Steam Jet Refrigeration Cycle

Compound 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 reexamined structure 26 September 2001; acknowledged 27 September 2001 Abstract Steam stream ejectors are a basic part in refrigeration and cooling, desalination, oil re? ning, petrochemical and concoction industries.The ejectors structure an essential piece of refining sections, condensers and other warmth trade forms. In this investigation, semi-experimental models are produced 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 intentio n steam pressure at the spout exit as an element of the evaporator and condenser pressures and the zone proportions as a component of the entrainment proportion and the stream pressures. This takes into consideration full structure 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 territories of the diffuser and the spout. The created relationships depend on huge database that incorporates maker structure information and test information. The model incorporates connections for the gagged ? ow with pressure proportions over 1. 8. Also, a connection 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, separately. Concerning the relationships for the intention steam pre ssure at the spout outlet and the zone proportions, all have R 2 qualities over 0. 99.  © 2002 Elsevier Science B. V. All rights held. Catchphrases: Steam stream ejectors; Choked ? ow; Heat siphons; Thermal fume pressure 1. Presentation Currently, a large portion of the customary 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 created by the burning of fossil uels and in this manner adds to an expansion in ozone depleting substances and the age of air toxins, for example, NOx, SOx, particulates and ozone. These toxins effectsly affect human wellbeing and nature. What's more, MVC refrigeration and cooling cycles utilize antagonistic chloro-? oro-carbon mixes (CFCs), which, upon discharge, adds to the pulverization of the defensive ozone layer in the upper air. * Corresponding creator. Te l. : + 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 second rate heat. These procedures receive entrainment and pressure of low weight fume to higher weights appropriate for various frameworks. The pressure procedure happens in retention, adsorption, concoction or fly ejector fume pressure cycles. Stream ejectors have the least difficult con? guration among different fume pressure cycles. As opposed to different procedures, ejectors are shaped of a solitary unit associated with tubing of thought process, entrained and blend streams. Additionally, ejectors do exclude valves, rotors or other moving parts and are accessible ommercially in different sizes and for various applications. Stream ejectors have lower capital and upkeep cost than the other con? gurations. The n again, the primary disadvantages of stream ejectors incorporate the accompanying: ? Ejectors are intended to work at a solitary ideal point. Deviation from this ideal outcomes in emotional 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 extremely low warm ef? iency. Utilizations of fly ejectors incorporate refrigeration, cooling, evacuation of non-condensable gases, transport of solids and gas recuperation. The capacity of the stream ejector contrasts 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 temperature. Thus, the cold evaporator ? uid can be utilized for refrigeration and cooling functions.As for the evacuation of non-condensable gases in heat move units, the ejector entrainment process forestalls their amassing inside condensers or evaporators. The nearness of non-condensable gases in heat trade units lessens the warmth move ef? ciency and expands the buildup temperature as a result of their low warm conductivity. Additionally, the nearness of these gases upgrades erosion responses. Nonetheless, the ejector cycle for cooling and refrigeration has lower ef? ciency than the MVC units, yet their benefits are showed upon the utilization of poor quality vitality that has restricted impact on the earth and lower ooling and warming unit cost. In spite of the fact that the development and activity standards of stream ejectors are notable, the accompanying segments give a concise rundown of the significant highlights of ejectors. This is important so as to fo llow the conversation and investigation that follow. The regular steam stream ejector has three primary parts: (1) the spout; (2) the attractions chamber; and (3) the diffuser (Fig. 1). The spout and the diffuser have the geometry of joining/wandering venturi. The widths and lengths of different parts shaping the spout, the diffuser and the pull 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 total of the rationale and entrained fume mass ? ow rates gives the mass ? ow pace of the packed fume. With respect to the ejector execution, it is de? ned regarding 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 an element of area along the ejector. H. El - Dessouky et al. /Chemical Engineering and Processing 41 (2002) 5 51 †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 intention steam strain to the entrained fume pressure. The pressure proportion (Cr) gives the weight proportion of the compacted 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 rationale steam enters the ejector at point (p ) with a subsonic speed. ? As the stream ? ows in the joining some portion of the ejector, its weight is diminished 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 wandering piece of the spout brings about a diminishing of the stun wave pressure and an expansion in its speed to supersonic conditions. ? At the spout outlet plane, point (2), the thought process steam pressure bec omes lower than the entrained fume weight and its speed runs 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 uniting segment of the diffuser or it might ? ow as two separate treams as it enters the consistent 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 due to the back weight opposition of the condenser. ? As the subsonic blend rises up out of the consistent cross segment region of the diffuser, further weight increment happens in the separating area of the diffuser, where part of the dynamic vita lity of the blend is changed over into pressure.The weight of the rising ? uid is marginally higher than the condenser pressure, point (c ). Rundown for various writing concentrates on ejector structure and execution assessment is appeared in Table 1. The accompanying diagrams the primary ? ndings of these examinations: ? 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 irrelevant impact on the ejector entrainment proportion. 553 ? At the basic condition, the ejector entrainment proportion increments at lower pressure for the kettle and condenser. Additionally, higher temperature for the evaporator expands the entrainment proportion. ? Utilization of a variable position spout can keep u p 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 builds the working reach and improves