Analytic solutions for the geometric and optical properties of stationary compound parabolic concentrators with fully illuminated inverted V receiver

Stationary low concentrator collectors (C < 2), of the CPC type, are of great interest to supply thermal energy for industrial processes, at temperatures below or around 90 °C. In particular, concentrators with fully illuminated inverted V absorbers have attractive properties for thermal energy production. Two classes of CPC’s with inverted V absorber are identified, according to the relationship between the vertex angle of the absorber (γ) and the acceptance angle of the cavity (θ_a), (γ  θ_a) or (γ < θ_a). The first class of CPC’s (γ  θ_a) converge to the fully illuminated CPC with horizontal flat receiver when (γ = 90°). The second class of CPC’s (γ < θ_a) converge to the fully illuminated CPC with vertical flat receiver when (γ = 0°). Both limiting cases have been published in the technical literature. This paper analyzes the class of concentrators satisfying (γ  θ_a). The ideal concentrator corresponding to a fully illuminated wedge absorber and (γ  θ_a) is a circular involute plus three parabolic segments. Closed-form analytic solutions are derived for its geometric and optical properties: reflector geometry, aperture, height, reflector length, angular acceptance function and average number of reflections for any degree of truncation. The equations obtained can be used as important design tools, for simulation techniques and optimization purposes. The collectible energy for North–South and East–West oriented collectors, for various receiver vertex angle and acceptance angle, was calculated. A cost-benefit figure, given by the relationship between collectible energy and reflector surface, is also estimated. Numerical results for any degree of cavity truncation are presented. As the degree of truncation varies, a clear minimum of the length over aperture ratio (L/A) occurs. The geometric and optical characteristics of different low concentration CPC’s (C, between 1 and 2, range of interest of stationary concentrators) show that the cavities with the minimal relationship between the length or height of the reflector surface and the aperture, (L/A) and (H/A), and the lower average number of reflections n correspond to the lowest angular acceptance concentrator (highest nominal concentration). If a concentration of 1.2 is desired, then the smallest ratios of (L/A), (H/A) and n, within the set of concentrators with maximal concentration (C) between 1 and 2, occur for (C = 2) (nominal acceptance half angle θ_a = 30°). Collectible energy results together with a cost-benefit relationship enable to conclude that a good choice for a well-designed collector for the city of Recife-PE, Brazil is: (a) East–West orientation; (b) receiver vertex angles (γ) of the order of (65°); (c) acceptance angle of the CPC (θ_a = 30°) and (d) concentration of the truncated cavity (C_t) in the interval (1.0–1.2).     

High Hydrostatic Pressure and Mild Heat Treatments for the Modification of Orange Peel Dietary Fiber: Effects on Hygroscopic Properties and Functionality

Fruit by-products, such as orange peels, are non-conventional sources of dietary fiber (DF) suitable for developing food ingredients with novel applications. Orange peels were processed at 600 MPa (come up time–CUT, 2, 5, 10, or 20 min) and two temperatures (55 or 70 °C) with the aim to study changes in total (TDF), soluble (SDF), and insoluble (IDF) dietary fiber contents, water-/oil-holding capacity (WHC/OHC), solubility, swelling capacity (SC), pH, tap density, and hygroscopic properties. Increments of 1.9 times on the SDF content were observed after HHP treatment at 55 and 70 °C, compared to the untreated sample content (7.17% dw). Constant values of TDF (51.2–54.6% dw) suggested the significant conversion of assayable IDF to SDF. An increase on SC (6.5%) and OHC (20.1%) values were observed in samples treated with CUT at 70 and 55 °C, respectively. Compared to control samples, HHP (55 °C/5 min) exerted changes on moisture isotherms expressed as relative water sorption content. HHP improved the adsorption and desorption water retention of samples in the 0.1–0.93 a _w range studied. Results indicate that HHP combined with heat treatment has potential to modify the functionality of orange peels with short processing times.     

