Zhiqing Lin

The effect of surfactants on bubble growth, wall thermal patterns and heat transfer in pool boiling

Abstract During nucleate pool boiling of pure water and water with cationic surfactant, the motion of bubbles and the temperature of the heated surface were recorded by a high-speed video camera and an infrared radiometer. All experiments were performed at saturated boiling conditions. The boiling curves for various concentrations were obtained and compared. The results show that the bubble behavior and the heat transfer mechanism for the surfactant solution are quite different from those of pure water. The heat transfer dependence on the relative changes of both the surface tension and the kinematic viscosity was discussed.

Enhanced heat transfer of drag reducing surfactant solutions with fluted tube-in-tube heat exchanger

Abstract Solutions containing drag reducing additives also show reduced heat transfer which limits their use in hydronic cooling and heating systems where heat exchange is critical. For Reynolds numbers 10,000–50,000 and test fluid inlet temperatures 50–70°C, a fluted inner tube heat exchanger showed increased heat transfer coefficients for both cationic and zwitterionic/anionic drag reducing surfactant solutions. The pressure drop penalty for heat transfer enhancement of the cationic surfactant solution flowing through the fluted tube is high while for the zwitterionic/anionic solution, significant heat transfer improvement was achieved with only a modest pressure drop penalty.

Comparison of the effects of dimethyl and dichloro benzoate counterions on drag reduction, rheological behaviors, and microstructures of a cationic surfactant

Arquad 16–50 (commercial CTAC, cetyltrimethylammonium chloride) (5 mM) with the counterions 3, 4-dichlorobenzoate (5 and 10 mM), 3, 4-dimethylbenzoate (5 and 10 mM) and 3, 5-dichlorosalicylate (5 mM) were studied to compare the effect of concentration of the counterion and its ratio to surfactant concentration (ξ) on drag reduction, rheological behavior, and microstructures. The first four solutions are good drag reducers at different temperature ranges. The 3, 4-dimethylbenzoate system (ξ=1) is effective at 5–40 °C and the 3, 4-dichlorobenzoate system (ξ=1) at 20–70 °C. Increasing the concentration ratio to ξ=2 increased the upper temperature limit 10 °C for each system. The counterion concentration changes affect microstructures in the quiescent state in different ways. The viscoelastic ξ=1 solution of 3, 4-dimethylbenzoate has a microstructure of both vesicles and threads in the quiescent state which probably transform to a threadlike micellar network under shear. However, its ratio of apparent extensional viscosity to shear viscosity is very low, unusual for a surfactant drag reducer. Its ξ=2 solution has typical surfactant drag reducer properties, viscoelastic, high extensional viscosity, and threadlike micellar networks. The ξ=1 solution of 3, 4-Cl-benzoate is like the ξ=2 solution of 3, 4-CH3-benzoate while its ξ=2 solution is nonviscoelastic with vesicles and spherical micelle microstructures in the quiescent state which also probably transform to a network structure in strong shear fields. The only system tested with a counterion having four-substituent groups, 3, 5-dichlorosalicylate, is not effective as a drag reducer, has water-like behavior, and contains very large vesicles.Arquad 16–50 (commercial CTAC, cetyltrimethylammonium chloride) (5 mM) with the counterions 3, 4-dichlorobenzoate (5 and 10 mM), 3, 4-dimethylbenzoate (5 and 10 mM) and 3, 5-dichlorosalicylate (5 mM) were studied to compare the effect of concentration of the counterion and its ratio to surfactant concentration (ξ) on drag reduction, rheological behavior, and microstructures. The first four solutions are good drag reducers at different temperature ranges. The 3, 4-dimethylbenzoate system (ξ=1) is effective at 5–40 °C and the 3, 4-dichlorobenzoate system (ξ=1) at 20–70 °C. Increasing the concentration ratio to ξ=2 increased the upper temperature limit 10 °C for each system. The counterion concentration changes affect microstructures in the quiescent state in different ways. The viscoelastic ξ=1 solution of 3, 4-dimethylbenzoate has a microstructure of both vesicles and threads in the quiescent state which probably transform to a threadlike micellar network under shear. However, its ratio of apparent extensi...

Influence of salts on dynamic properties of drag reducing surfactants

Abstract Many cationic and zwitterionic surfactants are considered excellent drag reducing agents. The properties of two of them, a cationic, CTAC, and a zwitterionic, SPE 98330, are compared in this paper. The hydrodynamic radius of the micelles, the shear and extensional viscosity of the solutions at concentrations appropriate for drag reduction were investigated and the influence of some low concentration salts, which are usually found in tap water, was examined.

Small-angle neutron scattering study of shearing effects on drag-reducing surfactant solutions

Drag-reducing surfactant solutions are very sensitive to shear. Shear can induce nanostructural transitions which affect drag reduction effectiveness and rheological properties. Literature reports on the effects of shear on different micellar solutions are inconsistent. In this paper, the effects of shear on three cationic drag-reducing surfactant solutions each with very different nanostructures and rheological behaviors, Arquad 16-50/sodium salicylate (NaSal) (5 mM/5 mM) (has thread-like micelles, shear-induced structure and large first normal stress (N(1))), Arquad S-50/NaSal (5 mM/12.5 mM) (has branched micelles, no shear-induced structure and first normal stress is about zero) and Arquad 16-50/sodium 3,4-dimethyl-benzoate (5 mM/5 mM) (has vesicles and thread-like micelles, shear-induced structure and high first normal stress (N(1))) are studied by small-angle neutron scattering (SANS), together with their rheological properties, drag reduction behavior and nanostructures by cryogenic-temperature transmission electron microscopy(cryo-TEM). The differences in the rheological behavior and the SANS data of the solutions are explained by the different responses of the nanostructures to shear based on a two-step response to shear.

Comparison of the Effects of Methyl and Chloro Substituted Salicylate Counterions on Drag Reducing and Rheological Behaviors and Microstructures of Cationic Surfactants

The chemical structure of the counterion affects the effectiveness of a cationic surfactant as a drag reducer, its rheological behavior and its micro structure. With the addition of certain negatively charged counterions, worm-like micelles can be formed. This worm-like micelle structure has been proposed as necessary for a surfactant solution to be drag reducing. Recently, however, we reported the first drag reducing system with a vesicle-dominated microstructure (Lin et al., 1997). The system was 5.0mM Arquad 16-50 (commercial CTAC) with 5.0mM 5-chlorosalicylate. This solution has a short swirl decay time but it has near zero first normal stress difference at 20 to 1000s−1 shear rates. In this paper, drag reduction, rheological properties, and microstructures from cryo-TEM imaging are described for Arquad 16-50 with 4-chlorosalicylate, 3-methylsalicylate, 4-methylsalicylate, and 5-methylsalicylate counterions, all at concentrations of 5.0mM Arquad 16-50/ 5.0mM counterion and they are compared with earlier results with 5-chlorosalicylate.