Superheated Steam Flow Research Articles

Preparation of porous carbons from cypress using super-heated steam. III. Performance in electric double layer capacitor

Cypress charcoals, which were prepared with different temperatures and transferring rates under a flow of super-heated steam, were used for the electrode of electric double layer capacitor (EDLC) with 1 M H2SO4 electrolyte. EDLC capacitance of cypress charcoals prepared was about 250 F/g with a current density of 20 mA/g, about 160 F/g with 50 mA/g and about 120 F/g with 1000 mA/g. Capacitance observed was shown to be governed by pore structure of cypress charcoal and was tried to explain by the contributions from microporous and external surface areas. Rate performance evaluated from the ratio of the capacitance measured with 1000 mA/g to that with 50 mA/g was relatively high, about 0.7, for cypress charcoals prepared.

Nanoporous carbons from cypress I. Preparation and pore structure

Nanoporous carbons were prepared from cypress chips under a flow of super-heated steam, and their surface area reached more than 1000 m 2/g without an additional activation process. Cypress charcoals prepared at a temperature of 800–870°C had a large external surface area of more than 400 m 2/g, comparable to the microporous surface area, even though only 30–40 m 2/g was obtained by carbonization in a flow of Ar gas. Cypress charcoals prepared above 900°C were microporous with a microporous surface area more than 800 m 2/g and an external surface area of about 150 m 2/g. The pore structure in cypress charcoals could be controlled by selecting the temperature of the steam.

Optimization of Multilayer Thermal Insulation for Pipelines

Thermal insulation economic analysis for a system of pipelines insulated by different materials composite layers is studied. The analysis is based on an explicit nonlinear cost function that includes the annual energy losses and the insulation initial costs. Practical ranges of different insulation thicknesses are included as a set of inequality constraints. Furthermore, the analysis accounts for the safety limits required for the temperature of the outer surface of the insulation. A search procedure, modified Hook and Jeeves, is employed to find the optimum thickness for the least annual cost within the domain bounded by the constraints. The procedure has been verified against the analytical solution for a single pipeline with a single insulation layer. The analysis is employed for a system of pipelines (4-10" nominal size) [1] with flow of superheated steam. Furfural, crude oil, and 300-distillate. The results show significant cost saving with optimal insulation compared to the dimensions of engineering practice. Detailed data for these cases are presented and discussed.

Influence of convection heat transfer on the reheating of a chilled ready-cooked dish in an experimental superheated steam cell

The objective of this study was to determine the influence of heat transfer by convection on the reheating of mashed potatoes with an experimental device. The device was composed of a cooking cell with injection of superheated steam and its analytical environment. The setting variables of the cooking cell were: temperature of the walls between 105 and 240 °C, mean velocity of atmosphere circulation between 0 and 2.5 m/s, and injection flow of superheated steam between 0 and 1.2 kg/h. Measurements on the food (temperature and mass), and composition analysis of the cell atmosphere allowed identification of the phenomena which occur on the cook-chill dish (mashed potatoes). When the mean velocity of the atmosphere increases, condensation rate reduces while drying rate increases. Above 0.7 m/s, the increase in convection had no influence on temperature rising rate.

Heat treatment of organic polymers in a flow of a gaseous heat carrier

Processes of heat and mass transfer are studied during heat treatment of organic polymers in a superheated-steam flow. Promising environmentally safe engineering processes of treatment of plant biomass, plastics, and rubber wastes that contain petroleum products of sludges and soils are described.

Calculation of spontaneously condensing steam flows in a plane turbine cascade

The results of a numerical analysis of stationary spontaneously condensing steam flows in a plane turbine cascade are presented and compared with the experimental and calculated results of other authors. The effect of the flow parameters on the position and strength of the condensation shocks is analyzed. The local and integral characteristics of superheated and wet steam flows are compared.

Flow of nitrogen and superheated steam through cement mortar

This work concerns quantifying the error of Darcy's expression over Klinkenberg's equation for gas flow in cement under elevated temperatures.

Characteristics of evaporation of water into superheated steam. 1st report; Characteristics of convective heat transfer at evaporating surface by laser holographic interferometry.

