Bypass flow

Fypass Flow Effects. There are several bypass flows, particularly on the sheUside of a heat exchanger, and these include a bypass flow between the tube bundle and the shell, bypass flow between the baffle plate and the shell, and bypass flow between the shell and the bundle outer shroud. Some high temperature nuclear heat exchangers have shrouds inside the shell to protect the shell from thermal transient effects. The effect of bypass flow is the degradation of the exchanger thermal performance. Therefore additional heat-transfer surface area must be provided to compensate for this performance degradation. 

AM(from equation 46) + AM(bypass flow) + AM(entrance/exit effects) + AM (baffle plates)... 

Install bypass piping back to suction vessel to increase flow through pump. Remember bypass flow may have to be as high as 50 percent of design flow. 

Fraction of crossflow area ovailable for bypass flow, F p... 

FIG. 11-17 Cor rection factor on pressure drop for bypass flow. 

The same procedure maybe used at other pump flows to permit plotting the series of balance-point curves as has been done in Fig. 29-61. From such curves, one can establish the maximum lean pump at any total tower outflow, and combining this with the semilean-pump performance curve results in Fig. 29-55. Bypass flow plotted in Fig. 29-55 is obtained by adding simultaneous lean- and semilean-pump flows and subtracting the recovery pump-turbine flow required to make the balance point at that lean-pump flow. 

The regenerator (Figure 4-80) is represented by a simplified model that ineludes the total volume and mass balanee ealeulation. The regenerator exit temperature is assumed eonstant for the duration of the transient. The third-stage separator is handled as a fixed volume and assoeiated pressure drop. Blow-down (bypass) flow is subtraeted from the input flow. 

Once the soil cores have been collected, all boreholes must be backfilled with untreated soil (with frequent tamping) to prevent bypass flow that could transport residues into the lower soil profile. After backfilling, flags or stakes should be placed at the boreholes. This serves as an additional check to ensure that sub-plots are not sampled more than one time during the study. (Note that these boreholes should... 

As can be seen from Figure 3b and 3d continuous flow systems bypass wastewater and recycle sludge to develop flexibility. Recycling is directed mostly to the first reactor. Bypass flow typically goes to anoxic or anaerobic tanks to supply electron donors for the removal of phosphorus and/or for denitrification. The equivalent action in an SBR is the application of aeration and mixing during react (except after static fill). 

Bypass flow, where a portion of the fluid bypasses the vessel or a particular flow region,... 

The reactor wells are pre-loaded with catalyst (diluted with silicon carbide if desired) and inserted into the module. Two graphite seals are used per well, one to pressure seal each vial and one to prevent bypass flow around the vial. A single central bolt in tension supplies the sealing force onto these seals (Fig. 3.12b). 

The more expensive the catalyst, the higher the optimum recycle flowrate (and reactor pressure drop). We are trading off recycle costs with reactor costs. No bypass flow is needed when the inlet temperature is 475 K or higher. The optimum y A/y B ratio decreases as recycle flowrate increases because the costs associated with heat transfer and compression are lower with more B in the gas because of its higher molar heat capacity. 

When reactor inlet temperature is decreased 10 K, production rate is decreased by only 4% and the exit temperature increases by 1.6 K. Note that the furnace heat input goes to zero at about 4 min, and the inlet temperature is maintained by using bypass flow around the FEHE. 

In this flowsheet the presence of the furnace provides an additional control degree of freedom, and there are now two controllers. The first G( (X) controls 7 lmx by manipulating bypass flow Fby. The second Gc2(s) controls Tm by manipulating furnace firing QF. The second controller sees the furnace transfer function GF2(S) which we assume to be a furnace first-order lag and three small lags (see Fig. 7.4b) ... 

The temperature 7 mix of the blended stream of gas from the heat exchanger and gas bypassing the heat exchanger is controlled by manipulating bypass flow-rate Fh y. 

Control with Only Bypass The important control loop in this process is the temperature controller that manipulates the bypass flow to control the temperature of the mixed hot and cold streams. The controller is direct acting (an increase in temperature opens the bypass valve). A 1-min deadtime is inserted in the loop, and a relay-feedback test is run that gives Tyreus-Luyben settings Kc = 0.48 and T/ = 4.0 min. The temperature transmitter span is 350-450 K. 

The performance of this control structure, which does not use the furnace, is shown in Figure 7.31. At 0.1 hours, the feed composition is changed from 5 to 7.5 mol% chlorine. The reactor outlet temperature climbs because of the increase in reaction heat generation. The hotter gas entering the FEHE raises the temperature of exit stream, which raises the temperature of the mixture. The temperature controller increases the bypass flow to hold the reactor inlet temperature at 400 K. 

Figure 7.35 gives results for the same scenario of feed composition disturbance used previously. When feed chlorine composition is increased, both the furnace heat input and the bypass flow respond. The furnace heat input QP drops to zero for about 0.7 h. When the composition of chlorine in the feed is decreased, the bypass flow goes to zero, but the furnace heat input increases and holds the reactor inlet temperature Tin at... 

Figure 3 shows the nodalisation of the HTTR-IS system model. The reactor consists of the internal flow path (P2), permanent reflector blocks (HS25), upper plenum (B4), reactor pressure vessel (RPV) (HS30), vessel cooling system, reactor core bypass flow (P10), lower plenum (B12) and reactor core. The... 

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