Heat inputs, typical

All weldments were prepared in the flat position. The multipass GMAW weldments were classified as moderate heat input, typical of industrial practice. The two-pass SAW weldment was classified as a high-heat input weldment. 

Induction heating is used to heat steel reactor vessels in the chemical process industry (5). The heat produced in the walls is conducted to the material within. Multisectioned cods are used to provide controlled heat input to the process material as it passes through the reactor. Figure 6 illustrates a cross section of such a typical installation. 

Ethylene Stripping. The acetylene absorber bottom product is routed to the ethylene stripper, which operates at low pressure. In the bottom part of this tower the loaded solvent is stripped by heat input according to the purity specifications of the acetylene product. A lean DMF fraction is routed to the top of the upper part for selective absorption of acetylene. This feature reduces the acetylene content in the recycle gas to its minimum (typically 1%). The overhead gas fraction is recycled to the cracked gas compression of the olefin plant for the recovery of the ethylene. 

Here, h is the enthalpy per unit mass, h = u + p/. The shaft work per unit of mass flowing through the control volume is 6W5 = W, /m. Similarly, is the heat input rate per unit of mass. The fac tor Ot is the ratio of the cross-sectional area average of the cube of the velocity to the cube of the average velocity. For a uniform velocity profile, Ot = 1. In turbulent flow, Ot is usually assumed to equal unity in turbulent pipe flow, it is typically about 1.07. For laminar flow in a circiilar pipe with a parabohc velocity profile, Ot = 2. 

Figure 5 shows the calculated heat Input and cooling coll heat removal rates In KW, the latter calculated from water flow and temperature differential by the computer when logging. As Is typical with non-reflux processes, actual heat Is within 5% of expected from the theoretical heat of reaction. 

A typical water heater contains 40 gal of water and has a heat input of42,000 Btu /hr. If the heater is equipped with a 150-psia spring relief device, compute the area required for relief. Hint Two-phase flow is expected. Assume no overpressure. 

Thermal Expansion Contained liquids may be subject to heat input that causes them to expand resulting in a pressure increase. Typical heat sources are direct sunlight and fire exposures. 

CSMPlug can predict the total dissociation time by two-sided depressurisation, and by evenly applied radial heat input to an accuracy of 10%, provided accurate plug properties are known. Predictions from the one-sided depressurisation module are less accurate than those of the other modules, but are within an order of magnitude of those observed dissociation times for laboratory scale hydrates are typically over predicted but industrial hydrates are under predicted. 

Given the heat of vapourisation of the mixture, the required heat input gR (in kW) can be found from the vapour flow rate V. In the calculations above, the reflux ratio was given. As mentioned earlier, different values are typically considered, and the calculations repeated, to determine the reflux ratio which gives the most economical column operation and design. 

A typical heat balance for Run LSF 34 on No. 6 oil is given in Table V. The calculated efficiencies are also given in the table. Heat input terms consist of the input heat from the fuel, the fuel sensible heat, and the makeup water sensible heat. The heat available from combustion of the fuel is calculated from the measured volumetric flow rate, the measured fuel heating value, and the measured fuel density at the nozzle temperature. The fuel sensible heat contains the fuel mass flow rate, the measured temperature at the nozzle, a reference temperature, and an estimated specific heat for the oil of 0.480 Btu/lb°F. The specific heat was taken from graphical information in the ASME Power Test Code. Similarly, the water sensible heat calculation contains a tabular value... 

The Q-Max design is typically tailored to provide optimal utility advantage for the plant site, such as minimizing heat input for stand- ... 

The magnitudes of various flowrates also come into consideration. For example, temperature (or bottoms product purity) in a distillation column is typically controlled by manipulating steam flow to the reboiler (column boilup) and base level is controlled with bottoms product flowrate. However, in columns with a large boilup ratio and small bottoms flowrate, these loops should be reversed because boilup has a larger effect on base level than bottoms flow (Richardson rule). However, inverse response problems in some columns may occur when base level is controlled by heat input. High reflux ratios at the top of a column require similar analysis in selecting reflux or distillate to control overhead product purity. 

A fourth degree of freedom is consumed to control column pressure. The valves available are condenser cooling (by far the most commonly7 used), reboiler heat input, and feed (if the feed is partially vapor). If a flooded condenser is used, the cooling water valve is wide open and an additional valve, typically located between the condenser and the reflux drum, is used to cover or expose heat-transfer area in the condenser. 

Most distillation columns have two control degrees of freedom, once pressure and feed conditions are set. The typical control structure holds the composition profile in the column by controlling a tray temperature somewhere in the column. The other degree of freedom is then normally consumed by fixing some other variable such as the flowrate of reflux, the reflux ratio, or the heat input. 

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