Single-core computational efficiency of several iterative methods for numerical solution of nonsymmetric linear systems originating from simplified fluid flow models is evaluated together with ...different preconditioning techniques in terms of solution behaviour and the overall rate of convergence. A previously developed simplified 3D CFD model, which involves the solution of linear systems of orders usually from units to tens of thousands, is used to generate test cases. The respective Java software application employs the Parallel Colt linear algebra library. This is to ensure that the corresponding sparse matrix computations needed in different solution and preconditioning methods are carried out in as efficient a manner as possible to minimize the influence of the computer implementation itself. Measures (warm-up phase etc.) are taken to eliminate the effects of JVM specific behaviour such as JIT compilation.
The vast majority of cephalopods of the order Tarphyceratida are known from regions that were located at mid- or low palaeolatitudes during the Ordovician (mainly Baltica, Laurentia, and Chinese ...palaeoblocks). Only a handful of tarphyceratid specimens are known from high palaeolatitude regions of peri-Gondwana and Gondwana. Here, we describe the two best-preserved trocholitid cephalopods known to date from the Ordovician of the Prague Basin. The first is from the late Darriwilian/early Sandbian Dobrotiva Formation and is assigned to Trocholites fugax, a species previously recorded from roughly coeval strata of Iberia, France, and Bohemia. The specimen thus strengthens previous hypotheses regarding the interchange of non-benthic faunas between Baltica and different regions of peri-Gondwana during the Middle/Late Ordovician boundary interval. The second specimen, assigned to a new species of Trocholites chaloupkai sp. nov., is from the late Sandbian-early Katian Zahofany Formation and thus represents one of the stratigraphically youngest Trocholites in the Ordovician of peri-Gondwana. Internal structures of the shell of the holotype of the new species were studied using micro-CT tomography. This revealed that T. chaloupkai sp. nov. closely resembles the stratigraphically older (Darriwilian) species Trocholites depressus from Estonia. Key words: Tarphyceratida, Trocholites, micro CT, Darriwilian, Sandbian/Katian, Prague Basin, Baltica, peri-Gond-wana.
The efficient utilization of waste heat from industrial processes can provide a significant source of energy savings for production plants, as well as be a driver of sustainable operations and the ...abatement of emissions. Industrial waste heat usually is contained in liquid or gaseous outlet streams. Although the possible ways to utilize waste heat are discussed in a wide variety of papers, these either provide only a general overview of utilization options and opportunities or focus on a narrow range of industrial processes. The aim of the present paper is to discuss the practical aspects of waste heat utilization in the European Union so that the reader can gain perspective on (i) the thermal classification of waste heat, (ii) liquid and gaseous waste streams and their typical temperatures for industrial use cases, (iii) the technical, economic, physical, and environmental aspects barring full utilization of the available waste heat, (iv) waste heat sources in various industries, and (v) standardized equipment and technologies applicable to industrial waste heat utilization, including their advantages, disadvantages, and weak points.
This is the second part of a two‐part paper focusing on the assessment of accuracy of turbulence‐related data from CFD simulations using effective numerical dissipation rate and effective numerical ...viscosity. Experimental setup has been discussed in the first part of this series. Here, the relevant solution data obtained via CFD are compared to the values from laser Doppler anemometry measurements, and it is studied whether the accuracy of such data can be assessed using the two mentioned quantities. The overall outcome is that although judging mesh quality generally is possible, alone the two quantities are insufficient to draw conclusions regarding the actual solution data.
The study focuses on the assessment of accuracy of turbulence‐related data from computational fluid dynamics simulations using effective numerical dissipation rate and effective numerical viscosity. The experimental setup was discussed in the first paper of the two‐part series. This second paper reports the results of the numerical experiments.
This is the first part of a two‐part paper focusing on the assessment of accuracy of turbulence‐related data from computational fluid dynamics (CFD) simulations using effective numerical dissipation ...rate and effective numerical viscosity. Setup of the CFD cases replicating a swirling pipe flow experiment from literature, for which turbulence‐related data measured via laser Doppler anemometry (LDA) had been reported, is presented. The way effective numerical dissipation rate and effective numerical viscosity were obtained for each mesh cell is also discussed. The results of the study are presented in the second part of this series.
The study focuses on the assessment of accuracy of turbulence‐related data from computational fluid dynamics simulations using effective numerical dissipation rate and effective numerical viscosity. In this first paper of the two‐part series, the experimental setup is discussed. The actual results are reported in the second part.
