1 Refrigerating System. Three-stage (ternary) cascade refrigeration system

seobrand@gmail.com (Administrator) — Fri, 21 Jan 2011 17:06:35 +0000

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Refrigerating Systems. Three-stage (ternary) cascade refrigeration system

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Cascade cooling cycles are commonly used in the liquefaction of natural gas, consisting mainly of hydrocarbons paraffin series, of which methane has a lower boiling point at atmospheric pressure. Cooling down the temperature can be provided at the triple cascade cooling cycle, using propane, ethane and methane, whose boiling point at atmospheric pressure 231.1 K, 184.5 K and 111.7 K (Haywood, 1980). Simplified schematic diagram of the cascade loop is shown in Fig. 3.40. In operation, compressed methane, steam and cooled by heat exchange with propane propane in the evaporator before being reduced by heat exchange with ethane ethane in the evaporator, which reduces the degree of irreversibility of participating in cooling and condensation of methane. In addition, due to the high temperature after compression gas at the compressor outlet passes first through a water-cooled chiller. In large-scale plant of this type compressors become rotary turbo machines instead of piston-type ones.

Chocolate

seobrand@gmail.com (Administrator) — Wed, 08 Sep 2010 13:18:42 +0000

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Chocolate

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Many confectionery products covered by a thin layer of chocolate. The latter is a mixture of chocolate, cocoa butter and other fats, merged, forming a suitable coating material. This layer melts at a temperature generally in the range of 27-34C. the manufacturer wishes to cover sweets in a thin solid layer, and then to strengthen this layer so that the product can be wrapped and Packed with the least latency on the production line.

Chocolate enrobing start with an element, passing through the coating process, and then through the cold air of the tunnel to be strengthened layer. The colder the air, the faster it will pass, but if the product comes out of the tunnel's too cold atmospheric moisture may condense on the surface and spoil the glossy coating expected by the consumer. The average air temperature in the tunnel can be between 2C and 7C, and air cooling in the refrigerator or in brine coil inside the tunnel. Sometimes it is necessary to condense the entire working area so that the dew point temperature is lower than the surface temperature confectionery, as she comes out of the tunnel...

Ready meals

seobrand@gmail.com (Administrator) — Wed, 08 Sep 2010 13:18:15 +0000

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Ready meals

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There is growing demand for ready-to-eat products for the final re-heating or cooking in microwave ovens. Applications for retail sale take-away meals and factory/office and catering establishments. Such products can be frozen and then have a long period of storage, but require a frozen storage.

You can pre-cook the product to a temperature of pasteurization and then cool, for short-term storage above freezing point. The required standards for temperature control and hygiene are very strict and subsequent shelf life is limited. The process is cheaper than freezing. The product leaves the oven at 100C can be cool in the ambient air up to 70C, if the conditions of hygiene are in a satisfactory condition. During this time it can be divided into food-size or other parts. As a rule, it should be in individual products of a thickness not exceeding 50 mm, or it will not cool at the specified time.

Trays product is loaded in the coldest of the Cabinet, and all its parts must be reduced to a temperature of storage in a timely manner to the Department of Health guidelines.{loadposition banner2} Since it is not required to freeze any part of the cooling air is the product may not be much below 0C, and cabinets for this purpose, have built-in refrigerating plants, which will air in 2C, and at a faster speed than the product of some 6.5 m/S. the product should be stored Refrigerated at a temperature of 3C or so. Shelf life can be a maximum of 5 days, but, as a rule, only a day or two...

Bakery products

seobrand@gmail.com (Administrator) — Wed, 08 Sep 2010 13:17:07 +0000

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Bakery products

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Bread dough are heated in the process of mixing and yeast can begin too early. Moisture content in the mixture can be chilled, or more machines, possibly with water cooling jackets to take the heat.

Test preparing some time before the final baking process and will remain, to " prove"that is, allow the yeast to start the work. Action may be slowed down cooling of the dough at this stage, and this process allows the load will be distributed through the day. As a rule, bread the next morning, now may be prepared on the previous day, before proving the stage, and then kept under cold, wet storage for a few hours before baking begins.

Dough-retarding cabinets currently used in most bakeries. Bread dough can be made at any time and keep at temperatures from -4C and + 3C, depending on the desired retard time, which can be up to 3 days. Automatic timer completes the loop cooling and bring to test proving temperature when required. Thus, pastes can be ready for the oven at the bakery staff begins early in the morning. Furthermore, the shares may be held prepared for unexpected requires additional costs.

The high share of sliced bread is sold, but it will be too hot for this at the outlet of the furnace. Large bakeries have tunnels cooling to reduce bread temperature, so it can be split. A high degree of hygiene should be, or slice will present airborne spores and bread will grow mold.

Vegetables

seobrand@gmail.com (Administrator) — Wed, 08 Sep 2010 13:16:47 +0000

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Vegetables

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Most vegetables contain very high percentage of water and realize how quickly they dry out. Storage conditions demand a high humidity level 90-98% saturation and temperatures close to their General freezing point 0C as possible. Some leafy vegetables sprinkled with pieces of ice to keep the damp, cold condition. Cold storage for fruits, not very large, evaporators for provision of these conditions of high humidity. In addition to the conservation of plant substances, growths mould and insect pests, are also subject to low temperature.

