Document 5BmGg7y749qL2EQp18Mw2350

American Society of Heating and Ventilating Engineers Guide, 1935 v prepared eleven schedules2 for the kiln-drying of practically all kinds, types, and thicknesses of softwoods and hardwoods. The tables given in these schedules range from 105 to 200 F dry-bulb, and from 20 to 80 per cent relative humidity. As a rule, the softer the wood, the higher the M average temperature used. The temperature and relative humidity in a lumber drying kiln are varied for all conditions, starting with a low dry-' bulb and a high relative humidity when the green lumber, containing a large percentage of moisture, is started to dry. As the moisture content of the lumber decreases, the dry-bulb temperature of the kiln is increased, and the relative humidity reduced. It is noted, however, that perfect drying does not necessarily result from following a schedule, and that an operator must be trained to watch the condition of the stock in the kiln Iand to immediately apply a remedy if he sees things going wrong. GREENHOUSES Table 3 lists customary dry-bulb temperature ranges for different J types of plants and flowers raised in greenhouses. Table 3. Customary Temperatures for Different Types of Greenhouses Ttfe or House Carnation........................................................ Conservatory (general collection)........ Cool.......................... -.........-....................:----Cucumber................ .. ..................................... Temperature Range Deg Fahb 45 to 55 60 to 65 45 to 50 65 to 70 Type op House Orchid, cool....... ....... Palm, warm,,...._...... Palm, cooL ........ ; Propagating............... Temperature Range Deg Farr 50 to 55 60 to 65 .50 to 55 55 to 60 Forcing............................................................ Lettuce.......................... ...........-........ ....... . Orchid, warm................................................. 60 to 65 40 to 45 65 to 70 Sweet pea.................. . Tropical.................... Violet...... .................... 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 fication or dehumidification, is not air conditioning. To be entitled to this classification according to the definition in Chapter 41, 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.' JTechnical Note Number 175. Forest Products Laboratory, U. S. Forest Service. Madison, Wis. Chapter 3--Industrial Air Conditioning Spray Generation Spray generation is obtained by (1) atomization, (2) impact, (3) hydraulic separation, and (4) mechanical separation. 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 pp--raer,,stTMisculner>es tiimmu ppaiinnggeess ddiirreeccttllyy oonn tthhee eenndd ooff aa ssmmaallll rroouunndd wwiirree., Wwnheeriee 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 ttfhhiceeiessn-uut-rrlyffaacsceemaoo-lffl aa-torraaubeppiidd.u.lltyyiliGzrreeeMvvdooillnvviinncggerdutaiiosivnc. atynpdesseopfamraetecshai-n-n-ti-co-alp,--ha-ur--tmi-c--lie-dsifiesrusf-. Spray Distribution Spray distribution is obtained by (I) air jet, (2) induction, and (3) fan proTphuelsaioirnj.et 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 of 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 die 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 .current is, forced through the humidifier by means of a fan mounted above the,unit.. 73. d