SE533409C2 - Device for dew precipitation from moist air - Google Patents

Description

533 409 steam condensation heated cooling water fl deserted in a lower gutter and recirculation of the cooling water outlet via a cooler.

The invention is described below in connection with the figures, wherein figure 1 shows the device in vertical cross section, figure 2 shows in section installation in a drying chamber for wood and figure 3 in planar connection to another drying process.

Within a space permeated by water, moist air 2, support diaphragms 11 are attached to bracket members 13, for example, made of 75 microns of polyester m ch with a width of 0.85 m and an optional height stretch. The membranes are fastened to the brackets suitably with double-sided, water-stable tape and the brackets are mounted on a wall-mounted rail 14 with a cc distance of the order of 15 cm. The carrier membranes 11 are stretched vertically, preferably by being arranged as band-found loops loaded by weights in the loop bottoms. The vertical surfaces of the support membranes 11 are covered by the cover membrane 12 of the same width loosely hanging and fixed to the support membrane with short pieces of 1.5 mm acrylic foam tape along the upper edges of the membranes. Between these pieces are inserted the oblique foam ends of thin, equally long plastic hoses 6 of dimension 3/5 mm. A suitable number of hoses are 6 evenly distributed over a membrane width of 0.85 m. The hoses are wound more or less over an open tubular vessel 61 mounted above each bracket pair and obliquely cut ends are pressed into wall holes in the vessel, suitably formed of plastic and thick-walled.

The membranes 11,12 thus form cooling surfaces 1. A cooling water fl fate 5 is distributed equally between all vessels 61. In each vessel water rises to a level 611, where to fl fate is equal to the outlets via 12 connected hoses 6. Since pressure drop and static driving force are equal for all hoses fl the fate is distributed equally between the hoses independently of mass fate. The flow thus evenly injected between the membrane pairs 11,12 propagates as capillary-distributed, heated cases 51 between the membrane pairs, is collected in a lower channel 52 and recirculated via a cooler 8.

All material in the cooling water circulation, possibly excluding cooler 8, consists of plastics with a high tolerance to a corrosive environment in drying air. Condensate precipitated on the cooling surface 1 can be mixed into the cooling water fl desolation 5 or, with easy arrangements, diverted to a separate bottom gutter.

The cooling surfaces 1 are covered by diffusion-open, heat-insulating layers 3, which means that the membranes 11,12 are not disturbed by heat movements, that wet cooling surface is not contaminated by dust in the flow 2 and that it is cooled to a very small degree. Heat transfer between flow 2 and cooling surface 1 takes place to about 95% via latent vein in steam diffusing through the cover layers 3,533,409 and condensing on the cooling surface. The cover layers 3 are designed as wooden frames 4 within which a number of layers of thin non-woven fabric 31 are stretched at intervals of stagnant air. Double frames 4 are joined by spacers 41 to stiffened cover elements 7, the space between the frames forming space for the flow 2. The cover elements are hooked onto the rail 14 between the membrane pairs 11, 12 and are stabilized in the wind with simple screw / cover joints. Made at a modest cost, durability is limited to about 2 years, after which an exchange takes place in a rational way.

In reference to Figure 2, the device installed in a typical existing drying chamber 9 for wood dehumidified via air exchange is illustrated. On a rail 14 attached to the rear wall, the required number of membrane loops 11/12 and cover elements 7 are suspended. . Air exchange 91 genuine 91 is blocked. The heat demand decreases from the 1.2 kwh of the air exchange process per expelled kg of water to 0.85 kwh including transmission losses. The vapor diffusion through the cover layers 3 is proportional to the difference between vapor pressure p ”in the flow 2 and vapor pressure p 'over the cooling surface 1. Measurements on the device in a chamber dryer indicate a vapor de fate = 10 g per hour, sqm membrane / cover layer surface and mbar vapor pressure difference. The value applies to a cooling water fl fate dimensioned so that the temperature rise in the same is in the order of 20 °, eg in temperature range + l5 ° / + 35 °. The vapor pressure difference p ”-p 'increases steeply with increasing drying temperatures, as illustrated below. 'Fall l. Dry temperature = + 65 °. RH on average during drying = 80% with p ”= 200 mbar and p '= 23 mbar with difference = 177 mbar and steam fl fate = 1.77 kg per sqm membrane / cover layer surface. The desired drying speed is 250 kg / h, which requires 250 / 1.77 = 140 sqm or 18 membrane loops of 7.5 sqm.

