Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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A pore inactivation model for describing oil uptake of French fries during pre-frying
Koerten, K.N. van; Schutyser, M.A.I. ; Somsen, D. ; Boom, R.M. - \ 2015
Journal of Food Engineering 146 (2015). - ISSN 0260-8774 - p. 92 - 98.
glass spg membranes - potato slices - mass-transfer - heat-transfer - water-loss - kinetics - emulsification - crust
The reduction of oil uptake during deep-frying is a subject with societal relevance, given the trend towards lower-fat foods. Since research into oil absorption during frying is limited, we here report on developing better mechanistic understanding of this process. The oil uptake for different frying temperatures and fry dimensions was measured as a function of the water evaporation rate and water loss. A pore inactivation model was developed based on the hypothesis that the crust is a porous layer through which the exuding moisture vapour flow inhibits oil migration. Decreases in water evaporation rates will cause pores to inactivate, allowing oil to penetrate into the crust. The model provides good predictions to the experimental data. Since the model has two parameters, a purely statistical comparison with a simple linear fit having one parameter, does not show a significant benefit; however, the model better describes the overall trend of oil uptake.
Microwave assisted flow synthesis: Coupling of electromagnetic and hydrodynamic phenomena
Patil, N.G. ; Benaskar, F. ; Meuldijk, J. ; Hulshof, L.A. ; Hessel, V. ; Schouten, J.C. ; Esveld, D.C. ; Rebrov, E.V. - \ 2014
AIChE Journal 60 (2014)11. - ISSN 0001-1541 - p. 3824 - 3832.
organic-synthesis macos - dry-media reactor - heat-transfer - thin-films - field - efficiency - catalysis
This article describes the results of a modeling study performed to understand the microwave heating process in continuous-flow reactors. It demonstrates the influence of liquid velocity profiles on temperature and microwave energy dissipation in a microwave integrated milli reactor-heat exchanger. Horizontal cocurrent flow of a strong microwave absorbing reaction mixture (ethanol¿+¿acetic acid, molar ratio 5:1) and a microwave transparent coolant (toluene) was established in a Teflon supported quartz tube (i.d.: 3 × 10-3 m and o.d.: 4 × 10-3 m) and shell (i.d.: 7 × 10-3 m and o.d.: 9 × 10-3 m), respectively. Modeling showed that the temperature rise of the highly microwave absorbing reaction mixture was up to four times higher in the almost stagnant liquid at the reactor walls than in the bulk liquid. The coolant flow was ineffective in controlling the outlet reaction mixture temperature. However, at high flow rates it limits the overheating of the stagnant liquid film of the reaction mixture at the reactor walls. It was also found that the stagnant layer around a fiber optic temperature probe, when inserted from the direction of the flow, resulted in much higher temperatures than the bulk liquid. This was not the case when the probe was inserted from the opposite direction. The experimental validations of these modeling results proved that the temperature profiles depend more on the reaction mixture velocity profiles than on the microwave energy dissipation/electric field intensity. Thus, in flow synthesis, particularly where a focused microwave field is applied over a small tubular flow reactor, it is very important to understand the large (direct/indirect) influence of reactor internals on the microwave heating process.
Modeling cooking of chicken meat in industrial tunnel ovens with the Flory-Rehner theory
Sman, R.G.M. van der - \ 2013
Meat Science 95 (2013)4. - ISSN 0309-1740 - p. 940 - 957.
water-holding capacity - protein cross-linking - cod gadus-morhua - mass-transfer - moisture transport - porous-media - heat-transfer - theoretical aspects - capillary-pressure - structural-changes
In this paper we present a numerical model describing the heat and mass transport during the cooking of chicken meat in industrial tunnels. The mass transport is driven by gradients in the swelling pressure, which is described by the Flory-Rehner theory, which relates to the water holding capacity (WHC). For cooking temperatures up to boiling point and practical relevant cooking times, the model renders good prediction of heat and mass transport and the total loss of moisture. We have shown that for cooking temperatures above boiling point, the model has to be extended with the dynamic growth of capillary water (drip) channels. Furthermore, we discuss that the Flory-Rehner theory provides the proper physical basis for describing the change of the WHC by a wide variety of factors like salt and pH. (C) 2013 Elsevier Ltd. All rights reserved.
