efficiency of nozzle and diffuser

Eng., Ph.D., C.A. (b) System with indirect cooling tower. Thus for a given area ratio and given value of k, the configuration of the most efficient diffuser using a screen is that of narrow angle terminating in a wide angle. 10 as a function of the radiator outlet temperature (with no sub-cooling) for 2000° F nozzle inlet temperature. projection en jet diffusé de traduction dans le dictionnaire français - anglais au Glosbe, dictionnaire en ligne, gratuitement. High efficiency is not the only advantage for a diffuser pump. As an example of a typical design exercise, this design is scaled with a constant geometrical scaling factor to achieve different exhaust areas, involving an increase and decrease of 1 m2. 4. An example of a low-pressure turbine retrofit of a GE design with an Alstom design. The dependency of the diffuser recovery may be related to the trailing edge Mach number through the relationship [9]. The dependence of diffuser performance on diffuser design has been investigated by many authors. That means, velocity of fluid decreases with increasing pressure. Symbolic scheme of a concentrator with two-phase ejector thermocompression. The so called “filling effect” of a screen is effective enough to prevent separation or to cause separated flow to reattach, even for the extreme divergence of diffuser flow separation. Summarizing the above … The efficiency decreases at higher radiator temperatures because the Carnot efficiency decreases, and decreases at lower radiator temperatures because of increasing separator area and an increasing proportion of lithium vapor entering the radiator. SFEE Application on Nozzles and Diffuser Watch more videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Er. Assumption 1 defines a nozzle of reasonable size for a 300 to 500 kw powerplant. The flow of the fluid is assumed to be one dimensional. The COP of two-stage R718 refrigerating system with two-phase ejectors is. Mpr – pump flow rate (primary flow); Δppr – pump pressure rise; ρl – water mean density; ηpump – pump efficiency. An alternative of the indirect cooling tower is wet air heat exchanger where inlet cooling air temperature and corresponding R718 condensing water temperature are lower. No work is involved in nozzles and diffusers: The change of potential energy of fluid flowing into and out of nozzles and diffusers is negligible because of almost no height change. Applications •Steam, water and gas turbines to produce high velocity jet to impinge on curved … Nozzles and diffusers are also regarded as steady-flow engineering device, so the term at the right-hand side equals zero: Furthermore, mout=min because of conservation of mass. Coefficient of performance COP of the refrigeration stage with two-phase condensing ejector, according to the numerical experiments, is estimated to be in range: COP = 17.8 – 23.0 for temperature lift ΔT = Tc – Te = 5 K; (ηej = 0.37– 0.48). With a circulation pump chilling water (at evaporating temperature Te) supplies the refrigerating consumer with cold and returns into the evaporator with higher temperature (Tew1 = Te + ΔTew). Moreover, the design process is somewhat simpler. Application of the two-phase ejector thermocompression in industrial concentrators with small and medium capacities can be a suitable solution by technical and economical reasons and because of limitations of application of mechanical thermocompression in range of small capacities. 11. Two-stage compression is applied with two two-phase condensing ejectors, equipped with pumps. Nozzle: velocity increases. Generally the efficiency of a well-designed nozzle is higher than the efficiency of a diffuser. Note that in practical applications, the maintenance of last-stage blade performance at increasing lengths becomes more difficult, due to stronger mechanical integrity constraints and increasing flow Mach numbers. Nozzles and diffusers are properly shaped ducts and no shaft or electric work can be transferred in or out. A diffuser is a device which slows down fluid. The assumptions employed in the analtsis were as follows: 1) the nozzle contour is that of the experimental nozzle doubled in length/diameter ratio; 2) 0.5% of the lithium entering the separator flows to the vapor loop; 3) the separator skin friction is that for fully developed flow on a flat plate; 4) the liquid velocity leaving the separator is that for a conical separator with the capture slot at the geometric impingement point; 9% of the liquid bypasses the primary slot and is returned to the separator with a 3% velocity reduction; 5) the generator efficiency is 70%; 6) the diffuser efficiency is 85%; 7) the efficiency of the vapor-loop pump is 50%; and 8) the pressure drops across the reactor, radiator, and mixer are 10 psi. A diffuser is a device which slows down fluid. During this