Systems with uniform temperature distribution

SYSTEMS WITH UNIFORM TEMPERATURE DISTRIBUTION Semenov assumed a pseudo zero order (that is, with no reactant consumption) exothermic reaction following an Arrhenius type rate law — that is, the rate of reaction and therefore the rate of heat production increa.ses exponentially with temperature. Thus for an irreversible nth order reaction A — B at constant volume V the rate of heat production is given by ... 

In this study, an integrated methanol reformer including an evaporator and a combustor was fabricated and tested. Previous tests of the reformer with a number of on-off cycles revealed that non-uniform temperature distribution caused hot spots within the combustion plate, resulting in cracking of the welded region of the reformer. Therefore, emphasis was made to achieve a uniform temperature distribution within the reformer. In addition, start-up characteristics of the complete reforming system were investigated. 

Figure 2.22 [2.6] demonstrates the method of a cooling circuit with recirculated flow An injector pump operated with just evaporated LN2 aspirates the warmer N2 coming from the condenser and feeds the mixture back in the condenser. The desired condenser temperature can be controlled by a throttle valve. To achieve a uniform temperature distribution, the gas mixture is alternately fed to one or the other end of the condenser. No results of such a system are given. 

For such chemical reactors which are characterized by an ideally well mixed reaction volume, therefore allowing the assumption of a uniform temperature distribution, a transfer of this differential heat balance to an integral balance is possible by multiplying it with the volume of the system balanced. This way the general integral heat balance for well mixed reactors is obtained ... 

SYSTEMS WITH NON-UNIFORM TEMPERATURE DISTRIBUTION These systems cannot be described by a single temperature, rather the temperature is a point function depending on the three spatial co-ordinates. The problem of analysing heat transfer and hence of deriving the critical conditions for thermal explosions therefore becomes extremely complex. 

Such a system reaches a state with stationary temperature distribution and a uniform heat flow J. (A stationary temperature T x) implies that the heat flow is uniform otherwise there will be an accumulation or depletion of heat, resulting in a time-dependent temperature.) The evolution of the temperature distribution can be obtained explicitly by using the Fourier laws of heat conduction ... 

Extensive cooling systems can also be realized with the laser sintering process. These systems are manufactured as a network structure under the surface to be cooled (Figure 2.99). Through this, the cooling medium (e.g., water or CO2) can be transported near the surface (2 mm) to achieve a uniform temperature distribution [9]. 

With the reactor filled to a predetermined level at room temperature, initial heating of the system was achieved by means of electrical heaters disposed around the outside of the vessel. Heat was applied until a core temperature of 240°C was attained heating by nuclear power was then initiated. With nuclear power a core temperature of 340°C was achieved, at which point the circulator was turned on. Only during the forced convection phase of the operation was a uniform temperature distribution established in the fuel solution previous to starting the circulator, the... 

Uniform temperature distribution in the mould is essentially dependent upon the mould temperature system. Adequate and imiform temperatures are of importance, not only in relation to the warping tendency, but also for economic reasons from the point of view of the unit time. It is necessary to wait imtil even the hottest part of the component has cooled enough before ejecting the component from the mould. Thus, a imiform intensity of temperature becomes a prerequisite for economic manufacture. With cores, when adequate temperature patterns often cost more to achieve, there are often signs of omission in the mould design in this connection. The mould certainly becomes cheaper then. But it means that a substantial increase in the cycle time - often up to 100% and more - must usually be taken into account. 

Visualizing efficiency makes it possible to dispense with cooling channels that contribute little to heat dissipation from the tool. At other points, repositioning the cooling channels can increase the efficiency of the cooling system. The objective is to achieve uniform temperature distribution at the surface of the mold. 

Uspenskaya, L. B., and S. M. Slavina. 1970. Experimental studies of temperature distribution in modular industrial spaces with a non-uniform hear source. In The Issues of Sanitary Technique Systems Design and Installation. VNIIGS, Leningrad. 

In static systems, the cooling jackets are normally filled with a glycol and water mixture to provide for uniform heat distribution within the cylinder. This system may be used where the AT of the gas is less than 150°F and discharge gas temperature is less than 190°F. 

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