Meristem temperature substantially deviates from air temperature, even in moderate environments: Is the magnitude of this deviation species-specific?
Savvides, A. ; Ieperen, W. van; Dieleman, J.A. ; Marcelis, L.F.M. - \ 2013
Plant, Cell & Environment 36 (2013)1. - ISSN 0140-7791 - p. 1950 - 1960.
shoot-tip temperature - climate-change - leaf development - effective thickness - light interception - boundary-layers - heat-transfer - crop yields - maize apex - plant
Meristem temperature (Tmeristem) drives plant development but is hardly ever quantified. Instead, air temperature (Tair) is usually used as its approximation. Meristems are enclosed within apical buds. Bud structure and function may differ across species. Therefore, Tmeristem may deviate from Tair in a species-specific way. Environmental variables (air temperature, vapour pressure deficit, radiation, and wind speed) were systematically varied to quantify the response of Tmeristem. This response was related to observations of bud structure and transpiration. Tomato and cucumber plants were used as model plants as they are morphologically distinct and usually growing in similar environments. Tmeristem substantially deviated from Tair in a species-specific manner under moderate environments. This deviation ranged between -2.6 and 3.8¿°C in tomato and between -4.1 and 3.0¿°C in cucumber. The lower Tmeristem observed in cucumber was linked with the higher transpiration of the bud foliage sheltering the meristem when compared with tomato plants. We here indicate that for properly linking growth and development of plants to temperature in future applications, for instance in climate change scenarios studies, Tmeristem should be used instead of Tair, as a species-specific trait highly reliant on various environmental factors
A coupling concept for two-phase compositional porous-medium and single-phase compositional free flow
Mosthaf, K. ; Baber, B. ; Flemisch, B. ; Helmig, R. ; Leijnse, A. ; Rybak, I. ; Wohlmuth, B. - \ 2011
Water Resources Research 47 (2011). - ISSN 0043-1397
boundary-conditions - numerical-simulation - fluid-flow - homogeneous fluid - jump coefficients - momentum-transfer - multiphase flow - heat-transfer - mass-transfer - interface
Domains composed of a porous part and an adjacent free-flow region are of special interest in many fields of application. So far, the coupling of free flow with porous-media flow has been considered only for single-phase systems. Here we extend this classical concept to two-component nonisothermal flow with two phases inside the porous medium and one phase in the free-flow region. The mathematical modeling of flow and transport phenomena in porous media is often based on Darcy's law, whereas in free-flow regions the (Navier-) -Stokes equations are used. In this paper, we give a detailed description of the employed subdomain models. The main contribution is the developed coupling concept, which is able to deal with compositional (miscible) flow and a two-phase system in the porous medium. It is based on the continuity of fluxes and the assumption of thermodynamic equilibrium, and uses the Beavers-Joseph-Saffman condition. The phenomenological explanations leading to a simple, solvable model, which accounts for the physics at the interface, are laid out in detail. Our model can account for evaporation and condensation processes at the interface and is used to model evaporation from soil influenced by a wind field in a first numerical example
Mixed motion in deterministic ratchets due to anisotropic permeability
Kulrattanarak, T. ; Sman, R.G.M. van der; Lubbersen, Y.S. ; Schroën, C.G.P.H. ; Pham, H.T.M. ; Sarro, P.M. ; Boom, R.M. - \ 2011
Journal of Colloid and Interface Science 354 (2011)1. - ISSN 0021-9797 - p. 7 - 14.
continuous particle separation - lattice-boltzmann simulations - lateral displacement - microfluidic devices - periodic arrays - heat-transfer - blood-plasma - flow - fractionation - classification
Nowadays microfluidic devices are becoming popular for cell/DNA sorting and fractionation. One class of these devices, namely deterministic ratchets, seems most promising for continuous fractionation applications of suspensions (Kulrattanarak et al., 2008 [1]). Next to the two main types of particle behavior, zigzag and displacement motion as noted by the inventors (Huang et al., 2004 [2]) and (Inglis et al., 2006 [3]), we have shown recently the existence of a intermediate particle behavior, which we named ‘mixed motion’. In this paper we formulate the hypothesis that the occurrence of mixed motion is correlated with anisotropy in the permeability of the obstacle array. This hypothesis we base on the comparison of experimental observations of mixed motion and the flow lane distribution as obtained from 2-D flow simulations.