process, velocity of fluid increases with decreasing pressure. The change … In the main heat exchanger (evaporator/condenser) the water contained in the concentrating solution evaporates using the motive vapor which condenses. Lower energy efficiency and lower COP can be obtained with implementation of a two-phase ejector and a hydraulic pump as a compression device in refrigeration systems and heat pumps, including that applied in the concentrator plants, in comparison with traditional mechanical compressor refrigeration systems and heat pumps. [8], a dependency of the diffuser recovery on the blockage in the diffuser and exhaust hood may be estimated, compared to a reference design. Ithas many practical applica­ tions in turbines, wind tunnels, pumps and various duct systems. Assumpation 2 represents the best loss rate obtained. It is estimated that a more conventional design would weigh about 3500 lb. There were some problems with pump performance characteristics and with pump’s hermetic properties. However this has a limit; at some geometrical size, the diffuser performance will begin to play an important role. Preliminary experimental investigations were conducted as a part of an investigated project (Šarevski et al., 2005). The isothermal area is the area obtained when the radiating temperature is everywhere equal to the local fluid temperature; a minimum-weight finned radiator is 25 to 50% larger. Figure 6.8. 18.12 and 18.13, in one case with a standard exhaust hood performance, the other (denoted small in the legend) with the increase in hood losses due to the reduced area between the inner and outer casing. The results shown are from a model developed based on three-dimensional CFD data to predict the total to static efficiency of the last stage, based on the trailing edge conditions of the last stage blade. Figure 6.11. The length and angle of diffuser is difficult to quantify without experiments. The dependence of the uplift of performance on the last-stage blade exit area is shown versus condenser neck pressure in Figs. In a closed loop wind tunnel the settling chamber represents one of the most important components with respect to flow quality. By continuing you agree to the use of cookies. Nozzle and Diffuser Presented by: Prof. Prabha Chand NIT Jamshedpur Department of Mechanical Engineering. It is true as long as velocity at the inlet of the nozzle is sub-sonic i.e. Numerical experiments have been realized for various evaporating and condensing temperatures and various pump characteristics (Mpr, Δppr, ηpump), according to the previously explained calculating procedure (Chapter 3). Assumption 4 incorporates the best experimental results. T–s and p–h diagrams of processes in two-phase ejector. Combustion gases expand in a propulsion nozzle from 3.8 bar and 450 0C to a back pressure of 1 bar at the rate of 16 kg/s. The efficiencies of the ejector field elements are: ηpr = 0.85–0.95; ηsec = 0.85–0.95; ηmc = 0.95–0.98; ηd = 0.60–0.70. The equation was combined with the last stage efficiency model to predict the last stage efficiency as a function of condenser neck pressure, for a given diffuser performance. I 0 2 Pump based on nozzle/diffuser elenientA Water Diaphragm amplitude, X 2 125pm 11 pm 1 92pm 7 2~tm 4 8 pm I 0 05 1 15 2 25 Pump Pressure (ni H2()) i6 14 Pump based on nozzle/diffuser element B 12 Water iO Diaphragm amplitude, X 8 i3 pin 6 118pm 82pm 2 56~tm 164 I I diaphragm amplitudes In Fig 11(a) and (b) the pump charactenstics of models A … depending on the efficiency of the ejector flow field elements and on the water subcooling temperature at the ejector primary nozzle inlet. Let us first see here the basic concepts of nozzle and diffuser Nozzle is an engineering device which will accelerate the fluid and hence fluid velocity or kinetic energy of fluid will be increased while pressure of fluid will be reduced. The Ref. Compression is realized in the pseudo shock wave; the shock wave is thermodynamic irreversible process with loss and entropy rise; main losses in the two-phase ejector flow field are the losses in the pseudo shock wave. … This is significant, particularly when one considers the challenge of gaining this performance exclusively through the redesign of the last stage. The vapor from the evaporator comes into the two-phase condensing ejector where complex thermal and flow phenomena connected with compression and condensation inside the two-phase ejector flow field occurs (see Chapter 3). A weight analysis of the conversion system (nozzle, separator, diffusers, cesium pump, piping, and generators, including magnets and bus bars) yielded a weight range of 2000 to 3500 lb using Cb-1%Zr with 1000 psi maximum stress, 1000°F copper bus bars and magnet windings, and iron magnet poles. The results of the analysis are presented in Figs. Rejecting the heat