A film model for heat and mass transfer with fog formation

An analysis is presented of a binary film with fog formation and a negligible induced velocity (traditionally referred to as “Stefan—Nusselt flow”). The governing equations of energy diffusion, coupled with the saturation condition, are solved and analytical correction factors are derived. Subsequently, the “negligible induced velocity” (NIV) fog film model is applied to channel flow, yielding analytical expressions for the variation of bulk vapour mass fraction, bulk temperature, and the possible creation of bulk fog. Multiplying the NIV correction factor for fog only by the classical film model correction factors for induced velocity, reveals that the product corresponds to the film model correction factors for the combined effects of fog and induced velocity. Furthermore, a thorough comparison with theoretical and experimental results of foregoing two-dimensional studies, concerning fog formation in the presence of free and forced convection, confirms the accuracy of the present fog film model

Rotational particle separator: a new method for separating fine particles and mists from gases

An account is given of the patented technique of the rotational particle separator for separating solid and liquid particles of diameter 0.1 µm and larger from gases. Attention is focused on the working principle, fluid mechanical constraints, particle design, separation performance, power consumption, dimensions, filter cleaning and costs. Furthermore, an overview is given of current developments to introduce this technique in industrial dust removal, in electricity generation and in the consumer goods market. The article concludes with a summary of the feature which distinguish this technique from existing filtering methods

Film models for transport phenomena with fog formation: The fog film model

In a preceding paper (Brouwers and Chesters, Int. J. Heat Mass Transfer35, 1–11 (1992)) possible supersaturation in a film and in the bulk of a binary mixture has been discussed. In the present analysis the exact conditions for fog formation and the magnitude of the fogging and superheated regions in the film are first determined. Next, the governing equation of diffusion and energy (coupled with the saturation condition) of the fog layer is solved numerically. An evaluation of various mixtures of water vapour and air illustrates the substantial effect of fog formation on heat and mass transfer rates. Subsequently, a thorough asymptotic analysis of the fog layer's governing equation yields an excellently matching approximation solution. Furthermore, this solution leads to analytical film model correction factors for the combined effects of fog formation and injection/suction on transfer rates. Finally, the fog film model is applied to channel flow of a binary mixture. This approach provides new procedures for the computation of condensers and evaporators, allowing both fog formation in the film (affecting transfer rates) and/or in the bulk (affecting the incremental balances of mass and energy)

Packing fraction of crystalline structures of binary hard spheres: a general equation and application to amorphization

In a previous paper analytical equations were derived for the packing fraction of crystalline structures consisting of bimodal randomly placed hard spheres H. J. H. Brouwers, Phys. Rev. E 76, 041304 2007. The bimodal packing fraction was derived for the three crystalline cubic systems: viz., face-centered cubic, bodycentered cubic, and simple cubic. These three equations appeared also to be applicable to all 14 Bravais lattices. Here it is demonstrated, accounting for the number of distorted bonds in the building blocks and using graph theory, that one general packing equation can be derived, valid again for all lattices. This expression is validated and applied to the process of amorphization

Basic principles for sampling and reporting for studies involving the measurement of carbon sequestration in soils : [Abstract 588]

Variation in soil organic carbon (SOC) levels due to differences in soil management has been the subject of much investigation over the past decades. More recently, growing concerns relating to the consequences of increasing carbon dioxide levels in the atmosphere have intensified a focus on carbon (C) sequestration in soils. In the plethora of scientific papers emanating from investigations of this kind, a lack of uniformity in terms of sampling methodologies and reporting units detracts from the usefulness of the acquired data. In this paper, we review briefly the order of magnitude in which atmospheric C is fixed above ground and in the soil for four types of agricultural land use (sugarcane, sugar beet, cereals and plantation forestry);.as well as ,the basic principles for a correct appraisal of organic carbon and for reporting on differences in SOC. These include (i) expressing C in mass per unit of surface up to a depth of at least 60 cm, (ii) listing of the typological characteristics of the soils, and (iii) sampling of the different soil horizons by taking into account the natural existing lateral variation in their characteristics and avoiding the mixing of soil material coming from different horizons. Because soil organic matter includes fractions with a relatively quick turnover rate as well as ones with a very slow mineralization rate, the fraction of SOC that should be considered as "fixed" atmospheric CO2 is evoked in the last part of this paper. In a final paragraph the question "which fraction of the crop residue may be used for energy production without compromising the capacity of the soil to stock organic carbon" is also evoked

The effect of blowing or suction on laminar free convective heat transfer on flat horizontal plates

In the present paper laminar free convective heat transfer on flat permeable horizontal plates is investigated. To assess the effect of surface suction or injection on heat transfer a correction factor, provided by the film model (or ldquofilm theoryrdquo), is applied. Comparing the film model predictions with numerical results of previous boundary layer analyses yields good agreement for a wide range of dimensionless transpiration levels

Topics in Cement and Concrete Research

In recent decades, the construction sector has faced many changes. One of these changes is the shift in the role of national government from one-sided practices in which the government was solely responsible for strategic and long-term spatial planning to a multi-actor and multi-level arena. One outcome was a rearrangement of the balance between public and private responsibilities. This has led to new procurement routes and contracts as Private Finance Initiative (PFI) and Public Private Partnerships (PPP), as well as to a more performance-oriented client (both public and private). At the same time, construction firms changed their strategic focus from cost efficiency to adding value for money for the client, resulting in new contract forms such as Design & Construct (D&C), Building, Operate & Transfer (BOT) and variants there from. So far, governments of most European countries have their own restrictive specifications for the use of building materials