Performance In Terms Of Coefficient Research Articles

Evaluation of water + imidazolium ionic liquids as working pairs in absorption refrigeration cycles

Ionic Liquids (ILs) have been proposed as alternative absorption media for water in absorption refrigeration cycles to replace the currently used lithium bromide, which suffers from problems like crystallization and corrosiveness. This work investigates the use of imidazolium based ionic liquids as water absorbents in absorption refrigeration cycles. A predictive procedure is followed for calculating the parameters that mostly affect the performance of the cycle, that is the Vapor-Liquid Equilibrium (VLE) of the working pair and its heat capacity: UNIFAC is employed for the VLE calculations while a new predictive method has been developed for the heat capacity of the ILs. The effect of the alkyl chain length of the cation and the type of the anion that compose the IL is investigated, and it is shown that ILs consisting of imidazolium cation with short alkyl chain and the anions [Cl] and [DMP] exhibit the best performance in terms of Coefficient of Performance (COP) and circulation ratio (f). Comparison with the conventional LiBr absorbent indicates that the best ILs exhibit higher COP values but higher f ratios as well. Also, double cycle configurations are studied revealing the major effect of the supplied heat temperature on COP, even for the higher temperatures, compared to the single effect one. Finally, it is shown that there is a clear correlation between the COP of the refrigeration cycle and the product of the circulation ratio and the specific heat capacity of the strong solution, which is proposed in this work as a new reliable index for screening different ILs as absorbents, without the necessity of solving the mass and energy balances of the cycle.

Performance Analysis of Domestic Refrigerators Condenser Coil By Applying Lampblack / Synthetic Black Blend

Abstract: Domestic refrigerators are usually used for cooling the bounded space by absorbing the heat through the evaporator and simultaneously rejecting the heat to the surrounding through the condenser coil. The black color coated condenser coil is the main part that rejects heat to the surrounding in the form of radiations. Herein, to increase rejection of the heat from the condenser coil, to increase its performance, a blend of lampblack/ synthetic black (various w/w ratio) was partially painted on. The three different compositions (w/w) are applied on the condenser coil and accordingly, the heat radiating coefficient and coefficient of performance are measured. Optimized composition of lampblack /synthetic black (4:6) provided maximum performance in terms of coefficient of performance 5.51% and with heat transfer coefficient 16.11%. The results show a costeffective approaches to increase the performance as well as the life time.

Comparison of Different Machine Learning Models for Modelling the Higher Heating Value of Biomass

The aim of this study was to investigate the potential of using structural analysis parameters for estimating the higher heating value (HHV) of biomass by obtaining information on the composition of cellulose, lignin, and hemicellulose. To achieve this goal, several nonlinear mathematical models were developed, including polynomials, support vector machines (SVMs), random forest regression (RFR) and artificial neural networks (ANN) for predicting HHV. The performed statistical analysis “goodness of fit” showed that the ANN model has the best performance in terms of coefficient of determination (R2 = 0.90) and the lowest level of model error for the parameters X2 (0.25), RMSE (0.50), and MPE (2.22). Thus, the ANN model was identified as the most appropriate model for determining the HHV of different biomasses based on the specified input parameters. In conclusion, the results of this study demonstrate the potential of using structural analysis parameters as input for HHV modeling, which is a promising approach for the field of biomass energy production. The development of the model ANN and the comparative analysis of the different models provide important insights for future research in this field.

Effect of Adsorbent on the Performance of Double Effect Adsorption Refrigeration Cycle with Adsorption Heat Recovery

This study investigates the performance of double effect adsorption refrigeration cycle that utilizes the adsorption heat of a high-temperature adsorbent heat exchanger for desorption of a low-temperature one. Because there is a freedom to select an adsorbent for each adsorbent heat exchanger, the combination of adsorbents such as silica gel, FAM-Z01, FAM-Z02 and FAM-Z05 were examined. The temperature of an external heat source was assumed to be 90°C. Dynamic cycle simulation was employed to estimate the performance in terms of coefficient of performance (COP) and specific cooling power (SCP). The results show that the combination of the adsorbents FAM-Z01 and FAM-Z02 for the low-temperature heat exchanger and high-temperature one, respectively, is the most effective to achieve high COP as well as high SCP. The results also indicate that the COP=1.0 is attainable when the mass allocation of the adsorbents and the cycle time are selected appropriately. From the viewpoint of maximizing the cooling power, COP=0.9 is suggested for the best design, where the mass of high-temperature side is equal to the mass of low-temperature side.

Reparameterization of the Weibull model for practical uses in food science.

