scholarly journals Evaluation of a Mesoscale Thermal Actuator in Open and Closed Operating Cycles

2019 ◽  
Author(s):  
Sindhu Preetham Burugupally
Keyword(s):  
Heat Input ◽  
Scaling Laws ◽  
Lumped Parameter Model ◽  
Thermal Actuator ◽  
Closed Cycle ◽  
Two Phase ◽  
Practical Applications ◽  
Thermal Actuators ◽  
Large Force ◽  
And Performance

Thermal-based actuators are known for generating large force and displacement strokes at mesoscale (millimeter) regime. In particular, two-phase thermal actuators are found to benefit from the scaling laws of physics at mesoscale to offer large force and displacement strokes; but they have low thermal efficiencies. As an alternative, a combustion-based thermal actuator is proposed and its performance is studied in both open and closed cycle operations. Through a physics-based lumped-parameter model, we investigate the behavior and performance of the actuator using a spring-mass-damper analogy and taking an air standard cycle approach. Three observations are reported: (1) the mesoscale actuator can generate peak forces of up to 400 N and displacement strokes of about 16 cm suitable for practical applications; (2) an increase in heat input to the actuator results in increasing the thermal efficiency of the actuator for both open and closed cycles; and (3) for a specific heat input, both the open and closed cycle operations respond differently \textemdash different stroke lengths, peak pressures, and thermal efficiencies.

scholarly journals Evaluation of a Combustion-Based Mesoscale Thermal Actuator in Open and Closed Operating Cycles

Actuators ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 73
Author(s):  
Sindhu Preetham Burugupally
Keyword(s):  
Heat Input ◽  
High Speed ◽  
Performance Metrics ◽  
Large Displacement ◽  
Lumped Parameter Model ◽  
Thermal Actuator ◽  
Free Piston ◽  
Lumped Parameter ◽  
Peak Pressures ◽  
Actuator Design

A combustion-based mesoscale thermal actuator is proposed and its performance is studied in both open and closed cycle operations using a physics-based lumped-parameter model. The actuator design is unique as it implements a free-piston complaint architecture where the piston is free to move in a linear direction. Our objective is to study the actuator behavior in both the cycles to help identify the benefits and highlight the differences between the two cycles. The actuator is modeled as a spring-mass-damper system by taking an air standard cycle approach. Three observations are reported: (1) for nominal heat inputs (140 J/cycle), the actuator can produce large displacement strokes (16 cm) that is suitable for driving mesoscale robots; (2) the efficiency of the actuator depends on the heat input; and (3) for a specific heat input, both the open and closed cycles operate differently—with different stroke lengths, peak pressures, and thermal efficiencies. Our study reveals that the performance metrics of the actuator make it an ideal candidate for high speed, large force, and large displacement stroke related applications.

scholarly journals Assessment of energy efficiency and performance in a two-phase anaerobic process for organic matter removal

2021 ◽  
Author(s):  
Andrea D. P. Hurtado ◽  
Diana M. Hernández ◽  
Karol L. Fuentes ◽  
Tatiana R. Chaparro
Keyword(s):  
Energy Efficiency ◽  
Synthetic Wastewater ◽  
Two Phase ◽  
Heating Value ◽  
The Real ◽  
Practical Applications ◽  
And Performance ◽  
The Stability ◽  
Lower Heating ◽  
The Ideal

Abstract The energy efficiency (EE) depends mainly on the lower heating values (LHVs) of hydrogen and methane selected from the thermodynamics tables at ideal conditions. However, for practical applications, the heating value should be calculated by considering some environmental factors under real conditions. Accordingly, this study compares the EE using the ideal LHV with the EE using the real LHV in a two-phase AD reactor treating synthetic wastewater. Additionally, the process performance and the stability were studied. The results show that the EE value calculated using LHVideal was, on average, 35% higher than that evaluated using LHVreal; these differences are relevant to the estimation of the real energy and also for the practical applications. At the same time, the index buffer IA/PA (intermediate alkalinity/partial alkalinity) showed to be more accurate than the value of the pH to analyze the stability of the process. With regard to COD, the removal efficiency in the methanogenic phase decreases drastically by utilizing 100% of the acidogenic phase. Future considerations in the optimization of each phase are highlighted.

scholarly journals Switched Capacitor DC-DC Converters: A Survey on the Main Topologies, Design Characteristics, and Applications

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2231
Author(s):  
Alencar Franco de Souza ◽  
Fernando Lessa Tofoli ◽  
Enio Roberto Ribeiro
Keyword(s):  
Voltage Regulation ◽  
Inherent Difficulty ◽  
Practical Applications ◽  
Dc Power ◽  
Higher Power ◽  
Voltage Doubler ◽  
Converter Design ◽  
Design Characteristics ◽  
And Performance ◽  
Full Charge

This work presents a review of the main topologies of switched capacitors (SCs) used in DC-DC power conversion. Initially, the basic configurations are analyzed, that is, voltage doubler, series-parallel, Dickson, Fibonacci, and ladder. Some aspects regarding the choice of semiconductors and capacitors used in the circuits are addressed, as well their impact on the converter behavior. The operation of the structures in terms of full charge, partial charge, and no charge conditions is investigated. It is worth mentioning that these aspects directly influence the converter design and performance in terms of efficiency. Since voltage regulation is an inherent difficulty with SC converters, some control methods are presented for this purpose. Finally, some practical applications and the possibility of designing DC-DC converters for higher power levels are analyzed.

