Steady condition

Cup anemometers have shaped cups mounted on the spokes of a wheel. The cups, under the action of the fluid forces, spin in a horizontal plane about a vertical shaft mounted in bearings. Vane or propeller types use a multibladed rotor, the axis of which is parallel to the flow direction as the rotating member. Both designs are commonly used for wind speed measurement or similar appHcations such as the velocity in ventilation ducts. Because of inertia, anemometers are most accurate under steady conditions. Velocity fluctuations cause readings that are too high. 

In applying this concept, the factor of particle size must be continuously borne in mind. A heterodisperse system can reach a steady state wherein the smaller particles are agglomerated and the larger particles are dispersed, giving the apparent effect of an equiUbrium. In ideal monodisperse systems under steady conditions, however, no such effects are noted. 

The adiahatic reaction temperature reaches essentially the steady conditions, X = 0.426 and T = 784, after about 70 axial increments. 

Normally when a small change is made in the condition of a reactor, only a comparatively small change in the response occurs. Such a system is uniquely stable. In some cases, a small positive perturbation can result in an abrupt change to one steady state, and a small negative perturbation to a different steady condition. Such multiplicities occur most commonly in variable temperature CSTRs. Also, there are cases where a process occurring in a porous catalyst may have more than one effectiveness at the same Thiele number and thermal balance. Some isothermal systems likewise can have multiplicities, for instance, CSTRs with rate equations that have a maximum, as in Example (d) following. 

Since this is a steady condition, the rate of reac tion in the film equals the rate of input to the film,... 

In Figure 2.17 the tank of water has a cross-sectional area +, and under steady conditions both the outflow and inflow is Va and the head is Ha-... 

Unless otherwise specified, normal operating conditions for motors shall be assumed to be rated full-load steady conditions. 

Under steady conditions the plant should be able to hold the design room rh up to the temperature given in psychrometric tables or a chart where the design room rh and test absolute moisture content (kg/kg) coincide. At the end of the test restore the temperature set point to the design value and any control of outside air volume to automatic. Observe that operation. 

Start main refrigeration system [34]. Allow to run on load until steady conditions are reached. 

Disturbances that increase water scarcity promote the physical uniformity of river systems and the decrease of biological diversity in streams and rivers. The structure and functioning of heavily impacted river systems become mutually and strikingly similar, irrespective of the river s origin and the climate. The more intense and persistent the disturbance, the greater is the resemblance. On the other hand, river organisms use resources most efficiently in spatially heterogeneous chaimels, and under moderate disturbance frequencies, rather than in steady conditions, to which they are not adapted. 

Columns are often started up with no product take-off and operated at total reflux till steady conditions are attained. The testing of columns is also conveniently carried out at total reflux. 

An open container 8 in. high with an inside diameter of 4 in. weighs 5 lbf when empty. The container is placed on a scale, and water flows into the top of the container through a 1 in. diameter tube at a rate of 40 gpm. The water flows horizontally out into the atmosphere through two 1/2 in. holes on opposite sides of the container. Under steady conditions, the height of the water in the tank is 7 in. 

All our measurements i/ere carried out in rooms with i < 1 hr1 and the radon concentration outdoors (c 5 Bq nr 3) i/as always much smaller than indoors (cj > 100 Bq m 3). Assuming a constant radon emanation, a homogeneous activity distribution and 100 % prefiltering of the free fractions of the incoming air, the radon, the free and attached radon daughter activity concentrations indoors (cj cjf cja) and outdoors (eg c f c a) under steady conditions are ... 

Figure 7.13f). Although addition of Cu initially promotes isomerization of 1-alk-ene (initially higher l-alkene/2-alkene ratio for 100Fe/4.6Si/5.0K/2.0Cu in comparison with 100Fe/5.1Si/5.0K catalyst Figure 7.13e), at steady conditions the effect is marginal.

Cold particles of glass ballotini are fluidised with heated air in a bed in which a constant flow of particles is maintained in a horizontal direction. When steady conditions have been reached, the temperatures recorded by a bare thermocouple immersed in the bed are ... 

