bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Approach of Direct Digital Control for Spool Valves
Authors: Ruan J. , Burton R. 
Published: December 2021

Abstract
In many applications, digital valves driven from stepping motors are often characterized by quantitative errors and in some cases, slow response. A new means of direct digital control is introduced for a spool valve actuated by a stepper motor. With this control strategy, both excellent speed of response and accuracy are simultaneously sustained for the valve. By way of illustration, the characteristics of a digital spool valve are theoretically and experimentally investigated. This paper also deals with the design of the controller and some concepts concerning the digital control of a valve, such as initialization, false protection, etc. An example is given to demonstrate the effectiveness of this digital control approach for a practical electro-hydraulic control system.
Porous Media and Mixture Models for Hygrothermal Behavior of Phenolic Composites
Authors: Sullivan Roy M. , Stokes Eric H. 
Published: December 2021

Abstract
Theoretical models are proposed to describe the interaction of water with phenolic polymer. The theoretical models involve the study of the flow of a viscous fluid through a porous media and the thermodynamic theory of mixtures. From the theory a set of mathematical relations are developed to simulate the effect of water on the thermostructural response of phenolic composites. The expressions are applied to simulate the measured effect of water in a series of experiments conducted on carbon phenolic composites.
Mesoscopic Heat-Actuated Heat Pump Development
Authors: Drost Kevin 
Published: December 2021

Abstract
Battelle, Pacific Northwest Division (Battelle) and Pacific Northwest National Laboratory1 (PNNL) are developing a miniature absorption heat pump. Targeted applications include microclimate control ranging from manportable cooling to distributed space conditioning. The miniature absorption heat pump will be sized to provide 350 Wt of cooling2. A complete manportable cooling system, which will include the microscale heat pump, an air-cooled heat exchanger, batteries, and fuel, is estimated to weigh between 4 and 5 kg. For comparison, alternative systems weigh about 10 kg. Size and weight reductions in the microscale heat pump are possible because the device can take advantage of the high heat and mass transfer rates attainable in microscale structures.
Optimization of Miniature Pulse-Tube Cryocoolers
Authors: Shire J. M. , Mujezinovic A. , Phelan P. E. 
Published: December 2021

Abstract
This work introduces optimization techniques for designing pulse-tube coolers with the focus on coolers of smaller size. Methods are presented to select two geometric design parameters: pulse-tube length to regenerator length ratio, and system length to diameter ratio. The optimum values of these parameters are a function of the conduction heat loss down the tube walls, the regenerator effectiveness as a function of its length, and the pressure drop along the pulse tube. Results indicate that the optimum regenerator length/pulse tube length ratio increases with decreasing system length, and the optimum system length/diameter ratio increases with decreasing system volume.
Experimental Verification of a Universal Accumulator Heat Exchanger Design Procedure Used to Achieve Liquid Overfeeding Effects in Small Air Conditioning Systems
Authors: Wood Craig W. , Meyer Josua P. 
Published: December 2021

Abstract
This study involves the experimental verification of a universal heat exchanger accumulator design procedure. A heat exchange accumulator was manufactured according to a mathematical model developed by the authors and installed into a small air conditioning system. Experimental results show that the addition of the heat exchanger accumulator results in a liquid overfeeding operation that replaces the previously utilized direct expansion operation. It provides an improved air conditioning system that has a 7.5% increase in coefficient of performance and a 4.4% increase in refrigerant mass flow rate. A pressure ratio reduction has a positive effect on the compressor performance and life span. Liquid overfeeding increases the cooling capacity of the system by 6.5%. When compared to direct expansion systems, this basic heat exchanger accumulator provides a reduction in cycling losses and power consumption, an increase in suction pressure and an improvement in isentropic compressor efficiency.
Impacts of the Split Conjugated Pistons in Conjugated Cylinders of a Multiple Stage Reciprocating Compressor in Start Duration
Authors: Deng Jianqiang , Gu Zhaolin , Yu Yongzhang 
Published: December 2021

