Wide, air curtains

There are many different combinations of supply inlets and exhaust hoods, where these have to be designed together. Some of these are described in some detail. Two examples of using air jets for special purposes are described and the use of wide air curtains is also described.  [c.1005]

TABLE 10.16 Airflow Rates for Heated Wide Air Curtains (Pressure Difference between Inside and Outside Is 15 Pa)  [c.1009]

Fans and blowers are the most widely used mechanical devices for moving air and gases in both large and small volumes (21). Uses include ventilation, mechanical draft for combustion (including forced- and induced-draft fans and primary- and secondary-air fans), local exhaust for fume and dust containment at hoods and equipment enclosures, forced- and induced-draft cooling for spray towers, cooling towers and ponds, and air-cooled heat exchangers, and conveying of soHds (see also HeaT-EXCHANGETECHNOLOGy). Other appHcations include air or gas movement in dryers, gas-recirculation fans, air supply for air curtains and air-blast operations, and a great many miscellaneous process industry uses often involving hot and corrosive gases. The range of performance required by fans for these various appHcations is enormous. Most ventilating appHcations require pressures ranging from 25 to 1500 Pa (0.1—6 in. of water). Induced-draft fans must often handle gases of 150—425°C containing various levels of suspended erosive particles. Such fans are frequendy equipped with replaceable wear pads of abrasion-resistant materials or are coated with wear-resistant surfaces.  [c.114]

Air curtains with heated indoor air  [c.554]

Air curtains with unheated indoor air  [c.554]

Combined air curtains with indoor air  [c.554]

Air curtains with unheated outdoor air  [c.554]

Air curtains for gates with long passages  [c.554]

Air Curtains with Heated Indoor Air  [c.554]

The traditional design pattern (to be described in Section 7.7.5) is recommended for air curtains with heated indoor air. The air curtain may be doublesided with horizontal supply (Fig. 7.S6a), or it may be single-sided (Fig. 7.86f ) with horizontal or vertical supply. In all cases, the air curtain is a flat jet discharged at an angle toward the pressure side of the opening.  [c.554]

Air Curtains with Unheated Indoor Air  [c.554]

Air curtains with unheated indoor air have a similar air supply arrangement. Only the design of the air intake duct might differ it may be extended to take in warm air, for example, from the upper overheated zone of the room. Air curtains with unheated indoor air are recommended in case the standard temperature of the air coming in through the aperture of the open gate can be maintained without heating the air in the curtain, as in the following cases  [c.554]

Air curtains with unheated outdoor air find application in unheated rooms and also in case there are no strict hygiene requirements for the microclimate in the gate zone (no working places near to the gate, e.g.). Air curtains with un-heated outdoor air should not be used in double-wing gates, in humid rooms, and in cases of transport with an open driver s cab through the gate.  [c.556]

Air curtains with unheated outdoor air do not provide for the necessary microclimate in the immediate vicinity of the gate, but since no thermal energy is used, they reduce heat losses from the room.  [c.556]

Combined Air Curtains with Indoor Air  [c.556]

Combined air curtains with indoor air are recommended with a doublesided supply of heated and unheated air fed to the room in the form of plane jets at an angle of 15° to one another (Fig. 7.86c).  [c.556]

Air Curtains with Unheated Outdoor Air  [c.556]

Recommended applications of combined air curtains with indoor air include  [c.556]

Combined air curtains with indoor air cut down expenses due to rational utilization of energy by the heated jets. Thermal energy savings are 25-60% depending on the dimensions of the gate and climatic region, and the reduction in expenditures is 30-70%.  [c.556]

Air curtains for cooled rooms are recommended with a one-sided supply of outdoor air from above in the form of a flat jet at an angle to the plane surface of the gate toward the cold indoor air (Fig. 7.87).  [c.556]

Air Curtains for Gates with Long Passages  [c.556]

