External heat input

Once a fusion reaction has begun in a confined plasma, it is planned to sustain it by using the hot, charged-particle reaction products, eg, alpha particles in the case of D—T fusion, to heat other, colder fuel particles to the reaction temperature. If no additional external heat input is required to sustain the reaction, the plasma is said to have reached the ignition condition. Achieving ignition is another primary goal of fusion research. 

Overpressure of Store drum at proper temperature material in drum, Keep drum away from heat source due to external heat input or self reaction is complete before drumming heating. Allow adequate freeboard for material Provide adequate sprinkler protection Thermally initiated venting (e.g., melt-out bungs) CCPS G-3 CCPS G-15 CCPS G-22 CCPS G-29... 

Onee the onset temperature is determined, it is then possible to obtain the maximum reaetion temperature by the adiabatie temperature rise and any eontribution due to external heat input. The theoretieal adiabatie temperature inerease is... 

The eontribution to the overall temperature inerease from external heat input is defined by... 

Overpressuring of a process or storage vessel caused by loss of control of reactive materials or external heat input... 

If Leung s method is inapplicable due to the presence of external heating, then alternative hand calculation methods are given in Annex 5 or a computer simulation could be used (see Annex 4). In either case, the thermal data should be obtained in a small-scale test which also simulates the external heat input. 

The method uses Leung s method (equation (6.5) or (6.9)), but with a modified value of the heat release rate per unit mass, q, to account for the additional external heat input. This modified value of q is given by ... 

The small-scale test (see A2.4)i which measures dT/dt, and hence q, for the.runaway reaction must be performed in a way which simulates the same external heating rate as for the full-scale reactor. This is to ensure that a safe value of q is obtained. If the small-scale test was not also externally heated, the relief pressure would be reached at a higher reactant conversion and consequent lower reaction rate, than in the full scale vessel with external heat input. It should also be noted that, as there is no mass loss in the small-scale test, the whole initial mass of reactants, mR, rather than mR/2 can be used in the calculation of the rate of temperature rise due to external... 

This method[8] is for vapour pressure systems when there is simultaneous runaway reaction and external heating. It has been derived by using an analogous method to that used to derive Leung s method (see 6.3) and it shares the same conditions of applicability, except that the method is valid when there is an external heat input. The method should be more accurate than that in A5.7 above, but requires an iterative procedure for evaluation. 

When using the method, it is essential that the heat release rate per unit mass due to the runaway reaction, q, is measured in an suitable calorimeter (see Annex 2) which simulates the external heat input. If this is not the case, then q can be underestimated since the external heating means that the degree of conversion of the reaction is less (and the reaction rate higher) at any given temperature compared with the adiabatic situation. 

The method assumes that the gas is ideal and that homogeneous two-phase relief occurs once the relief system operates. This assumption is potentially non-conservative for untempered systems and, the method should only be used where it is known that homogeneous vessel flow occurs (e.g. for inherently foamy systems)1111. It should not be used if there is external heat input to the reactor, or if the rate of any continuing feed streams is significant. 

Notice that there is no reboiler in this flash tower. All the heat input comes from the partially vaporized crude. Both the temperature and the percent vaporization of the crude are fixed. Hence, the external heat input to the preflash tower is constant. The pounds of vapor flowing to the bottom tray must also be constant. 

Consider the following. When the operator raises the top reflux rate, what happens to the weight flow of vapor going to the top tray Recalling that the external heat input to this tower is constant, does the pounds per hour of vapor flowing to the top tray increase, remain the same, or decrease The correct answer is increase. But why ... 

As the reflux rate is raised, the weight flow of vapor through the top tray, and to a lesser extent through all the trays below (except for the bottom tray), increases. This increase in the weight flow of vapor occurs even though the external heat input to the preflash tower is constant. The weight flow of vapor to the bottom tray is presumed to be solely a function of the pounds of vapor in the feed. 

The thermal efficiency is defined as the ratio of heating values of biocrude product and feedstock plus external heat input It has a theoretical maximum of 79%. The process designed here has a thermal efficiency of 75%. 

In the proposed two-step process, it is important to attain high efficiencies for conversion of coal to COx (CO -I- CO2) in the first-step reaction and then for conversion of CO2 to CO in the second-step reaction by an external heat input. From the thermodynamic conditions and the low cost, the redox pair of Fe304/a-Fe was one of the promising redox systems for the two-step process, but it still required the operating temperature above 1200°C[2]. It is well known that many kinds of metal ions can be incorporated into the spinel lattice structure of magnetite by replacing ferrous or ferric ions. There is the possibility that metal-substitution for Fe or Fe " in magnetite causes a phase transition to the metallic phase, which proceeds readily even at low temperatures and improves the conversion efficiencies of coal and CO2 to CO in the two-step process. 

Advantages Slurry density and yield can be controlled to some degree by adjustment or external heat input. 

An evaporative crystallizer operating under vacuum with suitable external heat Input will meet the material balance performance objectives. 

This technique uses periodic reversal of the flow direction of the reaction mixture through the fixed bed of catalyst (Fig. 3) which thereby serves both as an accelerator of chemical reactions and as a heat regenerator and/or accumulator [2], often flanked by layers of heat regenerative inert, typically ceramic, packing. Flow reversals induce continuous back-and-forth migration of the heat and reaction waves through the catalyst bed (Fig. 4). This allows for continuous autothermal operation without or with minimum external heat input. Theoretical basis of RFR operation, experimental results and commercial applications were described in a number of papers [2,35],... 

In the butene isomerization section (1), raffinate-2 feed from OSBL is mixed with butene recycle from the butene distillation section and is vaporized, preheated and fed to the butene isomerization reactor, where butene-2 is isomerized to butene-1 over a fixed bed of proprietary isomerization catalyst. Reactor effluent Is cooled and condensed and flows to the butene distillation section (2) where it is separated into butene-1 product and recycle butene-2 in a butene fractionator. Butene-1 is separated overhead and recycle butene-2 Is produced from the bottom. The column uses a heat-pump system to efficiently separate butene-1 from butene-2 and butane, with no external heat Input. A portion of the bottoms is purged to remove butane before it is recycled to the isomerization reactor. 

External heat input into liquid with evaporation and flow of a gas only through the relief device... 

The pressure balance is given by Equation (10.2). In the energy balance, the external heat input term is g = UaAT, where U is the overall heat transfer coefficient between the jacket and the reactor, a is the ratio of the heat transfer area and the reactor volume, and AT is the temperature difference between the jacket and the reactor at a length z. The overall coefficient, U, is constructed from the individual coefficients and the resistance of the tube wall. The overall heat transfer coefficient is calculated by the following equation (McCabe etal., 2001) ... 

Calculate the reflux heat, at Tray Dl. Reflux heat is defined as the apparent heat imbalance between external heat quantities at the point in question in the tower. These external heat quantities are denoted as Q with appropriate subscripts to signify their location. External heat input quantities are defined as the heat contained in the feed plus all heat to the system at product strippers either directly as steam or indirectly throu reboilers. External heat output quantities at a given tray are defined as the heat contained in liquid products leaving the system from points lower in the towier, the heat contained in the internal vapors of products plus steam and the heat contained by a product liquid flowing to the sidestream stripper. If the tray is nbt a sidestream draw tray, this latter quantity does not enter into the heat balance. 

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