Heat transfer liquid phase

Fischer-Tropsch (FT) synthesis is accompanied by an extremely large heat evolution (exothermic). To improve the characteristics of heat transfer, liquid phase synthesis using a slurry-type reactor has been developed. Although liquid phase synthesis has been operated using pulverized catalysts (ref. 1), it is interesting to use a catalyst of smaller particles, so-called ultrafine particle (UFP), for the purpose of enhancing the gas-liquid-solid interface contact. 

Two-phase mass transfer and heat transfer without phase change are analogous, and the results of mass-transfer studies can be used to help clarify the heat-transfer problems. Cichy et al. (C5) have formulated basic design equations for isothermal gas-liquid tubular reactors. The authors arranged the common visually defined flow patterns into five basic flow regimes, each... 

Use (561) Dielectric coolant for transformers (800) high temperature, liquid-phase, heat-transfer liquid. 

Knowledge of the relevant phase behavior is important for several reasons. Much of the detailed chemical engineering of the plant wiU depend upon the phase state of the reaction mixture. In the present case, totaUy different separation strategies will clearly be needed for a system where the catalyst is in a liquid phase with aU other components being in the gas phase, and a system with two (or more) liquid phases plus a gas phase. In addition, heat transfer is phase-dependent liquids conduct heat much better than gases and the thermal capacity of reaction mixtures close to their critical point can be anomalous. Finally, the outcome of a few reactions is phase-dependent, with SCF biphasic systems giving different products from homogeneous monophasic systems. 

The following current trends emanate from the analysis of the radial heat transfer two-phase downflow and upflow fixed-bed literature [98] (i) radial heat transfer is strongly influenced by the flow regime [96,99,100] (ii) the bed radial effective thermal conductivity always increases with liquid flow rate for both two-phase downflow and upflow [96, 100] (iii) Ar is very little dependent on gas flow rate in trickle flow, and it decreases with gas flow rate in pulsing flow regime and increases in dispersed bubble flow regime [99,100] (iv) Ar decreases with the increase of the liquid viscosity [101] (v) the inhibition of coalescence induces higher Ar values [101] (vi) Ar always increases with... 

As the catalytic reaction taking place inside the pellets is usually accompanied by heat effects, the particle-liquid heat transfer coefficient becomes a fundamental ingredient to be estimated for the assessment of the efficacy of the heat withdrawal from the particle level away to the reactor wall leveL In particular, when highly exothermic reactions are in play, impediment of liquid replenishment over the dried spots on the catalyst surface may favor inception of hot spots that are responsible for reactor runaway. As a result, evacuation of heat across the liquid-covered pellet spots becomes a critical issue. Not many studies in literature deal with particle-liquid heat transfer rates in three-phase fixed-bed reactors. The main reason is probably the difficulty to find an accurate experimental method. The following current trends emanate from the analysis of the particle-liquid heat transfer two-phase downflow fixed-bed literature (i) the transition from trickle to pulsing flow is accompanied by a... 

Thrash measured the retention of tetraethoxysilane relative to toluene on three different stationary phases. Wurst OO has reported the specific retention volume of tetraethoxysilane on a column containing silicone oil as the stationary phase. Taylor Ol studied the gas chromatographic separation of a number of symmetrical and mixed tetraalkoxysilanes present in a heat transfer liquid. 

Heat transfer at phase boundaries such as solid electrode-liquid electrolyte or solid electrode gaseous product is complex, being dependent on flow conditions, electrode geometry and electrode profile (as in the case of mass transfer). Tn a simple approach, we may consider a temperature boundary layer, by analogy with the concentration boundary layer (Chapter 1, section L2). The heat flow is then ... 

Overall mass transfer coefficients show similar variations with gas and liquid flow rates as in absorption (see Chapter 3). The effects of temperature and pressure are expected to be the same for the gas-film and liquid-film mass transfer coefficients as in absorption operations. Because liquid-film mass transfer coefficients, as well as the Henry s Law constant (H) and the equilibrium ratio (K), increase with rising temperature, stripping is facilitated by heating the liquid phase. 

Moving-Bed Type This concept uses a single-pass tube bundle in a vertical shell with the dividea solids flowing by gravity in the tubes. It is little used for sohds. A major difficulty in divided-sohds apphcations is the problem of charging and discharging with uniformity. A second is poor heat-transfer rates. Because of these hmita-tions, this tube-bundle type is not the workhorse for solids that it is for liquid and gas-phase heat exchange. 

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