Air curtains for gates with long passages use a pattern of air supply curtains in a channel (Fig. 7.88). The operating principle is based on the complete conversion of the jet impulse to counterpressure that prevents outdoor air from bursting into the room.  [c.556]

Air curtains for process equipment are designed to prevent the ingress of toxic constituents (gases, aerosols, heat flows) into the room through open apertures of the process equipment. They also support necessary parameters of technological processes in the plant. Processes running in the technological equipment are classified as isothermal (e.g., spray-painting chambers) and nonisothermal (e.g., heat dryers). In isothermal processes one uses damper-type air curtains for process equipment in combination with an exhaust system (Fig. 7.90). In nonisothermal processes one uses a circulation system based on the curtains in a channel operating principle  [c.558]

For air curtains with heated indoor air, unheated indoor air, or combined air curtains with indoor air f = 10-20  [c.562]

For air curtains with unheated outdoor air, air curtains for cooled rooms, air curtains with long passages, or air curtains for process equipment f = 20-40  [c.562]

Controlling the supply air temperature (in the case of air curtains with heated air) in proportion to the change in temperature of the outdoor air  [c.565]

When it is necessary to confine an air volume from the ambient environment and simultaneously have access for operators or machinery, plane air jets offer a possible and simple solution. Air jets (plane and round) are described in Chapter 7. This section describes plane air jets combined with exhaust openings. In principle, they are similar to the air jets described in Chapter 7 and Section 10.3, but the combination with an exhaust opening makes it necessary to consider the influence of the exhaust on the jet. Usually these curtains are used in large doors to shield the interior from the exterior when the door is open. For example, experimental results have shown that from the moment a door is opened, a short time interval, less than 1 minute, is sufficient to get complete development of the airflow through the door. An air curtain allows a reduction of the overall flow through the door. The principles and use of air curtains are described in many textbooks.Some basics of air curtains are described here.  [c.936]

Air curtains with the jet vertically upward arc shown m Fig. 10.65, The configurations differ in the internal or external placement of the air-handling  [c.938]

Line jets are used as curtains both in bench hoods such as laboratory fume hoods and in large openings such as doors and gates. These jets have to be designed carefully, usually together with an exhaust opening. They must withstand the pressure difference across the opening and their velocities should be of the correct magnitude for the intended purpose. This means that the jet velocity should not be too large, which results in contaminant spreading or high energy consumption. The jet velocity should not be so small that no curtain is achieved. One way to make it easier to enter a department store or pass through an industrial door is to use a wide air curtain instead of a line jet.  [c.1007]

In industrial ventilation the majority of air velocity measurements are related to different means of controlling indoor conditions, like prediction of thermal comfort contaminant dispersion analysis adjustment of supply airflow patterns, and testing of local exhausts, air curtains, and other devices. In all these applications the nature of the flow is highly turbulent and the velocity has a wide range, from O.l m in the occupied zone to 5-15 m s" in supply jets and up to 30-40 m s in air curtain devices. Furthermore, the flow velocity and direction as well as air temperature often have significant variations in time, which make measurement difficult.  [c.1152]

Filament. Eully drawn flat yams and partially oriented (POY) continuous filament yams are available in yam sizes ranging from about 3.3—33.0 tex (30—300 den) with individual filament linear densities of about 0.055 to 0.55 tex per filament (0.5—5 dpf). The fully drawn hard yams are used directly in fabric manufacturing operations, whereas POY yams are primarily used as feedstock for draw texturing. In the draw texturing process, fibers are drawn and bulked by heat-setting twisted yam or by entangling filaments with an air jet. Both textured and hard yams are used in apparel, sleepwear, outerwear, sportswear, draperies and curtains, and automotive upholstery.  [c.334]

