Document YjrXgVjQ9e3GEDeqm1Q1o11a8

772 CHAPTER 56 1960 Guide Table 9 .... Pipe Size* for Cooling Towers' Rated Tons of Refrig. Coating Water Gpm Pipe Sizes (Nominal inches) Into? to Tcwar Outlet front 3 to 5 7 to 15 20 25 35 50 75 100 150 200 250 10 to 18 20 to 45 55 86 115 170 225 300 450 600 750 IX 2 2X 2H 3 3 5 5 5 6 8 IX 2 3 4 4 4 6 6 8 8 8 piping. Velocities exceeding LQ (ps cause undesirable noise in the piping system. This will usually govern the size of the larger pipes in the system while, in the email pipe sizes the friction loss will usually govern the selection because the velocity is low compared with friction loss. Velocity is the governing factor in down-feed systems, where friction loes is Table 10 .... Maximum Daily (24-Hr) Requirements for Hot Water in Gallons Apartments end Number of Bathrooms 2345 _1 60 _ _ _2 70 -- __ __ _ _3 80 __ __ __ 4 90 120 __ 5 100 140 -- __ __ 6 120 160 200 __ __ _7 140 180 _8 160 200 240 250 9 180 220 260 275 __ 10 200 240 280 300 -- 11 -- 260 300 340 __ 12 -- 280 325 380 450 13 -- 300 350 420 500 14 -- -- 375 460 550 15 -- -- 400 .500 600 16 -- -- -- 540 650 -- -- -- 580 700 18 -- -- -- 620 750 -- -- -- -- 800 20 --. -- -- 850 Room with basin. Room with bath--transient. .. Room with bath--resident. 2 Rooms with bath........ 3 Rooms with bath........... I'ublic shower___ Public basins.... Slop sink.. Office BuOdiogs White-collar worker (per person)4 .. . 2-3 Other workers (ner Demon 1 . 4.0 Cleaning per 10,000 sq ft . 30.0 Hospitals Per bed___ 80-100 The vmlae for white-coifar worker* is for offiosoccupancyonly, oot indudias Uowft&c* far employee!' loach ruouia, dining room*, etc. Requirements far ttae arm* should be csfanlated separately. Table II.... Estimated Hot Water Demand Characteristics for Various Types of Buildings Type of Banding Residences, apartments, hotels, etc.b** Hof Water Required Per 20 to 40 gal per day* Max. Hourly Onscad in Retofjoo to Oafs Use of Peek lead Storage Capacity bi Relation to Day's Use Hoofing Capacity in Relation fa Day's Use ni 4 1/5 1/7 Office buildings 2-3 gal per day4 1/5 2 1/5 1/6 Factory buildings 5 gal per day4 1/3 1 2/5 1/8 Restaurants Restaurants 3 meals/day 1/10 8 1/10 1/5 1/10 1/10 Restaurants 1 meal/day l/s 2 2/5 1/6 a* no p. b Daily brtwaterrequirements and demand characteristic vary with the type of hotel. The better cbm hotel has a relatively high daily consumption with a low peak load. The commercial hotel has a lower daily an--hot a high peak load. "The inaaMing use of dishwashers and laundry washing marhlnm in resi dences and apartments requires additional allowances of 16 gsl per dishwasher and 40 gsl per laundry washer. usually neglected. Velocity in branches leading to pump suctions should not exceed 5 fps. If the street pressure is too low to adequately supply up per floor fixtures, means must be provided to increase the pressure. A gravity tank on top of the building, a hydro pneumatic tank in the basement, or a booster pump may be used. Flow control valves are available for installation at the individual fixtures which, under conditions of varying pres sure, automatically adjust the flow at the fixture to a pre determined quantity. By using these valves the designer may (1) limit the flow at the individual outlet to the minimum suitable for the purpose, (2) hold the total demand f0r the system more closely to the required minimum, and (3) be able to design the piping system as accurately as is practica ble for the requirements. COOUNG WATER PIPING Water is very frequently used in refrigeration systems, cooling towers, and other rimilnr installations. In daligning the piping system of such installations, the principles of hy draulics, as already outlined, are employed. Nevertheless, there are several practical items having particular applica tion to cooling installations which are outlined in the fol lowing paragraphs. It is important that the Hwagn^r be familiar with them. In choosing pipe material, the problem of corrosion should be kept in mind to prevent failure of the system. If the water is not severely corrosive, wrought-iron or steel piping may be used; otherwise, galvanized-steel piping may be preferred. If sea water is used as the circulating medium, it is advisable to use alloys such as admiralty metal in pipe and tubing. In refrigeration condensers where water is the cooling