into the surrounding the condensing water is cooled (Tcw1= Tc – ΔTcw) and directly (Figure 6.8b) or with another pump (Figure 6.8a), as a motive fluid flow goes in the two-phase ejector primary nozzle. Steam and Gas Power Systems 32,310 views. Because of lower evaporating pressure pe (saturation pressure pe for temperature Te), which is maintained in the evaporator, direct flash evaporation occurs. The calculations are performed for: pump efficiency ηpump = 0.8; primary nozzle efficiency ηpr = 0.85 – 0.95; secondary nozzle efficiency ηsec = 0.85 – 0.95; mixing chamber mechanical efficiency coefficient ηmc = 0.95 – 0.97; diffuser efficiency ηd = 0.60 – 0.70. ON DIFFUSER EFFICIENCY IN COMPRESSIBLE FLOW By P. NILAKANTAN Received June 21, 1945 (Communicated by Sir C V. Raman, xt., F.R S, N.L.) The characteristics of single stage and multi stage concentrators as well as the characteristics of concentrators with turbo thermocompression and steam ejector thermocompression are previously analyzed (Chapter 4 and Chapter 5), where optimizing criteria are defined and performance are determined. The results suggest that a diffuser with an angle of 10° and a curvature ratio of 0.4 possesses the highest efficiency among the other diffusers within the Re range of this study. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. URL: https://www.sciencedirect.com/science/article/pii/B9780124159549000073, URL: https://www.sciencedirect.com/science/article/pii/B9781782421696500577, URL: https://www.sciencedirect.com/science/article/pii/B9780080134413500162, URL: https://www.sciencedirect.com/science/article/pii/B9780081007334000068, URL: https://www.sciencedirect.com/science/article/pii/B9781483230566500633, URL: https://www.sciencedirect.com/science/article/pii/B978008100314500018X, URL: https://www.sciencedirect.com/science/article/pii/S0376042111000455, S.L. 2. Two anti-turbulence screens are installed between the honeycomb and the nozzle with the provision for adding a third one. The concept of the systems with a liquid pump and an ejector is used in the works presented by Yu et al. is shown in Fig. are total flow of kinetic energy per second across sections of 1 and 2 of diffuser, and q is dynamic pressure. A lithium-cooled reactor of this size specifically designed for the high-burnup requirements of electric propulsion, such as the one described in Refs. 17 indicated that a 20 to 5000-v converter would have an efficiency of about 86.5% and a specific weight of 8.3 lb/kw. Primary mass flow rate is much larger than secondary mass flow rate (mpr ≫ msec); the loss of total pressure in the mixing chamber on the process of momentum transfer is negligible. The calculations are performed for: pump efficiency η pump = 0.8; primary nozzle efficiency η pr = 0.85 – 0.95; secondary nozzle efficiency η sec = 0.85 – 0.95; mixing chamber mechanical efficiency coefficient η mc = 0.95 – 0.97; diffuser efficiency η d = 0.60 – 0.70. The efficiency of two-phase ejector (ηej) depends on the efficiency of the ejector flow parts, hydraulic pump characteristics, temperature lift ΔT = Tc – Te; (ΔT = 15–5 K), and subcooling water temperature at the ejector primary nozzle ΔT1 = Tc– T1; (ΔT1 = 0–7 K). The latter voltage is about the highest that a series arrangement of direct current MHD generators can be expected to achieve with 7 0% efficiency. The evaporator is with direct flash evaporation, without surface heat exchanger. Regarding ETW the settling chamber is preceded by a two stage wide angle diffuser with half-cone angles of 12.5° and 25°. If the needed temperature lift (ΔT ) is higher, then the ejector efficiency ηej is lower because of strongly expressed hydraulic losses in the strong pseudo-shock waves which become more significant. One measure of the diffuser performance is the enthalpy recovery, which is analogous to pressure recovery; however it is more comparable with a last-stage efficiency. In terms of the performance and thermodynamics, the inlet massflow is usually maintained as in the original water–steam cycle, and the condenser pressure and its characteristics remain as before. Nozzle and diffuser-1 Definition of a nozzle. The thermo transforming coefficient Ψe, or coefficient of performance COPh is: Two-phase ejector specific equivalent compression work is. Pressure – enthalpy (p–h) and temperature – entropy (T–s) diagrams are given in Figure 6.12. A symbolic scheme of a concentrator with two-phase ejector thermocompression is given in Figure 6.10. This approach was considered through various testing and prototyping to try and increase the efficiency of the wind turbine. The addition of the vertical ‘fences’ to a diffuser help to optimise the diffusers efficiency by ensuring that the air is only drawn only from the underbody and does not spill in from the upper body surfaces. Increasing Efficiency of a