Analysis of the land surface heterogeneity and its impact on atmospheric variables and the aerodynamic and thermodynamic roughness lengths
Ma, Y.M. ; Menenti, M. ; Feddes, R.A. ; Wang, J.M. - \ 2008
Journal of Geophysical Research: Atmospheres 113 (2008). - ISSN 2169-897X - 11 p.
boundary-layer - heat-transfer - fluxes
The land surface heterogeneity has a very significant impact on atmospheric variables (air temperature T-a, wind speed u, and humidity q), the aerodynamic roughness length z(0m), thermodynamic roughness length z(0h), and the excess resistance to heat transfer kB(-1). First, in this study the land surface heterogeneity has been documented through the comparison of surface reflectance r(0), surface temperature T-0, net radiation flux R-n, and sensible heat flux H partitioning over the different land cover types in the experimental areas of the Global Energy and Water Cycle Experiment (GEWEX) Asian Monsoon Experiment on the Tibetan Plateau (GAME/Tibet), the Coordinated Enhanced Observing Period (CEOP) Asia-Australia Monsoon Project on the Tibetan Plateau (CAMP/Tibet), the Heihe Basin Field Experiment (HEIFE), the Arid Environment Comprehensive Monitoring Plan, 95 (AECMP' 95), and the Dun Huang Experiment (DHEX). The results show that the surface heterogeneity was very significant in the areas of the HEIFE, the AECMP' 95, and the DHEX and that it was less significant in the areas of CAMP/Tibet and GAME/Tibet. Second, the vertical profiles of T-a, u, and q in the near-surface layer and above the blending height z(b) have been analyzed using the atmospheric boundary layer (ABL) tower data, radiosonde data, and tethered balloon data observed during the HEIFE, the DHEX, and the CAMP/Tibet. The results show that the land surface heterogeneity leads in the near-surface layer to different vertical profiles of u, T-a, and q overlying the surfaces of the Gobi and the oasis in the areas of the HEIFE and DHEX. The values of u, T-a, and q become well mixed above a height of about 300 m at the HEIFE and 150 m at the DHEX. z(0m), z(0h), and kB(-1) over the different land surfaces have also been determined in this study. The results show that the land surface heterogeneity leads to different aerodynamic and thermodynamic parameters over the areas of the HEIFE, the AECMP' 95, and the GAME/Tibet
Modelling of simultaneous effect of moisture and temperature on A. niger growth in solid-state fermentation
Hamidi-Esfahani, Z. ; Shojaosadati, S.A. ; Rinzema, A. - \ 2004
Biochemical Engineering Journal 21 (2004)3. - ISSN 1369-703X - p. 265 - 272.
rhizopus-oligosporus - heat-transfer - coniothyrium-minitans - transfer simulation - biomass estimation - culture - system - cultivation
In the present work a two factorial design of experiments was applied to study the simultaneous effect of temperature and moisture on A. niger growth in the solid-state fermentation (SSF). The increase of water content to more than 55% at the temperatures 35 and 40degreesC decreases microorganism growth. The logistic model was used to calculate growth kinetic parameters at different levels of temperature and moisture in solid-state fermentation. Ratkowsky equation was used to express the effect of temperature on specific growth rate. Quadratic polynomials express relationship between moisture content and growth parameters (maximum biomass and maximum specific growth rate) of A. niger inoculated on steamed wheat bran. The highest value of mu(m) and X-m were 0.29 h(-1) and 0.22 g biomass g DW-1 at 35degreesC and 55%, respectively. (C) 2004 Elsevier B.V. All rights reserved.
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