Several products, such as cucumbers and some potato crop, better keep at higher temperatures. These conditions differ depending on the species, state of maturity, when he took and the required storage period. Onions and garlic are exposed to wet conditions, which favour the formation of mould, and stored at a relative humidity of 65-70%. Can not be stored together with other vegetables for a short time.

The convenience of having a high-quality production, aligned and ready for cooking resulted in high demand for frozen vegetables in the UK.{loadposition banner2} Peas, carrot, beans, and some leafy vegetables, frozen in the air. There are slight changes in the texture, but the texture was subsequently altered by cooking.

A few points, strawberries, other soft fruits and pieces of cauliflower, frozen using liquid nitrogen. Frozen vegetables and fruits, Packed in polyethylene bags and stored at a temperature of -18C or below. Humidity at temperature not important.

Fruits

seobrand@gmail.com (Administrator) — Wed, 08 Sep 2010 13:16:25 +0000

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Fruits

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Fruits are seasonal in a temperate climate, and a good harvest can be accompanied by a shortage if no method of preservation. Hard fruit, apples and pears, traditionally stored in a cool place, and then can last for several months, depending on the variety. Refrigeration extended shelf-life and made it more reliable.

Artificial cooling allowed the fruit grown anywhere in the world, to be brought to any market. Climacteric fruit, such as bananas harvested green and pass controlled ripening on the ship. Conditions of refrigerated depends on many factors, and the temperature and relative humidity are shown in Table 16.1 common ranges specified. More precise information should be used for the operation for a particular product. A large volume of perishable food now travels by air and temporary protection against low temperatures may be necessary in case the cargo is not under pressure.

Storage of fruit requires careful monitoring of the atmosphere in the shop, as well as temperature. Shops were built to support such a controlled atmosphere, in addition to temperature control, generally referred to as the gas storages.{loadposition banner2} They have a gas-tight structure to prevent the spread. Fruits can be downloaded and store sealed. Within a few days they consume share of free oxygen, and traces to maintain the correct proportions chemical removal or ventilation system. Climacteric fruit also require control eth-ylene since the gas effects of the ripening process. Considerable research over the last 60 years, mainly in the UK, has determined the correct balance of gases extend the shelf life of various varieties of apples and pears, both home-grown and imported.

Soft drinks

seobrand@gmail.com (Administrator) — Wed, 08 Sep 2010 13:16:05 +0000

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Soft drinks

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Feature of most soft drinks is that they " carbonated", that is, they have a share of dissolved carbon dioxide, which causes bubbles and typical wines taste. The amount of gas dissolved in the water will amount to 3.5-5 volumes, that is, in each liter of water soluble 3.5-5 liters of carbon dioxide. Production technology is to dissolve the required amount of gas in the drinks and then get it on his or bottle.

The solubility of carbon dioxide in the water depends on temperature and pressure. The relationship between the temperature and pressure of 3,5 and 5 volumes shown in Fig. 16.9 . It will depend on the amount of air already dissolved in the water. Raw water, so carefully filtered and de-oxygen under vacuum up sugar and spices are added.

Since the gas will dissolve at a much lower pressure at low temperatures, drinks, cooled to a temperature of about 0C, either before or during the introduction of the gas. The liquid can be pre-cooled in a heat exchanger, using chilled water or alcohol ethyl alcohol in water, although, as a rule, propylene glycol-water.{loadposition banner2} One of carbonization method is to host a final cooling stage during Baudelot cooler which is installed inside the pressure vessel. Gas presented to the pressure, necessary for dissolution of the required proportions, and gas meets the fluid as it flows in thin film on the surface of the cooler.

It is then bottled as quickly as possible, before the gas is time to bubble again. Once it is sealed in a bottle, cooling is not required for storage. Cooling brine for refrigeration, as a rule, are in the shell-and-tube evaporators. In Baudelot cooler in the pressure vessel can be cooled or jellied expansion of the refrigerant, or brine.

Wines and spirits

seobrand@gmail.com (Administrator) — Wed, 08 Sep 2010 13:15:46 +0000

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Wines and spirits

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Optimum temperature of fermentation of wine depends on the type, red wines, the best work about 29C, while white wines require a cooler state of about 16C. Heat is given by a chemical process of fermentation. Then they traditionally Mature and are stored in caves, cellars or about 10C. Much of the production and most of the storage is now in the rooms is controlled by a mechanical refrigeration. Spirits don't need low-temperature storage.

The clarity of the final drink affected by small particles tartrates and other substances that sediment during storage. To get a product that will remain clear storage, a lot of wine and spirits are cooled by cooling to a temperature just above freezing point, and then fine filtration...

