Steam Jet Refrigeration Cycle

Synthetic Engineering and Processing 41 (2002) 551†561 www. elsevier. com/find/cep Evaluation of steam stream ejectors Hisham El-Dessouky *, Hisham Ettouney, Imad Alatiqi, Ghada Al-Nuwaibit Department of Chemical Engineering, College of Engineering and Petroleum, Kuwait Uni6ersity, P. O. Box 5969, Safat 13060, Kuwait Received 4 April 2001; got in overhauled structure 26 September 2001; acknowledged 27 September 2001 Abstract Steam fly ejectors are a fundamental part in refrigeration and cooling, desalination, oil re? ning, petrochemical and compound industries.The ejectors structure a vital piece of refining sections, condensers and other warmth trade forms. In this examination, semi-experimental models are created for plan and rating of steam fly ejectors. The model gives the entrainment proportion as an element of the development proportion and the weights of the entrained fume, thought process steam and packed fume. Additionally, connections are created for the rationale stea m pressure at the spout exit as a component of the evaporator and condenser pressures and the region proportions as an element of the entrainment proportion and the stream pressures. This takes into account full plan of the ejector, where de? ing the ejector load and the weights of the thought process steam, evaporator and condenser gives the entrainment proportion, the intention steam pressure at the spout outlet and the cross segment zones of the diffuser and the spout. The created connections depend on huge database that incorporates maker structure information and trial information. The model incorporates connections for the stifled ? ow with pressure proportions over 1. 8. Moreover, a relationship is accommodated the non-stifled ? ow with pressure proportions underneath 1. 8. The estimations of the coef? cient of assurance (R 2) are 0. 85 and 0. 78 for the stifled and non-gagged ? w connections, individually. With respect to the connections for the thought process steam pressur e at the spout outlet and the region proportions, all have R 2 qualities over 0. 99.  © 2002 Elsevier Science B. V. All rights saved. Catchphrases: Steam fly ejectors; Choked ? ow; Heat siphons; Thermal fume pressure 1. Presentation Currently, the vast majority of the ordinary cooling and refrigeration frameworks depend on mechanical fume pressure (MVC). These cycles are controlled by a top notch type of vitality, electrical vitality. The inef? cient utilization of the vitality required to work such a procedure can be produced by the burning of fossil uels and hence adds to an expansion in ozone harming substances and the age of air toxins, for example, NOx, SOx, particulates and ozone. These toxins effectsly affect human wellbeing and the earth. Furthermore, MVC refrigeration and cooling cycles utilize unpleasant chloro-? oro-carbon mixes (CFCs), which, upon discharge, adds to the demolition of the defensive ozone layer in the upper environment. * Corresponding creator. Tel. : + 965-4811188ãâ€"5613; fax: + 9654839498. E - mail address: [emailâ protected] kuniv. edu. kw (H. El-Dessouky). Ecological contemplations and the requirement for ef? cient se of accessible vitality require the improvement of procedures dependent on the utilization of poor quality warmth. These procedures receive entrainment and pressure of low weight fume to higher weights reasonable for various frameworks. The pressure procedure happens in retention, adsorption, substance or stream ejector fume pressure cycles. Stream ejectors have the most straightforward con? guration among different fume pressure cycles. As opposed to different procedures, ejectors are framed of a solitary unit associated with tubing of thought process, entrained and blend streams. Likewise, ejectors do exclude valves, rotors or other moving parts and are accessible ommercially in different sizes and for various applications. Fly ejectors have lower capital and upkeep cost than the other con? gurations. Then aga in, the principle disadvantages of fly ejectors incorporate the accompanying: ? Ejectors are intended to work at a solitary ideal point. Deviation from this ideal outcomes in sensational weakening of the ejector execution. 0255-2701/02/$ †see front issue  © 2002 Elsevier Science B. V. All rights saved. PII: S 0 2 5 †2 7 0 1 ( 0 1 ) 0 1 7 6 †3 552 ? H. El - Dessouky et al. /Chemical Engineering and Processing 41 (2002) 551 †561 Ejectors have low warm ef? iency. Uses of fly ejectors incorporate refrigeration, cooling, expulsion of non-condensable gases, transport of solids and gas recuperation. The capacity of the stream ejector varies significantly in these procedures. For instance, in refrigeration and cooling cycles, the ejector packs the entrained fume to higher weight, which takes into account buildup at a higher temperature. Additionally, the ejector entrainment process continues the low weight on the evaporator side, which permits vanishing at low temperat ure. Accordingly, the cold evaporator ? uid can be utilized for refrigeration and cooling functions.As for the expulsion of