Convective heat transfer characteristics at the evaporating surface of water in laminar streams of superheated steam have been investigated experimentally and compared to air by means of a real-time holographic interferometry technique. The situation considered here is a laminar boundary layer flow of superheated steam or air over a water surface. Surface temperature and thermal gradient at the water surface are determined from the visualization obtained by holographic interferometer and the temperature is measured both in the gas phase and liquid phase under adiabatic evaporation conditions. Temperature profiles in a thermal boundary layer of superheated steam and air are different because the superheated steam is a real gas with radiative participation. The local and average Nusselt numbers at water surface are calculated from the thermal gradient and evaporation rate respectively, which are compared with those of a flat plate for the same Reynolds number. It has been confirmed here that, for the adiabatic evaporation, the convective heat transfer characteristics at an evaporating surface are similar to those of a flat plate.

Shock Wave/Boundary Layer Interaction in Dry and Wet Transonic Steam

As part of the continuing technological advance towards the design of transonic steam turbine blades by analysis, rather than by experience based on time-consuming field testing, a series of experiments in a one-dimensional Laval nozzle was conducted to determine the nature of self-excited fluctuations due to shock wave/boundary layer interaction. Results in superheated steam flow showed peak-to-peak pressure fluctuations reaching 80 percent of the ideal across a normal shock wave, with a frequency spectrum having a fairly flat response to 150 Hz. Results in wet flow showed a distinctly different spectrum with decreased activity up to 200 Hz, but a shock wave interacting with incipient condensation near the nozzle throat produced additional broad spectral strength at 500 and 700 Hz. In addition, shock wave fluctuation in supercooled flow could trigger condensation in advance of the natural Wilson point.

Laboratory investigations of steam flow in a porous medium

Experiments were carried out in the laboratory to test a theory of transient flow of pure steam in a uniform porous medium. This theory is used in modeling pressure transient behavior in vapor dominated geothermal systems. Transient, superheated steam flow experiments were run by bringing a cylinder of porous material to a uniform initial pressure and then making a step increase in pressure at one end of the sample while monitoring the pressure transient breakthrough at the other end. It was found in experiments run at 100°, 125°, and 146°C that the time required for steam pressure transients to propagate through an unconsolidated material containing sand, silt, and clay was 10–25 times longer than predicted by conventional superheated steam flow theory. It is hypothesized that the delay in the steam pressure transient was caused by adsorption of steam in the porous sample. In order to account for steam adsorption, a sink term was included in the conservation of mass equation. In addition, energy transfer in the system has to be considered because latent heat is released when steam adsorption occurs, increasing the sample temperature by as much as 10°C. Finally, it was recognized that the steam pressure was a function of both the temperature and the amount of adsorption in the sample. This function was assumed to be an equilibrium adsorption isotherm, which was determined by experiment. By solving the modified mass and energy equations numerically, subject to the empirical adsorption isotherm relationship, excellent theoretical simulation of the experiments was achieved.

Heat and mass transfer in the vicinity of an evaporating droplet

The problem of heat and mass transfer around an evaporating water drop located in a superheated steam flow is studied using singular perturbation methods. The perturbation scheme involves three regions and some results concerning the Nusselt number and the drag coefficient of the drop are presented.

Steam-flow measurement by the total-sample method

Steam flows may be measured by the total-sample method using tritium as a tracer. No information about the properties of the steam is required. A single pulse of tracer water is injected into the steam line. Downstream, a small amount of the steam is passed through a condenser, and the condensate is collected over an interval during which the tracer wave passes the sampling point. Tritium activity in the collected water samples is measured with a liquid scintillation counter. The method was successfully tested on saturated and superheated steam flows ranging from 10,000 to 100,000 lb/hr.

Discussion: “Flow of Superheated Steam in Pipes” (Foster, E. H., 1907, Trans. ASME, 29, pp. 247–250)

Discussion: “Flow of Superheated Steam in Pipes” (Foster, E. H., 1907, Trans. ASME, 29, pp. 247–250)

Flow of Superheated Steam in Pipes

Flow of Superheated Steam in Pipes