Flow pattern and heat transfer characteristics of R-134a refrigerant during flow boiling in a horizontal circular mini-channel

Flow boiling heat transfer of R-134a refrigerant in a circular mini-channel, 600 mm long with a diameter of 1.75 mm, is investigated experimentally in this study. The test section is a stainless steel tube placed horizontally. Flow pattern and heat transfer coefficient data are obtained for a mass flux range of 200–1000 kg/m² s, a heat flux range of 1–83 kW/m² and saturation pressures of 8, 10, and 13 bar. Five different flow patterns including slug flow, throat-annular flow, churn flow, annular flow and annular-rivulet flow are observed and the heat transfer coefficient data for different flow patterns are presented. The heat transfer coefficient increases with increasing heat flux but is mostly independent of mass flux and vapour quality. In addition, it is indicated from the experiments that the higher the saturation pressure, the lower is the heat transfer coefficient. Comparisons of the present data with the existing correlations are also presented.     

Increasing validity through replication: an illustrative TDD case

Software Quality Journal - Software engineering (SE) experiments suffer from threats to validity that may impact their results. Replication allows researchers building on top of previous...     

Simulation and Experiment of the Homogeneously Catalyzed Production of Terpenyl Amine

Continuous terpenyl amine production via a homogeneously catalyzed hydroamination is presented. For the recycling of the catalyst a liquid‐liquid system combined with a subsequent acid complexation as capturing step for the terpenyl amine was used. The whole process was run in pilot plant scale. At first, batch experiments were conducted to determine reaction equilibria of the hydroamination and the acid complexation. On this, a process model was developed which is based on equilibrium stages. This process model was validated by running the continuous process and was able to predict the continuous process in good agreement with experimental data. So, it allows a reduction of the experimental effort.     

An inspection of viscosity model for homogeneous two-phase flow pressure drop prediction in a horizontal circular micro-channel

This study analyzes several well-known two-phase viscosity models in order to address the appropriate correlations among them for application to micro-channel. Pressure drop data is obtained from adiabatic two-phase air–water flow experiments. A fused silica channel, 320 mm long, with an inside diameter of 0.53 mm is used as the test section. The measured data is compared with the homogeneous flow predictions calculated using the existing viscosity models and detailed comparisons are discussed.     

Utilization of rice-husk packed beds as fine dust collectors at heavy dust loadings

Typical rice mills generally generate tonnes of biomass which is rice husks and a significant quantity of coarse and fine dusts from the paddy, resulting in public health concern. Instead of normal air cyclones which are not efficient for collecting fine soft-hair (detached pubescence) particles smaller than a few microns, a new system using packed beds of rice husks was developed for collection fine dusts. It was found that the rice-husk packed beds could exhibit an effective performance in capturing fine dusts at various dust loadings with collection efficiency higher than 85% by mass. The filtrating phenomenon could be observed as an integrated effect of cake and deep-bed filtrations due to the heavy dust loads, agglomeration of dusts, and cohesion between the dusts and bed of irregularly shaped rice husks. Both the pressure drop across the bed and the overall filtration efficiency remarkably increased at the initial clean stage, then increased more slowly due to the recurrent fracture of the dust cake layer.     

A Look at 25 Years of Data

Is 25 years enough time to build up a coherent body of knowledge that can help point to useful principles? As a testbed for helping us answer this question, software testing techniques are a good place to start. Few software practices are as important as testing, and testing techniques are amenable to measurement and reasoning about their effectiveness. Because they're aimed at removing faults, measuring the number and type of such removed faults seems like a natural part of applying these techniques. To make sense of this data, Universidad Politecnica de Madrid researchers have spent some time worrying about how to put 25 years' worth of work together usefully.     

Two-phase air-water flow in micro-channels: An investigation of the viscosity models for pressure drop prediction

Adiabatic two-phase air-water flow is experimentally studied in this work. Two channels, made of fused silica, with different diameters of 0.53 and 0.15 mm are used as test sections. The void fraction data for both tubes are obtained by image analysis. For the larger channel, the void fraction is found to be a linear relationship with the volumetric quality. In the case of the smaller one, however, the non-linear void fraction is obtained. The measured frictional pressure drop data are compared with the predictions regarding the homogeneous flow assumption. Several well-known two-phase viscosity models are subsequently evaluated for applicability to micro-channels.