Suction Effects

In addition to the usually imavoidable electroosmotic fiow, movements in the electrolyte solution can also occur which are controllable. Should the supporting layer not have been completely saturated with liquid at the beginning of the experiment, an initial suction from both sides towards the centre occurs, even without application of an electric field. Evaporation takes place if the carrier layer becomes warmer than its surroundings, as a result of the heat generated by the current. The layer thus sucks buffer solution out of the electrode compartments. This evaporation suction causes electrolyte flow from the sides towards the centre of the coated plate. 

Initial and evaporation suctions diminish as one moves towards the centre of the layer and become zero there. Substances which migrate rapidly are consequently relatively held up, which militates against the separation. 

If the electrode compartments are not filled to equal heights or the apparatus is not horizontal, a flow of electrolyte occurs also towards the lower level (siphoning effect). 

---

Pressure factor The test ratio between the suction effect and air velocity passing over a cowl or roof outlet, represented by... 

Mud temperatures of 150° can present critical suction problems. Under low pressure or vacuum existing in the cylinder on the suction stroke, the mud can boil, hence decreasing the suction effectiveness. Furthermore, hot mud accelerates the deterioration of rubber parts, particularly when oil is present. Large mud tanks with cooling surfaces usually solve the problem. 

This is a condition which occurs when the feedwater pump is unable to deliver feedwater to the boiler although the feed tank has water available. The temperature of the feed-water coupled with the possible suction effect from the feedwater pump in the line between the feed tank and the pump effectively drops the pressure, causing the feed-water to flash to steam. The pump then loses its water supply. 

Drying mercury fulminate has always been a difficult problem. For a long time cylindrical vacuum driers (Fig. 41) were used in which the suction effect of the vacuum pressure (100-200 mm Hg), normally held the lids tightly in place. 

The mercury concentration remaining in the spent cartridge case was considerably higher than previously experienced. This test did not reproduce the conditions experienced during the discharge of a round of ammunition, where much higher temperatures and pressures are attained, plus the possible suction effect in the wake of the bullet. To simulate actual conditions a further test was devised (Figure 22.2). 

Figure 3.28 Sketch of the plateau border in a surfactant foam. Due to the curvature (radius r) a suction effect in the direction of the arrows results.

The pressure drop created between capillaries in evaporation and condensation zones forces the liquid upward, so that in each dodecahedral cell circulation of liquid and gas as well as pressure drops APf and APg occur. Due to gravitation, hydrostatic pressure AP acts in each cell. Therefore, the suction effect of capillaries is... 

As a first approach deep bed filtration in planned, using sand as the filtration media. The pressure loss across the filter will be observed and when necessary, the sand will be renewed. Eventually, a pump will be installed after the filter to avoid high overpressure inside the gasifier. The engine will have a suction effect later on. 

The CE-ICP-MS interface based on the sheath-flow (make-up buffer) and pneumatic concentric nebulizers described by Lu et al. is the most widely used CE-ICP-MS interface, and it has also been applied to electrospray MS interfaces.The sheath-flow or make-up buffer acts to complete electrical connection to the exit end of the electrophoretic capillary grounding is achieved by having a metal tube or metal tee near the connection to the nebulizer (Fig. 3) or by coating the capillary with silver (Fig. 4). The second function of the sheath flow is to compensate for the suction effect. Low pressure created near the tip of the pneumatic nebulizer by the flow gas of the operating nebulizer can induce laminar flow through... 

B H3mier Day, J.A. Caruso, J.A. Evaluation of a micro-concentric nebulizer and its suction effect in a capillary electrophoresis interface with inductively coupled plasma-mass spectrometry. Appl. Spectrosc. 2000, 54, 1040-1046. 

Polyhedral gas cells produced on aging thin flat walls are produced with junction points of the interconnecting channels (plateau borders). Due to the interfacial curvature, the pressure is lower and the film is thicker in the plateau border. A capillary suction effect of the liquid occurs from the centre of the film to its periphery. 

To keep the foam stable (i.e., to prevent complete rupture of the film), this capillary suction effect must be prevented by an opposing disjoining pressure that acts between the parallel layers of the central flat film (see below). The generalised model for drainage involves the plateau borders forming a network through which the liquid flows due to gravity. 

The powder hopper is positioned above a feed frame, a frame that retains a powder bed above the dies when the lower punch is in the filling position. As the lower punches pass below the feed frame, they descend within the die to their lowest possible position so the whole die cavity can be filled with powder. The powder is filled into the dies by the suction effect caused by their descent and gravity from the feed frame above. To optimise filling, the feed frame is designed so that the powder in contact with the die table and following the rotary action of the table is directed in a manner that makes it pass to and fro across the dies. Some machines... 

Non-flushing samplers employ a suction effect for sampling. This is caused by a pressure difference between the device chamber and water... 

Romero, E., Gens, A. Lloret, A. 2003. Suction effects on a compacted clay under non-isothermal conditions. Geotechnique 53 (I) pp. 65-81. 

Abstract Chalk is the constituent material of numerous oil reservoirs in North Sea. The mechanical behaviour of a saturated chalk has been largely studied. However, different aspects of its behaviour are not yet well understood material characteristics depend on the saturating fluids and chalk response is time-dependent. This paper proposes the PASACHALK numerical model an elasto-plastic constitutive law is presented, which reproduces the different plastic mechanisms of the chalk (pore collapse and shear failure) and the influence of pore fluids. The water sensitivity of this soft rock is explained by the existence of suction effects in chalk. Finally, a simulation of a hypothetical reservoir is proposed to show the response of the elasto-plastic model during depletion phase and water injection phase. 

This paper presents the developed constitutive model, which is a cap type plasticity model coupled with the Barcelona one (Alonso et al. 1990) for taking the suction effect into account. 

As far as the suction effect is concerned, the model adopts the approach developed in the Barcelona Basic Model (Alonso el al. 1990) where the suction is considered as an independent variable. Suction modifies yield surfaces and produces reversible and irreversible deformations. 

A multimechanism model is developed to describe the chalk behaviour during water flooding. The main assumption is that water sensitivity of chalk could be related to oil-water suction effects. The Barcelona model concepts are integrated into the PASACHALK constitutive law in order to reproduce suction dependency behaviour of chalk. 

Another important aspect of chalk is its time dependent behaviour. We are currently developing an elasto-visco-plastic model including suction effects. This constitutive law will be able to deal with the main issues related to chalk. 

The cold water feed can be provided by direct coimec-tion to the mains (in which case all components must be able to withstand mains pressure) or from a feeder tank (which is in an elevated position and filled from the mains through a float valve similar to the water closet-cistern float valve). For mains pressure systems most utilities or water supply authorities require the installation of a nonreturn valve. Whereas low pressure (feeder tank) systems are open to the atmosphere through a vent pipe, mains pressure systems must be protected against overpressure (due to thermal expansion of water as heated) by a pressure relief valve, as well as against collapse (implosion), which could be caused by a suction effect (vacuum formation) in case of an aceidental water discharge, by an air intake (or breather) valve. 

---