Document NEe0X1yQq1ZBaw9zqXGjjgJ3E

Heating Ventilating Air Conditioning Guide 1939 9,0 What cooling medium is used for condensing the refrigerant in a railrnoj air conditioning system? ; Outdoor air, sometimes with the aid of evaporative cooling. 10 O How may adequate cooling of condensers be provided in hot desert regi0n8 By evaporative cooling with water sprays. 11 O How is the temperature controlled in railroad cooling systems? By intermittent operation of the compressor, the steam jet or the ice water circulating pump. * 12 9 IIow much steam is required for car heating on the coldest days? Pullmans 250 lb per hour, coaches 150 to 175 lb per hour, baggage cars 150 lb per hour 13 9 At present costs which is likely to be the greater, fixed charges or operating costs? ^ The fixed charges for steam and mechanical compression systems, and operating costs for ice systems. 14 9 What would be the annual operating cost for a car equipped with an iceactivated system under the. following conditions: a total mileage of 150,000 car-miles per year, a cooling season of 5 months, and an average train speed of 50 mph? $1,705.00. 638 Chapter 33 INDUSTRIAL AIR CONDITIONING Atmospheric Conditions Required, General Requirements, Classification of Problems, Control of Regain, Moisture Con tent and Regain, Conditioning and Drying, Control of Rate of Chemical Reaction, Control of Rate of Biochemical Re actions, Control Rate of Crystallization IN the application of air conditioning to industrial processes, too much stress cannot be laid upon a thorough understanding by the air con ditioning engineer of the problems involved. A complete knowledge of these problems is necessary before a satisfactory design can be made. Individual processes and machines are changing rapidly and air con ditions must be constantly revised to meet the new conditions. ATMOSPHERIC CONDITIONS REQUIRED The most desirable relative humidity during processing depends upon the product and the nature of the process. As far as the behavior of the material itself and its desired final condition are concerned, each material and process presents a different problem. The best relative humidity may range up to 100 per cent. Similarly the most desirable temperature may range between wide limits for different materials and treatments. Ex tremes in either relative humidity or temperature require relatively expensive equipment for maintaining these conditions automatically. In departments where people are working, their health, comfort, and productive efficiency must be considered and often a compromise between the optimum conditions for processing and those required for the comfort of the worker is desirable.. It is generally considered that relative humidities below 40 per cent are on the dry side, conducive to low regains, a brittle condition of fibrous materials, prevalence of static electricity, and a tendency toward dryness of the skin and membranes of human beings. At the other end of the scale, humidities above 80 per cent are relatively damp, conducive to high regains, extreme softness, and pliability. Table 1 lists desirable temperatures and humidities for industrial pro cessing. In using this table, care must be taken in qualifying the process. In.preparing many materials, conditions are not maintained constantly, but different temperatures and humidities are held for varying lengths of time. 639