Forced convection heat transfer liquids

An important mixing operation involves bringing different molecular species together to obtain a chemical reaction. The components may be miscible liquids, immiscible liquids, solid particles and a liquid, a gas and a liquid, a gas and solid particles, or two gases. In some cases, temperature differences exist between an equipment surface and the bulk fluid, or between the suspended particles and the continuous phase fluid. The same mechanisms that enhance mass transfer by reducing the film thickness are used to promote heat transfer by increasing the temperature gradient in the film. These mechanisms are bulk flow, eddy diffusion, and molecular diffusion. The performance of equipment in which heat transfer occurs is expressed in terms of forced convective heat transfer coefficients. 

Wang BX, Peng XF (1994) Experimental investigation of liquid forced-convection heat transfer through micro-channels. Int J Heat Mass Transfer 37 73-82 Wasekar VM, Manglik RM (2002) The influence of additive molecular weight and ionic nature on the pool boiling performance of aqueous surfactant solutions. Int J Heat Mass Transfer 45 483-493... 

Referring to Fig. 12, it is clear that not all the three regions need necessarily be present when a liquid is boiled in a tube. For instance, the exit velocity of the two-phase mixture may never exceed that required for two-phase forced convection to take place, or the heat flux may be such that with an inlet velocity F, nucleate boiling cannot occur and only forced convective heat transfer takes place. 

Witte, L. C. An Experimental Study of Forced-Convection Heat Transfer from a Sphere to Liquid Sodium, J. Heat Transfer, vol. 90, p. 9, 1968. 

Wang, B.X. and Peng, X.F., Experimental Investigation of Liquid Forced-Convection Heat Transfer Through Microchannels, Int. J. Heat Mass Transfer, 1994, 37, Suppl. 1,... 

The use of thermal conductivity, heat capacity and rheological properties for [C4mim][NTf2] was also shown by Chen et al. [123] to correlate with Shah s equation for forced convective heat transfer in the laminar flow regime, indicating that knowledge of these parameters can successfully be used to model heat transfer behavior of ionic liquid systems at the larger scale. 

The correlations that we have studied so far are valid only for Pr > 0.7, which exclude liquid metals (recall Fig. 5.12). As we learned in Chapter 5, the forced-convection heat transfer associated with liquid metals is described by the relation... 

A.27 [27] L. C. Witte. An experimental study of forced convection heat transfer from a sphere to liquid sodium. J. Heat Transfer, 90,1968. 

R. Lemlich and J. G Armour, Forced Convection Heat Transfer to a Pulsed Liquid, in AIChE Preprint 2 for 6th Nat. Heat Transfer Conf, AIChE, New York, 1963. 

In a liquid bath used for melting, there may be slow melting of submerged metal solids because of poor liquid-to-solid heat transfer. (See fig. 3.29.) Heating from the top down in a liquid bath depends on conduction or convection. Some stirring or pumping velocity can be supplied to add forced convection heat transfer. The pumping equipment can be expensive to buy and to maintain. 

Entropy generation of forced convection heat transfer of liquid fluid over the horizontal surface with embedded open parallel microchannels at constant heat flux boundary conditions may be formulated by an integral of the local entropy generation. Embedded open parallel microchannels within the surface can sufficiently reduce both friction and thermal irreversibilities of liquid fluid through slip-flow conditions (Kandlikar et al., 2006 Yarin et al., 2009). 

B. X. Wang, X. F. Peng, Experimental investigation on liquid forced-convection heat-transfer through microchannels. International Journal of Heat and Mass Tranter, 1994, 37, 73-82. 

R. Rathnasamy, J. H. Arakeri, K. Srinivasan, Experimental investigation of forced convective heat transfer to air, liquids and liquid mixtures in a long narrow channel. Proceedings of the Institution of Mechanical Engineers Part E -Journal of Process Mechanical Engineering, 2005, 219, 311-317. 

Colburn, A.P. 1933. A method of correlating forced convection heat transfer data and a comparison with liquid friction. Trans AIChE 29 174—210. 

For forced-convection heat transfer, Nup replaces Shp and Pr replaces Sc, but such a conventional analogy between heat and mass transfer in liquid-fluidized beds has been questioned by Briens et al., 1993.) However, in fluidized beds, unlike fixed beds, s is not an independent variable but is related to Re and the properties of both liquid and particles as incorporated in the Archimedes number, Ar, and exemplified by equations such as (61), (62), or (64), whereby... 

Equations (13-115) to (13-117) contain terms, for rates of heat transfer from the vapor phase to the hquid phase. These rates are estimated from convective and bulk-flow contributions, where the former are based on interfacial area, average-temperature driving forces, and convective heat-transfer coefficients, which are determined from the Chilton-Colburn analogy for the vapor phase and from the penetration theoiy for the liquid phase. 

Consider a vessel containing an agitated liquid. Heat transfer occurs mainly through forced convection in the liquid, conduction through the vessel wall, and forced convection in the jacket media. The heat flow may be based on the basic film theory equation and can be expressed by... 

Convection. Heat transfer by convection arises from the mixing of elements of fluid. If this mixing occurs as a result of density differences as, for example, when a pool of liquid is heated from below, the process is known as natural convection. If the mixing results from eddy movement in the fluid, for example when a fluid flows through a pipe heated on the outside, it is called forced convection. It is important to note that convection requires mixing of fluid elements, and is not governed by temperature difference alone as is the case in conduction and radiation. 

Convective heat exchange, natural or forced Radiant heat transfer, e.g. furnaces Evaporation, e.g. in evaporators Condensation, e.g. in shell and tube heat exchanges Heat transfer to boiling liquids, e.g. in vaporizers, boilers, re-boilers ... 

Conductive and Convective Heat Transfer, Thermo Explosion by. There are three fundamental types of heat transfer conduction, convection radiation. All three types may occur at the same time, but it is advisable to consider the heat thransfer by each type in any particular case. Conduction is the transfer of heat from one part of a body to another part of the same body, or from one body to another in physical contact with it, without appreciable displacement of the particles of either body. Convection is the transfer of heat from one point to another within a fluid, gas or liquid, by the mixing of one portion of the fluid with another. In natural convection, the motion of the fluid is entirely the result of differences in density resulting from temp differences in forced convection, the motion is produced by mechanical means. Radiation is the transfer of heat from one body to another, not in contact with it, by means of wave motion thru space (Ref 5)... 

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