An lci agitated thin film evaporator tfe or wiped film evaporator wfe or wiffe provides short residence time and open, low pressure drop configuration, allowing continuous, reliable processing of many heat sensitive, viscous, or fouling materials without product degradation. Process modelling and optimization of design parameters in a. A brief survey is made of the state of the art of thermal design for vertical intube falling film evaporators. Generally 816 lcmhr in a falling film tubular evaporator in the beet industry and for falling film tubular evaporators in the cane industry, a much higher wetting rate of 12 to 15 lcmhr is recommended. Best product quality due to gentle evaporation, mostly under vacuum, and extremely short residence times in the falling film evaporator. In the first stage, process liquid enters the falling film evaporator through the inlet feed pipe and is directed to the top liquid distributor. Falling film evaporators are vertical shell and tube heat exchangers. Inlet vapour temperature oc tube od mm outlet vapour temperature o c.
The distributor is the key component in the fallingfilm evaporator, which determines the uniformity of the distribution of the refrigerant in the falling film evaporator. In a normal evaporating process, the most common types are wavy laminar film evaporation and turbulent film evaporation. An even thin film enters the heating tubes via a distribution device in the head of the evaporator, flows downward at boiling temperature, and is partially evaporated. According to peiter rein down take dia consider less than 25% of the tube plate dia p. Thermal vapor recompression tvr evaporator swenson thermal vapor recompression tvr evaporators use a thermocompressor to reduce the steam required per pound of evaporation. An internal distributor ensures the tubes are equally wetted. Design of vertical falling film evaporator 03242011 4. Calculates the heat transfer area for a singleeffect evaporator that is used to concentrate a salt solution. Evaporation calculations evaporation heat transfer. Bt9 vertical tube falling film evaporation stateofthe. Falling film evaporation is controlled by two different heat transfer processes.
Then, the blades fitted at the rotor spread the liquid as a thin film of min. The optimum design of fallingfilm evaporator and numerical. For the rising film evaporator, distribution was easy since. The liquid forms a film along the inside of the tubes. Vapor is recovered at the top, and remaining liquor collected at the bottom or recycled. The falling film evaporators have many advantages over flooded and vertical tubes that make them best candidate for processes industries application. Isgec has developed an improved design of falling film evaporator with a novel juice distributor. Falling film evaporator tubes are available with different corrugations to enhance the heat transfer rates as compared to vertical tube evaporators. The internal structure of horizontaltube falling film evaporator in order to solve the problem that the middle refrigerant speed is too large and the both sides speed is too small in traditional structure. Shell and tube heat exchanger is designed by trial and error calculations. This will help to design efficient falling film evaporators for processes industries. Falling film tubular following development of the rising film principle, it took almost half a century for a falling film evaporation technique to be perfected figure 4. Operation the liquid to be concentrated is supplied to the top of the heating tubes and distributed in such a way as to flow down the inside of the tube walls as a thin film.
This evaporator has some advantages over the current evaporator. Hermes center for applied thermodynamics, department of mechanical engineering, federal university of parana p. In falling film evaporators, liquid and vapors flow downwards in parallel flow. This new type of costeffective rising film evaporator rapidly became a success in the beet sugar industry and has subsequently spread to many other applications. This proposed falling film heat transfer coefficient is useful for falling film evaporator design. Multiple effect evaporator design selection of type of evaporator using some parameters is presented for the best design of multiple effect evaporator in table 1. The liquid to be concentrated is preheated to boiling temperature. Falling film evaporators provide high steam economy, defined as the amount of vapor generated per unit mass of process steam. This paper will summarise past work and will attempt to show that fouling in falling film evaporators can be minimised by appropriate attention to design. We also demonstrated the effect of salt concentration on heat transfer and lmtd. May 29, 2017 the falling film plate evaporators need a similar system, although the wetting rate required is lower. In case of multipleeffect evaporation plants, the exhaust vapors from the product are used to heat the downstreamarranged evaporation effect so.
