Thermal characteristics of louvered fins with a low-reynolds number flow

A heat recovery system is crucial for the effective use of energy where heat rejection from production processes is unavoidable and must be reused. The response of the louvered fins to the low-Reynolds number hot gas is yet to be reported in the literature for the application of a heat exchanger on low-speed hot plume arising from heat sources in production processes. This study focuses on the effects of the louvered fin heat exchanger’s design parameters, which include the louver pitch and louver angle, on the convective heat transfer, which defines the thermal interaction between the hot, buoyant, naturally-induced air and the louvered fins. The resulting Colburn factors (j) are compared with those derived under forced convection with a similar range of low Reynolds number (233 to 1024). All experiments are done on a 15:1 scaled-up model. The fin aspect ratios between the fin spacing and louver pitch are set at 0.75, 1, and 1.5, while the louver angles are set at 18°, 23°, 30°, 35°, and 40°. The Colburn factor strongly depends on the louver angle, especially at the lower range of the Reynolds number. The decreasing aspect ratio induces more hot buoyant air into the louver-formed channels, increasing the heat transfer rate. When the fin angle increases towards 30°, a larger Colburn factor is produced. However, the heat transfer characteristic drops as the angle goes beyond 30°. The highest j for the low speed flow is attained when the louver angle is 30° and the fin aspect ratio is 1.     

Optimized electrode arrangement in solar air heater

Laminar forced convection inside the solar air heater with various wire electrode arrangements are numerically examined for heat transfer enhancement using electrohydrodynamic technique. The electric field is generated by the wire electrodes charged with DC high voltage ranging from 7.5 to 17.5 kV. Reynolds number corresponding to the flow considered is between 100 and 2000. The numerical modeling of computational fluid dynamics includes the interactions among electric field, flow field, and temperature field. It is found that the enhancement of heat transfer coefficient with the presence of electric field increases in relation with the supplied voltage but decreases when the Reynolds number and the distance between electrode and channel surface are augmented. The optimized electrode arrangement, which obtains the best heat transfer enhancement is investigated incorporating with the pressure drop consideration. The heat transfer enhancement is also depended on the number of electrodes per length and the channel dimension.     

Numerical modeling of natural convection in partially open square cavities under electric field

Numerical modeling of the electric field effect on natural convection in the partially open square cavities is investigated. The interactions between electric, flow, and temperature fields are analyzed by using a computational fluid dynamics technique. The results indicate that the flow and heat transfer enhancements are the decreasing function of Rayleigh number. Moreover, the volume flow rate and heat transfer coefficient are substantially improved by the electric field effect, especially at the low aperture size and high aperture position. The effect of number of electrodes and inclined angle to the flow and heat transfer enhancements are also achieved.     

Numerical modeling of the electrohydrodynamic effect to natural convection in vertical channels

The electrohydrodynamic effect to natural convection inside the vertical channels is numerically investigated by computational fluid dynamics technique. The range of parameters considered are 10⁴ = Ra = 10⁷, 7.5 = V₀ = 17.5 kV, and 2 = aspect ratio = 10. Flow and temperature distributions are affected with supplied voltage at the wire electrodes, and the heat transfer enhancement is significantly influenced at low Rayleigh number. The augmented volume flow rate of fluid is indicated in relation with the number of electrodes. Moreover, heat transfer enhancement also depended on the electrode arrangement while the number of electrodes is initially fixed. The relation between channel aspect ratio and number of electrodes that performs the maximum heat transfer is expressed incorporating with the optimum concerning parameters.     

Supporting Service Discovery,Querying and Interaction in Ubiquitous Computing Environments

In this paper, we contend that ubiquitous computing environments will be highly heterogeneous, service rich domains. Moreover, future applications will consequently be required to interact with multiple, specialised service location and interaction protocols simultaneously. We argue that existing service discovery techniques do not provide sufficient support to address the challenges of building applications targeted to these emerging environments.This paper makes a number of contributions. Firstly, using a set of short ubiquitous computing scenarios we identify several key limitations of existing service discovery approaches that reduce their ability to support ubiquitous computing applications. Secondly, we present a detailed analysis of requirements for providing effective support in this domain. Thirdly, we provide the design of a simple extensible meta-service discovery architecture that uses database techniques to unify service discovery protocols and addresses several of our key requirements. Lastly, we examine the lessons learnt through the development of a prototype implementation of our architecture.     