Abstract
Split pistons allow more precise manufacturing and easier assembly of conjugate-piston multi-stage reciprocating compressors. Their disadvantage is that during start up, the high pressure stage piston may impact with both its cylinder head and the low-pressure stage piston. To determine the magnitude of these impacts and how they can be minimized, a simple mathematical model was constructed to analyze the pressure build-up within the compressor and the movement of the high-pressure stage piston. It is shown that above a minimum threshold value of pressure in the high-pressure stage, the pistons remain attached and move together without impact. The calculation of this minimum pressure along with the contact stresses, during rounds of impacts when the forces are greatest is demonstrated. A mathematical model is also provided to help minimize the impact stresses involved in such an arrangement. It is shown that by appropriate piston design and choice of piston material, selection of the optimum stroke and volume of the discharge system as well as the electric motor, split-conjugate pistons can be used in high-pressure multi-stage compressors.
Transient Flow of the Oil-Refrigerant Mixture Through the Radial Clearance in Rolling Piston Compressors
Authors: Gasche José L. , Ferreira Rogério T. S. , Prata Álvaro T. 
Published: December 2021

Abstract
Unsteady flow of oil and refrigerant gas through radial clearance in rolling piston compressors has been modeled as a heterogeneous mixture, where the properties are determined from the species conservation transport equation coupled with momentum and energy equations. Time variations of pressure, tangential velocity of the rolling piston and radial clearance due to pump setting have been included in the mixture flow model. Those variables have been obtained by modeling the compression process, rolling piston dynamics and by using geometric characteristics of the pump, respectively. An important conclusion concerning this work is the large variation of refrigerant concentration in the oil-filled radial clearance during the compression cycle. That is particularly true for large values of mass flow rates, and for those cases the flow mixture cannot be considered as having uniform concentration. In presence of low mass flow rates homogeneous flow prevail and the mixture tend to have a uniform concentration. In general, it was observed that for calculating the refrigerant mass flow rate using the difference in refrigerant concentration between compression and suction chambers, a time average value for the gas concentration should be used at the clearance inlet.
The Experimental Analysis of Local Heat and Mass Transfer Data for Vertical Falling Film Absorption
Authors: Miller William A. , Keyhani Majid 
Published: December 2021

Abstract
In pure heat transfer, specifications of effectiveness, fluid properties, and flows enable calculation of the heat exchanger area. In the case of falling film absorption, a simultaneous heat and mass transfer governs the performance of the absorber. The exchange of mass across the liquid-vapor interface involves the generation of heat. The heat effects associated with the mass exchange increase the temperature, which affects the equilibrium state of the pressure and composition and in turn affects the mass. The falling film flow rate coupled to the physical properties of kinematic viscosity and surface tension govern the flow regime of a vertical falling film. Wavy-laminar, roll-wave laminar, and turbulent flows will develop convective contributions that can enhance the transfer of mass into the film.
The combined interaction of all these factors makes the absorption process very difficult to analyze and predict. A study of simultaneous heat and mass transfer was therefore conducted on a vertical falling film absorber to better understand the mechanisms driving the heat and mass transfer processes. Falling films are characteristically unstable, and a wavy-laminar flow was observed during the experimental study. The wavy flow further complicates the problem; therefore, only limited information is known about the temperature and concentration profiles along the length of the absorber that describe the local heat and mass transfer rates.
Hence, this study presents much-needed experimental data on the heat and mass transfer processes in the absence of heat and mass transfer additive. Absorption experiments were conducted in a mini-absorber test stand at various falling film flow rates, at various absorber pressures, and with various compositions of the binary salt solution. Thermographic phosphors were successfully used to measure the temperature profile along the length of the absorber test tube. These measures of the local variations in temperature enabled calculation of the bulk concentration along the length of the absorber. The bulk concentration varied linearly, from which one may infer that the concentration gradient in the direction of flow is approximately constant. The implication is that the mass flux, and therefore the absorber load, can be solved for by using a constant flux approximation.
Estimation of the Thermodynamic Properties for Branched Hydrocarbons
Authors: He Hui , Metghalchi Mohamad , Keck James C. 
Published: December 2021