Example 3.2 Consider a combustor using air and methane under steady conditions. A stoichiometric reaction is assumed and diffusion effects are to be neglected. The reactants and products are uniform in properties across their flow streams. Find the mass fraction of carbon dioxide in the product stream leaving the combustor. 

Methane is supplied to a burner in a room for an experiment at 10 g/s. The measurements indicate that air flow into the room doorway is 800 g/s and the door is the only opening. The exhaust leaves the room through the upper part of the doorway at a uniform temperature of 400 °C. Assume that the methane bums completely to C02 and H20 and that steady conditions prevail in the room. 

We follow the analysis of Frank-Kamenetskii [3] of a slab of half-thickness, rG, heated by convection with a constant convective heat transfer coefficient, h, from an ambient of Too. The initial temperature is 7j < 7 ,XJ however, we consider no solution over time. We only examine the steady state solution, and look for conditions where it is not valid. If we return to the analysis for autoignition, under a uniform temperature state (see the Semenov model in Section 4.3) we saw that a critical state exists that was just on the fringe of valid steady solutions. Physically, this means that as the self-heating proceeds, there is a state of relatively low temperature where a steady condition is sustained. This is like the warm bag of mulch where the interior is a slightly higher temperature than the ambient. The exothermiscity is exactly balanced by the heat conducted away from the interior. However, under some critical condition of size (rG) or ambient heating (h and Too), we might leave the content world of steady state and a dynamic condition will... 

We will avoid the kinetics subsequently in solving for the burning rate and the flame temperature, but it is important in understanding extinction. The solutions for the burning rate and flame temperature are quasi-steady solutions for the gas phase. Where steady conditions do not exist, we have extinction ensuing. Extinction will be addressed later in Section 9.10. 

By substituting for the flame convective heat flux from Equation (9.108) for steady conditions and no external heat flux (and no char and water), the analogue to Equation (9.116) follows for the diffusion flame ... 

Under steady conditions, or where the transient term is negligible, this is simply... 

A fire bums in a compartment under steady conditions. The fuel supply rate (nip) is fixed. 

At 100 s, the burning rate has not significantly changed, and the compartment has reached a quasi-steady condition with countercurrent flow at the doorway. At this new time, compute the following ... 

Control systems may produce small fluctuations of the process variables, as in the sinusoidal cases of problem P4.09.34. When they occur while the system is at an unstable point, the temperature will migrate to that at a neighboring steady condition. In problem P4.10.01, as the unstable condition is approached (T = 280, C = 2.4), the profiles of temperature and... 

Figure (a) plots the steady state Eqs (6) and (7). Only one steady condition appears when Tf = 300, with C = 0. With a feed temperature of 250 there are three steady states, of which the middle point is unstable,... 

It is suspected that this nonlinear rate form, which has a maximum value, may cause certain regions of unstable operation with multiple steady states. How should the operation be conducted to ensure unique steady conditions ... 

Whether or not a steady condition in a CSTR is stable depends on the relative magnitudes of the generation and removal of heat. When generation is greater than removal, the temperature will rise, and when it is smaller the temperature will fall. 

Steady processes are ones that do not change with the passage of time. If denotes a property of the flowing fluid, for example the pressure or velocity, then for steady conditions... 

For steady conditions, the couple on each cylinder must be equal and opposite. Thus, denoting the magnitude of the shear stress on the inner and outer cylinders by r, and t0 respectively, the couple C is given by... 

The auto-acceleration observed under such conditions is reduced ( = 1.15) and could partially result from non-steady-conditions but also from a "matrix effect" operating on the surface of unswollen polymer particles. It should be noted in this respect that the post-polymerization which is induced by the growing chains occluded in the precipitated polymer exhibits an initial rate very much lower than the rate observed during irradiation (Curve 1 in Figure 91 which suggests that the contribution of the growth of occluded chains to the over-all rate is small. 

From the results presented above it can be concluded that the auto-accelerated conversion curves observed in the polymerization of acrylic acid, methacrylic acid and acrylonitrile are not caused by non-steady conditions arising as a result of the occlusion of growing chains in the precipitated polymer. This occlusion which is responsible for the post-polymerization observed in these systems only contributes to a limited extent to the over-all rates. 

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