degree or certification. This will allow the highest potential earnings. Trade schools will offer programs in HVAC training that will typically require from 6 months to 2 years of education. This will cover the following:

• Operation
• Design
• Construction
• Installation
• Maintenance
• Repair

A more inclusive program will also include training in areas such as blueprint reading, computer applications, electronics, applied physics, mechanical drawing and shop mathematics. Completion of training and passing the licensing exam will be required for certification.

Degrees in HVAC and HVAC/R

As stated, many choose a career in HVAC as well as refrigeration since the fields are so closely related. A bachelor’s degree can include basic classes as well as advanced. The mechanics of each of the systems include courses in the same basics that are required by trade schools. Additionally they require courses including schematics, drawings, specifications, estimating, industry codes, regulations and Computer-Aided Drafting and Design.

The Bachelor’s Degree

The bachelor’s degree will provide students with the necessary skills for complying with environmental laws, HVAC/R building codes and regulations that include local, state and federal procedures. In addition, they will learn how to perform inspections, design, testing and maintain heating, cooling and refrigeration systems, estimate costs and read specifications and blueprints.

Skills learned in the bachelor’s degree program will provide students with the knowledge to install systems as well as improve energy efficiency, repair defects or dangerous leaks and provide required climate control.

The Associate’s Degree

An associate’s degree in HVAC will include the basics of servicing the systems. Included are troubleshooting, American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) standards, psychometrics, thermal comfort, air distribution and indoor air quality. The student will learn how to install, service, find and eliminate problems associated with the control mechanisms including relays, pneumatics and HVAC Ethernet controls.

Online Certificate Programs

Online certificate programs are available. There are two – HVAC installation and repair or design of HVAC systems. The training to learn installation and repair and prepare for entry-level positions require 320 credit hours, which will include up to 16 courses. This program is designed to prepare students for entry-level positions. After receiving the online certificate, the North American Technician Excellence Certification Examination may be taken.

When choosing HVAC training, such as the certification program for design, this will require completion of 4 to 5 courses. In addition, experience in engineering as well as a bachelor’s degree is required. The opportunities afforded by completing certification and degree programs include competitive salaries and many receive other benefits such as company cars, bonuses and reimbursement for further training.

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Source by Lorn H.

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An air cooled water chiller removes heat from water or other process fluid by use of a refrigeration system that then dissipates that same heat into the air. The energy efficiency is given by the chiller COP.

 

The chiller operates by using the change of state of a refrigerant gas which when forced through an orifice at high pressure changes state from a liquid to a gas, absorbing heat through the chiller evaporator heat exchanger. This cold expanded gas then travels to the chiller refrigeration compressor where it is compressed into a hot, dense gas and pumped to the chiller condenser. The volume that the compressor can pump, the refrigeration gas used, and the operating conditions determine how much heat is removed.

 

At the air cooled chiller condenser the refrigerant is forced by the compressor through smaller copper tubes which have thin aluminum fins mechanically bonded to them. Ambient air is then forced through the condenser coil by the chiller fans. This causes the hot refrigerant gas to condense into a liquid, changing state, and releasing the heat that the gas collected at the chiller evaporator. The waste heat is then carried away into the ambient air by the fans. The liquid is then forced through the orifice and the process starts again.

 

The heart of the chiller is the refrigeration compressor. This is a pump that uses electrical energy to pump refrigerant around the system. Depending on the application like size or operating temperature, a different compressor pumping technology is used. Smaller chillers use refrigeration compressors like rotary compressors, scroll compressors, and reciprocating compressors. Larger chillers use refrigeration compressor like reciprocating compressors, screw compressors, absorption compressors, and centrifugal compressors.

 

Each type of refrigeration compressor can operate more or less efficiently in the air cooled water chiller depending on the water or glycol outlet temperature required, the ambient air temperature conditions and the chiller refrigerant used.

 

The efficiency of the chiller compressor is given by the COP or Coefficient of Performance which is the ratio of kW of heat removed to kW electrical input required. The higher the chiller COP is, the better the energy efficiency. For example a COP of 3 means that for every 1 kW of electrical input, 3kW of heat is removed from the water. A chiller COP of 5 means that for every 1kW of electrical energy input, 5kW of heat energy is removed from the water.

 

Typically chiller COP will vary as follows:

1. Holding the chiller condensing temperature constant: a lower chiller evaporating temperature will use more electrical power per kW heat removed and the chiller COP will be worse, while a higher chiller evaporating temperature will use less electrical power per kW of heat removed and the COP will be higher. 