The reparameterization of the Weibull cumulative distribution function and its survival function was performed to obtain meaningful parameters in food and biological sciences such as the lag phase (λ), the maximum rate ( ), and the maximum increase/decrease of the function (A). The application of the Lambert function was crucial in order to achieve an explicit mathematical solution. Since the reparameterized model is applicable only when the shape parameter (α) is greater than one, the Weibull model was modified with the introduction of a new parameter ( ) that represents the model rate at time β (scale parameter). All models were applied to literature data on food technology and microbiology topics: Microbial growth, thermal microbial inactivation, thermal degradation kinetics, and particle size distributions. The Weibull model and the reparameterized versions showed identical fitting performance in terms of coefficient of determination, residual mean standard error, values of residuals, and estimated values of the parameters. Some faults in the datasets used in this study permitted to re-mark the criticality of a good experimental plan when data modeling is approached. The parameter resulted in an interesting new rate parameter that is not correlated with the scale parameter ( =0.64 ± 0.37)and highly correlated with the shape parameter ( =0.90 ± 0.11). Also, the reparameterization of the Weibull probability density function was performed by using both the standard and new parameters and applied to experimental data and gave useful information from the distribution curve, such as the value of the mode ( ) and a measure of the curve skewness (λ).

Analysis of organic Rankine cycle integrated multi evaporator vapor-compression refrigeration (ORC-mVCR) system

In this study, a multi evaporator vapor-compression refrigeration (mVCR) system driven by Organic Rankine Cycle (ORC) is proposed as a refrigeration system for supermarkets, restaurants, etc. The system is analyzed for its thermodynamic performance in terms of coefficient of performance (COPs) and exergetic efficiency (ηex). A zeotropic mixture of hexane and R245fa is used as working fluid over pure fluid to assess its impact on the thermodynamic performance of the system. Moreover, the system is optimized using an evolutionary algorithm called genetic algorithm (GA) to determine the optimal values of the operating parameters for the maximum exergetic efficiency of the system. The results indicate that COPs and ηex are maximum at the mass fraction of 0.5 of the zeotropic mixture. The maximum values of COPs and ηex are 0.425 and 31.1% respectively. The system can achieve an exergetic efficiency of 58% at the optimal set of operating parameters. The corresponding optimal values of the temperature of the ORC evaporator, VCR evaporator 1, VCR evaporator 2, and the condenser are 388 K, 268 K, 268 K, and 303 K respectively.

Wear Behavior of Ti6Al4V Surfaces Functionalized through Ultrasonic Vibration Turning

Even if titanium alloys are widely used for biomedical applications, the tendency they show to wear is a matter of concern for their durability. In this research work, Ultrasonic Vibration Turning (UVT) was used to generate texturized surfaces on Ti6Al4V cylinders for improving their wear performances. To prove that, in vitro wear tests were performed, during which the UVT-ed Ti6Al4V cylinders were made to slide against polyethylene disks to replicate a currently used biomedical pair. It was shown that the UVT-ed Ti6Al4V cylinders were characterized by enhanced performances in terms of coefficient of friction and wear rate, which were reduced to 52 and 25%, respectively, compared to polished Ti6Al4V surfaces.

Use of Genetic Programming for the Estimation of CODLAG Propulsion System Parameters

In this paper, the publicly available dataset for the Combined Diesel-Electric and Gas (CODLAG) propulsion system was used to obtain symbolic expressions for estimation of fuel flow, ship speed, starboard propeller torque, port propeller torque, and total propeller torque using genetic programming (GP) algorithm. The dataset consists of 11,934 samples that were divided into training and testing portions in an 80:20 ratio. The training portion of the dataset which consisted of 9548 samples was used to train the GP algorithm to obtain symbolic expressions for estimation of fuel flow, ship speed, starboard propeller, port propeller, and total propeller torque, respectively. After the symbolic expressions were obtained the testing portion of the dataset which consisted of 2386 samples was used to measure estimation performance in terms of coefficient of correlation (R2) and Mean Absolute Error (MAE) metric, respectively. Based on the estimation performance in each case three best symbolic expressions were selected with and without decay state coefficients. From the conducted investigation, the highest R2 and lowest MAE values were achieved with symbolic expressions for the estimation of fuel flow, ship speed, starboard propeller torque, port propeller torque, and total propeller torque without decay state coefficients while symbolic expressions with decay state coefficients have slightly lower estimation performance.

Design and Evaluation the Anti-Wear Property of Inorganic Fullerene Tungsten Disulfide as Additive in PAO6 Oil

Inorganic fullerene-like tungsten disulfide particles have been proved to have good anti-friction and anti-wear properties as lubricating materials. As far as we know, however, when it is used as a lubricant additive, its behavior and action mechanism in the friction process are rarely studied. Herein, IF–WS2 particles were synthesized by a Chemical Vapor Deposition (CVD) method. The effect of IF–WS2 particle concentrations in the PAO6 oil on the tribological behaviors was investigated with a four-ball wear machine at both 75 and 100 °C. Additionally, the analyzed morphology and composition of nanomaterials and worn surfaces were analyzed by Scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The friction behavior in actual working conditions was studied by a wear testing machine. The experimental results show that compared with the original PAO6 oil, at a dispersion of 0.25 wt% in PAO6 oil, the IF–WS2 particles showed the best performance in terms of coefficient of friction, wear scar diameter and wear mass, which significantly reduced by 27%, 43% and 87%, respectively. At the same time, in the process of friction, it was found that IF–WS2 particles accumulated in the depressions to fill the scratches, and adsorption films and chemical films, including FeS2, WS2 and WO3, were formed on the worn surfaces to avoid the direct contact among the friction pairs more effectively, resulting in the improved anti-wear performances. Additionally, the addition of IF–WS2 particles effectively delayed the rise of lubricating oil temperature. In addition, dispersant span 80 can effectively improve the dispersion and stability of IF–WS2 in PAO6. This work provides us for understanding the effective lubrication mechanism of IF–WS2 particles in more detail and having a new acknowledge of the comprehensive performance of IF–WS2/PAO6 oil.

