Heat transfer condition

PFRs, under isothermal, adiabatic, or heat transfer conditions in one or two phases. Outputs can provide profiles of composition, pressure, and temperature as well as vessel size. 

Even the good heat transfer conditions turned out to be false, however, if the correlation derived for single cylinders by McAdams (1954) were extrapolated to Rep < 100. Nelson and Galloway (1975) pointed out that at low Reynolds numbers the real heat transfer coefficient could be four... 

In a recuperative heat exchanger, each element of heat-transferring surface has a constant temperature and, by arranging the gas paths in contra-flow, the temperature distribution in the matrix in the direction of flow is that giving optimum performance for the given heat-transfer conditions. This optimum temperature distribution can be achieved ideally in a con-tra-flow regenerator and approached very closely in a cross-flow regenerator. 

This design has a number of tubes embedded inside the turbine blade to provide channels for the water (Figure 9-23). In most cases, these tubes are constructed from copper for good heat-transfer conditions. The water, which is converted to steam by the time it reaches the blade tips, is then... 

In some convection equations, such as for turbulent pipe flow, a special correction factor is used. This factor relates to the heat transfer conditions at the flow inlet, where the flow has not reached its final velocity distribution and the boundary layer is not fully developed. In this region the heat transfer rate is better than at the region of fully developed flow. 

When testing for corrosion under heat-transfer conditions, the heat flux must be realistic. It is not good enough to merely reproduce the correct temperatures... 

The common heater block shown in Fig. 19.23 can itself be subject to corrosion leading to different heat transfer conditions for different tubes, and in some later versions of the apparatus individual short heating jackets are used for each tube, which are heated with oil from either a steam-heated or electrically heated heat exchanger. This modification not only avoids corrosion problems but also obviates the necessity to machine a length of the outside of each tube to fit the semi-circular notches in the single heater block. The oil flow is adjusted to give an oil temperature of 95°C at each outlet. 

Mercer, A. D., Laboratory Research in the Development and Testing of Inhibited Coolants in Boiling Heat Transfer Conditions , in Engine Coolant Testing Slate of the Art 1979. ASTM STP 705, W. H. Ailor, ed., 53-80 (1980)... 

Test method for corrosion of cast aluminium alloys in engine coolants under heat-transfer conditions... 

Another approach is to improve the heat transfer conditions from the product. This can be accomplished in several ways. One way is to operate in a coolant medium that would also act as the lubricant for the system. The heat transfer to a liquid is usually much better than to air, and the liquid can be cooled by passing it through a heat exchanger device. A second approach is to improve the heat transfer to air. This can be done by increasing the surface area of the product by means of fins or other surface projections. The larger area will increase the heat flow... 

Isothermal and adiabatic heat transfer conditions can be obtained with different values of the Biot number. The wall temperature, 0w, is assumed to be a piecewise linear function of the axial position and is treated as a known quantity based on experimental evidence. 

The predictive power of tendency models is obviously limited. However, the models can be useful in evaluation of the effect of changing heat-transfer conditions upon scale-up of reactors. Tendency models can be extremely useful for improvement and optimization of existing industrial reactors/reactions, especially for the improvement of the time-temperature policy and the policy of addition of component(s) to the reaction mixture. 

Equation 10.3.6, the reaction rate expression, and the design equation are sufficient to determine the temperature and composition of the fluid leaving the reactor if the heat transfer characteristics of the system are known. If it is necessary to know the reactor volume needed to obtain a specified conversion at a fixed input flow rate and specified heat transfer conditions, the energy balance equation can be solved to determine the temperature of the reactor contents. When this temperature is substituted into the rate expression, one can readily solve the design equation for the reactor volume. On the other hand, if a reactor of known volume is to be used, a determination of the exit conversion and temperature will require a simultaneous trial and error solution of the energy balance, the rate expression, and the design equation. 