2. Holding chiller evaporating temperature constant: a higher chiller condensing temperature will have a worse chiller COP that having a lower chiller condensing temperature.

 

A customer’s process cooling requirement will determine the operating temperature for the air cooled water chiller. For example an air conditioning chiller will require water typically at 7 deg C outlet from the chiller evaporator and 12 deg C return. This would require a chiller refrigerant like R407C which is fine for ambient air environments of up to 45 deg C.

 

Where a higher chiller water outlet temperature is required a chiller refrigerant gas like R134a would be acceptable and this has the added benefit of allowing the chiller to operate in much higher ambient conditions – for example – chillers in the Middle East and chillers in Australia – remote locations like mine sites – are often located where the ambient air can be 50 deg C or above.

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Source by Daniel Rollston

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Refrigerated vans are not only a very helpful way to transport products, but also a nice method to start a profitable business. Either way, you should find out more about these vans. It will assist you better to recognize how they can help people.

You should know for the very start that buying refrigerated vans will charge you a lot, and the prices vary between $38,000 and $78,000. These values are for new vans, but it’s pretty much the only choice you’ve got, if you want to make sure you get a quality product. By purchasing a second-hand van, you risk a lot and on the long run, the money saved here will be lost on repairs and other nuisances.

Refrigerated trucks are huge trucks, and if you’re just starting out and you don’t know how well your business is going to do, it would be better to invest in a small trailer, such as a reefer trailer. Much cheaper than a regular truck, this trailer also has the advantage of being cheaper to insure. This will keep you initial venture to a minimum, while you see how things go.

Reefer trailers are not hard to find if you want to buy one, but choosing one is a bit of a challenge. Positive testimonials and low energy consumption are two of the things you should be looking for, when buying or renting such a van. If you are pointed into the right direction, you’ll have no problem in finding the right prices to either rent or buy such vehicles.

One more advantage that reefer trailers have is the fact that they can be easily detached from the main vehicle and that vehicle will be able to perform other tasks. So simply tow the trailer to its destination, leave it there, do your business, and then come back to get it! When your business is just starting out, and you need your vehicles in different places during the day, there’s nothing better than being able to do so!

A refrigerated van on the other hand offers much more space. However, do you really need all that space? You may not need all of it, and you may not use it, but you’re certainly paying for it. If you know that you won’t have items to take up all the space, and you think this won’t change in the near future, then there’s no point in investing in a large van.

Choosing between a refrigerated truck and a reefer trailer is a very vital decision and once it is made it will have a major impact on your business. If you need the additional space than a truck is the best choice, while if you need the resources for something else, go for the latter with no hesitations.

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Source by JC Tena Tolentino

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In the days when humans were hunter-gatherers, subsistence consumption was the only way humans knew for gathering food. There was no technology to store anything for long periods of time, so people were forced to hunt or collect only what they could eat immediately. With the advent of civilizations, the concentration of so many people created dedicated farming classes that could support people who spent their excess leisure time thinking of ways to solve problems such as this. The solution to this problem would eventually become our modern refrigeration systems.

Early refrigeration systems were simple pits lined with ice and snow, then covered with straw for insulation. Many cultures had come up with ingenious ways of combating food spoilage, but the most impressive solution to this problem was the one designed by the ancient Persians in about 500 BCE. This civilization build large domed structures called “yahkchals” which kept ice to a temperature equivalent to that of modern refrigerators. This is a clear case of necessity being the mother of invention, as the Persians required large amounts of ice to preserve food in the deserts that they lived in and around. These yahkchals were marvels of engineering, yet surprisingly simple. They achieved what they did simply by creating these buildings with thick walls made of a resilient, water-tight mortar known as sarooj. This material was made of sand, clay, animal hair, egg, and other substances in specific proportions, and it yielded a very thick material that could be built into an effective refrigeration system due to sarooj’s resistance to heat transfer. While food preservation was a necessity, the yahkchals were also used to preserve luxury foods for the Persian royalty because they were often the richest people who owned the largest and most numerous refrigeration systems.

Throughout the European Industrial Revolution, modern refrigeration systems began to be constructed that employed gas compression in order to preserve food for long distances. This brought forth a qualitative shift in shipping that opened up an entire industry when people realized food could be moved from any part of the world to another. This movement began in New Zealand when in 1881 a large merchant vessel named the Dunedin was fitted with a large cold storage unit to transport frozen meat to Great Britain. Despite the tremendous distance, this early foothold in what would quickly become a massive industry ensured New Zealand would dominate the meat shipping business in England for a hundred years. This method would not have worked with regular ice storage because merchant ships cannot deliver the same stable conditions as a Persian yahkchal. Gas compression became the wave of the future.