Calendering is a process uniquely appHed to mbbery polymers, mainly semirigid and flexible PVC, for making sheeting of uniform thickness from 0.75—0.05 mm after stretching (67—70). A calender has four heavy, large steel roUs, which are usually assembled in an inverted "L" configuration as shown in Eigure 16. This design is preferred for thick sheeting because it gives a long dwell for full heating. The forces generated between the roUs are considerable and sufficient to bend the roUs, resulting in uneven sheet thickness. A common method of compensating for roU bending is by grinding an opposite contour on the roU. A two-roU mill, a Banbury mixer, or an extmder melt the resin, which is subsequendy transferred to the calender. Sheet can be made 2.5 m wide and production rates can be as high as 100 m /min (71). Calendering is often followed by printing, laminating, and embossing. PVC calenders are mn at temperatures approaching 200°C to produce highly oriented sheets for items such as shower curtains, rainwear, luggage, and wall paneling.  [c.143]

Fluid and spouted beds offer ideal conditions for drying provided the feed material is consistently suitable for fluidization or spouting however, if the drying operation is preceded by mechanical Hquid separation, eg, centrifugation, use of these dryers should be considered with caution. Fluid and spouted beds do not tolerate sticky materials and oversize lumps. Successful appHcations are particulate and pelleted polymers, grain, sand, coal, and mineral ores, appHcations whereia the physical size and character of the feed material is known and controllable 100% of the time. Fluid and spouted beds are attractive for iaert gas and organic Hquid drying because the vessels are stationary. Superheated steam drying is carried out ia fluid beds. This is an attractive alternative environmentally, but a process which was stalled for many years because of the lack of a suitable process vessel. The volumetric drying capacity of a fluid bed is many times that of a rotary dryer. The reason is that gas flowing through the latter moves between a series of parallel particle curtains ia which the gas must be entrained and mixed to contact particle surfaces. In the former, small bubbles of gas enter through the distributor and immediately penetrate and mix with a cloud of particles. Figure 14 shows that whereas the dryer efficiency of a cocurrent rotary dryer and fluid bed may be comparable, because both are siagle-stage vessels, the vessel size requirements are quite different. To approach the dryer efficiency of a countercurrent rotary dryer, two or more fluid beds with countercurrent gas flow must be operated ia series. Figure 15 shows one form of a two-stage fluid bed.  [c.250]

Air curtains with heated indoor air are used for relatively small gates (up to 3.6 X 3.6) in genial climate and in buildings without skylights, and also in case constructions prevent the installation of combined air curtains (e.g., not enough space at the gate). Air curtains with heated indoor air guarantee the necessary temperature of the air mixture entering through the gate, but they also consume a relatively large amount of thermal energy.  [c.554]

Air curtains with unheated indttor air are more restricted in application than air curtains with heated indoor air, but they do not require the insrallatton of ail heaters in the curtain devices.  [c.555]

Air curtains with unheated outdoor air are recommended with a onesided lateral supply of outdoor air in the form of a flat jet at an angle to the plane surface of the gate aperture toward the outdoor air (Fig. 7.8hA>). In  [c.555]

Air curtains for cooled rooms are used in all types of rooms with artificial cooling of air vegetable stores, cold rooms, freezers, air-conditioned plants and storehouses, etc. Installation of air curtains for cooled rooms considerably reduces cold losses through the open gate and also reduces undesirable variations in temperature in the gate zone inside and outside the cooled room.  [c.556]

This short outiine suggests that it is difficult to find Optimal design para-meters for air curtains. CFD may provide a more effective design method for air curtains (see Chapter 13). There are some published articles applying CFD to air jets, but comparison with experimental data is lacking.  [c.943]

Cross-flow fans have a blade arrangement similar to that of a back-flow centrifugal fan but the casing arrangement allows the incoming air to enter along the width of the blades, avoiding the 90° turn. Long narrow shapes can be arranged, making them suitable for use in small airhandling units, fan heaters or air curtains.  [c.449]