Beer and brewing

seobrand@gmail.com (Administrator) — Wed, 08 Sep 2010 13:15:23 +0000

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Beer and brewing

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Manufacture of beer and cider requires fermentation sugary liquid under the action of yeast, cooling, filtration, clarification, and store the resulting alcohol-water mixture. The starting mixture for beer warm infusion based on grains, sugar, and flavorings. This " wort " leaves hot brewing process and is cooled to the desired temperature brewing - about 10C lagers and 20C for traditional liqueurs. It was originally carried out with Baudelot coolers, but now plate heat exchangers are used, mainly, with chilled water as the heat carrier.

The fermentation process gives off heat, and tanks, may need to be cooled with heat exchanger, jackets, or cooling " cellar", in which tanks are located. After the fermentation, a lot of beer now pasteurized, in the same way as milk. Beer then cooled to just above zero, filter and left 'age'. Before the final bottling or kegging canning he undergoes subtle filtering to increase clarity.

Refrigeration equipment necessary for refrigerating chambers and provide chilled water for plate heat exchangers.{loadposition banner2} "Cellars " very wet areas, and refrigeration plants should be designed to maintain low humidity as possible, to help preserve the structure of the building.

Beer at the point of sale is traditionally stored in the cellars to keep them cool. Beer in kegs or transferred in bulk tanks. Refrigeration these places usually Packed with beer cellar coolers (see Fig. 16.8) , and this is something akin to split-system air conditioners. Bulk tanks, perhaps, built-in refrigeration units. Drinks such as beer, which is usually drunk colder than other varieties of beer, walked through a chilled water, bath or double-pipe heat exchanger for final cooling.

Bottled beer and other drinks are stored on cooled trays or bottle cabinets, including cooling base tray and an integrated cooling system.

Ice-cream

seobrand@gmail.com (Administrator) — Wed, 08 Sep 2010 13:14:38 +0000

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Ice cream

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Ice cream is a product that has been designed with a mechanical refrigeration became available. Ice-cream mixtures are fats (not always milk), milk protein, sugar and additives such as emulsifiers, stabilizers, colorants, together with additional elements, such as fruit, nuts, chocolate pieces and others, depending on the appearance and taste. The presence of this mixture components means that the freezing process covers a wide range of temperatures, starting just below 0C and not finishing until 18C or below. The production process takes place in three main stages mixing, freezing to a plastic state and hardening

The basic mixture consists in liquid form, pasteurized, homogenized and cooling, using chilled water plate heat exchangers. It was then that the " aged " for several hours, and for this, it will be stored on 2-3C in the tank jacket, with chilled water shirt.

At the next stage freeze it quickly, with the introduction of controlled share of air to give him a light, edible texture. Cellular mix about 50% of air, 50% of the ice cream mixture on volume transmitted in one end of the trunk, which forms inside the flooded evaporator.{loadposition banner2} The mixture solidifies on the inner surface of the barrel and then scraped off the rotating stainless steel beater blade, and passes through the barrel of a continuous process of freezing, beatings and mixing. The most common refrigerant for ice-cream freezers continuous ammonia, which will be at the boiling point 35C to 30C. About half of the total heat freezing laughs, and ice cream leaves at about 5C, depending on the particular type of product. Continuous ice-maker process is shown in Fig. 16.5.

Ice cream is still plastic as it comes from the freezer, and she pulled final sales form - box, bath, safety Deposit box stick or product. Then he must be hardened cooling storage temperature 25C or below, during which half of it heat of freezing is removed. Stick products that fall into the trays and directly to the hardening of the tunnel. Fig. 16.6 shows four lanes sticks on their way hardening of the tunnel. This tunnel can handle up to 36 000 PCs/hour. Extrusion head is in the upper right corner. Flat boxes can be chilled between refrigerating plates, as shown in Fig. 7.14(a) although the tunnels are used most often.

An important factor of the final RIA, is that it should be as fast as possible to limit the size of the ice crystals in ice cream. Quick freezing implies a high heat transfer coefficient and, therefore, very low temperature refrigerant. A powerful stream of air 40C is common. Two stage compression systems are used.

Ice cream should be stored at low temperatures, up to the point of final consumption. If it is allowed to soften the entrained air bubbles may escape and original texture will be lost. If it is soft, and then froze again, hard, hard skin forms, making the product inedible. Ice cream should always be handled quickly passing through transit stages from the factory to the consumer.

Novelties of the frozen products on a wooden stick produced in large quantities, and these products, frozen in metal forms/trays, which are immersed in salt tank with a built-in cooling coil or plate chiller. The novelty of the device, which can take various forms is shown in Fig. 16.7 . As ice and water ice products can be processed. Cooling, low temperature brine or carbon dioxide. Brine tank temperature the temperature, which can be between 28C and 35C, depending on the process. Forms are made of stainless steel or Nickel, and pass it into the ranks through the brine bath. Different layers of the confection can be built by allowing one outer layer freeze, sucking the unfrozen centre and filling mixed with the other. Sticks are inserted before the center freezes solid. Mold, finally, go through the defrosting in section warm brine production of the product with mold, and extractor grab bars sticks, remove the products and throw them in the packaging bags.