Document RaON3xJppOG8VB268nNyE35av

American Society of Heating and Ventilating Engineers Guide, 1934 days, the fruit should be held at from 60 to 62 F. Temperatures below 62 F are not advisable for very thin fruit. The humidity should be the same as for fast ripening, and ventilation (up to 3 or 4 air changes per hour) should be used provided the humidity can be maintained. Ethylene gas treatment will not be required. For holding ripened bananas, temperatures between 56 and 60 F are recommended. A reduction in humidity is beneficial in toughening the 'peel and reducing the mould, but too low a humidity will cause shrinkage. Although exact humidity control is not essential, the desirable range is between 75 and 80 per cent. GREENHOUSES Table 3 lists customary dry-bulb temperature ranges, for different types of plants and flowers raised in greenhouses. Table 3. Customary Temperatures for Different Types of Greenhouses Type op House Temperature Range Deg Fahr Type op House Temperature Range Deo Fahs Carnation.. Conservatory (general collection, winter garden, etc.). .... .................... Cool Cucumber.................................................... Fern. ........................................... ............... Forcing........ ............................................. General purpose-- ..................................... Lettuce...................................................... Orchid, warm 45 to 55 ' 60 to 65 45 to 50 65 to 70 60 to 65 60 to 65 55 to 60 40 to 45 65 to 70 Palm, warm_______ Palm, cool. _______ Propagating____ :__ Tomato..... ........... ..... Tropical. _________ 50 to 55 60 to 65 50 to 55 55 to 60 55 to 60 45 to 50 65 to 70 65 to 70 40 to 45 APPARATUS FOR INDUSTRIAL CONDITIONING Apparatus for industrial air conditioning may be divided into two distinct groups, namely, (1) humidifiers for increasing the moisture con tent of the air and for producing cooling by evaporation and (2) dehu midifiers for removing moisture from the air and for producing cooling by contact with water or surfaces at a lower temperature than the air. Strictly speaking, humidity control alone, whether it involves humidi- c fication or dehumidification, is not air conditioning. To be entitled to this classification according to the definition in Chapter 42, the process should include the simultaneous control of temperature, humidity and air motion. Industrial humidifiers may be--divided into the following general types, according to the method of operation: > 1. Direct, which spray into the room. 2. Indirect, which introduce moistened air. 3. Combined direct and indirect. Spray Generation Spray generation is obtained by (1) atomization, (2) impact, (3) hydraulic separation, and (4) mechanical separation. 54 Chapter 3--Industrial Air Conditioning Atomization involves the use of a compressed air jet to reduce the water particles to a fine spray. With the impact method, a jet of water under pressure impinges directly on the end of a small round wire. Where hydraulic separation is employed, a jet of water enters a cylindrical chamber and escapes through an axial port with a rapid rotation which causes it immediately to separate in a fine cone-shaped spray. In the mechanical separation process, water is thrown by centrifugal force from the surface of a rapidly revolving disc and separates into particles suf ficiently small to be utilized in certain types of mechanical humidifiers. Spray Distribution Spray distribution is obtained by (1) air jet, (2) induction, and (3) fan propulsion. The air jet which generates the spray in atomizers also carries the spray through a space sufficient for its distribution and evaporation, and this method of distribution is termed air jet. Where distribution is obtained by induction, the aspirating effect of an impact or centrifugal spray jet is utilized to induce a current of air to flow through a duct or casing and this air current distributes the spray. Fan propulsion obviously consists of the utilization of fans to entrain and distribute the spray. Industrial type direct humidifiers are commonly classified as (1) atomizing, (2) high-duty, (3) spray and (4) self-contained or centrifugal. Atomizing Humidifiers There are several types of atomizing humidifiers, all of which rely upon compressed air as the atomizing and distributing agency, similar to the familiar method used in ordinary nasal atomizers. Compressed air (ordinarily about 30 lb per square inch) is supplied from a centrallylocated air compressor through pipe lines to the atomizing units. The air lines are usually horizontal and parallel to water lines which supply water by gravity from a float tank. The water in the tank is maintained at a constant level slightly lower than the outlets of the atomizers them selves and is drawn constantly to the atomizer by aspiration when com pressed "air is supplied. This aspiration ceases and the flow of water stops when the air supply is cut off. The water should not be supplied under pressure to atomizers because of the possibility of leakage, drip, or coarse spray which cannot be permitted when water is supplied by aspiration. High-Duty Humidifiers Water is supplied to high-duty humidifiers under high pressure (usually about 150 lb per square inch) through pipe lines from a centrally-located pumping unit. The spray-generating "nozzle which is of the impact type is located in a cylindrical casing. A drainage pan provides for the collec tion and return of unevaporated water which flows through a return pipe to a filter tank, from which it is recirculated. A powerful air curr.ent is forced through the humidifier by means of a fan mounted above the unit. The air enters from above, is drawn through the head, charged with moisture, and cooled to the wet-bulb temperature. It then escapes from the opening below at a high velocity in a complete and nearly horizontal circle. The spray is quickly evaporated and the resulting vapor is rapidly 55