Case 2. Dry temperature = + 70 °. RH on average during drying = 80% with p ”= 265 mbar and p '= 23 mbar with difference = 242 mbar and anguity = 2.42 kg per sqm membrane / cover layer surface. The desired drying speed is 300 kg / h, which requires 300 / 2.42 = 125 sqm or 16 membrane loops of 7.5 sqm.

The membrane loops fit well along the width of the drying chamber, approx. 6.6 m, with a cc distance of approx. 0.3 m. An installation of the device results in a heat saving of approx. 0.35 kwh / kg evaporated water or annually in the order of 600,000 kwh. The material cost for simply produced membranes / cover layer surfaces is in the order of SEK 10,000. 533 405 There are different options for radiator 8. If the condensation barrier in the order of 1.2 million kwh annually from cooling surfaces l is not intended to be recovered, the cooler can constitute a water reservoir such as a lake or watercourse or consist of a cooling site.

With the use of the free condensation friend obtained, the cooler can be an effective counter-current heat exchanger water / air, whereby cooling water fl fate cooled approx.

The radiator can be the evaporator (in the form of a plate protection exchanger) for a heat pump for operating the dryer. The system means a radical improvement of common so-called condenser dryers, which suffer partly from corrosion problems on their air-heated evaporators installed in the chamber and partly from the fact that these cooling surfaces sensitively cool down the drying air. With a cooling factor of approx. 2.5 on the heat pump, the efficiency is improved to 0.3 kwh / kg water from today's approx. 0.7 kwh / kg.

In reference to Figure 3, the device is illustrated in other drying processes, where, as in the case above, it cannot be installed directly in the drying air flow.

This can apply to drying of eg paper, pulp or the like.

The device is mounted in a side channel 92 to the dryer 9a and a part fl of 2 'of the drying air circulation 2 is blown cross-current through one or fl your packages of cooling surfaces 11,12 and cover elements 7. Cooler 8 may be of the above-mentioned type.

Claims (1)

1 533 403 5 Patent claims. . Device for dew deposition from a flow ring (2) of moist air against a cooling surface (1), which is covered against the flow of diffusion-open, heat-insulating cover layers (3), characterized in that the cooling surface comprises support membrane (11) along the upper edges attached to bracket means (13). ), the support membranes are vertically stretched preferably by a design such as band-shaped loops weight-loaded (15) in the loop bottoms and the support membranes supplemented with connecting cover membranes (12), further comprising means (6,61) for injecting a cooling water gap (5) between the upper edges of the membrane widespread falls (51) of the water between the membranes facing each other, further comprising collecting cooling water heated by substantially steam condensation in a lower channel (5 2) and recirculating the cooling water fl via a cooler (8). . Device according to claim 1, characterized in that said cover layer (3) comprises frames (4), in the frames attached a number of parallel layers of thin erv fabric (31), double frames rigidly joined with a gap for said flow (2) to cover elements (7) hooked between the cooling surfaces (1) -. Device according to claims 1-2, characterized in that said means (6,61) comprise for each pair of support membrane (1 1) and cover membrane (12) a number of small, at the ends foam plastic hoses (6) of equal lengths inserted evenly between the upper edges of the membrane distributed along the membrane width, the hoses more or less wound up over a tubular vessel (61) mounted over the bracket means and pressed in through wall holes in the vessel, openly filled with said cooling water fl desolate (5). . Dryer comprising a drying chamber (9) and a device for dew deposition according to claims 1-3, characterized in that the device for dew precipitation is mounted directly within the drying air flow (2) in the drying chamber (9) or indirectly in a side channel (92) to the drying chamber (9a) of a partial stream (2 ') of the drying air stream (2). . Device according to claims 1-4, characterized in that said cooler (8) alternatively consists of a watercourse, cooling tank, water / air heat exchanger or evaporator for a heat pump.