Jet systems

Steam-Jet Systems. Low pressure water vapor can be compressed by high pressure steam in a steam jet. In this way, a vacuum can be created over water with resultant evaporation and cooling water, therefore, serves as a refrigerant. This method frequently is used where moderate cooling (down to 2°C) is needed. The process is inefficient and usually is economically justified only when waste steam is available for the motive fluid in the steam jet. 

Fig. 19. Ink-jet system (a) piezoelectric ink-jet firing chamber and (b) bubble formation ia thermal ink-jet technology.

There was a logical progression of technology development from continuous to piezoelecttic ink jet. Designers of continuous ink-jet systems ensure that the ink stream breaks into drops of constant size and frequency by applying vibrational energy with piezoelecttic crystals at the natural frequency of drop formation. This overcomes the effects of any random forces from noise, vibrations, or air currents. 

DP Speed Factor. Pumping-speed efficiency depends on trap, valve, and system design. For gases having velocities close to the molecular velocity of the DP top jet, system-area utilization factors of 0.24 are the maximum that can be anticipated eg, less than one quarter of the molecules entering the system can be pumped away where the entrance area is the same as the cross-sectional area above the top jet (see Fig. 4). The system speed factor can be quoted together with the rate of contamination from the pump set. Utilization factors of <0.1 for N2 are common. 

Ejector (steam-jet) refrigeration systems are used for similar apph-cations, when chilled water-outlet temperature is relatively high, when relatively cool condensing water and cheap steam at 7 bar are available, and for similar high duties (0.3-5 MW). Even though these systems usually have low first and maintenance costs, there are not many steam-jet systems running. 

Despite being simple, rugged, reliable, requiring low maintenance, low cost, and vibration free, steam-jet systems are not widely accepted in water chilling for air-conditioning due to characteristics of the cycle,... 

FIG. 11-108 Steam demand versus cbilled-water temperature for typical steam-jet system (ASHRAE 1983 Equipment Handbook). 

Unhke other refrigeration systems, the chiUed-water flow rate is of no particular importance in steam-jet system design, because there is, due to direct heat exchange, no influence of evaporator tube velocities and related temperature differences on heat-transfer rates. Widely varying return chiUed-water temperatures have Uttle effect on steam-jet equipment. 

Multistage Systems The majority of steam-jet systems being currently instaUed are multistage. Up to five stage systems are in commercial operation. 

Fabric filters are limited by physical size and bag-life considerations. Some sacrifices in efficiency might be tolerated if higher air-cloth ratios could be achieved without reducing bag life (improved pulse-jet systems). Improvements in fabric filtration may also be possible by enhancing electrostatic effects that may contribute to rapid formation of a filter cake after cleaning. 

Eor good control, design the pressure drop for the control valve between the fractionating system and the jet system for sonic velocity (approximately 2 1 pressure ratio). This means that the jets suction must be designed for half the absolute pressure of the evacuated system. 

A fruitful approach for velocity computation in the first three zones of jets supplied from outlets with finite size was developed based on the hypothesis that momentum diffuses with distance from the source in the same manner as heat energy." 40 approach, developed by Elrod,Shepelev and Gelman, - and Regenscheit, utilizes the method of superposition of jet momentum from the multiple-jet system. These jets originate from the points with supply air veloc-... 

Li Z., L. L. Christianson, J, S. Zhang, and A. Zhivov. 1994. Cold air jets systems effects on the occupied regions. In Roomvent 94 Proceedings of the Fourth International Conference on Air Distribution in Rooms, vol. 2. Krakow, Poland. 

Sometimes it is necessary to include the exhaust air when designing an air jet system (see Sections 10.4.2 and 10.4.3). Normally the descriptions assume that the jet is not disturbed by exhaust air, nearby surfaces, or other air movement in the room (see Chapter 7). 

Steam jet systems. These are used to smotlier some fires in closed containers or in confined spaces. 

For design of a new system, it is recommended that the results of the summation above be multiplied by 2 or 3 to establish the jet system inert (noncondensables) capacity, and add to this the non-condensed process vapors that are released into the jet suction system. 

Researchers have already been using ink jet systems to print several types of novel materials, some of which have been used to fabricate circuit electrodes and interconnects. The four main types of materials used are metallo-organics, conductive polymers, molten metals, and metallic nanoparticle suspensions. 

European machines in particular are operated with very low water levels in order to save energy and water. It is therefore important to ensure that the laundry load is soaked in water or suds as quickly as possible so that dry textiles do not rub unnecessarily against the drum or the rubber seal. This is achieved in European machines by constructional features that improve water absorption, shown in Fig. 3.3, such as lifter bars, circulation (jet) systems or direct injection. 

Following successful testing of the bubble jet system [3] at pilot scale, the plant was scaled to full technical size (2.5 m2 elements) and successfully tested. The anolyte flow-out of the elements showed a completely pulsation-free operation with all benefits for the membrane lifetime. Despite the rather good results of this first run a design review was started to improve the electrolyser element design. 

Owing to the fact that nearly all the heat generated by this type of electrolyser has to be dissipated via the anolyte flow, for the full industrial-scale demonstration electrolyser with an element size 2.5 m2 it was decided to use the bubble jet system [3], which was successfully tested previously with the chlor-alkali method. For FIC1 electrolysis, which from the material side is optimised to an approximate operation temperature of 60°C, an intense vertical temperature-profile flattening is essential to reduce the external flow rates and to allow rather low anode-side inlet temperatures. The intensive vertical mixing with the bubble jet proved to be suitable for this purpose. 

Pressure leaf filters are supplied in a wide range of size and materials of construction. One typical design is the Verti-jet unit with a vertical tank and vertical leaf filter, as shown in Figure 7.12, with rectangular leaves mounted individually but connected to a common outlet manifold. For sluice cleaning either a stationary or oscillating jet system... 

FIGURE 6.9 Flame shapes as predicted by Burke-Schumann theory for cylindrical fuel jet systems (after Burke and Schumann [9]). 

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