non-condensable gases in heat move units, the ejector entrainment process forestalls their gathering inside condensers or evaporators. The nearness of non-condensable gases in heat trade units diminishes the warmth move ef? ciency and expands the buildup temperature on account of their low warm conductivity. Additionally, the nearness of these gases improves consumption responses. Be that as it may, the ejector cycle for cooling and refrigeration has lower ef? ciency than the MVC units, however their benefits are showed upon the utilization of poor quality vitality that has restricted impact on nature and lower ooling and warming unit cost. Despite the fact that the development and activity standards of stream ejectors are notable, the accompanying segments give a concise synopsis of the significant highlights of ejectors. This is important so as to follow the conversation and investigation that follow. The traditional steam fly ejector has three primary parts: (1) the spout; (2) the pull chamber; and (3) the diffuser (Fig. 1). The spout and the diffuser have the geometry of uniting/wandering venturi. The distances across and lengths of different parts shaping the spout, the diffuser and the attractions chamber, along with the stream ? ow rate and properties, de? e the ejector limit and execution. The ejector limit is de? ned as far as the ? ow paces of the thought process steam and the entrained fume. The whole of the thought process and entrained fume mass ? ow rates gives the mass ? ow pace of the compacted fume. With respect to the ejector execution, it is de? ned as far as entrainment, extension and pressure proportions. The entrainment proportion (w ) is the ? ow pace of the entrained fume Fig. 1. Variety in stream weight and speed as a component of area along the ejector. H. El - Dessouky et al. /Chemical Engineering and Processing 41 (2002) 551 †561 isolated by the stream pace of the intention steam.As for the development proportion (Er), it is de? ned as the proportion of the thought process steam strain to the entrained fume pressure. The pressure proportion (Cr) gives the weight proportion of the packed fume to the entrained fume. Varieties in the stream speed and weight as a component of area inside the ejector, which are appeared in Fig. 1, are clarified underneath: ? The thought process steam enters the ejector at point (p ) with a subsonic speed. ? As the stream ? ows in the combining some portion of the ejector, its weight is decreased and its speed increments. The stream arrives at sonic speed at the spout throat, where its Mach number is equivalent to one. The expansion in the cross segment zone in the separating some portion of the spout brings about an abatement of the stun wave pressure and an increment in its speed to supersonic conditions. ? At the spout outlet plane, point (2), the ratio nale steam pressure becomes lower than the entrained fume weight and its speed extends somewhere in the range of 900 and 1200 m/s. ? The entrained fume at point (e ) enters the ejector, where its speed increments and its weight diminishes to that of point (3). ? The thought process steam and entrained fume streams may blend inside the attractions chamber and the combining area of the diffuser or it might ? ow as two separate treams as it enters the steady cross segment region of the diffuser, where blending happens. ? In either case, the blend experiences a stun inside the steady cross segment territory of the diffuser. The stun is related with an expansion in the blend weight and decrease of the blend speed to subsonic conditions, point (4). The stun happens in view of the back weight obstruction of the condenser. ? As the subsonic blend rises up out of the steady cross segment zone of the diffuser, further weight increment happens in the wandering segment of the diffuser, where pa rt of the active vitality of the blend is changed over into pressure.The weight of the developing ? uid is marginally higher than the condenser pressure, point (c ). Synopsis for various writing concentrates on ejector structure and execution assessment is appeared in Table 1. The accompanying blueprints the principle ? ndings of these investigations: ? Ideal ejector activity happens at the basic condition. The condenser pressure controls the area of the stun wave, where an expansion in the condenser pressure over the basic point brings about a quick decrease of the ejector entrainment proportion, since the stun wave moves towards the spout exit.Operating at pressures beneath the basic focuses has immaterial impact on the ejector entrainment proportion. 553 ? At the basic condition, the ejector entrainment proportion increments at lower pressure for the evaporator and condenser. Likewise, higher temperature for the evaporator expands the entrainment proportion. ? Utilization of a va riable position spout can keep up the ideal conditions for ejector activity. Subsequently, the ejector can be kept up at basic conditions regardless of whether the working conditions are changed. ? Multi-ejector framework expands the working extent and improves