Document 2qw6G6GM6VYegv393ZvLo47wL

590 CHAPTER 21 1958 Guide formula (Equation 8, Chapter 4) with values of the density and viscosity of water chosen for 300 F. When corrections are desirable Fig. ;24 may be used to correct the friction loss as found in Fig. 23. The friction loss in fittings expressed in equivalent feet of pipe is given in Table 5. Circuits High temperature water is used directly in unit heaters, air heating coils, steel heating panels, and process equipment. Evaporators or steam genera tors are used for generating steam where required for steam heating sys tems and equipment. Converters or heat exchangers are also used for building heating and domestic hot water service systems. Smaller district heating systems pressurized at 12 to 15 psig with dis tribution at 250 F are in common use. In such installations the water is VEU. IN,/SEC Fig. 24. Correction of 300 F Friction Loss for Other Water Temperatures Reprinted by permission from Reference 17. drawn into the individual building systems and recirculated by means of a conventional circulator. Temperature is controlled in each system by a con trol valve at the high temperature line. The control is usually of the indoor-ovldoor type, but many variations are used. Sufficient pressure head is usually available to permit circulation of the high temperature water through domestic water heaters for individual supply in each building. Pumps for High Temperature Systems Circulating pumps form one of the most important components of the system, and are installed in the flow main to increase the static pressure in the main and thereby maintain a satisfactory temperature-pressure rela tionship and keep the pressure in the system at all times above the evap; oration temperature of the water. It is common practice to use single-inlet single-stage centrifugal pump? operating at 1750 rpm and having water-cooled bearings and glands (al- Hot Water Heating Systems 591 Table 5.' Head Loss in Fittings* (For turbulent flow) Fittikos 10 8 Feet of Same Size Pipe Havxho Equal Loss0 6 5 4 3 2H 2 m W 1 H H Globe Valve.................. 340 270 200 170 135 105 83 70 55 45 36 28 . 21 Gate Valve................... 7 5.75 4.5 3.5 3 2.2 1.7 1.5 1.2 1 0.8 0.6 0.5 90 Welding Elbow___ 11 8.5 6.5 5.5 4.5 3.5 2.6 2.2 1.8 1.5 1.2 0.9 0.7 45 Welding Elbow___ 7 6 4.5 3.6 3 2.4 1.7 1.5 1.2 1 ' 0.8 0.6 0.5 22J4 Welding Elbow.. 5 4 3 2.5 2 1.6 1.3 1.1 0.9 0.7 0.6 0.5 0.3 Lateralb.......................... 26 20 16 13 11 8 6.5 5.5 4 3.5 .2.8 2.2 1.6 Lateral*................ ...... 17 14 10 8.5 7 5 4 3.5 2.8 2.5 1.8 1.5 1.1 Welding Tee*................ 13 10 8 7 5.5 4 3.2 2.6 2 1.7 1.4 1.2 0.8 Concentric Reducers4 \ 10 8 6 5 4 3 2K 2 m 1M 1 M K From \ 10 \ \ 1 2.5 3 2.8 8 3.5 V \ 1.2 2 2.2 2.2 C DNTRAC TIN G 6 10 3.5 \ \ 0.5 1.3 1.8 1.7 \5 12 7.5 1.5 \ 0.5 1.2 1.4 1.5 \4 12 9.5 4.5 1.5 \ 0.6 1.2 1.4 1.5 3 10 7 5 1.8 \ \ 0 0.8 1 1 2J4 7.5 6 3.8 0.7 \ \ 0 0.7 0.8 0.75 -- 2 6 5 2.5 0.8 \ \ 0 0.6 0.6 0.6 \m 5 3.8 2.8 9 6 0.5 0.5 0.5 4 3 2 0.3 \\ 0 0 0.3 \\i El4LA tGn4G 3 2.5 1.25 0.5 0 0.3 H 2.5 2 1.3 0.5 \ \ 0 H 2 1.8 1.5 0.8 \ Cilc?CK5a ^ugh branch, d SJnlSW Va,*ht through fitting. * Emiivolor,*1L.5^ilcerB,.the values read for concentric reducers must be increased by 33^%. vaient length of pipe having a Fanning friction coefficient of 0.006. mechanical seals are coming into use). With pumps of this typ total differential head should not exceed 150 ft. to^ temperature must be specially designed and construct the higher pressure and temperature, at which they wil g' and the higher stresses involved. For space heating loads wher althouW}iVaneS great'y> it is common practice to use two or more pumps one or CarC s^10ui<i t*e taken in motor sizing to avoid overloading whe: lieht lnaH0r!i t>'^rnPs "ay not be in operation. By use of multiple pump 6 oaos during off peak periods can be handled economically.