Oxygen concentration convection

Exceptions to these rules of thumb abound, however. For example, although diffusion is faster at elevated temperatures, dissolved oxygen concentration may be lower. Convective transport is stimulated by high temperatures, but increased... 

Slime is a network of secreted strands (extracellular polymers) intermixed with bacteria, water, gases, and extraneous matter. Slime layers occlude surfaces—the biological mat tends to form on and stick to surfaces. Surface shielding is further accelerated by the gathering of dirt, silt, sand, and other materials into the layer. Slime layers produce a stagnant zone next to surfaces that retards convective oxygen transport and increases diffusion distances. These properties naturally promote oxygen concentration cell formation. 

This case, displayed in Fig. 1.17(d), occurs at a low inlet oxygen concentration or a high initial coke loading - that is, the combustion is oxygen-limited. The heat of combustion is carried away downstream by convection. For wr Wtherm the effective temperature rise approaches asymptotically the value... 

In all of these tests, the specimens, 75 mm square and up to 25 mm thick, are exposed to radiant heat with and without a pilot flame(s). Decomposition takes place inside a closed cabinet of 0.51 m3. There is no control of the air flow or oxygen concentration through the fire zone and the effluent is mixed by natural convection, as it accumulates within the closed cabinet. Gases are sampled using probes mounted in the center of the cabinet. 

C = oxygen concentration at the reaction surface, kg = convective mass transfer coefficient, ks = intrinsic reaction rate constant,... 

It is not surprising that the oxygen flux decreases or that the consumption of fuel decreases with time as the ash thickness increases. What one obtains, however, is an inverse square root dependence with time and a square root dependence with concentration. Thus for an ash-forming fuel in which ash remains Arm throughout the combustion process, the burning rate is proportional to the square root of the oxygen concentration and is independent of the convective nature of the oxidizer stream. 

Free convection mode is not sufficient to assure a satisfactory oxygen concentration at the cathode surface and then an acceptable fuel cell power [11], Thus, the most adopted solution for the design of oxidant feeding section is represented by the utilization of a compact air compressor device [1], The overall air supply system is based on the air compressor, but could also include an expander in high pressure plants (pressure higher than 2 bar), to recover a part of pressure energy. 

The loss of water is more critical during intensive care of premature babies, as these babies show a greater extent of skin respiration with a greater loss of water. The convection heating in the incubator causes additional dehydration. Therefore, a state-of-the-art incubator for neonatal intensive care is equipped with sensors to monitor oxygen concentration, humidity, and temperature and with an automatic control to adjust these parameters by controlling the gas blends and adding water vapor. 

Fig. 13 Influence of oxygen concentration on the corrosion rate of unalloyed steel in salt solution at 25 °C (free convection) (a) 1.5 x 10 M CaCh (b) solution with KCl ( ), Na2S04 (o), NaCi (x) [17].

This is based on a boundary layer thickness of 0.5 mm, which represents conditions with only free (not forced) convection, and further on a saturation oxygen concentration at 20 C of 2.5 moFcm, a diffusion coefficient of 2.5 cmVs, z = 4, and F = 96,500 C/mol e. ... 

Here, Nq2 designates the oxygen flux at the surface and Co2,b the oxygen concentration in the bulk. The overall mass transport coefficient, contains two terms the coefficient km which characterizes the convective transport and the coefficient kf. 

This fin tube failure could have been prevented by sampling the flue gas just below the convective section inlet. The oxygen concentration at this point represents the true amount of excess air available for combustion in the firebox. 

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