In this 1 year ive gained decent knowledge regarding the design and working of this beast. Internship huntsman the design of falling lm evaporators. Our distribution is a twostage system, featuring high accuracy and a wide operating range. Rising falling film plate this is the original plate type evaporator. The principle of operation for the rising falling film plate evaporator rffpe involves the use of a number of plate packs or units, each consisting of two steam plates and two product plates. Htri has developed initial recommendations for the design of distributors to be used in falling film evaporators. In this paper, the mathematical model of the refrigerant flow in the curly top surface structure of distributor was established and the model was studied using numerical simulations.
Results and discussion a steady state model of a multi effect falling film evaporator is shown in figure 5. High energy efficiency due to multipleeffect arrangement or heating by thermal or mechanical vapor recompressor, based upon the lowest theoretical temperature difference. A distribution ring on the rotor distributes the liquid evenly across the periphery. Parker has attempted to test the suitability of each basic design for dealing with the problems encountered in practice, and the basic information is presented in the form shown in figure 14. Shorttube vertical evaporators operate in the same way as climbing film longtube vertical evaporators.
Falling film evaporation an overview sciencedirect topics. The internal structure of horizontaltube fallingfilm evaporator in order to solve the problem that the middle refrigerant speed is too large and the both sides speed is too small in traditional structure. If ignoring the disturbing influences on film falling from vapor, eqs. We developed falling film heat transfer coefficient ffhtc correlation for saline water evaporation from 280 to 305 k saturation temperatures. The internal structure of horizontaltube fallingfilm evaporator is shown in fig. Earlier htri publications on this subject are htri report bt5 may 1980 and htri research brief 35 may 1986.
Worldwide about 300 sugar factories and refineries are working with various design of falling film evaporators. The optimum sizing is achieved with our proprietary design tool. Typical tema types are bem, nen or a combination of the two. Mean dia of the tube dm in mtr tube od tube thickness in some designers. Our wiped film evaporator is the ideal apparatus, if you need a continuous pr ocessing of your heatsensitive, viscous and or fouling products design our wiped film evaporator consists in contrast to a falling film evaporator of merely one single evaporation tube fitted with a mechanical rotating device, the socalled rotor. Thermal vapor recompression tvr evaporator swenson. Design of industrial falling film evaporators intechopen.
Aquasol deahp evaporator is a horizontaltubesfalling. Thermal vapor recompression tvr evaporator swenson technology. Evaporator selection considered in detail in volume 6, has been discussed by moore and hesler20 and parker21. To reduce energy consumption, water vapor from an evaporator is entrained and compressed with high pressure steam in a thermocompressor so it can be condensed in the. Selection of a distribution design depends on operating conditions and fluid characteristics in two process categories. Evaporation calculation methods for multipleeffect evaporators. The alfavap plate evaporator is the result of development work done in collaboration with beet sugar manufacturers in the late 1980s. Process modelling and optimization of design parameters in. What are the steps involved in evaporator designing.
The main problem was how to design an adequate system for the even distribution of liquid to each of the tubes. As the product spirals down the wall, the high rotor tip. It also includes concentration factor to accommodate operational. The first three type of evaporators are used in sugar industries and recently also use the plate type evaporator. Fallingfilm evaporator plant for a cane sugar factory. The heat transfer area is the key parameter in designing of an evaporator and many correlations are available to estimate the size of. If the heat flux is more than what is required for phase change, nucleate. Multieffect evaporators are energy efficient and are used to mini mise effect of increasing energy cost. Robert type evaporator design calculation sheet input data to be give in yellow colour cells heating surface m 2. In general evaporation takes place inside vertical tubes, but there are also applications where the process fluid evaporates on the outside of horizontal or vertical tubes.
