Heat transferred from the reactor

The nomenclature is as follows Qm is the rate of heat transfer from the reactor to the reactor wall, Qj is the rate of heat transfer from the reactor wall to the jacket, and... 

The rate of change of the outlet temperature times the heat capacity of the jacket equals the heat accumulated by the water flow plus the heat transferred from the reactor to the jacket minus the heat transferred from the jacket to the environment. 

Determining Model Parameters. To simplify fitting this first order equation to the actual data/ the UN-SS equation must be reduced. Heat transfer to the environment/ the U A term/ may be assumed negligible (for a first approximation anyway). With no reaction occurring and the reactor empty/ the heat transfer from the reactor to the jacket/ and the heat retained in the jacket walls/ the UA terra/ may be assumed to be zero. The remaining equation (2 f3) is ... 

Temperature control for laboratory reactors is typically easy because of high heat transfer area-reactor volume ratios, which do not require large driving forces (temperature differences) for heat transfer from the reactor to the jacket. Pilot- and full-scale reactors, however, often have a limited heat transfer capability. A process development engineer will usually have a choice of reactors when moving from the laboratory to the pilot plant. Kinetic and heat of reaction parameters obtained from the laboratory reactor, in conjunction with information on the heat transfer characteristics of each pilot plant vessel, can be used to select the proper pilot plant reactor. 

Various levels of models can be used to describe the behavior of pilot-scale jacketed batch reactors. For online reaction calorimetry and for rapid scale-up, a simple model characterizing the heat transfer from the reactor to the jacket can be used. Another level of modeling detail includes both the jacket and reactor dynamics. Finally, the complete set of equations simultaneously describing the integrated reactor/jacket and recirculating system dynamics can be used for feedback control system design and simulation. The complete model can more accurately assess the operability and safety of the pilot-scale system and can be used for more accurate process scale-up. 

The physical characteristics of the plastic input influence the carbonization process. In static conditions, the heating rate of small particles is higher than for large particles. In this case, difficulties could occur for the extrapolation from small-scale carbonization data to pilot- and industrial-scale units. The physical and chemical properties of the material are of great importance in order to be able to evaluate the heat transfer from the reactor inside the material. 

The synthesis of methanol from carbon monoxide and hydrogen is carried out in a continuous vapor-phase reactor at 5.00 atm absolute. The feed contains CO and H2 in stoichiometric proportion and enters the reactor at 25 C and 5.00 atm at a rate of 17.1 m /h. The product stream emerges from the reactor at 127 C. The rate of heat transfer from the reactor is 17.05 kW. Calculate the fractional conversion achieved and the volumetric flow rate (m /h)of the product stream. (See Example 9.5-4.)... 

During the pyrolysis process, the final conversion mainly depends on three phenomena the heat transfer from the reactor to the feedstock, the feedstock movement in the reactor and the kinetics of pyrolysis reactions. The heat transfer rate determines the rate of temperature increase of the feedstock. The feedstock movement behaviour determines the residence time of the feedstock particles in the reactor. In turn the heating rate and the residence time control the quantity of energy transferred and thus the ten Jerature distribution throughout the feedstock in the reactor. Once the tenqserature distribution is known, the kinetic behaviour of the feedstock determines the final conversion at the reactor outlet. 

At the conditions reported in this paper where the total pressure is closer to 1000 psig and the feed gas to the FDP reactor is an approximately equimolar mixture of hydrogen and methane, the total carbon conversions are closer to the fraction of carbon that instantaneously reacts and kinetic interpretation is even more difficult. Therefore the kinetic analysis is not yet complete. However for the purposes of FDP reactor simulation, a mathematical model was used that assumed all the carbon reacts at a rate dictated by Equation 1 rather than assuming a portion of this carbon reacts instantaneously. This assumption is felt to be conservative because it does not allow for the fraction of carbon that may react at a considerably faster rate than the final amount of carbon conversion which was used to evaluate the rate constant k. The temperature dependency of k used for our initial reactor simulation studies (11) has been reported (I). While the more detailed kinetic analysis may result in a modified rate equation, the results of our simulation study (11) indicate that radiant heat transfer plays a dominant role in small FDP reactors such as the one used in this study. Because the effect of radiant heat transfer from the reactor walls diminishes as the diameter of the reactor increases, temperature profiles in commercial reactors will be considerably different from those existing in our present 3-inch id FDP reactor this indicates the necessity of using larger diameter pilot plants to obtain reliable scaleup data. 

The occurrence of multiple steady states can be illustrated at best by a CSTR in which a high exothermic reaction takes place. A simple method is to examine separately the behaviour of the two terms of the energy balance heat generated by reaction, and heat transferred from the reactor. The heat generated is proportional with the reaction rate and the thermal effect ... 

The boundary conditions that take into account heat transfer from the reactor walls into the cooling (heating) liquid or vice versa are... 

The heat transferred from the reactor in part (a) now goes to heat the product solution from... 

Heat transfer area. The flooding of the silo with molten salt increases the effective surface area of heat transfer from the reactor vessel to the silo wall. If the silo is full of molten salt, the entire silo wall, not a small section of the wall, rejects heat to the environment. The placement of the reactor core at the very bottom of the reactor vessel allows foil utilization of the complete silo area. Because molten salt heat fluid is used for heat transfer, heat rejection rates can be further increased by (1) increasing silo depth or (2) designing the top of the silo with its shorter pathway for heat rejection to the environment. The effective heat transfer area is thus doubled. 

The term for heat transfer from the reactor to the surroundings, AQ, is typically given by the following expression ... 

Comparison of Eqs. (96) and (97) shows that the temperature difference across the film surrounding the catalyst pellet must be very low for a fully wetted particle, but could be important for a non-wetted particle. The design engineer must ensure that scale-up of reactor diameter for highly exothermic reactions does not diminish heat transfer from the reactor, or increase evaporation of liquid and generation of hot spots. To test for these effects, a pilot plant should be operated so that evaporation can occur leading to the development of dry zones. When this condition is found detailed axial temperature measurements should be taken. 

The high heat accumulating capability of water in the reactor pool ensures slow changing of coolant parameters during transient and emergency conditions and reliable heat transfer from the fuel elements, even if controlled heat transfer from the reactor is not available. Fuel temperatures are moderate. 

The RCCS removes heat transferred from the reactor vessel to the cavity around the vessel. The basic functions and requirements of the RCCS are ... 

The rate of heat transfer from the reactor contents to the coolant is given by... 

No heat flux was modeled for heat transfer from the reactor core. All emissivities are modeled as 0.80. 

A.22. The moderator system should have its own cooling system to remove heat transferred from the reactor structure and the heat generated by radioactive decay in the moderator system. 

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