Waste Heat Recovery Technologies Revisited with Emphasis on New Solutions, including Heat Pipes, and Case Studies

Industrial processes are characterized by energy losses, such as heat streams rejected to the environment in the form of exhaust gases or effluents occurring at different temperature levels. Hence, waste heat recovery (WHR) has been a challenge for industries, as it can lead to energy savings, higher energy efficiency, and sustainability. As a consequence, WHR methods and technologies have been used extensively in the European Union (EU) (and worldwide for that matter). The current paper revisits and reviews conventional WHR technologies, their use in all types of industry, and their limitations. Special attention is given to alternative “new” technologies, which are discussed for parameters such as projected energy and cost savings. Finally, an extended review of case studies regarding applications of WHR technologies is presented. The information presented here can also be used to determine target energy performance, as well as capital and installation costs, for increasing the attractiveness of WHR technologies, leading to the widespread adoption by industry.

Electric Power Amplification in Fusion Power Plants

Fusion power concepts that are heated by electrical devices for the purpose of producing high levels of electrical output are in effect electric power amplifiers. Three systems are considered: A hypothetical electric power version of the ITER experiment, the ARIES-1 fusion reactor design, and a modified version of ARIES-1 with stainless steel structural material. We find that an ITER power plant with a reasonable electric power conversion system would produce no net electric power at its target energy amplification factor of 10. The ARIES-1 conceptual power plant, as conceived, would have an energy amplification of 22 and an electric amplification of 6. If stainless steel were substituted for the SiC composite material assumed, the ARIES-1 electric power amplification would drop to roughly 3. We conclude that practical fusion power plants will likely require a near-ignition operating mode and qualified high temperature materials as prerequisites for commercial viability.

Energy target achievement and its determinants in critically ill COVID-19 patients in Indonesia

Introduction. Achievement of energy target in critically ill Covid-19 patients in Intensive Care Unit (ICU) is challenging. This study was aimed to depict the possibility of achieving energy target and its determinants in critically ill Covid-19 patients. Methods. A cross sectional study was conducted in ICU of dr. Kariadi Hospital Semarang, Indonesia. Secondary data were obtained from Covid-19 patients who were in ICU for minimum 3 days, from March to December 2020. Data collected included age, sex, Body Mass Index (BMI), comorbidities, Modified Nutrition Risk in Critically Ill (mNUTRIC) score, energy intake, route of nutrition delivery (enteral or combination of enteral and parenteral nutrition), lactate status, ICU length of stay (LOS), duration of mechanical ventilator and mortality. Risk Prevalence calculations were conducted to measure risks. Variables with significant associations and p< 0.25 were included in multiple logistic regression. Results. A total of 188 subjects were included in the analysis. Most patients were male (62.8%) and obese (61.8%). As much as 56.9% patients were able to achieve energy target of 20 kcal/kgBW on day 3 of ICU stay. Those with low risk mNUTRIC score and nutrition delivery was through enteral and parenteral route were more likely to achieve target energy of 20 kcal/kgBW in the first 3 days in the ICU. Conclusions. Achieving energy target of 20 kcal on day 3 of ICU stay for critically ill Covid-19 patients is feasible. Low mNutric score and nutrition delivery through enteral and parenteral route were two determinants for the achievement.

Analytical Analysis for Parameter Design of Attached Nonlinear Energy Sink

The dynamic responses of a linear primary structure coupled with a nonlinear energy sink (NES) are investigated under harmonic excitation in the 1 : 1 resonance regime. In civil engineering, initial conditions are usually zero or approximately zero. Therefore, in this study, only these conditions are considered. The strongly modulated response (SMR), whose occurrence is conditional, is the precondition for effective target energy transfer (TET) in this system. Therefore, this study aims to determine the parameter range in which the SMR can occur. The platform phenomenon and other related phenomena are observed while analyzing slow-varying equations. An excitation amplitude interval during which the SMR can occur is obtained, and an approximate analytical solution of the optimal nonlinear stiffness is found. The numerical results show that the NES based on the optimal stiffness performs better in terms of control performance.

