The best pump efficiency (ηopt) is the highest efficiency for the rotational speed and fluid handled as … Diffusers are used in centrifugal compressor. The 1 st law of thermodynamics: No work is involved in nozzles and diffusers: ΣW j =0. Since the differently sized stages have a similar total to static efficiency characteristic with flow coefficient, the larger the last stage blade exit area, the higher the volume flow or lower the back pressure where peak performance is achieved. It is true as long as velocity at the inlet of the nozzle is sub-sonic i.e. The redesign could proceed in two ways—either the non-dimensional stage loading is allowed to change with the change in stage mean diameter, or the stage is redesigned to achieve the same stage loading. 18 and 19 would weigh about 1500 lb. In a closed loop wind tunnel the settling chamber represents one of the most important components with respect to flow quality. 10 as a function of the radiator outlet temperature (with no sub-cooling) for 2000° F nozzle inlet temperature. Additional compression is realized in the subsonic diffuser; the role of the subsonic diffuser is negligible. In the main heat exchanger (evaporator/condenser) the water contained in the concentrating solution evaporates using the motive vapor which condenses. 18.11. The fluid experiences small or no change in its elevation as it flows through the nozzle or diffuser. Ψe = COPh = 11.5 – 14.8 for temperature lift ΔT = Tc – Te = 8 K; (ηej = 0.33–0.46). Filling means the flow passage taking place throughout all the available volume in the diffuser, either because of diffuser design or because of the effect of a screen. Lecture 18: Nozzles and Diffusers- Efficiency and Critical Pressure - Duration: 24:18. The Ref. An intercooler – economizer is installed between the stages. With these component weights, the total unshielded powerplant weight would lie between 8300 lb (28 lb/kw) and 13, 400 lb (45 lb/kw). So now we obtain a simplified expression for nozzles and diffusers: q + (hin +o.5∙c2in) – (hout+o.5∙c2out) =0. Total efficiency of the two phase ejector (ηej), defined as a ratio between isentropic compression power from the evaporating pressure (point 3, Figure 6.8) to the condensing pressure (point 9s) and pump power consumption, is obtained to be in the range ηej = 0.28 – 0.48, according to the results of numerical experiments and previously explained calculating procedure. (2006, 2007). Moreover, the design process is somewhat simpler. That causes additional costs associated with degasifying and cleaning. The lower values for COPh and for efficiency ηej obtained for lower efficiencies of two-phase ejector flow field elements are more reliable. Usually, the energy leaving the last stage for HP and IP turbines is relatively low, due to the low stage pressure ratios and velocities. It has been estimated that a 10% increase in the enthalpy-based diffuser efficiency corresponds to a 1% increase in rear stage efficiency [7]. Under the stated assumptions, the cycle efficiency reaches a maximum of 5.7% at a radiator temperature of about 1270°F. The dependency of the diffuser recovery may be related to the trailing edge Mach number through the relationship [9]. John Green, Jürgen Quest, in Progress in Aerospace Sciences, 2011. The compression is realized by a two-phase ejector using pressurized water with a hydraulic pump. There were some problems with pump performance characteristics and with pump’s hermetic properties. The performance of the LP cylinder versus condenser pressure with the consideration of different exhaust sizes. 20 was 1.35 lb/ft2, giving a weight of 2300 lb here. Estimated unshielded weight of a 300 kw liquid MHD powerplant. These temperature differences ΔT, ΔTe, and ΔTr have an important influence on the pump power consumption as a motive power for two-phase ejector thermocompression, as well as on the optimization of the main heat exchanger (evaporator/condenser) surface. A diffuser is a device which slows down fluid. Eng., Ph.D., C.A. 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. 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 … le1 and le2 are two-phase ejector specific equivalent compression work for the first and the second compression stages and k is coefficient of flow rate k ≈ (qe + le1)/qe. COP = 7.0 – 9.6 for temperature lift ΔT = Tc – Te = 11 K; (ηej = 0.32– 0.44). Both exercises were undertaken; however, due to the significant redesign required to maintain the stage loading and the subsequent loss of comparability, it was decided to allow the nondimensional stage loading to change and not redesign the stage. A lithium-cooled reactor of this size specifically designed for the high-burnup requirements of electric propulsion, such as the one described in Refs. The estimations of the characteristics of the two-phase ejector refrigerating systems show the following main features: Flow at the outlet of the primary nozzle is supersonic; the nozzle profile is convergent-divergent. Scheme of a two-stage R718 refrigerating system with two-phase ejectors. In the present study, the modeling of the last-stage performance was extended to include the performance of the radial diffuser and exhaust hood. It is more typical that the original design has an area that leads to an operating exit Mach number that is above the optimum; here the performance will benefit from an increase in last-stage blade exit area. Estimated efficiency of cesium-lithium cycle. It has been estimated that a 10% increase in the enthalpy-based, A short history of the European Transonic Wind Tunnel ETW. 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. It is provided with the two so-called filling screens, to assure a maximum filling of the settling chamber by avoiding flow separation during this rapid expansion process. Pressure – enthalpy (p–h) and temperature – entropy (T–s) diagrams are given in Figure 6.12. Its main objective is to minimise any time- and spacewise unsteadiness of the incoming flow and to maximise the homogeneity of the 3-dimensional outgoing flow [58,59]. Ithas many practical applica­ tions in turbines, wind tunnels, pumps and various duct systems. The larger the rear stage, the less space there is between the inner and outer casings (where the outer casing is fixed), and the more the performance of the combined exhaust hood diffuser is penalized. For the gases take I. McBean, in Advances in Steam Turbines for Modern Power Plants, 2017. Also, application of the two-phase ejector thermocompression in small concentrators can be favorable in comparison with steam ejector thermocompression because of additional expenses and complex plant for steam production and higher COPs. Development history of the idea for compression with a pump and an ejector in refrigeration is given by Elbel (2011). The length and angle of diffuser is difficult to quantify without experiments. General-Flow Analysis of a Nozzle: Assumptions: 1. 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. Pump flow rate (Primary flow) is Mpr; Pump pressure rise is Δppr; Water mean density is ρl; Pump efficiencyηpump; Concentrator capacity – mass flow of evaporating water (Secondary flow) is Msec. 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