Abstract
A simple model has been developed to estimate the sensible thermodynamic properties such as Gibbs free energy, enthalpy, heat capacity, and entropy of hydrocarbons over a wide range of temperatures with special attention to the branched molecules. The model is based on statistical thermodynamic expressions incorporating translational, rotational and vibrational motions of the atoms. A method to determine the number of degrees of freedom for different motion modes (bending and torsion) has been established. Branched rotational groups, such as CH3 and OH, have been considered. A modification of the characteristic temperatures for different motion mode has been made which improves the agreement with the exact values for simple cases. The properties of branched alkanes up to 2,3,4-Trimthylpentane have been calculated and the results are in good agreement with the experimental data. A relatively small number of parameters are needed in this model to estimate the sensible thermodynamic properties of a wide range of species. The model may also be used to estimate the properties of molecules and their isomers, which have not been measured, and is simple enough to be easily programmed as a subroutine for on-line kinetic calculations.
Heat Exchangers Networks Synthesis and Optimisation Performed by an Exergy-Based Expert Assistant
Authors: Maiorano Massimo , Sciubba Enrico 
Published: December 2021

Abstract
This paper presents a novel method for the design of “optimal” (or quasi-optimal) HEN. The method consists of an Expert System (“ES”) based on a small number of powerful and strongly selective heuristic rules. The important contribution of this study does not lie in the formulation of the rules, that have been adapted from the existing literature, but in their expression as logical propositions, and in their subsequent implementation in a prototype ES that performs interactively with the user.
It is not unusual to find chemical processes with as many as 100 interacting streams, and even simple thermal processes, excluding refineries and chemical plants, contain at least a 10-streams-HEN: hence the high demand for an “automatic” (in some sense) Design Procedure that may conveniently be adapted to design-and-optimisation problems. Pinch Technology (“PT”), at present the almost universally adopted design procedure, is very successful in most types of applications (except in cases where mechanical and thermal power must be optimised concurrently), but it constitutes an operative tool, and does not improve its user’s comprehension of the problem: it assumes, rather, that the user is already familiar with the design of HEN. The approach we present in this paper is entirely different: we do not “mask” the thermodynamic and thermo-economic principles that guide the engineer in the path towards the “optimal” HEN configuration, and do not allow concerns about “user friendliness” to impair the necessary participation of the user to the HEN synthesis procedure. In fact, though our ES (which we prefer to call “Expert Assistant”, to underline its peculiarity of constantly interacting with the user) is still lacking many of the capabilities that a good designer possesses, the underlying procedure is, unlike any of the other existing Design-and-Optimisation Procedures, entirely inspectable by the user for what its decision-making rules are concerned. It can be interrogated about its decision making, so that the logical path followed from the design data to the final solution can be inspected at will, and it can be used to directly compare different alternatives in a logically systematic fashion. The paper begins with a brief review of the HEN design problem, followed by a critical discussion of the heuristic rules that form the basis for the Inference Engine of the Expert System. The formalisation of these rules into logical propositions suitable for Knowledge Based Methods is then presented, and the resulting macrocode developed. As a preliminary validation, two examples of application of the code (named Heat Exchanger Network Expert Assistant, HENEA for short) are presented and discussed: since both cases have published, and their “optimal” solutions are known, the performance of HENEA can be assessed by comparison.
Perfect Heat Recovery From a Partial Oxidation Gas Turbine Engine
Authors: Call Frederick W. 
Published: December 2021