Nanostructured Polymeric Coatings Based on Chitosan and Dopamine‐Modified Hyaluronic Acid for Biomedical Applications

In a marine environment, specific proteins are secreted by mussels and used as a bioglue to stick to a surface. These mussel proteins present an unusual amino acid 3,4‐dihydroxyphenylalanine (known as DOPA). The outstanding adhesive properties of these materials in the sea harsh conditions have been attributed to the presence of the catechol groups present in DOPA. Inspired by the structure and composition of these adhesive proteins, dopamine‐modified hyaluronic acid (HA‐DN) prepared by carbodiimide chemistry is used to form thin and surface‐adherent dopamine films. This conjugate was characterized by distinct techniques, such as nuclear magnetic resonance and ultraviolet spectrophotometry. Multilayer films are developed based on chitosan and HA‐DN to form polymeric coatings using the layer‐by‐layer methodology. The nanostructured films formation is monitored by quartz crystal microbalance. The film surface is characterized by atomic force microscopy and scanning electron microscopy. Water contact angle measurements are also conducted. The adhesion properties are analyzed showing that the nanostructured films with dopamine promote an improved adhesion. In vitro tests show an enhanced cell adhesion, proliferation and viability for the biomimetic films with catechol groups, demonstrating their potential to be used in distinct biomedical applications.     

Optimization of Low Sodium Salts Mix for Shoestring Potatoes

Several studies have shown the close relationship between the sodium consumption and health problems such as hypertension and cardiovascular disease. Thus, the demand for products with reduced sodium content, but with sensory quality, is increasing every day. In this context, this study aimed to optimize a low sodium salts mix using sodium chloride, potassium chloride, and monosodium glutamate to the development of shoestring potatoes with low sodium content and high sensory quality, through mixture design and response surface methodology. The salts mix that promotes the same salting power and similar sensory acceptability that the shoestring potatoes with 1.6% sodium chloride (ideal concentration) and at the same time promotes the greatest possible reduction of sodium, about 65%, should provide the composition as follows: 0.48% of sodium chloride, 0.92% of potassium chloride, and 0.43% of monosodium glutamate.     

Effects of airflow induction on heat transfer and energy consumption while freezing passion fruit pulp in stacked boxes

The objectives of this work were to characterize the energy consumption and the heat transfer process by the determination of the convective heat transfer coefficient (h) of passion fruit pulp contained in high-density polyethylene (HDPE) boxes and frozen in two conditions: without and with airflow induction, which was achieved through the installation of obstacles. To determine the convective heat transfer coefficients, HDPE boxes containing passion fruit pulp (contained in polyethylene bags) were interspersed with boxes containing metal tanks filled with low freezing point solutions. Three types of solutions were used: ethylene glycol, propylene glycol, and ethanol. The airflow induction under the stacks of passion fruit pulp provided higher h values than without airflow induction. The calculated average values and standard deviation were 6.340?±?0.87 W/m² °C, respectively, without airflow induction and 8.419?±?1.39 W/m² °C with airflow induction. The average reduction of the freezing time was 25 % for the boxes located at the top and 20 % in the base of the stack. This proved that directing the airflow under the stacked product promoted more uniform and efficient heat transfer. The analysis of the electrical parameter measurements revealed an approximate decrease of 16.7 % in energy consumption due to the reduction of the freezing time, without compromising the quality and operation of the electrical system. This practice was shown to be viable for small producers and agribusinesses that desire reductions in processing time and energy consumption and, consequently, the overall cost of the final product.     

Antioxidant activity of grape products and characterization of components by electrospray ionization mass spectrometry

Grapes are known for their health benefits and high antioxidant activity due to phenolic content. Our work provides metabolic fingerprints of three grape products, namely grape juice (GJ), grape juice concentrate (GJC) and grape skin extract powder (GSE). Using direct infusion electrospray ionization mass spectrometry (ESI–MS) and evaluating the relationship between total lphenolic content and antioxidant activity, it is possible to compare which product has the best effectiveness. Fingerprints of GJC and GSE showed similar characteristic distributions of resveratrol and pterostilbene in relatively significant abundances. GJC provided higher antioxidant activity/phenolic ratio; therefore, the identified phenolic compounds from GJC may offer enhanced antioxidant potential when compared to the other two samples (GJ and GSE).