These are hung in a frame which resembles that of a plate heat exchanger figure 8. To reduce energy consumption, water vapor from an evaporator is entrained and compressed with high pressure steam in a thermocompressor so it can be condensed in the evaporator heat exchanger. Falling film evaporation on a tube bundle with plain and. The falling film evaporators also have many advantages over vertical tubes evaporators such as. Thermal design of cooling and dehumidifying coilschapter is on the description of the methodology should be used in thermal design of the cooling coil either chilled water coil or dxcoil. The internal structure of horizontaltube falling film evaporator is shown in fig. In case of multipleeffect evaporation plants, the exhaust vapors from the product are used to heat the downstreamarranged evaporation effect so that the steam. This bulletin is intended to provide an introduction to the primary types of evaporators which are implemented in various industries today. Rising film evaporator ltv low operating cost low propensity for foaming low liquor viscosity and high flowrate are ideal conditions only used today in wbl preevaporation where foaming is an issue. The key elements of a vertical thin film evaporator are shown here process design, mechanical design and physicalproperty parameters must all be taken into account william b. Sep 19, 2012 calculates the heat transfer area for a singleeffect evaporator that is used to concentrate a salt solution.
Risingfalling film plate this is the original plate type evaporator. Every evaporator design will have a means of transferring heat energy through a heat transfer surface as well as a means to effectively separate the vapors from the residual liquid or. In a falling film evaporator, weak liquor is pumped to the top of the unit and distributed to the tubes where it runs down as a film. The main steps of design following the kern method are summarized as follows. In order to study the heat transfer of the falling film evaporator with phase change on both sides, in this paper we built the mathematical model and the physical model where the liquid film inside the tube is laminar and turbulent. Evaporators visual encyclopedia of chemical engineering. The most of criteria in this table are selected and classifications are made by using the letters in various grades. Smaller size as compared to vertical tubes for same capacity due to high heat transfer coefficient. High energy efficiency due to multipleeffect arrangement or heating by thermal or mechanical vapor recompressor, based upon the. Review of heat transfer coefficient correlations for different evaporator design and operation conditions. Presentation of the concept and operating results abstract in the cane sugar industry, robert evaporators are generally considered the preferred evaporator design because of the issues associated with the scaling of heating surfaces. The evaporator is a special type of heat exchanger. Falling film evaporator gea engineering for a better world.
A falling film evaporator is an industrial device to concentrate solutions, especially with heat sensitive components. Product is introduced above the heated zone and is evenly distributed over the evaporator s inner surface by the rotor. Thermodynamic design of condensers and evaporators. The high performance evaporators are important for process industries such as food, desalination and refineries. Generally 816 lcmhr in a falling film tubular evaporator in the beet industry and for falling film tubular evaporators in the cane industry, a much. These reports have not been replaced by this present report and should still be referred to for additional information. The chosen concept is a vertical plate falling lm evaporator. The model concept for the flow in the thin film evaporator assumes that prior to each rotor blade a. The rotor blades not only deposit the liquid on the wall, but also promote turbulence in the liquid layer. The heated surface will transfer the energy to the falling film and as the film gets slided over the heat transfer area. The lci agitated thin film evaporator also commonly referred to as a wiped film evaporator consists of two major assemblies. Pdf development of falling film heat transfer coefficient. The major difference between a typical shell and tube heat exchanger and a falling film evaporator is the liquid distribution at the top of the unit.
Establishment of the falling film evaporation model and. The thin film evaporation is a heat transfer mechanism controlled by conduction andor convection across the film, with phase change occurring at the film interface. In this article mainly discussed about robert type evaporator body design criteria. The falling film plate evaporators need a similar system, although the wetting rate required is lower. The falling film evaporator is used for liquor concentration. This paper will summarise past work and will attempt to show that fouling in fallingfilm evaporators can be minimised by appropriate attention to design. In the last part of the report the alternatives for the current evaporator will be discussed. Adam donaldson1, anjana thimmaiah2 1dalhousie university, 2national institute of technology karnataka corresponding author. These recommendations are based on current open literature publications and patents. Process modelling and optimization of design parameters in a falling film plate and frame evaporator dr. Iblow heat recovery 10 falling film evaporator vapor steam inlet vapor outlet liquor feed liquor product condensate outlet ncg vent recirculating. Tube thickness mm velocity of inlet vapour msec tube length. On the rear of the condenser, seawater passes through a pipe into the solar collector 1, where the water absorbs sunlight energy, the temperature is further increased to the highest temperature of the design, and then comes to a falling film evaporator via line 8 entrance into the evaporator at the top of the solution distribution tube as. Equipment design in shorttube vertical evaporators, feed enters the evaporator from the bottom.
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