Total mass flow rate

The above criteria are a guide for detecting potential problems with gas letdown systems and apply for the first 90 m of piping downstream of the pressure reducer under concern. Systems with only liquid flow are not considered potential problems and need not be investigated. For systems with two phase flow, use the conservative assumption of the total mass flow rate as gas. Any system exceeding these criteria should be further evaluated. 

Total mass flow rates are given by the product of volumetric flow multiplied by density. Component mass flows are given by the product of volumetric flow rates multiplied by concentration. 

G Total mass flow-rate per unit area ML-2T- ... 

The interfacial area a was not measured, and the quantity (Ua/V) was correlated versus the total mass flow rate. From results of this type, the general parameters given in Eqs. (30) cannot be evaluated. Therefore, the only design that can be safely performed is for the Aroclor-water system in a 3-in. pipe. 

The total mass flow rate is then 29.58(89.86) = 2658 g/sec or 2.658 kg/sec. For 1000 tubes in parallel the available cross section for flow is given by... 

Example 15-2 Estimate the pressure gradient (in psi/ft) for a two-phase mixture of air and water entering a horizontal 6 in. sch 40 pipe at a total mass flow rate of 6500 lbm/min at 150 psia, 60°F, with a quality (a) of 0.1 lbm air/lbm water. Compare your answers using the (a) omega (b) Lockhart-... 

The case for evaporation of a volatile from a pool of liquid has already been considered in chapter 3. The total mass flow rate from the evaporating pool is given by Equation 3-12 ... 

The flow of gas-liquid mixtures in pipes and other items of process equipment is common and extremely important. In some cases the quality, that is the mass fraction of gas in the two-phase flow, will vary very little over a large distance. An example of this is the flow in many gas-oil pipelines. In other cases, boiling or condensation occurs and the quality may change very significantly although the total mass flow rate remains constant. 

Consider a fixed volume V into which fuel and air are injected at a fixed total mass flow rate m and temperature T0. The fuel and air react in the volume and the injection of reactants and outflow of products (also equal to rii) are so oriented that within the volume there is instantaneous mixing of the unbumed... 

The shape factors range from 0 to 1 and approach 1 for shallow channels that is, H/W fti 0. It Is Important to Include the shape factors when evaluating commercial screw channels. This becomes extremely Important for deep channels where H/W does not approach 0. The total mass flow rate, 0, Is calculated by combining the flow components as provided In Eq. 1.29 for the total mass flow rate. As stated previously, the rate, rotational flow, and pressure flow calculations should be performed at the start of every troubleshooting project. 

The trend observed in Fig. 17.5 illustrates the importance of swirl. The image sequence corresponds to data points using front swirl angles of 31°, 41°, and 68° with all other parameters fixed 4> = 0.68, RMS = 0.1, L = 12 in. (30.48 cm), total mass flow rate of 0.03 kg/s, and rear swirl angle of 85°). The chamber averaged swirl is defined as the sum of the front and rear drive angular momentum divided by the chamber radius and total mass flow. This provides a measure of the swirl experienced by the combustion chamber confined flow and allows comparison between different test conditions. The flame speed ratio... 

Compute total mass flow rate at nozzle throat by mg = AAxVxpp... 

The original correlation showed a scatter of nearly 50% in predicting two-phase pressure drops, and, in addition, a decided dependence on liquid rate (which the correlation averaged out). Much of this scatter seemed to be a systematic drift depending on total mass flow rate. This dependence on mass flow was pointed out by Gazley and Bergelin (L6) and by Isbin et al. (12). In the following summary, satisfactory predictions can be taken to mean prediction of pressure drops no worse than the above, and, in some cases, considerably better. 

Wallis states that if bubbles were uniformly dispersed, and nonrigid, then their effect at a constant total mass-flow rate would be simply to increase the stream velocity, and at a constant friction factor, the pressure-drop would be,... 

The decrease in film burn-out heat flux with increasing mass velocity of flow at constant quality has been explained by Lacey et al. in the following way. At constant quality, increasing total mass flow rate means increasing mass flow of vapor as well as liquid. It has been shown that above certain vapor rates increased liquid rates do not mean thicker liquid layers, because the increased flow is carried as entrained spray in the vapor. In fact, the higher vapor velocity, combined with a heat flux, might be expected to lead to easy disruption of the film with consequent burn-out, which seems to be what actually occurs at a constant steam mass velocity over very wide ranges of conditions—that is, the critical burn-out steam quality is inversely proportional to the total mass flow rate. 

The pressure gradient is known to be a constant, but its value may not be known. In this case, some further independent information is required to determine a unique particular solution. As an illustration of this point, assume that the total mass flow rate in the annular space is independently specified ... 

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