medium, iron pipe is commonly employed. Water treatment is commonly used, especially in recircu- Water Services 773 lating systems. See Chapter 65 for more detailed discussion of this subject. In regard to assembly, cast-iron flanges or welded joints are to be preferred to screwed joints wherever posable. Valves used in circulating systems may be of the globe, gate, or angle types. If water is the circulating medium, brass valves are usually used. However, if the circulating medium is an electrolyte, such as brine, then it is preferable to use valves made of the same material as the piping itself. The friction los3 in the piping may be determined from Fig. 4 for fairly rough pipe. If the coolant is brine, a correc tion for the proper density must be made. Experience indi cates that in airing piping for cooling systems, a pressure drop of the order of 2 to 3 pa per 100 ft of pipe length, and a fluid velocity of 3 to 8 fps, are within good practice. In the case of cooling towers, the amount of circulating water is about 3 gpm. per ton of refrigeration, when based on a design wet-bulb temperature of about 75 to 78 F. Table 9 gives pipe rises frequently used for various rises of cooling towers, fmsnrning a hot water temperature of 95 F and a cold water temperature of 85 F.1 These conditions are typical of refrigeration plants, electrically driven. Systems operated by condenring-steam turbines, or steam-operated absorption systems, require more water or produce a higher water tem perature, or both. See also Chapter 40. ESTIMATING HEATING LOAD AND STORAGE CAPACITY The maximum drily and the maximum hourly hot water demand form the basis for the selection of the heater and the storage tank, For residential dwellings, a design value of about 20 to 30 gal per (person) (day) may be assumed, but it should be remembered that the hot water used will depend primarily on the number of persons in any house or apartment. Table 10 gives estimates of the maximum hot water re quirements in 24 hr in various types of buildings. These may be used for the number of rooms and bathrooms if the person count is not available. The values in Table 10 are not suitable for large buildings. For these the person count as a basis is better. In estimating the size of hot water storage tank required, and the heating capacity to be provided, either from the boiler or from an independent domestic hot water heater, it is necessary to know the total quantity of water to be Table 12.... Hot Water Demand per Fixtures for Various Types of Buildings Galloru of water per hour per fixture, caiccrfoted at a final temperature of 140 F Aportment Hawse Club Gymoadorn Hospital Hotel industrial Plant Office Bmkfing Private Residence School YM.CA. 1. Basins, private lavatory____ 2 .2 2 2 2 2 2 2 22 2. Basins, public lavatory......... 3. Bathtubs......................................... 4. Dishwashers4................................ 4 20 15 6 20 50-150 8 30 68 20 20 50-150 50-200 12 20-100 6 15 8 20 30 15 20-100 20-100 5. Foot basins................................... 3 3 12 3 3 12 3 3 12 6. Kitchen sink................................ 10 20 20 30 20 20 10 20 20 7. Laundry, stationary tubs. 8. Pantry sink........................... 9. Showers........................................... 20 5 30 28 10 150 28 10 225 75 28 10 75 225 20 28 10 5 10 10. 30 30 225 225 10. Slop sink......................................... 20 20 20 30 20 20 15 20 20 11. Bydro-ther&peuticehowers.. 400 12. Hubbard baths....................... 77 GOO 13. Leg baths....................................... 100 14. Arm baths..................................... 35 15. Sits baths...................................... 30 16. Continuous-flow baths............ 165 17. Circular wash sinks................. 18. Semi-circular wash sinks___ 19. Demand factor............................ 20. Storage capacity factor*____ 0.30 1.25 0.30 0.90 0.40 1.00 20 20 10 10 0.25 0.25 0.60 0.80 30 15 0.40 1.00 20 10 0.30 2.00 0.30 0.70 30 15 0.40 1.00 0.40 1.00 4 Detnuho requirements should be takes from manufacturers' data far tbs model to be used. U this is known. Sons models require op to 400 c*l pet hr. b Ratio of stones teak capacity to probable wwininM demand per hour. Storage rapacity may be reduced where an unlimited supply of steam it available from a central streetsteam system or hy plant.