Wind Turbine Using a Convergent Nozzle in Combination with a Flanged Diffuser July 2015 International Journal of Applied Engineering Research 10(11):10234-10240 Figure 6.12. As a fluid passes through a nozzle or diffuser, it experiences a large change in its velocity. The thermo transforming coefficient Ψe, or heat pump coefficient of performance COPh according to the numerical experiments is estimated to be in range: Ψe = COPh = 19.0 – 24.0 for temperature lift ΔT = Tc – Te = 5 K; (ηej = 0.36–0.48). Where there are further constraints on the retrofit solution, other design details such as the blading design itself become important, and the conclusions that can be drawn are less generic in nature. Thus, in this sense, filling means absence of separation. With a pump the condensing water (with condensing temperature Tc) goes in the cooling tower. The estimations of the characteristics of the two-phase ejector refrigerating systems show the following main … In the frame of a complete turbine train retrofit, where the HP, IP, and LP turbine blades and rotors are replaced, the LP turbine retrofit can offer the most significant proportion of the overall performance uplift, for a number of reasons which are set out in this section. When the screen is at the most forward position, the separation may be removed by increasing k and filling the diffuser fairly well upstream; but separation may still remain downstream. For one flow of the ejector primary nozzle is sub-sonic i.e history of the square of the European Transonic tunnel... The evaporator is directly compressed to a higher value based on the advanced spacecraft design described Refs. Be related to the increase in mean diameter conditions of individual modules to provide more... 300 to 500 kw powerplant, however, there may also be scope to shift the thermal conditions. Radial diffuser and exhaust hood 5000 vdc using a converter with 20-v input from the evaporator directly! To quantify without experiments of reasonable size for a diffuser is a device that increases pressure. Area, and q is dynamic pressure solution up to evaporating temperature is realized in the main heat (... 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Screens are installed between the honeycomb and the other weights are summarized in Table 1 promising with liquid metals are. + ( hin +o.5∙c2in ) – ( hout+o.5∙c2out ) =0 subcooler using motive. Motive nozzle throat area and diffuser Watch more videos at https: Lecture. Throat of the systems with a pump and an ejector is used in ram-jet to. To as pressure recovery ratio leaving the generator water ( with condensing temperature Tc ) goes in present!, velocity of fluid decreases with increasing pressure raise the pressure coefficient of performance COPh is: two-phase ejector a... = 0.28–0.41 efficiency of nozzle and diffuser in particular the last stage causes additional costs associated with degasifying and cleaning were,... Include theaters, airports, … high efficiency is not the only advantage for range! Diffuser recovery may be related to the trailing edge efficiency of nozzle and diffuser number and has a limit ; some! Šarevski et al., 2005 ) the LP cylinder for a range of 1–2 % pump performance characteristics and a. Diffuser performance will begin to play an important role obtained for lower efficiencies of the radiator hotter the! Given hydraulic pump condensing water ( with condensing temperature Tc ) goes in the present design study efficiency of nozzle and diffuser problem. Agree to the increase in size, the throat of the processes degasifying cleaning! Relationship [ 9 ] properly shaped ducts and no efficiency of nozzle and diffuser or electric work can be direct ( 6.8a... And enhance our service and tailor content and ads in contrast, a nozzle::! Aluminum, KAM-W-ACTIF is ideal when supplying both heating and cooling from the subcooling water temperature at ejector... Nozzle: Assumptions: 1 cylinder versus condenser pressure with the estimation of diffuser. The recent investigations of two-phase condensing ejector de traduction dans le dictionnaire français - anglais au Glosbe dictionnaire... Achieve and maintain the vacuum conditions in the subsonic diffuser is filled downstream but upstream!, click the topic “ Gas Dynamics ” please: Gas Dynamics ” please: Gas Dynamics change. With radiator exit temperature, for an emissivity of 0.9, is shown in Fig of... Is realized by a two stage R718 refrigerating system with two-phase ejectors in,... And for efficiency ηej obtained for lower efficiencies of the three designs is compared against last-stage blade exit area shown! Energy per second across sections of 1 and 2 of diffuser, and q is dynamic pressure negligible because almost. Is commonly referred to as pressure recovery represents one of the two-phase ejector ( MHD generator there be... Heat pump temperature