Modified stainless steel surfaces targeted to reduce fouling – Evaluation of fouling by milk components

Several stainless steel based surfaces with different properties were evaluated according to their fouling behaviour for different dairy products under different conditions. Surface properties were obtained by the following modification techniques: , and TiC ion implantation; diamond-like carbon (DLC) sputtering; DLC, DLC–Si–O and SiO_x, plasma enhanced chemical vapor Deposition (PECVD); autocatalytic Ni–P–PTFE and silica coating. Aqueous solutions that simulate milk (SMUF – simulated milk ultrafiltrate for the mineral components, β-lactoglobulin for the protein components and FMF – fouling model fluid for complex milk systems) were used to study the fouling behaviour during pasteurisation. Bacteriological deposition studies were also performed with two heat resistant strains of Bacillus. The experiments were carried out at laboratory scale for the evaluation of calcium phosphate and protein deposition, and at pilot scale for adhesion of bacteria and deposits from complex milk systems.

In all cases, the fouling behaviour was affected by the surface material, although in different ways for the deposition or the cleaning phases. For the non-microbiological deposits (calcium phosphate, whey protein and FMF milk-based product), the Ni–P–PTFE surface was the most promising one, since it generally promoted less deposit build up and, in all cases, was the easiest to clean. On the other hand, for bacterial adhesion, the most suitable surface was the ion implanted (TiC) surface, which also showed less spores after the cleaning process.     

Optimizing critical high-intensity pulsed electric fields treatments for reducing pectolytic activity and viscosity changes in watermelon juice

A response surface methodology was used to determine the combined effect of high-intensity pulsed electric fields (HIPEF) variables such as frequency, pulse width and polarity on the inactivation of pectolytic enzymes involved in viscosity changes of juices. Pectin methylesterase (PME) and polygalacturonase (PG) activities as well as viscosity were determined in watermelon juices processed at pulse frequencies from 50 to 250 Hz and pulse widths ranging from 1.0 to 7.0 μs in monopolar or bipolar mode. Electric field strength and total treatment time were maintained constant in all treatments at 35 kV/cm and 1,000 μs. Second-order expressions were accurate enough to fit the experimental results. The great PME reduction contrasted with the low impact of HIPEF on the PG activity of watermelon juice within the range of assayed conditions. Minimal residual PME activity values (15%) were obtained by selecting pulse widths higher than 5.5 μs at 250 Hz in bipolar mode, whereas the lowest PG residual activities (60%) were achieved after applying 7.0-μs bipolar pulses at 250 Hz. Moreover, watermelon juice viscosity increased throughout the range of studied conditions. The highest viscosity observed in the juice after applying 7.0-μs bipolar pulses at 250 Hz was related to the lowest PME activities obtained in the product treated under those conditions. Hence, the HIPEF processing optimization through frequency, pulse width and polarity could contribute to assure enzymatic inactivation while keeping valuable attributes of juices.     

An alkaline water electrolyzer with nickel electrodes enables efficient high current density operation

Low-temperature industrial water electrolysis is typically conducted using either liquid alkaline electrolytes or acidic polymer electrolyte membranes (PEMs). The latter approach is considered to be more efficient but also more expensive as it requires Pt and Ir based catalysts. This study reports on an alkaline water electrolyzer with Ni electrodes that operates at a current density of 2 A/cm² with a cell voltage of 1.85 V, which provides a comparable voltage-current characteristic to the state-of-the-art PEM water electrolyzers. Thin Ni mesh electrodes with surface areas that are thousand times higher than the geometric area were manufactured by an easily scalable and cheap process, i.e. metallurgical hot dip galvanization with subsequent de-alloying. With a thin porous polymer of approximately $140\text{μm}$ as the diaphragm a low cell resistance of 0.11 Ω cm^?2 was obtained.     

