Effect of water flow

By means of this relation, the effect of water-flow rate and the required temperature drop in the refrigeration unit can he visualized. Thus, if the water requirement increases, hut is at a smaller At, it is possible that an existing unit may he capable of handling the load. 

Strictly speaking, in this formulation the effective diffusion coefficient, is replaced by an empirical dispersion coefficient, D, to account for the effect of water flow on diffusion. However, in practice, the rate of transpirational water flow is sufficiently slow that dispersion effects are minimal and Eq. (8) can be used without error. This is because the Peclet number (see Sect. F.2) is small. For the same reason, in almost all cases diffusion is the most important process in moving nutrients to the root and the convection term can be omitted entirely. 

PESCATORE AND MACH1ELS Effects of Water Flow Rates on Leaching 351... 

Turner, E.J., Zimmer-Faust, R.K., Palmer, M.A., Luckenbach, M., and Pentcheff, N.D., Settlement of oyster (Crassostrea virginica) larvae effects of water flow and a water-soluble chemical cue, Limnol. Oceanogr., 39, 1579, 1994. 

Y.-J. Kim, C. C. Lin, R. Pathania, Effect of Water Flow Velocity on Electrochemical Corrosion Potential of Stainless Steel in 288 °C Water, presented at CORROSION 93, New Orecans, LA, March 8-12, 1993, Paper 621. 

Effect of water flow velocity on the corrosion of steeL Increased oxygen leads first to higher corrosion, then to oxygen passivation that lowers corrosion. 

Use of Unsupported Anode Catalysts (Iridium Black) and the Effect of Water Flow Rate and Water Purity... 

MEA 25 was then used to test the effects of water flow rate on SPE electrolyzer performance. Data was collected using flow rates between 2 and 4.5 mL/s. Each data point obtained was stable over 300 s during chronocoulometry with a GPES system at a temperature of 23 °C. The cell resistance was 164 mQ. As expected, the current density increased with faster flow rates (Figure 8.7a), and can be simply attributed to improved transport phenomena i.e., optimal movement for ingress of reactants and removal of products. The lowest flow rate with the maximal current density, with this test module, was found to be 3.27mL/s, above which minimal improvement in the current density was observed (Figure 8.7a). 

Table 6-13 Effect of Water-Flow Rato on SiFt Absorption in Cocumnt Spray Tower ...

A = 4.05 X lO " cm/(s-kPa)(4.1 X 10 cm/(s-atm)) and = 1.3 x 10 cm/s (4)//= 1 mPa-s(=cP), NaCl diffusivity in water = 1.6 x 10 cm /s, and solution density = 1 g/cm . Figure 4 shows typical results of this type of simulation of salt water permeation through an RO membrane. Increasing the Reynolds number in Figure 4a decreases the effect of concentration polarization. The effect of feed flow rate on NaCl rejection is shown in Figure 4b. Because the intrinsic rejection, R = 1 — Cp / defined in terms of the wall concentration, theoretically R should be independent of the Reynolds... 

FIG. 26-49 Effect of water vapor coodeosatioo 00 voliioie flow rate of air ioto taok. Fullaiton, Evtipidis, and Schliinder, 1987, hy permission of Elsevier Science S.A., Lausanne, Switzerland.)... 

Impingement attack Copper may occasionally suffer this form of attack in systems where the speed of water flow is unusually high and the water is one that does not form a protective scale, e.g. a soft water containing appreciable quantities of free carbon dioxide . Ball valve seatings may also suffer an erosive type of attack. The corrosion of ball valves, including the effect of chlorination of the water, has been studied by several workers... 

The specimens should be oriented so that their flat surfaces are parallel to the direction of water flow and so that one specimen will neither shield an adjacent specimen from effects of water velocity nor create any considerable extra turbulence upstream of it. 

A flow of I kg/s of an organic liquid of heat capacity 2.0 kJ/kg K is cooled from 350 to 330 K by a stream of water flowing countcrcurrently through a douhle-pipe heat exchanger. Estimate the effectiveness of the unit if the water enters the exchanger at 290 K and leaves at 320 K. 

The diffusivity of water vapour in air is 2.4 x It) 5 nr/s and the mass transfer resistance is equivalent to that of a stagnant gas film of thickness 0.25 mm. Neglect the effects of bulk flow. 

Experimental and numerical analyses were performed on the heat transfer characteristics of water flowing through triangular silicon micro-channels with hydraulic diameter of 160 pm in the range of Reynolds number Re = 3.2—84 (Tiselj et al. 2004). It was shown that dissipation effects can be neglected and the heat transfer may be described by conventional Navier-Stokes and energy equations as a common basis. Experiments carried out by Hetsroni et al. (2004) in a pipe of inner diameter of 1.07 mm also did not show effect of the Brinkman number on the Nusselt number in the range Re = 10—100. 

Alterations of water flow, independent of the cause, impact the stmcture and function of aquatic ecosystems. Extended drought produces the loss of hydrologic connectivity between stream compartments, and affects the biota. Therefore, flow cessation triggers a chain of cascading effects, eventually affecting community structure and ecosystem functioning. 

Water quality descriptor Effect of low flow Effect on biota Affected process... 

If the effect of water stress is to alter regulation of the pathway such that the rate constant for reaction A G is increased or A CP is decreased (which would have an overall effect of conserving nitrogen), then the fractionation at G can be shown to be thereby increased. At present this is speculative, but in fact explanations for the water-stress effect using flow-models are rather constrained. For example, it is not possible to relate what might happen at the kidneys (e.g., resorption of urea) to the amino acid body pool, since the urea cycle is non-reversible. It should be possible to design experiments that test this suggestion. 

Studies described in earlier chapters used cellular automata dynamics to model the hydrophobic effect and other solution phenomena such as dissolution, diffusion, micelle formation, and immiscible solvent demixing. In this section we describe several cellular automata models of the influence of the hydropathic state of a surface on water and on solute concentration in an aqueous solution. We first examine the effect of the surface hydropathic state on the accumulation of water near the surface. A second example models the effect of surface hydropathic state on the rate and accumulation of water flowing through a tube. A final example shows the effect of the surface on the concentration of solute molecules within an aqueous solution. 

Example 6.2. Influence of water flow rate on wall effect... 

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