Today nearly all modern refrigerators employ gas compression technology. Throughout the past hundred years various innovative steps have been taken in improving the technology of refrigeration systems that generally caused quantitative leaps by allowing new transportation methods to be refrigerated, such as trucks and planes. The final quantitative leap yielded safer chemicals that allowed for commercial refrigerators to exist in smaller spaces such as households across the united states.

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Source by Dan S Thaler

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Most refrigerators and walk-ins seem virtually indestructible and problem free, but you’ll get longer life out of yours by following these safety and maintenance tips. Clean the door gaskets and hinges regularly. The door gaskets, made of rubber, can rot more easily if they are caked with food or grime, which weakens their sealing properties. They can be safely cleaned with a solution of baking soda and warm water. Hinges can be rubbed with a bit of petroleum jelly to keep them working well. Dirty coils force the refrigerator to run hotter, which shortens the life of the compressor motor. They should be cleaned every 90 days, preferably with an industrial-strength vacuum cleaner.

Walk-in floors can be damp-mopped but should never be hosed out. Too much water can get into the seals between the floor panels and damage the insulation. A refrigerator only works as well as the air that’s allowed to circulate around its contents. Cramming food containers together so there’s not a spare inch of space around them doesn’t help. Also try to keep containers (especially cardboard ones) from touching the walls of the cabinet. They may freeze and stick to the walls, damaging both product and wall. Use a good rotation system: First in, first out (FIFO) is preferable. Or put colored dots on food packages, a different color for each day of the week, so everyone in your kitchen knows how long each item has been in the fridge.

WALK-IN COOLERS AND FREEZERS

A walk-in cooler is just what its name implies: a cooler big enough to walk into. It can be as small as a closet or as large as a good-size room, but its primary purpose is to provide refrigerated storage for large quantities of food in a central area. Experts suggest that your operation needs a walk-in when its refrigeration needs exceed 80 cubic feet, or if you serve more than 250 meals per day. Once again, you’ll need to determine how much you need to store, what sizes of containers the storage space must accommodate, and the maximum quantity of goods you’ll want to have on hand. The only way to use walk-in space wisely is to equip it with shelves, organized in sections. Exactly how much square footage do you need? The easiest formula is to calculate 1 to 1.5 cubic feet of walk-in storage for every meal you serve per day. Another basic calculation: Take the total number of linear feet of shelving you’ve decided you will need (A), and divide it by the number of shelves (B) you can put in each section.

This will give you the number of linear feet per section (C). To this number (C), add 40 to 50 percent (1.40 or 1.50) to cover “overflow”-volume increases, wasted space, and bulky items or loose product. This will give you an estimate of the total linear footage (D) needed. However, linear footage is not enough. Because shelves are three dimensional, you must calculate square footage. So multiply (D) by the depth of each shelf (E) to obtain the total square footage amount (F). Finally, double the (F) figure, to compensate for aisle space. Roughly half of walk-in cooler space is aisle space. Another popular formula is to calculate that, for every 28 to 30 pounds of food you’ll store, you will need 1 cubic foot of space. When you get that figure, multiply it by 2.5. (The factor 2.5 means only 40 percent of your walk-in will be used as storage space; the other 60 percent is aisles and space between products.)

The result is the size of the refrigerated storage area you will need. For a walk-in freezer, simply divide your walk-in refrigerator space by two. Larger kitchens, which serve more than 400 meals a day, may need as many as three walk-in refrigerators for different temperature needs: one for produce (41 degrees Fahrenheit), one for meats and fish (33 to 38 degrees Fahrenheit), and one for dairy products (32 to 41 degrees Fahrenheit). The walk-in is used most often to store bulk foods. Because this often means wheeling carts or dollies in and out, the floor should be level with the kitchen floor.

This leveling is achieved by the use of strips (called screeds) that are applied to the floor. Coolers don’t come as a single unit; they are constructed on-site. The walls, ceilings, and floors are made of individual panels. Wall panels should be insulated to a rating of R-30, which means a 4-inch thickness. They come in various lengths and widths, with 12-by-12-inch corner panels at 90-degree angles. They can be as short as 71?2 feet or as tall as 131?2 feet. The most common type of insulation inside the panels is polyurethane, and the outside walls of the panels can be made of stainless steel, vinyl, or aluminum. Stainless steel is the most expensive, and aluminum-because it’s the least expensive-is the most popular choice. If the walk-in is an outdoor installation, aluminum is the most weather resistant.