Laboratory reactors and industrial scale equipment are seldom operated under similar flow and heat transfer conditions. To obtain a... 

Proper calibration of the DSC instruments is crucial. The basis of the enthalpy calibration is generally the enthalpy of fusion of a standard material [21,22], but electrical calibration is an alternative. A resistor is placed in or attached to the calorimeter cell and heat peaks are produced by electrical means just before and after a comparable effect caused by the sample. The different heat transfer conditions during calibration and measurement put limits on the improvement. DSCs are usually limited to temperatures from liquid nitrogen to 873 K, but recent instrumentation with maximum temperatures close to 1800 K is now commercially available. The accuracy of these instruments depends heavily on the instrumentation, on the calibration procedures, on the type of measurements to be performed, on the temperature regime and on the... 

When passage of a sugar solution at 90°C through a weak-base anion exchange resin was interrupted, an explosion occurred. This was attributed to an exothermic Maillard reaction (interaction of an amino acid with a glycosidic OH group) under the poor heat transfer conditions in a particulate bed without fluid flow. 

In this case, the linear growth rate is usually a function of the mass and heat transfer conditions at the surface of the crystal. The linear growth rate may... 

Gas compression in closed-cell polymer foams was analysed, and the effect on the uniaxial compression stress-strain curve predicted. Results were compared with experimental data for a foams with a range of cell sizes, and the heat transfer conditions inferred from the best fit with the simulations. The lateral expansion of the foam must be considered in the simulation, so in subsidiary experiments Poisson s ratio was measured at high compressive strains. 13 refs. 

Select the engine coolant or antirust with care to ensure adequate corrosion protection. Use only those products conforming to recognized standards such as ASTM D 3306 for engine coolant. Additionally, if your vehicle engine contains major cast aluminum components, be certain the engine coolant meets the heat rejection corrosion limits in ASTM specification D 3306 as determined by ASTM Test Method for Corrosion of Cast Aluminum Alloys in Engine Coolants Under Heat-Transfer Conditions (D 4340). 

Wiggle, R. R., Hospadaruk, V., and Tibaudo, F. M., Corrosion of Cast Aluminum Alloys under Heat Transfer Conditions, Technical Report No. SR-81-11, Research Staff Report, Ford Motor Company, Dearborn, MI, 1981. 

Influence of Flow Nonuniformity on the Mass and Heat Transfer Conditions in Cooling Towers)... 

The second justification for the angular condition is that this condition is necessary for the determination of the radius of the crystal at the trijunction as a function of heat-transfer conditions and pull rate. This argument is simple. The dimensionless Young-Laplace equation of capillary statics gives the shape of an axisymmetric melt-ambient meniscus as... 

After evacuation and at the start of heating, the trend of Tice approaches too close to the maximum tolerable Tice. A reduction in the operation control pressure (pc) will immediately stop this trend (Figure 2.88) (if the desired Tice is not reached p could be raised.) The slope of the function Tice =j[pt) can become unfavorably steep. In this case, the shelf temperature should also be lowered or raised, but the effect of this change will take time before an equilibrium state is reached again (e.g. 0.5-1 h) depending on the heat transfer conditions and the heat capacity of the shelves and the heat transfer medium. 

For highly exothermic reactions the so-called HEX reactors present a very promising option. The basic common feature of all HEX reactors is much more favorable heat transfer conditions in comparison with conventional reactors (heat transfer coefficients typically 3500-7500 W/m2K, heat transfer areas up to 2200 m2/m3). A HEX reactor developed by BHR Group Ltd. (Figure 14) was able to decrease the by-product formation in one of ICI Acrylics processes by 75% (41) and to decrease the processing time in a Hickson Welch fine chemical process from 18 hours to 15 minutes, saving 98.6% of batch time (42). 

As mentioned earlier, work on validation of computational approaches to simulating multi-phase systems under realistic momentum and heat-transfer conditions is growing PEPT represents one of very few ways of doing this convincingly. 

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