Steam-Fluid Flow

The above results show close agreement between the experimental and theoretical friction factor (solid line) in the limiting case of the continuum flow regime. The Knudsen number was varied to determine the influence of rarefaction on the friction factor with ks/H and Ma kept low. The data shows that for Kn 0.01, the measured friction factor is accurately predicted by the incompressible value. As Kn increased above 0.01, the friction factor was seen to decrease (up to a 50% X as Kn approached 0.15). The experimental friction factor showed agreement within 5% with the first-order slip velocity model. 

The influence of compressibility was assessed by varying the Mach number in the range 0 Ma 0.38, while Kn and ks/H were kept low. Friction factor data were reported only with Ma 1 at the exit, to ensure the flow rate was controlled by viscous forces alone. A mild increase in the friction factor (8%) was observed as Ma approached 0.38. This effect was verified independently by numerical analysis for the same conditions as in the experiment. The range of relative surface roughness tested was 0.001 ka/H 0.06, yet there was no significant influence on the friction factor for laminar gas flow. 

Thome et al. (2004) and Dupont et al. (2004) proposed the first mechanistic analysis for vaporization in a micro-channel, with a three-zone flow boiling model describing 

The micro-scale flow patterns described by Revellin et al. (2006) were categorized as follows  

Bubbly flow. Here the bubbles were shorter than the tube diameter and the vapor phase was distributed as discrete bubbles in a continuous liquid phase (Fig. 2.30a). 

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The Curtis and the Parsons turbine designs are based on different fundamental principles of fluid flow. The Curtis turbine has an impulse design, where the steam expands through nozzles so that it reaches a... 

Given the rate of fluid flow to be relieved, the usual procedure is to first calculate the minimum area required in the valve orifice for the conditions contained in one of the followng equations. In the case of steam, air or water, the selection of an orifice may be made directly from die capacity tables if so desired. 

The H-S plot is called a Mollier diagram and is particularly useful in analyzing throttling devices, steam turbines, and other fluid flow devices. A Mollier diagram for steam is presented in Figure 2-37 (standard engineering units) and in Figure 2-38 in SI units. 

Bankoff, S. G., 1960, A Variable-Density, Single-Fluid Model for Two-Phase Flow with Particular Reference to Steam-Water Flow, Trans. ASME, J. Heat Transfer 52 265-272. (3)... 

Our initial work on reaction thermal effects involved CFD simulations of fluid flow and heat transfer with temperature-dependent heat sinks inside spherical particles. These mimicked the heat effects caused by the endothermic steam reforming reaction. The steep activity profiles in the catalyst particles were approximated by a step change from full to zero activity at a point 5% of the sphere radius into the pellet. 

Chisholm, D., The influence of mass velocity on frictional pressure gradients during steam-water flow. Paper 35 presented at 1968 Thermodynamics and Fluid Mechanics Convention, Institution of Mechanical Engineers, Bristol, March (1968). 

A Rankine/Rankine cycle (Fig. 5.16) uses steam as the working fluid with 1 kg/sec mass flow rate through the top Rankine cycle, and Freonl2 as the working fluid in the bottom Rankine cycle. The steam condenser (FIXl) pressure is 20 kPa, the boiler pressure is 3 MPa, and the steam superheater temperature is 400°C. The steam mass flow rate is 1 kg/sec. 

Fluid Flow. See under Fluid Mechanics or Dynamics and die following Refs Refs 1) R.F. Steams et al, Flow Measurements eith Orifice Meters , VanNostrand, NY (1951), 384pp 2) J.R. Caddell, "Fluid... 

Fixed- or packed-bed reactors refer to two-phase systems in which the reacting fluid flows through a tube filled with stationary catalyst particles or pellets (Smith, 1981). As in the case of ion-exchange and adsorption processes, fixed bed is the most frequently used operation for catalysis (Froment and Bischoff, 1990 Schmidt, 2005). Some examples in the chemical industry are steam reforming, the synthesis of sulfuric acid, ammonia, and methanol, and petroleum refining processes such as catalytic reforming, isomerization, and hydrocracking (Froment and Bischoff, 1990). 

BASIC Programs for Steam Plant Engineers Boilers, Combustion, Fluid Flow, and Heat Transfer, V. Ganapathy... 

Because of priority requirements the hot fluid flow rate for the exchanger in Probs. 10-19 and 10-20 must be reduced by 40 percent. The same water flow must be heated from 35 to 85°C. To accomplish this, a shell-and-tube steam preheater is added, with steam condensing at I50°C and an overall heat-transfer coefficient of 2000 W/m- °C. What surface area and steam flow are required for the preheater ... 

Cracking is carried out in a fluid bed process as shown in Fig. 7.9. Catalyst particles are mixed with feed and fluidized with steam up-flow in a riser reactor where the reactions occur at around 500°C. The active life of the catalyst is only a few seconds because of deactivation caused by coke formation. The deactivated catalyst particles are separated from the product in a cyclone separator and injected into a separate reactor where they are regenerated with a limited amount of injected air. The regenerated catalyst is mixed with the incoming feed which is preheated by the heat of combustion of the coke. 

In these types of heat exchangers the two fluids are separated by the tube walls. As one fluid flows through the shell— the region outside the tubes — the other fluid flows through the tubes. Heat transfer occurs so as to cool, and perhaps even condense, the hotter fluid, and heat, and even vaporize, the cooler fluid. Heat exchangers are called by various names depending on their function such as chillers, condensers, coolers, heaters, reboilers, steam generators, vaporizes, waste heat boilers, and so on. 

Minimize the throttling of fluid flow, steam, or other gases. 

This process is technologically more difficult to implement, because it requires the use of muldtube reaction systems with heat transfer fluid flow outside the tubes. However, it is justified by the energy gains and the better performance achieved by operation at a lower reactor feed inlet temperature, and consequently with a lower steam ratio than with adiabatic operation. 

In the separator unit, steam separates the catalyst from the hydrocarbon products. The internals of the stripping unit contain cyclones which remove residual catalyst from the hydrocarbon fluids. The fluids flow to a distillation column which separates the products into various fractions. 

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