Study on target energy transfer of 3D acoustic cavity - plate coupling system with the membrane nonlinear energy sink

The target energy transfer (TET) between a membrane nonlinear energy sink (NES) and the acoustic medium inside a rectangular cavity is studied. The acoustic medium is interacted with a plate and multi-order modes coupling of the 2 structure is considered. Based on the modal expansion approach, with Green's function, Helmholtz equation and the boundary conditions of the acoustic medium and the plate, the coupling coefficient matrix of the mode of 2 structures is derived. The equations of the membrane NES, multi-order modes of the acoustic medium and multi-order modes of the plate are established, and numerical analysis is used to investigate the TET phenomenon. The results show that in condition of a single-point excitation to the plate, under a certain range of excitation levels, the membrane can be seen as a kind of NES, and the energy in the acoustic medium can be unidirectionally transmitted to the membrane NES and attenuated, reducing the sound pressure level in the cavity. At the same time, it is found that the NES can suppress multi-order sound pressure of the acoustic medium at the same time, and realize the control of cascaded resonance noise.

Variations on the Maiani-Testa approach and the inverse problem

We discuss a method to construct hadronic scattering and decay amplitudes from Euclidean correlators, by combining the approach of a regulated inverse Laplace transform with the work of Maiani and Testa [1]. Revisiting the original result of ref. [1], we observe that the key observation, i.e. that only threshold scattering information can be extracted at large separations, can be understood by interpreting the correlator as a spectral function, ρ(ω), convoluted with the Euclidean kernel, e−ωt, which is sharply peaked at threshold. We therefore consider a modification in which a smooth step function, equal to one above a target energy, is inserted in the spectral decomposition. This can be achieved either through Backus-Gilbert-like methods or more directly using the variational approach. The result is a shifted resolution function, such that the large t limit projects onto scattering or decay amplitudes above threshold. The utility of this method is highlighted through large t expansions of both three- and four-point functions that include leading terms proportional to the real and imaginary parts (separately) of the target observable. This work also presents new results relevant for the un-modified correlator at threshold, including expressions for extracting the Nπ scattering length from four-point functions and a new strategy to organize the large t expansion that exhibits better convergence than the expansion in powers of 1/t.

Quasi-Continuous Metasurface Beam Splitters Enabled by Vector Iterative Fourier Transform Algorithm

Quasi-continuous metasurfaces are widely used in various optical systems and their subwavelength structures invalidate traditional design methods based on scalar diffraction theory. Here, a novel vector iterative Fourier transform algorithm (IFTA) is proposed to realize the fast design of quasi-continuous metasurface beam splitters with subwavelength structures. Compared with traditional optimization algorithms that either require extensive numerical simulations or lack accuracy, this method has the advantages of accuracy and low computational cost. As proof-of-concept demonstrations, several beam splitters with custom-tailored diffraction patterns and a 7 × 7 beam splitter are numerically demonstrated, among which the maximal diffraction angle reaches 70° and the best uniformity error reaches 0.0195, showing good consistency with the target energy distribution and these results suggest that the proposed vector IFTA may find wide applications in three-dimensional imaging, lidar techniques, machine vision, and so forth.

Algorithms and Methods for Induction Motors Performance Research Based on Testing Automation

New electrical machines design assumes the execution of research and test-design works with a choice and selection of the effective technical solutions. The prototypes characteristics control is implemented by testing them in laboratory using the automated tools and methods. The automation provides relevant datasets for further analysis. In the paper the algorithms and methods for studying the general purpose induction motors performance characteristics have been proposed. The changes of dependence of the motor efficiency on the output power alterations, caused by using different technical solutions, have been studied. Based on experience of the electrical machines testing in a specialized laboratory, the task of evaluating the induction motors energy efficiency when operating in S1 mode (continuous duty) with overloads occurrence, has been formulated. A method for solving the problem based on the efficiency curves has been proposed. The results have been implemented in a computer program and can be used to improve the technical solutions, allowing an achievement of the target energy efficiency indicators.