Document YrQjmjYNbZbLpm9jOo9OVn6jO

816 CHAPTER 75 1962 Guide And Data Bool<^^ * 817 Table 9.,.. Pipe Sizes for Cooling Towers* Rated Tom of JUfrig. Cwefing Water Gpo Pipe Sizai (Nominal Inched Met to Tower Outlet from Tower 3 to 6 7 to 15 20 25 35 50 10 to 18 20 to 45 65 86 115 170 1H 2 2X 2* 3 3 IX 2 3 4 4 4 75 225 5 6 100 300 5 6 150 450 6 8 200 600 6 8 250 750 8 8 piping. Velocities exceeding 10 fpe cause undesirable noise in the piping system. .This will usually govern the size of the larger pipes in the system while, in the small 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 lng is Table 10 .... Maximum Daily (24-Hr) Requirements for Hot Water in Gaflons No. of Rooms Number of Bathrooms 234 5 Apartments 2 60 70 r - - _3 80 -- -- __ _4 90 120 -- -- _5 100 140 --. -- __ 6 120 160 200 __ 7 140 180 220 __ __ _8 160 200 240 250 _9 180 220 260 275 10 200 240 280 300 -- 11 -- 260 300 340 -- 12 -- 280 325 :n 450 13 -- 300 350 420 500 14 -- -- 375 460 550 15 -- -- 400 500 600 16 ---- -- 540 650 17 -- -- -- 580 700 18 -- -- -- 620 750 19 -- -- -- __ 800 20 -- -- -- -- 850 Hotels Room with basin. Room with bath-- Room with bath--resident......... 2 Rooms with bath......... 3 Rooms with bath......... Public shower___ Public basins... Slop sunk .. 10 .. 50 .. 60 .. 80 .. 100 .. 150 Office Buildings White-collar worker (per person)*... . 2-3 Other workers (per person)___ . 4.0 Cleaning per 10,000 sq ft........... . 30.0 Hospitals Per bed... 80-100 * Tbe Tslae far wiut*^Qar workers n for office oocupeneyonly, not iadudinx eO^enee for emptoyem'luneh name, dining rooms, elc. Bequirements far tiese mu ehoald be *--i--,t'***< separately. Table 11.... Estimated Hot Water Demand Characterisfe* for Various Types of Buildings Type of Budding Hot Water Per Person Mom. Hourly Duration Demand la of Peak Storage Capodfy ^uliss Capet*. Retotion load Rstoiioti feKefctfm to Day's Use Howw to Day's Use to Do/* Um Residences, apartments, hotels, etc.b** 20 to 40 gal per day* 1/7 4 1/5 l/T"' Office buildings 2-3 gal per day* 1/5 2 1/5 1/6 Factory buildings 5 gal per day* 1/3 2/5 1/B Restaurants Restaurants 3 meals/day 1/10 8 1/10 1/5 1/10 1/10 Restaurants 1 meal/day 1/5 2 2/5 1/6 At 140 F. b Daily hot water requirement*end demand chuTarteriattca vary with the type of hoteL The betto dam botd baa a relatively high daily consumption ( low peak load. The eommereia] botd baa a lower daily consumption but a high * Tbe increasing urn of dishwashers and laundry washing machines in 'tddeaees and apertmenta (equina additional allowance! of IS pi pm dishwasher and 40 cal 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 providttl 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 for the system more closely to the required minimum, and (3) be able to design tbe piping system as accurately as is practica ble for the requirements. s COOUNG WATER PIPING Water is very frequently used in refrigeration systems, cooling towers, and other similar installations. In designing 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 designer be familiar with them. In choosing pipe material, the problem of corrosion should be kept in mind to prevent failure of the system. If tbe 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-1 refrigeration condensers where water is tie cooling medium, iron pipe is commonly employed. Water treatment is commonly used, especially in recircu- systems. See Chapter 15 of the 1961 Guide And Data KS for more detailed discussion of this subject. rS regard to assembly, cast-iron flanges or welded joints re to be preferred to screwed joints wherever possible. ^Valves used in circulating systems may be of the globe, te, or angle types. If water is the circulating medium, valve are usually used. However, if the circulating is an.electrolyte, such as brine, then it is preferable ^ose valve made of the same material as the piping itself. .The friction loss in the piping may be determined from pv 4 for fairly rough pipe. If tbe coolant is brine, a correc tion for the proper density must be made. Experience indic8teS that in sizing piping for cooling systems, a pressure drop of the order of 2 to 3 pa per 100 ft of pipe length, and a floid velocity of 3 to 8 fps, are within good practice. In the of cooling towers, the amount of circulating nter is about 3 gpm per ton of refrigeration, when based on , wet-bulb temperature of about 75 to 78 F. Table 9 gives pipe sizes frequently used for various sizes of cooling towers, osmiming a hot water temperature of 95 F and a cold water temperature of 85 F * These conditions are typical of refrigeration plants, electrically driven. Systems operated by condensing-eteam 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 matimnm daily and the Tnarimuin- hourly hot water demand form the basis for the selection of the heater and tbe 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 tbe person count is not available. The values in Table 10 are not suitable for large buildings. For these tbe 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 GaOoof of wafer per boar per fixture, eafeafafed af a final temperature at 140 F Apartment Chib Gym nasium Hospital Hotel Industrial Plant Office ' Private BuSding Residence School TJW.CA 1; Basins, private lavatory____ 2 2. Basins, public lavatory:------ 4 3. Bathtubs......................................... 20 4. Dishwashers*............................... 15 5. Foot basins............................... 3 6. Kitchen sink................................ 10 7. Laundry, stationary tubs... . 20 S. Pantry sink.................................. 5 9. Showers........................................... 30 10. Slop sink......................................... 20 11. Hydro-therapeutic showers.. 12. Hubbard baths........................... 13. Leg baths................ ................... 14; Arm baths...................................... 15. Sit* baths...................................... 16. Continuous-flow baths......... 17. Circular wash ainkn................. 18. Semi-circular wash sinks-- 19. Demand factor............................ 0.30 20. Storage capacity factor*____ 1.25 2 6 .20 50-150 3 20 28 10 150 20 0.30 0.90 22 2 86 8 30 20 20 50-150 50-200 12 3 3 20 30 28 28 10 225 75 10 75 20 30 400 . 600 100 35 30 165 20 20 10 10 0.40 0.25 0.25 1.00 0.60 0.80 2 12 20-100 12 20 225 20 30 15 0.40 1.00 2 2 22 6 15 8 20 30 15 20-100 20-100 3 3 12 20 10 20 20 20 28 10 5 10 10 30 30 225 225 20 15 20 20 20 10 0.30 2.00 0.30 0.70 30 15 0.40 ' 1.00 0.40 -- 1.00 ` Dishwasher requirements should be Uken from Table 14 or from manufacturer*' date for b Ratio oi stance mpedty to probable maxanuns demand par hour; Stance capacity may be reduced where as unlimited auppty ol steam b available tram ceetnl street etcaun ayatan or large bailer plant.