Ammonium Phospha.tes, These salts were first recommended for flame retardancy of theater curtains by Gay-Lussac ia 1821. Monoammonium phosphate [7722-76-1] NH4H2PO4, and diammonium phosphate [7783-28-0] (NH 2HPC4, or mixtures of the two, which are more water-soluble and nearly neutral, are used ia large amounts for nondurable flame-retarding of paper (qv), textiles (qv), disposable nonwoven ceUulosic fabrics, and wood (qv) products (7—9) (see Flame retardants for textiles). The advantage is high efficiency and low cost. Ammonium phosphate finishes are resistant to dry-cleaning solvents but not to laundeting or even to leaching by water. One general advantage of ammonium phosphates and phosphoms compounds as flame retardants, especially ia comparison to borax which is also used for nondurable ceUulosic flame retardancy, is the effectiveness ia preventing afterglow.  [c.476]

The hydrogen fluoride industry has undertaken a significant effort to investigate the behavior of HE releases so as better to define the risks associated with an accidental spiH, and to design effective mitigation systems. A series of tests conducted in the Nevada desert in 1986 showed that spills of pressurized, super-heated HE under certain conditions could form a heavier-than-air vapor cloud consisting of flashed, cold HE vapor and an entrained aerosol of HE droplets. The HE did not form Hquid pools as expected, reducing the effectiveness of diking in mitigating the effect of a release (43). The effect of water sprays in mitiga ting an HE release was studied in detail as one of several components of the Industry Cooperative Hydrogen Fluoride Mitigation and Ambient Impact Assessment Program (ICHMAP). Water spray curtains or water monitors were found to remove between 25 and 95% of HF released in field tests. The removal efficiency depended primarily on the ratio of water to HF volume. The higher removal efficiency was obtained at a 50 1 ratio with a single spray curtain (44).  [c.200]

Ammonium Sulfamate. A number of flame retardants used for ceUulosic materials, including fabrics and paper products, are based on ammonium sulfamate (56). These products are water-soluble and therefore nondurable if treated fabrics are washed or exposed to weathering conditions. For most fabric and paper constmctions, efficient flame retardancy can be provided with no apparent effect on color or appearance and without stiffening or adverse effects on the feel of the fabrics. A wide variety of materials are treated, including ha2ardous work-area clothing, drapes, curtains, decorative materials, blankets, sheets, and specialty industrial papers (57).  [c.65]

Several patents (128—130) deal with methods for preventing the formation of deposits in heat exchangers, reducing corrosion and avoiding the need for corrosion—resistant materials. Copper is widely used for lining the reactors and for piping, and some heat exchangers are made of phosphor bron2e. Eastman Kodak Co. (131) advocates the use of a stainless-steel-clad reactor lined with overlapping copper curtains or shingles for corrosion resistance. A Hibemia-Chemie patent (96) claims that a copper lining in the reactor has a limited life and can promote the formation of cuprene. A porous carbon brick lining with a Cu—Ag alloy between the brick and the reactor wall is described (126).  [c.407]

Direct-Heat Rotaiy Dryers The direct-heat rotary diyer is usually equipped with flignts on the interior for hfting and showering the solids through the gas stream during passage through the cylinder. These flights are usually offset eveiy 0.6 to 2 m to ensure more continuous and uniform curtains of sohds in the gas. The shape of the flights depends upon the handhng characteristics of the solids. For free-flowing materials, a radial flight with a 90° hp is employed. For sticky materials, a flat radial flight without any hp is used. When materials change characteristics during drying, the flight design is changed along the diyer length. Many standard drver designs employ flat flights with no hps in the first one-third of tlie diyer measured from the feed end, flights with 45° hps in the middle one-third, and flights with 90° lips in the final one-third of the cylinder. Spiral flights are usually provided in the first meter or so at the feed end to accelerate forward flow from under the feed chute or conveyor and to prevent leakage over the feed-end retainer ring into the gas seals.  [c.1201]

See pages that mention the term Wide, air curtains : [c.587]    [c.1007]    [c.2321]    [c.992]   
Industrial ventilation design guidebook (2001) -- [ c.1007 , c.1008 ]