Experimental pressure drop value

The experimental pressure drop value, acc. to Bornhutter, was found to be approx. 650... 

Based on the constant value of the parameter Cb = 0.4s m, it is possible to verify by calculation 85% of the experimental pressure drop values for irrigated packing elements of any type or size as well as for type Y structured packings (for the latter, the wall factor K = 1 must be substituted into Eq. (4-48) or (4-49), see Chap. 3). The calculation is performed with a relative error of less than 15 %. This was the result of the evaluation of approx. 10000 experimental data items of various systems. The resistance coefficients xf of the tested packing elements for the transition range and the turbulent flow range of the gas phase are listed in Tables 6-la-c. 

Figure 5.2-23. Predicted values of the pressure drop (Eqn. 5.2-24) versus the experimental pressure drop data (after Wammes et al. [33]).

Figure 20 shows the calculated pressure drop factor and the experimental values. We observe that the model of Liu et al. (32) predicts the experimental pressure drop both in the Darcy s flow regime, the transition, and the Forchheimer regimes. The two-dimensional model gives a much better prediction than that using the one-dimensional model. The Ergun equation significantly overpredicts the experimental data. 

In particular, it is necessary to check self-similarity of the processes with regard to Peclet number, to study the effect of initial conditions, system pressure drop values, etc. For this purpose, simple flat water model has been constructed at the SSC RF IPPE. This model will be used for studying the effect of various factors and similarity criteria on the accuracy of modeling of the natural sodium flow (LMFR DHRS) on the water experimental rig. 

The important outcome of this study is that under the conditions of experimentation, the occurrence of a maximum in bulk viscosity and in screen factor at a certain NaCl concentration does not correspond with the pressure drop results. Except for this disagreement, the variations in the screen factor and viscosity are faithfully followed by pressure drop values in the flow rate range of 4 to 8 ml/min. 

Power input, a decisive parameter for benchmarking technical reactors, has been investigated using the experimental pressure drop and compared with conventional contactor as shown in Table 15.5. The comparison reveals that the liquid-liquid slug flow microreactor requires much less power than the alternatives to provide large interfacial area - as high as a = 5000 m m in a 0.5 mm capillary microreactor, which is way above the values in a mechanically agitated reactor (a 500 m m ). 

A simplified one-dimensional analysis of the momentum change in the test section, which neglected viscous shear, produced pressure-drop values that are equivalent to the experimental values. These predicted pressure distribution curves are superposed on the experimental data of Fig. 6 to illustrate the good agreement of analysis and experiment. 

In Figure 8 the experimental pressure drops and those calculated with the Friedel model are reported for all the runs, along with the corresponding statistical indicators. The indicators present slightly higher values than in the case of straight pipelines, but the average error is still quite low. 

Note Because of the high sensitivity of the Ergun equation to the value of e, which typically varies over the range 0.3 to 0.6, it is often preferable to extract R values from experimental pressure drop-flow rate data or to simply set Q/A = V at some "safe" value, say 0.1 m/s. The Ergun equation provides a valuable check and quantifies the dependence on e and dp. 

The same table also contains the numerical values of the form factors (f>p,exp for more than 200 types of packings, which were determined by evaluating experimental pressure drop data relating to packings with single-phase flow. 

The evaluation of the experimental pressure drop data Ap/H and Apo/H for various test systems - air/water, chlorobenzene/ethylbenzene, ethylbenzene/styrene, methanol/ethanol, toluene/n-octane etc. - acc. to Eq. (4-51), led to the following mean Cb value for the random and type Y structured packings listed in Tables 6-la-c ... 

The experimental pressure drop of a column with ds = 1.0 was found to be (Ap/H)exp = approx. 90 Pam [3], which leads to a relative deviation from the calculated value of ... 

Fig. 54 illustrates the comparison of the experimental pressure drop of wettEri packings, either up to the loading point or above it, with the values calculated by Eqs, (179) and (180). 

The term essentially a drag coefficient for the dust cake particles, should be a function of the median particle size and particle size distribution, the particle shape, and the packing density. Experimental data are the only reflable source for predicting cake resistance to flow. Bag filters are often selected for some desired maximum pressure drop (500—1750 Pa = 3.75-13 mm Hg) and the cleaning interval is then set to limit pressure drop to a chosen maximum value. 

It should be noted that most of these theories for the prediction of the pressure losses in cyclones ultimately require the assignment of certain experimentally determined quantities in order to produce reasonable agreement between theory and experiment. The involvement of these empirical constants almost certainly restrains the use of the theories to the limited group of cyclones that the experiment has covered in order to produce good predictions of pressure drops through the cyclone. Therefore, these empirical theories may be used only as a preliminary estimate of the energy consumption in cyclones. Prototype cyclone experiments may well be required in order to obtain an accurate value of the pressure loss for a newly designed cyclone. 

Valve capacities can be compared by use of the Kv (or Cv when Imperial units are used) values. These factors are determined experimentally, and the Kv value is the number of cubic meters per hour of water that will flow through a valve with a pressure drop of one bar. The Cv value is the number of gallons per minute of water that will flow through the valve with a pressure drop of one-pound f. per square inch. As the gallon is a smaller unit in the USA, the number of gallons passed is greater, and the US Cv is 1.2 times the UK Cv. The Kv is about 0.97 of the UK Cv value. 

In the usual case h and hf are falling in the direction of flow and Ah and Ahf are therefore negative. Values of frictional pressure drop, — APtpf may conveniently be correlated in terms of the pressure drop —APL for liquid flowing alone at the same volumetric rate. Experimental results obtained for plug flow in a 25 mm. diameter pipe are given as follows by Richardson and Higson(6) ... 

Pressure drop and heat transfer in a single-phase incompressible flow. According to conventional theory, continuum-based models for channels should apply as long as the Knudsen number is lower than 0.01. For air at atmospheric pressure, Kn is typically lower than 0.01 for channels with hydraulic diameters greater than 7 pm. From descriptions of much research, it is clear that there is a great amount of variation in the results that have been obtained. It was not clear whether the differences between measured and predicted values were due to determined phenomenon or due to errors and uncertainties in the reported data. The reasons why some experimental investigations of micro-channel flow and heat transfer have discrepancies between standard models and measurements will be discussed in the next chapters. 

Bowers and Mudawar (1994a) performed an experimental smdy of boiling flow within mini-channel (2.54 mm) and micro-channel d = 510 pm) heat sink and demonstrated that high values of heat flux can be achieved. Bowers and Mudawar (1994b) also modeled the pressure drop in the micro-channels and minichannels, using the Collier (1981) and Wallis (1969) homogenous equilibrium model, which assumes the liquid and vapor phases form a homogenous mixture with equal and uniform velocity, and properties were assumed to be uniform within each phase. 

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