Pressure loss, head gain

Test methods described in the literature inelude the bubble method, helium mass speetrometiy, liquid tracer (dye), head spaee analysis, vacuum and pressure decay, weight loss and gain, and high voltage leak deteetion [6]. 

The sum of velocity head valves and fittings, and the frictional pipe run loss with the static head gain or loss, make up the entire pipe pressure loss ... 

In addition to pressure head, elevation head, and velocity head, head also can be added to the system (usually by a pump) and head can be removed from the system due to friction or other disturbances within the system. These changes in head are referred to as head gains and head losses. By balancing the energy between two points in the system, we can obtain the energy equation (Bernoulli s Equation) ... 

Flow Summary shows the values of fC-pipe and fC-fittings. These are the indications of pressure drop contribution by the pipe and fittings. In the Pressure Drop frame, there are a few pressure drop calculations, which include the contribution of static pressure drop (elevation loss or gain), velocity head (change in velocity due to reducer or expander), and control valve. The result also shows the frictional pressure drop per 100 m. This is sometimes very useful, because most operating companies establish some basic value of pressure drop per 100 m. 

The 35 ft of elevation (about 15 psi of head pressure) that the water had to gain to climb to valve B. Of course, this 15 psi of head loss was regained when the water flowed back down to the cooling-water return header. 

The problem is that the condensate rising from the steam trap will begin to lose pressure due to the gain in elevation. As it rises above the reboiler level, the hot saturated water will start to flash, undergo vapor lock as described above, and thus choke off the flow. The condensate will back up in the charmel head of the reboiler shown in Fig. 13.4 and become subcooled enough to suppress steam evolution until the condensate enters the drum. The required subcooHng may easily floods half or more of the surface area of the reboiler. The loss of reboiler... 

For the reducer, because V2 is more than v, the downstream pressure P2 will reduce however, for the expander, the downstream pressure p2 will increase. This velocity head loss/gain is calculated with the consideration of no frictional loss. 

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