Manifold design

The operating principle of externally-heated manifolds has already been described in Chapter 1.2. This is the traditional manifold design, which is still the dominant one in the market. 

Manifolds are divided in terms of their mechanical design into  

1 - sprue bushing 2 - melt filter 3 - support pad 4 - aligning pin 5 -dowel pin 6 -pressure disc 7 - end plug 8 - metal seal 9 - HR nozzle 10 - tubular heater 11 -thermocouple 12 - reflector sheet 13 - insulation plate 14 - pin Reproduced with permission from Hasco Normalien Hasenclever GmbH Co.) 

The channel must be polished. In the centre of the manifold is a sprue bushing (1), on the opposite side is a support pad (3) taking the pressure from the injection machine cylinder and a pin (4) aligning the manifold. A second pin (5) located in the end of the manifold sets its angular position. The manifold is pressed against the HR nozzles located in the mould by pressure pads (6) on the opposite side of the manifold. The transfer from the 

In the example given, the manifold is an intermediate product intended for completion and assembly at the user/mould manufacturer. Standardisation of this sort has enabled the manifold to be delivered without delay to the mould manufacturer. 

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It has become quite popular to optimize the manifold design using computational fluid dynamic codes, ie, FID AP, Phoenix, Fluent, etc, which solve the full Navier-Stokes equations for Newtonian fluids. The effect of the area ratio, on the flow distribution has been studied numerically and the flow distribution was reported to improve with decreasing yiR. 

Mak has developed an improved method of relief valve manifold design. The APT has adopted this method, which starts at the flare tip (atmospheric pressure) and calculates backwards to the relief valves, thus avoiding the trial and error of other methods. This is especially helpful when a large number of relief valves may discharge simultaneously to the same manifold. 

Mak, New Method Speeds Pressure-Relief Manifold Design, Oil and Gas Journal, Nov. 20, 1978. 

Several studies (Klein et al. 2005 Mishan et al. 2007) showed that manifold design plays an important role in the liquid distribution among parallel micro-channels, which can lead to spanwise temperature gradients on the device surface, increase the thermal stresses and reduce reliability. To study the effect of entrance conditions... 

The manifold design allows for the determination of ammonia concentration in the range 0.2-20 xg/l as NH4 over a salinity range 35- 10%o, with negligible interference from amino acids. 

In the continuous processing of discrete samples in the AutoAnalyzer system, the reaction-time is held constant by the manifold design, and because the rise-curve is exponential the degree of attainment of steady-state conditions is independent of concentration. Consequently it is unnecessary for the analytical reaction to proceed to completion for Beer s Law to be obeyed. This confers a considerable advantage upon the AutoAnalyzer approach and one which is frequently emphasized. The relationship between degree of attainment of steady state and IT,/, can be generaHzed in the semi-logarithmic plot of Fig. 2.16 [10], where time is expressed in units of IT,/,. 

In a 200 mm OPS line, the die is usually 1.0-1.3 m wide. These dies are generally of the coat hanger manifold design with separate choker bar and... 

For compressible fluid flow in plant piping, one can use Mak s Isothermal flow chart (Figure 1). Mak s chart was provided originally for relief valve manifold design and adopted by API. The relief valve manifold design method, and its derivation, is discussed in Section 20, Safety. Mak s methods can be applied to other common plant compressible flow situations. 

Since Mak s Isothermal flow chart is intended for relief manifold design, it supports calculations starting with P2, the outlet pressure, that is atmospheric at the flare tip, and back-calculates each lateral s inlet pressure. Pi. These inlet pressures are the individual relief valves back pressures. The chart parameter is M2, the Mach number at the pipe outlet. Having M2 is very useful in monitoring proximity to sonic velocity, a common problem in compressible flow. 

Note This case (given P2 and W) is the same as an individual lateral in relief manifold design. 

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