Landfilling is still the most common way of municipal waste treatment in around half of the EU countries. It has been shown that diverting some of the waste-to-energy recovery makes it possible to ...reduce emissions of various pollutants, especially when the waste replaces lower-quality fossil fuels in heating plants. A methodology is presented to determine the influence of a waste-to-energy plant with a processing capacity in the range of 10 to 150 kt/y integrated into an existing district heating system on the air pollution load in the surrounding area. The change in emission production is determined using an optimisation tool previously developed in the GAMS environment. The parameters of the existing heating plant, such as the fuels used, the boiler output range, etc., are considered. A Gaussian scatter model is then used to determine the immission loads of individual pollutants in the surrounding area. Using the methodology, it is possible to directly quantify the impact of waste-to-energy plant integration on the health burden of the surrounding population in comparison with the reference state. This strategy is presented via a case study involving real-world data, in which it turned out that the immission load can be significantly reduced (up to 83%) compared to the original state in the calculation scenario.
Graphical abstract
This study investigates the industrial-scale application of a simple convective solar drying process of pineapples as part of a circular economy strategy for developing countries. A renewable energy ...concept is presented, which follows the circular economy aims by effectively employing a simple system for biogas production and a two-stage drying system. Both these systems meet the requirements for implementation in the specific conditions of developing countries, of which Togo, where pineapple is a major crop, is taken as an example. With respect to earlier findings available in the literature, the paper focuses on the solar drying process, which is critical to the proposed strategy. A portable solar dryer working in indirect heating mode was built and later also modified to enhance its performance. Three main factors influencing the convective drying process, namely, drying time (270 min, 480 min), solar radiation intensity (650 W/m2, 1100 W/m2), and slice thickness (6–8 mm, 12–14 mm), were considered. The statistical Design of Experiments (DOE) method was applied to reduce the number and scope of experiments. In the best case, the moisture content was reduced from 87.3 wt % in fresh samples to 29.4 wt % in dried samples, which did not meet the quality requirements for dried fruit. An additional conventional post-solar drying procedure would, therefore, still be necessary. Nonetheless, the results show that in the case of pineapple drying the consumption of fossil fuels can be decreased significantly if convective solar pre-drying is employed.
Combustion and radiant chambers with inbuilt heat transfer surfaces are integral parts of a wide range of process and power equipment such as fired heaters, power boilers, or incinerator furnaces. ...Operating problems that many of these combustion chambers suffer from are typically due to the design procedures using data of insufficient accuracy regarding the calculated local heat transfer data in individual parts of the chambers equipped with modern low-NOx burners. These problems, obviously, force the designers to devise more accurate design procedures for the respective equipment. The paper therefore discusses the main results obtained so far in the course of a several years long research effort and presents a basic outline of an up-to-date, novel approach to proper design of combustion and radiant chambers with inbuilt heat transfer surfaces. The three most important and – considering the current design practice – also original components of the presented novel approach which significantly improve the quality of the resulting combustion chamber designs are (i) experimental determination of the actual burner heat flux distribution, (ii) determination of the actual fuel burnout profile of the burner from the obtained heat flux profile using the validated MPF model, and (iii) utilisation of the respective fuel burnout profile in the course of design of the combustion chamber and its inbuilt heat transfer surfaces together with calculation of the local heat flux distribution via the plug-flow-based method, thus replacing the currently used design methods based on the “well stirred” models.
A new strategy for fast, approximate analyses of fluid flow and heat transfer is presented. It is based on Finite Element Analysis (FEA) and is intended for large yet structurally fairly simple heat ...transfer equipment commonly used in process and power industries (e.g., cross-flow tube bundle heat exchangers), which can be described using sets of interconnected 1-D meshes. The underlying steady-state model couples an FEA-based (linear) predictor step with a nonlinear corrector step, which results in the ability to handle both laminar and turbulent flows. There are no limitations in terms of the allowed temperature range other than those potentially stemming from the usage of fluid physical property computer libraries. Since the fluid flow submodel has already been discussed in the referenced conference paper, the present article focuses on the prediction of the tube side and the shell side temperature fields. A simple cross-flow tube bundle heat exchanger from the literature and a heat recovery hot water boiler in an existing combined heat and power plant, for which stream data are available from its operator, are evaluated to assess the performance of the model. To gain further insight, the results obtained using the model for the heat recovery hot water boiler are also compared to the values yielded by an industry-standard heat transfer equipment design software package. Although the presented strategy is still a “work in progress” and requires thorough validation, the results obtained thus far suggest it may be a promising research direction.
PDF
