Cream flow rate

In the guide to inspections of topical products [28], it is indicated that water deionizers are usually excellent breeding areas for microorganisms, where flow rates, temperature, surface area of resin beds, and microbial quality of the feed water all influence microbial growth. Since topical products (e.g., creams, ointments)... 

The pressure drop and pumping requirements are functions of the type of flow and of the rheological properties of the dispersion. If the flow rate in a pipeline falls below the critical deposit velocity then particles or emulsion droplets will either sediment or cream to form a layer on the bottom or top wall, respectively, of the pipe. Some correlations that have been developed for the prediction of critical deposit velocity are discussed by Nasr-El-Din [86] and Shook et al. [90]. 

FIGURE 5-41. Determination of triamcinolone acetonide (peak A) and benzyl alcohol (peak B) from a steroid cream. Column 500 A Ultrastyragel 7.8 mm ID x 30 cm. Mobile phase THF. Flow rate 1 mL/min. Detection UV, 254 nm, 0.2 AUFS. (Reprinted from reference 13 with permission.)... 

FIGURE 11-4. Separation of an antifungal cream. Mobile phase methylene chloride. Flow rate 1 mL/min. Detector 280 nm. Column Ultrastyragel (100 A). Sample size 5-/xL injection of 0.843 g of cream dissolved in 5 mL of THF. Active ingredient tolnaftate is claimed on the label to be 1%. (Note Actual separation will depend upon the quality of the mobile phase and column packing.)... 

Econazole nitrate has been determined in tablets, creams, lotions and powders by HPLC19. Samples were extracted in methanol prior to analysis. Chromatography was performed on a Micro-Pak C18 column (30 cm x 4.0 mm) using a mobile phase consisting of methanol - aqueous 0.05 M ammonium dihydrogen phosphate (85 15) at a flow rate of 2.0 ml/min. Clotrimazole was used as internal standard. 

A stability-indicating assay of econazole nitrate in cream and lotion formulations has been reported9. Samples of cream or lotion are dispersed in tetrahydrofuran and extracted into methanolic and aqueous methanolic solutions. They are then filtered prior to analysis. Chromatography was performed on a Waters uBondapak C18 Column (30 cm x 3.9mm) and UV detection at 220 nm was used. The mobile phase consisted of 780 ml of methanol, 20 ml of tetrahydrofuran and 200 ml of ammonium carbonate solution (0.1% w/v), at a flow rate of 2.0 ml/min. The method was shown to be capable... 

Figure 22.8 Photograph of cream samples generated at two different flow rates and va ing content of emulsifiers (60 °C). Source Institut fur Mikrotechnik Mainz GmbH, Mainz, Germany.

The device has been investigated experimentally, whereby pressure drops up to 300 bar over the valve occurred. The flow rate of cream was up to 14 Lh and that of the skim milk up to 112 L h . The investigations demonstrated that it is feasible also to homogenize cream with up at least 32vol.% fat without a decrease in product quality compared with conventional processing. 

The estimation of flow functions from an actual experiment is reported next. A multi-rate primary drainage experiment was conducted on a Texas Cream limestone sample. Hexadecane was used as the oleic phase and deuterium oxide (D20) was used as the aqueous phase. Protons are imaged, so only the oil phase is observed. The pressure drop data, production data and saturation data are shown in Figures 4.1.11-... 

Studies of flow-induced coalescence are possible with the methods described here. Effects of flow conditions and emulsion properties, such as shear rate, initial droplet size, viscosity and type of surfactant can be investigated in detail. Recently developed, fast (3-10 s) [82, 83] PFG NMR methods of measuring droplet size distributions have provided nearly real-time droplet distribution curves during evolving flows such as emulsification [83], Studies of other destabilization mechanisms in emulsions such as creaming and flocculation can also be performed. 

The Bingham plastic model usually provides a good representation for the viscosity of concentrated slurries, suspensions, emulsions, foams, etc. Such materials often exhibit a yield stress that must be exceeded before the material will flow at a significant rate. Other examples include paint, shaving cream, and mayonnaise. There are also many fluids, such as blood, that may have a yield stress that is not as pronounced. 

Materials in a colloidal state are frequently preferred in industrial processing operations because their large surface areas per unit volume enhance chemical reactivity, adsorptive capacity, heat transfer rates, and so on. Therefore, one cannot overlook the importance of the flow behavior and properties of colloids since they exert a significant influence on the performance, efficiency, and economy of the process. Note that some examples of this (e.g., ceramic processing, electrophoretic display devices, and food colloids) were mentioned in the vignettes presented in Chapter 1. In addition, one often uses the flow properties and behavior of the products as measures of the microstructure (or, morphology ) of the products and as a means of quality control (e.g., printing inks, toners, paints, skin creams, blood substitutes,... 

An example of such a flow curve is presented in Fig. 6, and viscosity as a function of shear strain rate is depicted in Fig. 7. Many pharmaceutical ointments and creams show a similar shape of the flow curve with an extended upper Newtonian region. In these cases, an extrapolation of the linear portion of the flow curve to zero shear strain rate in order to obtain a dynamic yield stress is often utilized.l ... 

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