The installer will be sure the unit has interior lighting. The floor panels for walk-ins are similar to the wall panels. Load capacities of 600 pounds per square foot are the norm, but if you plan to store very heavy items (like beer kegs), a reinforced floor can be purchased with a load capacity of up to 1000 pounds per square foot. The refrigeration system of a walk-in is a more complex installation than a standard refrigerator, primarily because it’s so much bigger. Matching the system (and its power requirements) with the dimensions of the walk-in and its projected use is best left to professionals, but it’s important to note that a walk-in accessed frequently throughout the day will require a compressor with greater horsepower to maintain its interior temperature than one that is accessed seldom.

A 9-foot-square walk-in would need at least a 2-horsepower compressor. The condenser unit is located either on top of the walk-in (directly above the evaporator) or up to 25 feet away, with lines connecting it to the walk-in. The latter, for obvious reasons, is known as a remote system, and is necessary for larger-than-normal condensing units with capacities of up to 7.5 horsepower. In a remote system, the refrigerant must be added at the time of installation. For smaller walk-ins, there’s also a plumbing configuration called a quick-couple system, which is shipped from the factory fully charged with refrigerant. This definitely simplifies installation. However, you may need the added power of a remote system if your kitchen has any of these drains on the walk-in’s cooling ability: frequent door opening, glass display doors, multiple doors per compartment, or an ambient kitchen temperature that’s near 90 degrees Fahrenheit.

Modern walk-ins sometimes offer a frozen-food section in addition to the regular cooler space. There are pros and cons to this concept. It may ease the load on the freezer, because it’s already located inside a chilled airspace; but it also can’t help but reduce overall usable space, because it requires a separate door. You can also order your walk-in with a separate, reach-in section that has its own door and shelves. Although this may save the cost of purchasing a separate reach-in, some critics claim that a walk-in is not designed to do a reach-in job, such as storing uncovered desserts. Do you really want them in the same environment as cartons of lettuce and other bulk storage items? There may be cleanliness or food quality factors to consider.

The doors should open out, not into the cooler itself. The standard door opening is 34 by 78 inches. Several door features are important for proper walk-in operation. These include: A heavy-duty door closer. Self-closing, cam-lift door hinges. If the door can be opened past a 90-degree angle, the cam will hold it open. A heavy-duty stainless steel threshold. This is installed over the galvanized channel of the door frame. A pull-type door handle, with both a cylinder door lock and room to use a separate padlock if necessary. Pressure-sensitive vents, which prevent vacuum buildup when opening and closing the door. An interior safety release so no one can be (accidentally or otherwise) locked inside the cooler.

Other smart features that can be ordered for walk-ins are: A thermometer (designed for outdoor use, but mounted inside the cooler) with a range of 40 to 60 degrees Fahrenheit. A monitoring and recording system that keeps a printout of refrigeration temperature or downloads to a computer. Glass, full-length door panels (like those in supermarkets and convenience stores), sometimes called merchandising doors, either hinged or sliding. Heavy-duty plastic strip curtains inside the door. (One manufacturer claims a 40 percent energy savings with this feature.)

A foot treadle, which enables you to open the door by pressing on a pedal or lever with your foot when both hands are full. Three-way interior lighting, which can be turned on from outside or inside the cooler, with a light-on indicator light outside. Inside, the light itself should be a vapor-proof bulb with an unbreakable globe and shield. When space is at a premium, think about whether it is practical to install an outdoor walk-in unit. This is an economical way to add space without increasing the size of your kitchen, and you can purchase ready-to-use, stand-alone structures with electricity and refrigeration systems in place. They come in standard sizes from 8 to 12 feet wide and up to 50 feet in length, in 1-foot increments.

They range in height from 7.5 to 9.5 feet. Look for a unit with a slanted, weatherproof roof, a weather hood, and a fully insulated floor. Outdoor walk-ins cost about half of the price of installing an indoor kitchen walk-in, so this is a money-saving idea if it works in your location. If your demands for walk-in space are seasonal, consider leasing a refrigerated trailer, available in most metropolitan areas on a weekly or monthly basis. They can provide an instant 2000 cubic feet of additional storage space, which can be kept at any temperature from 40 to 80 degrees Fahrenheit. They use basic 60-amp, 230-volt, three-phase electricity. Ask if the lease agreement includes hookup at your site and service if anything goes wrong.

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Source by Franco Zinzi

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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