Advances in MXene Films: Synthesis, Assembly, and Applications

2021 ◽  
Author(s):  
Xiaohua Li ◽  
Feitian Ran ◽  
Fan Yang ◽  
Jun Long ◽  
Lu Shao
Keyword(s):  
Spin Coating ◽  
Reaction Mechanisms ◽  
Membrane Separation ◽  
Synthesis Methods ◽  
Metal Carbides ◽  
Max Phases ◽  
Practical Applications ◽  
Coating Methods ◽  
And Performance ◽  
Important Form

AbstractA growing family of two-dimensional (2D) transition metal carbides or nitrides, known as MXenes, have received increasing attention because of their unique properties, such as metallic conductivity and good hydrophilicity. The studies on MXenes have been widely pursued, given the composition diversity of the parent MAX phases. This review focuses on MXene films, an important form of MXene-based materials for practical applications. We summarized the synthesis methods of MXenes, focusing on emerging synthesis strategies and reaction mechanisms. The advanced assembly technologies of MXene films, including vacuum-assisted filtration, spin-coating methods, and several other approaches, were then highlighted. Finally, recent progress in the applications of MXene films in electrochemical energy storage, membrane separation, electromagnetic shielding fields, and burgeoning areas, as well as the correlation between compositions, architecture, and performance, was discussed.

Random Forces Resulting From Internal Two-Phase Flow on Bends and Tees

2006 ◽  
Author(s):  
E. de Langre ◽  
J. L. Riverin ◽  
M. J. Pettigrew
Keyword(s):  
Two Phase Flow ◽  
Experimental Results ◽  
Time Dependent ◽  
Phase Flow ◽  
Water Mixture ◽  
Dimensionless Form ◽  
Two Phase ◽  
Practical Applications ◽  
Random Forces

The time dependent forces resulting from a two-phase air-water mixture flowing in an elbow and a tee are measured. Their magnitudes as well as their spectral contents are analyzed. Comparison is made with previous experimental results on similar systems. For practical applications a dimensionless form is proposed to relate the characteristics of these forces to the parameters defining the flow and the geometry of the piping.

Design and performance of a thermal actuator driving a preloaded linear translation stage

2021 ◽  
Vol 71 ◽  
pp. 187-199
Author(s):  
Chunjie Fan ◽  
D.J. Hastings ◽  
Joshua A. Tarbutton ◽  
Stuart T. Smith
Keyword(s):  
Thermal Actuator ◽  
Translation Stage ◽  
And Performance

Modeling of Vapor Compression Cycles for Multivariable Feedback Control of HVAC Systems

1997 ◽  
Vol 119 (2) ◽  
pp. 183-191 ◽  
Author(s):  
Xiang-Dong He ◽  
Sheng Liu ◽  
Haruhiko H. Asada
Keyword(s):  
Feedback Control ◽  
Phase Interface ◽  
Heat Pumps ◽  
Lumped Parameter Model ◽  
Vapor Compression ◽  
Two Phase ◽  
Lumped Parameter ◽  
Fan Speed ◽  
Linearized Model ◽  
Multivariable Feedback

This paper presents a new lumped-parameter model for describing the dynamics of vapor compression cycles. In particular, the dynamics associated with the two heat exchangers, i.e., the evaporator and the condenser, are modeled based on a moving-interface approach by which the position of the two-phase/single-phase interface inside the one-dimensional heat exchanger can be properly predicted. This interface information has never been included in previous lumped-parameter models developed for control design purpose, although it is essential in predicting the refrigerant superheat or subcool value. This model relates critical performance outputs, such as evaporating pressure, condensing pressure, and the refrigerant superheat, to actuating inputs including compressor speed, fan speed, and expansion valve opening. The dominating dynamic characteristics of the cycle around an operating point is studied based on the linearized model. From the resultant transfer function matrix, an interaction measure based on the Relative Gain Array reveals strong cross-couplings between various input-output pairs, and therefore indicates the inadequacy of independent SISO control techniques. In view of regulating multiple performance outputs in modern heat pumps and air-conditioning systems, this model is highly useful for design of multivariable feedback control.

Packaging of In-Plane Thermal Microactuators for BioMEMS Applications

2005 ◽  
Author(s):  
Hrishikesh V. Panchawagh ◽  
Faheem F. Faheem ◽  
Cari F. Herrmann ◽  
David B. Serrell ◽  
Dudley S. Finch ◽  
...  
Keyword(s):  
Flip Chip ◽  
Atomic Layer ◽  
Thermal Actuator ◽  
Mems Devices ◽  
Thermal Actuators ◽  
Layer Deposition ◽  
Comb Drives ◽  
Small Clearance ◽  
Surrounding Liquid ◽  
Packaging Technique

This paper addresses two issues related to in-plane, electro-thermal actuators for BioMEMS applications. First, in order to protect the actuator from biological debris and particulates, a packaging technique using a flip-chip bonded polysilicon cap is demonstrated. The encapsulated actuator transmits motion outside the package via a piston, which moves through a small clearance. The second issue addressed is the reduction in efficiency of the thermal actuator in liquids. By coating the packaged actuator with a thin conformal hydrophobic layer via an atomic layer deposition (ALD) process, the liquid is prevented from entering the encapsulation. This avoids direct contact between the actuator and the surrounding liquid thereby improving its efficiency. The unpackaged and packaged actuators were tested in both air and de-ionized water. Although the packaging resulted in a reduction in the performance of the thermal actuator in air, the actuation efficiency in water was significantly improved due to the isolation of the hot arms from the liquid. This packaging technique is also applicable to other MEMS devices and in-plane actuators such as electrostatic comb drives for engineering as well as biological applications.

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