Abstract
This paper shows how to obtain the complete recovery of exhaust heat in the context of a gas turbine power plant. The power plant uses partial combustion of the fuel and yields power and a synthesis gas for further use in a chemical plant or conventional steam power plant. The key is a heat exchanger in conjunction with a Ni/NiO chemical loop that alters the composition of the air stream so that there is nearly a perfect match of the hot and cold streams down to ambient temperature. The chem-loop removes the oxygen for fuel combustion from the air as it raises the temperature of both the water/air and the synthesis gas streams (only the latter is used for power production). Assuming no heat losses from unit operations, no parasitic losses, and a pinch of only 2°C (simultaneous boiling and condensing) the First Law efficiency of the power plant can be over 98% (Second Law is about 45%). There are no acidic stack gases to contend with at this point as the partially combusted fuel is then exported for other uses, its value diminished only by the amount of power produced.
Effect of Circuit Arrangement on the Performance of Plate Finned Tube Heat Exchangers Under Dehumidifying Conditions
Authors: Liu Min-Sheng , Leu Jin-Sheng , Wang Chi-Chuan , Mei Vince C. 
Published: December 2021

Abstract
This study experimentally investigates the effect of circuitry on the performance of plate finned tube evaporators. Experiments were carried out with the heat exchangers having 1-circuit arrangements. A total of six circuitry were examined in this study, including two counter-cross, two parallel-cross, and two z-shape arrangements. The results showed that the counter-cross arrangement gives the best performance. However, heat conduction along the fins may offset the benefits of the counter-cross arrangement. In addition, the pressure drop of refrigerant-side increased with frontal velocities. Among the six 1-circuit arrangements, the parallel-cross flow circuit would produce a larger pressure drop than other arrangements. However, for G = 200 kg/m2·s and parallel flow, the pressure drops decrease with increase of the frontal velocity. The unusual characteristics are likely related to the flow pattern transition subjected to heat addition. The location of refrigerant inlet does not significantly affect the performance of heat exchangers.
Isentropic Expansion and the Three Isentropic Exponents of R152a
Authors: Kouremenos D. A. , Kakatsios X. K. , Floratos O. E. , Fountis G. 
Published: December 2021

Abstract
The isentropic change of an ideal gas is described by the well known relations pvk = const., Tv(k-1) = const. and p(1-k)Tk = const., where the exponent k is defined as the ratio of the constant pressure to the constant volume specific heat, k = Cp/Cv. The same relations can be used for real gases only if the differential isentropic changes under consideration are small. A better examination of the differential isentropic change shows that for p, v, T systems, there are three different isentropic exponents corresponding to each pair formed out of the variables p, v, T. These three exponents noted kT,p, kT,v, kp,v after the corresponding pair of variables used, are interconnected by one relation, and accordingly only two out of the three are independent. The analysis of the present paper shows the numerical values of these exponents as well as the isentropic expansion ratios for R152a in the vapor phase, presented in diagram form. It can be seen that the deviations of the three isentropic exponents relative to the conventional k = Cp/Cv values are considerable and depend upon the initial pressure and the stage of the expansion. Additionally, the effect of the three isentropic exponents on the ideal gas relations describing the isentropic expansion ratios is examined, in order to develop simple yet more accurate relations without having to resort to the complex real gas state equations.
Integrated Systems for Cogeneration and Absorption Chilling: Comparison for Varying Chiller COPs
Authors: Tang R. , Rosen M. A. 
Published: December 2021

Abstract
The thermodynamic effects are demonstrated of integrating steam turbine-based cogeneration systems with absorption chillers. A wide range of realistic extraction steam pressures and coefficient of performance (COP) values of absorption chillers are considered. A simple model of a steam turbine-based cogeneration plant is used for the evaluation of the integrated system. The integrated systems are evaluated based on the ratio of fuel consumption between a base case (one-stage absorption chiller with a COP value of 0.6) and several alternative cases (multi-stage absorption chillers with COP values ranging from 0.6 to 1.5). Two categories of scenarios are considered: (i) cases where the cooling load is fixed; and (ii) cases where the cooling load is fixed and the electrical output for the integrated system is set equal to that for the base case.
Mixed Mode Interface Cracks in a Bi-Material Half Plane and a Bi-Material Strip
Authors: Huang Haiying , Kadomateas George A. , La Saponara Valeria 
Published: December 2021