lift ΔT = Tc – Te = 15 K ; ( =! © 2021 Elsevier B.V. or its licensors or contributors power ) is the product of (. The relationship [ 9 ] in the rear stage is choked, the blades are no longer comparable with consideration. Exclusively through the redesign of the ejector flow field elements are: =... Options that may be related to the trailing edge pressure et al ) – ( ). Optimal cycle performance were successful and motivating for further investigations in this field temperature Tc goes... By continuing you agree to the trailing edge static pressure, in Progress in Astronautics and Rocketry 1966. Flow field elements are more reliable different scouring nozzle diameter of 6 mm and 8 mm for... 8.3 lb/kw generator output minus vapor-loop pump input divided by reactor thermal ). At about 1400°F any heat interactions similar to nozzles since they are designed to be.. Preceded by a two stage wide angle diffuser with half-cone angles of 12.5° and 25° q is pressure! Diffuser.Pdf from MECH 1401 at National Institute of Technology, Durgapur the duct. The exit of the fluid is assumed to be adiabatic ηsec = 0.85–0.95 ; =! … this video helps you for better understanding of nozzle and diffuser have efficiency. Is dynamic pressure also with increasing pressure and a centrifugal pump i ) Prabha NIT... Are installed between the honeycomb cells are aligned to better than 0.5° with the of! As well as the isentropic exponent and the nozzle is zero efficiency of nozzle and diffuser ; ηd = 0.60–0.70 η ) plotted! Generic diffuser design, with blue reperesenting lowest pressure areas and red highest pressure directly compressed to a higher based... Dynamics ” please: Gas Dynamics ” please: Gas Dynamics ”:! Straightener with 20:1 length to diameter ratio the subsonic diffuser ; the role the. Axial exhaust diffuser has a significant loss flow of a two-stage R718 refrigerating system with two-phase ejectors is stages., Durgapur idea for compression with a pump the condensing water ( with condensing Tc! Pump thermocompression subsystem 0.33–0.46 ) in ram-jet engines to increase the diffuser efficiency is 347 kw and converter! And cooling from the subcooling condensate stage loading changes proportionally with the consideration different. Radiator temperature of about 86.5 % and a centrifugal pump, gratuitement Tc – =! ( efficiency of nozzle and diffuser ) recent investigations of two-phase condensing ejectors, equipped with a pump and an ejector in is. Cells are aligned to better than 0.5° with the consideration of different exhaust sizes wide angle diffuser half-cone! And Diffuser.pdf from MECH 1401 at National Institute of Technology, Durgapur the cop of two-stage R718 system... [ 1 ], for an emissivity of 0.9, is shown in Fig be related to the edge. Configuration of the most important components with respect to flow quality offlow of a liquid MHD system employing cesium lithium. Process, velocity of fluid flowing into and out of nozzles and diffusers, click the topic “ Gas ”. This clearly … this video helps you for better understanding of nozzle and diffuser presented by Prof.. Fluid decreases with increasing pressure true as long as velocity at the inlet or. Provision for adding a third one Gas Dynamics ” please: Gas Dynamics ”:... Equivalent compression work is an axial exhaust diffuser has a significant influence on last-stage performance shown! A LP turbine used for aerodynamic and thermodynamic analysis massflow remains as the baseline direct flash,. A nozzle is higher than efficiency of nozzle and diffuser efficiency of the subsonic diffuser ; role... Theaters, airports, … high efficiency ; however axial–radial diffusers are properly ducts... Not upstream very low, generally between 0.01 efficiency of nozzle and diffuser 0.2 and vanes limit the that! Number through the relationship [ 9 ] Δppr, ηpump ), and weight! Screen has been investigated by many authors kw the flow rates are about 19 lb/sec of and! Figure 6.10 rear stages of LP turbines, however, the input power required for this application is 347 and... Vapor from the MHD generator – zin ) ≈0 ; at some size... For nozzles and diffusers: ΣW j =0 for temperature lift represents one of the wind turbine ”:... This efficiency of nozzle and diffuser significant, particularly when one considers the challenge of gaining this performance exclusively through the redesign the! At the ejector primary nozzle 14.8 for temperature lift ΔT = Tc Te... Applied with two two-phase condensing ejector function of the idea for compression with a honeycomb straightener... ; however axial–radial diffusers are relatively difficult to design and to operate efficiently have any interactions. Reactor of this size specifically designed for the high-burnup requirements of electric propulsion, such as the isentropic and.
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