Thermal design heat exchanger pdf

The shell side fluid is constant thermal properties drop occurs high mark and total pressure drop is 0. The fluid flow and heat transfer processes are bar in Figure 3. Hence, it is observed that three baffle gives better pressure drop compare with other baffle over allowable pressure drop for oil cooler for Locomotive. So, number of baffles 3 is good for theoretical and simulation. Above the calculation result table, determined shell Figure 5. In Figure 4, the flow is obseved to be well developed.

The cross flow throughout the shell Table 3. Verification with Existing Data volume and the recirculation zone appears little. So, Result Industrial Calculated Data the pressure drop is effectively average shown in Data Figure 5, the simulation result is gained the pressure Shell diameter, 0. Sekulic, Fundamentals results have been compared with number of baffle. In of Heat Exchanger Design. Wiley New York. Thom, , "Wolverine.

Design pressure drop for www. Hesseini, A. Hesseini-Ghaffar, M. Soltani, drop. The bigger the nozzle diameter, the less transfer coefficient and pressure drop for an oil pressure drop becomes. The less pressure drop, the cooler shell and tube heat exchanger with three better the efficient it gets. E-Fawal, A. Fahmy and B. Delaware method for shell side design. Heat exchanger: thermal- hydraulic fundamentals and design.

New York: Hemisphere; Shell side water flow pressure drop distribution measurements in an industrial-sized test heat exchanger Eng ; Pressure drop on the shell side of the shell side of shell and tube heat exchangers with segmental baffles. Chem Eng Process ; End-of-chapter problems enable students to test their assimilation of the material.

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Time duration of each load rate 3. Load factor 4. Nature of the load constant or fluctuating The load factor is the actual energy produced by a power plant during a given period, given as a percentage share of the maximum energy that could have been produced at full capacity during the same period. The design will determine the boiler's ability to carry a normal load at a high efficiency as well as to meet maximum demand and rapid load changes.

It will also determine the standby losses and the rapidity with which the unit can be brought up to full steaming capacity. In smaller boiler sizes it is possible to select a standardized unit that will meet the requirements; larger units are almost always custom designed. Fuel type effect on furnace size The most important item to consider when designing a utility or large industrial steam generator is the fuel the unit will burn.

The furnace size, the equipment to prepare and burn the fuel, the amount of heating surface and its placement, the type and size of heat recovery equipment, and the flue gas treatment devices are all fuel dependent.

The major differences among boilers that burn coal or oil or natural gas result from the ash in the products of combustion. Natural gas produces no ash. For the same power output, due to the high ash content of coal, coal-burning boilers must have larger furnaces and velocities of the combustion gases in the convection-based heat exchangers must be lower. Figure 9 presents an example of the relative sizes of furnaces using three different fuels: natural gas, oil and coal.

The power of the boiler is the same in all three cases. Typical furnace outlet temperatures Furnace outlet temperature is the flue gas temperature after the radiation-based heat transfer surfaces before entering the convection-based heat transfer surfaces. The outlet temperature depends on the characteristics of the combusted fuel. If the temperature is too high, ash layers build up on the surface of the superheater tubes.

This leads to poorer heat transfer, increased corrosion and it can even block flow paths. It is necessary to provide air in excess of this quantity to assure complete combustion. The amount of this excess air is determined by the following factors: 1.

Composition, properties, and condition of fuel when fired 2. Method of burning the combustible 3. Arrangement and proportions of the grate or furnace 4. Allowable furnace temperature 5.

Turbulence and thoroughness of the mixing of combustion air and volatile gases Excess air reduces efficiency by lowering the furnace temperature and by absorbing heat that would otherwise be available for steam production. NOx can be reduced decreasing temperature, decreasing air excess, or using low-nox-burners. In using low-nox-burner air will be fed into flame in two or three phases. CFB furnace design When dimensioning a circulating fluidized bed CFB furnace the high content of sand has to be taken into consideration.

This means that the temperature profile and thus the heat transfer near to the furnace wall differs from other types of furnaces. The furnace of a CFB circulating fluidized bed boiler contains a layer of granular solids, which have a diameter in the range of 0,,3 mm.

It includes sand or gravel, fresh or spent limestone and ash. The solids move through the furnace at much lower velocity than the gas; solids residence times in the order of minutes are obtained.

The long residence times coupled with the small particle size produce high combustion efficiency and high SO2 removal with much lower limestone feed than in conventional furnaces. Figure 10 shows a flow chart of a typical CFB boiler. After the furnace flue gas moves through a cyclone named compact separator in figure 13 , where solids are separated from the gas and are returned to the furnace.

Flue gas from the cyclone discharge enters the convection back-pass in which the superheaters, reheaters, economizers and air preheaters are located. A dust collector is separates the fly ash before the flue gas exits the plant. The amount of cyclones also has an influence on the shape of furnace. Circulating fluidized bed boilers have a number of unique features that make them more attractive than other solid fuel fired boilers.

Fuel flexibility is one of the major attractive features of CFB boilers. A wide range of fuels can be burned in one specific boiler without any major change in the hardware. The combustion efficiency of a CFB boiler is high. Sulphur capture in a CFB is very efficient, due to the possibility to inject sulphur absorbing limestone directly into the bed.

The low emission of nitrogen oxides is also a major attractive feature of CFB boilers. Sand is often used to improve bed stability, together with limestone for SO2 absorption. As the coal particles are combusted and become smaller, they are elutriated with the gases, and subsequently removed as fly ash. In-bed tubes are used to control the bed temperature and generate steam. The flue gases are normally cleaned using a cyclone, and then pass through further heat exchangers, raising steam temperature.

Fuel is fed onto the bed mechanically. Moist fuel will dry T. Rintala] fast, when it is fed to the sand bed. Many different kinds of fuels can be combusted in a BFB furnace. Air is fed in several phases. BFB furnaces with an atmospheric operational pressure are mainly used for boilers up to about 25 MWe, although there are a few larger plants where a BFB boiler has been used to retrofit an existing unit.

The HRSG consists of the same heat transfer surfaces as other boilers, except for the furnace. However, a HRSG can be equipped with a supplementary burner as can be seen in figure 12 for raising the flue gas temperature. A HRSG can have a horizontal or vertical layout, depending on the available space. To maximize the steam power of the boiler, the pinch-point must be chosen as small as possible. The approach temperature is the temperature difference of the input temperature Evaporator in the evaporator and the output of the economizer.

The pressure drop usually mbar of the flue gas side has also an effect on the efficiency of power Superheater plant.