Using Multispectral Imaging for Spoilage Detection of Pork Meat

The quality of stored minced pork meat was monitored using a rapid multispectral imaging device to quantify the degree of spoilage. Bacterial counts of a total of 155 meat samples stored for up to 580 h have been measured using conventional laboratory methods. Meat samples were maintained under two different storage conditions: aerobic and modified atmosphere packages as well as under different temperatures. Besides bacterial counts, a sensory panel has judged the spoilage degree of all meat samples into one of three classes. Results showed that the multispectral imaging device was able to classify 76.13 % of the meat samples correctly according to the defined sensory scale. Furthermore, the multispectral camera device was able to predict total viable counts with a standard error of prediction of 7.47 %. It is concluded that there is a good possibility that a setup like the one investigated will be successful for the detection of spoilage degree in minced pork meat.     

Thermal characterization of wood of nine European tree species: thermogravimetry and differential scanning calorimetry in an air atmosphere

European Journal of Wood and Wood Products - This paper presents a thermal characterization of hardwoods of Hungarian origin. The study covers the wood of the following tree species: sessile oak...     

Extraction of chitin from prawn shells and conversion to low molecular mass chitosan

Extraction and depolymerisation of chitin and chitosan from prawn shells was carried out using various chemical procedures. Sodium hydroxide and hydrochloric acid solutions were used for deproteination and demineralisation, respectively, while acetone was used for decolourisation. The amount of chitin and subsequently chitosan obtained was ∼35% and 25% respectively of the dry weight of the shells. The chitin was deacetylated using sodium hydroxide at 100 °C and the influence of the concentration of the reagent and duration of the reaction was investigated. The degree of deacetylation (DD) of the chitosan was evaluated by FTIR and NMR spectroscopy and the molecular mass distribution was determined by Gel Permeation Chromatography. It was found that the final DD was significantly higher using 50% sodium hydroxide solution (73% ± 9%) compared to 25% sodium hydroxide solution (40% ± 5%). It was noted also that the deacetylation reaction was more than 80% completed after 2 h but the chitosan produced had higher molecular mass while chitosan produced after 10 h had lower molecular mass and higher degree of deacetylation. The molecular mass distribution was bimodal for all the samples and consisted of a broad high molecular mass peak (peak 1) and a sharp low molecular mass peak (peak 2). The Mw of peak 1 decreased from ∼1.3 × 10⁶ after 2 h reaction with sodium hydroxide to 3.1 × 10⁵ after 10 h reaction indicating that depolymerisation and deacetylation occurred simultaneously. Peak 2 had a Mw of ∼2.4–9.9 × 10³.     

Stabilization of an Amylase from Neurospora crassa by Immobilization on Highly Activated Supports

The amylase from Neurospora crassa is an interesting enzyme, having higher stability than amylase from Aspergillus oryzea under a broad range of pH values. Moreover, the N. crassa enzyme may be immobilized on different supports with good retention of enzyme activity. The best stabilizations were achieved using Eupergit C 250 L or glyoxyl agarose, with which the enzyme remained fully active at 60°C for 24 h while the soluble enzyme remained about 17%. The glyoxyl agarose immobilized enzyme had high thermostability, high optimal temperature (65°C) and broad pH/activity profile, suggesting that this enzyme has potential for food and industrial applications for starch modification.     

A Porphyra columbina hydrolysate upregulates IL-10 production in rat macrophages and lymphocytes through an NF-κB,and p38 and JNK dependent mechanism

The marine environment represents a relatively untapped source of functional ingredients. Here we characterise a hydrolysate obtained from Phorphyra columbina (PcRH) and its effects on primary splenocytes, macrophages and T lymphocytes in vitro. Our product had a high degree of hydrolysis, due to the use of a mixture of endo-peptidase and exo-peptidase, and was enriched in Asp, Ala and Glu. PcRH had mitogenic effects on rat splenic lymphocytes. IL-10 secretion was enhanced by PcRH in splenocytes (235%), macrophages (150%) and in lymphocytes (472%), while the production of TNFα and other proinflammatory cytokines by macrophages was inhibited (15–75%), especially under lipopolysaccharide stimulation. The effect of the hydrolysate on IL-10 was evoked by JNK, p38 MAPK and NF-κB dependent pathways in T lymphocytes. We conclude that PcRH has immunomodulatory effects on macrophages and lymphocytes, activating NF-κB and MAPK dependent pathways, and predominantly inducing IL-10 production.