Series/parallel piping systems

Components of a piping system that are connected in series produce additive pressure drops, while components that are connected in parallel must produce the same pressure drop. 

American Gas Association method, 121 Complex pipe systems, 122 Low pressure air, steam, 131 Panhandle formula, 120, 121 Panhandle-A formula, 121 Parallel system, 122 Series system, 122 Transmission factors, 120 Weymouth formula, 120 Flowsheet symbols, 17... 

Piping systems often involve interconnected segments in various combinations of series and/or parallel arrangements. The principles required to analyze such systems are the same as those have used for other systems, e.g., the conservation of mass (continuity) and energy (Bernoulli) equations. For each pipe junction or node in the network, continuity tells us that the sum of all the flow rates into the node must equal the sum of all the flow rates out of the node. Also, the total driving force (pressure drop plus gravity head loss, plus pump head) between any two nodes is related to the flow rate and friction loss by the Bernoulli equation applied between the two nodes. 

A system for distribution of fluids such as cooling water in a process plant consists of many interconnecting pipes in series, parallel, or branches. For purposes of analysis, a point at which several lines meet is called a node and each is assigned a number as on the figure of Example 6.6. A flow rate from node i to node / is designated as Qij-, the same subscript notation is used for other characteristics of the line such as /, L, D, and NRc. 

Typically, the temperature drop between the evaporator and condenser of a heat pipe is of particular interest to the designer of heat pipe thermal control systems and is most readily found by utilizing an analogous electrothermal network. Figure 12.4 illustrates the electrothermal analogue for the heat pipe illustrated in Fig. 12.1. As shown, the overall thermal resistance is composed of nine different resistances arranged in a series-parallel combination. These nine resistances can be summarized as follows ... 

On the other hand, in bipolar cells, only the terminal cells are connected by intercell conductors, and there are typically many unit cells electrically in series between the terminal cells (Fig. 5.2). The two basic types of bipolar cells are the flat plate cell and the finger type cell. A group of bipolar cells that have a common piping system for the fluids, via manifolds, is referred to as an electrolyzer or sometimes a series or a stack. Within a single bipolar electrolyzer, there are sometimes more than one set of terminal cells. Bipolar electrolyzers can be connected via an external bus within a DC circuit in series or in parallel, but usually not both. Furthermore, in the case of mercury-cell plant conversions to membrane cells, the electrolyzers are connected electrically in parallel as shown in Fig. 5.3. 

Hot water generators are the simplest systems overall, although many larger institutional and commercial hydronic heating plants contain fairly complex distribution systems that may include high and low flow rate subsystems and primary and secondary piping schemes in either series or parallel configurations. 

Refer to the portion of Figure 4.6 where the source tank fluid level is below the center line of the impeller in either the system connected in parallel or in the system connected in series. At the surface of the wet well (point 1), the pressure acting on the liquid is equal to the atmospheric pressure Patm minus the vapor pressure of the liquid Py. This pressure is, thus, the atmospheric pressure corrected for the vapor pressure and is the pressure pushing on the liquid surface. Imagine the suction pipe devoid of liquid if this is the case, then this pressure will push the fluid up the suction pipe. This is actually what happens as soon as the impeller starts moving and pulling the liquid up. As soon as a space is evacuated by the impeller in the suction pipe, liquid rushes up to flU the void this is not possible, however, without a positive NPSH to push the liquid. Note that before the impeller can do its job, the fluid must, first, reach it. Thus, the need for a driving force at the inlet side. 

T0 reduce the quantity of sodium leakage, the drain system was found to require two improvements. One is the addition of a new drain line pipe at the inlet of the secondary pump. The other is the replacement of all drain lines by pipes of larger diameter. In the existing system, each drain line has two drain valves in series to prevent accidental draining by single valve action error. In future so as to assure the draining, each drain line will have double drain valves in parallel. After these improvements, the drain time will be shortened from approximately 50 minutes to 20 minutes. It is estimated that it takes 40 minutes from the occurrence of sodium leakage to finish the drain for the secondary circuit. The modified drain system is shown in Fig.9. 

FIGURE 10 Three ways of coupling an auxiliary heater with the solar space heating system (1) In the storage tank, (2) in the distribution circuit flow pipe (series connection), and (3) In a storage bypass (parallel connection). 

The adsorl)er sy.stem contains two activated charcoal-filled units connected in parallel to the gas line from the reactor. JCach unit consists of 40 ft of - -in. pipe, 40 ft of 1-iii. pipe, 40 ft of 2-in. pipe, and GO ft of G-in. pipe connected in series. I he entire system is contained in a water-tilled pit, which is liuried underground for gamma. shielding purpo.ses. Kach unit is filled with approximately 520 It) of Columl)ia C activated charcoal, 8 to 14 mesh. 

Horizontal loops. Horizontal loop designs vary fi om a single, in-series pipe to multipipe parallel systems. Pipes are laid in trenches 4-6 ft deep, using a baddioe or trencher, and pressure tested, and then the trench is backfilled. See Fig. H-3. 

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