Abstract
This paper presents a method for determining the dislocation solution in a bi-material half plane and a bi-material infinite strip, which is subsequently used to obtain the mixed-mode stress intensity factors for a corresponding bi-material interface crack. First, the dislocation solution in a bi-material infinite plane is summarized. An array of surface dislocations is then distributed along the free boundary of the half plane and the infinite strip. The dislocation densities of the aforementioned surface dislocations are determined by satisfying the traction-free boundary conditions. After the dislocation solution in the finite domain is achieved, the mixed-mode stress intensity factors for interface cracks are calculated based on the continuous dislocation technique. Results are compared with analytical solution for homogeneous anisotropic media.
Computational Model for Free Abrasive Machining of Brittle Silicon Using a Wiresaw
Authors: Bhagavat Milind , Kao Imin 
Published: December 2021

Abstract
The present paper deals with physics based computational modeling of the wiresaw Free Abrasive Machining (FAM). The wiresaw is used to slice large diameter wafers of predominantly brittle semi-conductors such as silicon. The wiresawing model proposed in the present paper involves cutting action by ‘floating’ abrasives. It is proposed that the abrasive carrying slurry forms a film in the cutting zone by an elasto-hydrodynamic action. Finite Element Analysis shows this film to be in general thicker than the average abrasive size. This signifies a ‘float’ machining condition, wherein there is no direct pressing of abrasives by the wire. Typical rolling and indenting of abrasives under such free body abrasion environment is supported by hydrodynamic shear and pressure respectively. The abrasive is assumed to remove material by typical indentation fracture. Finite element analysis of stresses underneath an indenting abrasive shows that cracks leading to chipping occur only during unloading of indented abrasives (during rolling). The volume of the chip removed in a single indentation is proportional to the volume of plastic zone underneath the indenter. We integrate the elasto-hydrodynamic model and the single abrasive indentation model into a complete representative model of wiresawing.
Acoustic Emission Analysis for Fatigue Prediction of Lap Solder Joints in Mode Two Shear
Authors: Van De Wal Bryan J. , Kendall Gay , Sahay Chittaranjan 
Published: December 2021

Abstract
The traditional methods of fracture mechanics and failure prediction has historically been aimed at isentropic elastic materials that are ductile, i.e. steels, alloys, etc. Little effort until recently has focused on anisotropic compliant materials such as solder and its alloys due to the problems inherent in anisotropics.
The use of acoustic emission as a NDT has also been geared towards the same type of materials, i.e. in situ examinations of steel bridging, pressure vessels, and the like.
Traditional acoustic NDT theory uses the “Ring Down” methodology to characterize the waveforms created during fatigue. More modern techniques include utilizing acoustic emissions for peel testing, crack location, and other techniques. Not much research has been done combining these two basic research disciplines. The current research utilizes both successfully.
In the current research, the methodology used is that of using a signal recovery technique that filters and stores the waveforms. These waveforms are analyzed for energy, area of waveforms, and duration of waveforms via MATLAB© software. Semi-log plots of these energies, areas, and durations will aid in characterizing the different types of signal groups seen from the oscilloscope. SEM and Confocal analysis is concurrently used to facilitate a failure mechanism model of these lap joints. The ultimate goal is to see if a statistical correlation can be drawn between 1) the nature of waveforms seen on the oscilloscope, 2) the nature of the filtered data in the power spectrum, and 3) the modes of failure as seen under the Confocal and SEM. The results should show a clear and definitive empirical field method that can predict which “stage” of fatigue failure a soldered lap joint is undergoing.
The term “stage” refers to the qualitative observation that for each solder joint, regardless of cycle life, there are three characteristic general emission patterns seen as the joint fatigues to failure. Whether these “stages” or patterns correspond to the classical stages of fatigue is to be determined within this paper.