Characteristics of liquid

techicien — Sat, 13 Mar 2010 13:12:36 +0000

Concentration

properties of the feed to an evaporator cannot exhibit unusual problems. However, as the liquor is concentrated, can drastically change the properties of the solution. Density and viscosity may increase with solid content until the heat transfer performance is decreased or the solution becomes saturated. Boiling continues a saturated solution can cause form crystals which often must be removed to avoid deficiencies or soil surface heat transfer. The boiling point of a solution increases significantly as is concentrated.

Blowing

Some materials can foam during steaming. Stable Foams may cause excessive swipes. Foaming may be caused by gases dissolved in liquor, from a loss of air under the level of the liquid and the presence of surfactants or finely divided particles in liquor. Many antifoaming agents can be used effectively. Foams can be suppressed by operating at low levels of liquids, mechanically or hydraulic methods.

Temperature sensitivity

many chemicals are compromised when heated to moderate temperatures for relatively short time. When the evaporation of those materials, special techniques are needed to control the characteristics of the time/temperature evaporator system.

Salting

Salting refers to the growth of a matter that a solubility increases with increasing temperature on surfaces evaporator. Can be reduced or eliminated by keeping the evaporation of liquid in close or frequent contacts with a large surface area of solid crystallized.

Scale

scale is growth or deposition on the surfaces of insoluble or heating has a solubility that decreases with increasing temperature. It may also derive from a chemical reaction in the evaporator. Both in scale and salting liquids usually best are handled in a rotary evaporator not based on boiling for operation.

Fouling

Fouling is the formation of deposits several meeting rooms or scale. They may be due to corrosion, solids entering feed or deposits formed by side heating medium.

Corrosion

Corrosion might influence the selection of the type of evaporator because expensive building materials indicate evaporators offering high rates of heat transfer. Corrosion and erosion are often more serious in evaporators compared to other types of equipment for the high speed of liquid and vapor, the frequent presence of suspended solids and concentrations requests.

Quality product

quality may require holdup low and high temperatures. Low-holduptime requirements may eliminate the application of certain types of evaporator. Quality of the product may also dictate special building materials.

Other properties of Fluid

other smooth property must be considered. These include: heat solution, toxicity, explosion hazards, radioactivity and ease of cleaning. Salting, resizing and dirty the result steadily heat transfer speed, until the evaporator must be shut down and cleaned. Some deposits can be difficult and costly to remove.?

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Flow-Induced Vibration in Evaporations

techicien — Sun, 28 Feb 2010 16:06:21 +0000

Concern for the flow-induced vibration of the tube has become a serious consideration in the design of shell-and-tube equipment. These problems can lead to pipes and tubejoints that loss, increased pressure drop and noise shellside intolerably high. The result is that equipment must be removed from service for repair and modification.

Flow-induced vibrations can damage the tubes in evaporators. All tubes vibrate in all flow conditions! However, we are concerned with the vibrations that cause significant damage to the pipe. As larger evaporators, bring more speed and more shellside become more prevalent, the vibrations of the pipe damage are more likely to occur. N. evaporator design is complete without considering the possibility of damage due to flow induced vibrations.

The damage is most likely to occur with gases or vapors on shellside than with liquids. Flow induced vibrations also occur with liquids on shellside, but the damage is often limited to localized areas of relatively high speed. In severe cases, the pipes can leak in a few days or even hours after the device was placed in service. More often, the damage will appear a year after startup. Give the tube will develop after the initial damage was repaired, but the number and frequency of further damage will diminish with time.

In a number of cases, by a heat exchanger tube failures attributed to vibrations flowinduced consequential damages caused to other devices within a plant. Failures of this type have proven to be the most destructive, most costly, and required the closure of plants longer for the correction.

Currently available methods for the prediction of flow induced vibration damage is not sufficient to predict failures. At best, they identify the equipment that are susceptible to damage. The main reason for this lack of precision is that the flow induced vibrations are extremely complex. We learned a lot, but the probability of its occurrence is not yet known. However, the penalty cost for equipment designed to completely avoid the harmful vibrations is small and is almost always easily justified.

Some problem areas in question, with the prediction of vibration include:

1. the complex pattern of flow through a tube bundle
2. complex fluid mechanics of a bank of vibrating tubes
3. the role of damping
4. rates of wear and fatigue.

However, it is possible to develop design criteria, especially when tempered with experience, to ensure that the material will be safe from harm vibration.

Flow-induced vibration problems in equipment tubulars are commonly regarded as consisting entirely of mechanical failure of the tubes. However, the vibration may increase the pressure drop shellside, sometimes twice. Furthermore, a unit of acoustic vibration can produce an unacceptably high level of noise. With a growing emphasis on controlling noise, vibration noise must be an important consideration in plant design tubular

techology » Liquids

Characteristics of liquid

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Flow-Induced Vibration in Evaporations

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