Synthesis and Tribological characteristics of a nano CuO particle-filled water-based lubricants

The oil-based lubricating system tends to produce high cutting temperatures owning to the low cooling capability of oil lubricants. The addition of lubricating additives in nanoscale could increase the tribological and lubrication performance of the water-based lubricants. In this work, nano CuO particle-filled water-based lubricants as cutting fluids were developed using ultrasonication process. The Thermophysical Properties of synthesized nano filled water-based lubricant was tested and analyzed. The tribological characteristics were fairly investigated using four-ball and pin on disc apparatus testing units. The results indicated that nano CuO filled water-based lubricant shows enhanced tribological performance in terms of coefficient of friction (COF) and wear scar diameter (WSD) compared with base coolant. The superior performance of CuO filled water-based lubricant was credited to the detail that CuO nanoparticle additives arrived the rubbing interface and made a tribo-thin layer of CuO. Water-based lubricant showed the highest surface deformation compared to nano-based lubricants which indicate that the damage was due to adhesive wear.

Effects of hybrid carbon-aramid fiber on performance of non-asbestos organic brake friction composites

The present investigation aims to explore the influence of simultaneous loading of aramid/carbon fibers, as high-performance reinforcements, on thermal, mechanical, and frictional behaviors of phenolic-resin-based non-asbestos organic (NAO) friction materials. The hybrid composite specimens were made at different ratios of carbon and aramid fibers but at a total fixed fiber loading of 8 vol%. The influence of carbon fiber on the improvement of impact strength and thermal conductivity was found to be more prominent than aramid fiber. The thermal stability of friction composites under nitrogen and real condition was investigated. The frictional data drawn from a Chase type friction tester revealed that the coefficient of friction and fade behavior were improved by incorporating aramid fiber. However, carbon fiber improved the wear resistance significantly in comparison with aramid fiber. The surface morphology of the composites was investigated precisely using scanning electron microscopy. Taking all the characterizations (physical, thermal, and tribological) into account, it was revealed that the sample holding 6 vol% aramid fiber and 2 vol% carbon fiber presented the best performance in terms of coefficient of friction, wear rate and fade behavior.

Mechanical and abrasive wear response of PTFE coated glass fabric composites

The present study evaluates the influence of hybridization on the interlaminar shear and abrasive wear properties of composites manufactured with polytetrafluoroethylene (PTFE) coated glass fabrics. Homogeneous composites were manufactured using two dimensional plain woven (2D), three dimensional knitted (3D) and satin weave (SW) fabrics. Hybrid composites were manufactured with the same fabrics and a steel metal mesh (MM) stacked on the top and bottom of the laminates. The interfacial property was obtained through interlaminar shear strength (ILSS) tests. Abrasive wear tests were performed against a silicon carbide (SiC) paper of grit size 120 μm using a plate on plate apparatus. Loads ranging from 10 N to 50 N were applied at an interval of 10 N with a speed of 10 rad/s. Incorporation of MM influenced the physical properties like thickness, density and void content. Hybridization of homogeneous composites with MM improved the ILSS by 56%, 10% and 18% for 2D, 3D and SW composites, respectively. All the hybrid composites showed better wear performance in terms of coefficient of friction (COF) and specific wear rate (K0). SW and SW-MM composites exhibited better wear performance in all the wear properties as compared to the 2D, 2D-MM, 3D and 3D-MM composites. Scanning electron microscopy (SEM) revealed that the bonding between fibre and matrix could be improved in the case of 2D and 2D-MM composites.

Comparative performance assessment of pineapple and Kevlar fibers based friction composites

Novel friction composites materials using pineapple fiber as a sustainable alternative for automotive industry were developed by increasing its amount from 5−20wt.% in the step of 5 %. To compare the performance of pineapple fiber, friction composites with 5−10wt.% of Kevlar fiber were also manufactured. The results of physico-mechanical properties reveal that density, hardness and ash content decrease whereas water absorption, porosity and compressibility increase with the increased pineapple/Kevlar fiber contents. Further, the friction and fade performance were found to decrease whereas the recovery performance and wear was found to increase with increased pineapple fiber content. Among pineapple fiber reinforced composites, the best composite is the one having 5wt.% pineapple fibers that exhibits the highest performance in terms of coefficient of friction (0.548), lowest fade-% (36.31 %) along with the lowest specific wear rate (3.49×10−8cm3/N-m). Nonetheless, the results show that the 5wt.% Kevlar fiber based composite reveals good performance in terms of coefficient of friction (0.592) with slightly lower fade-% (35.98 %), recovery-% (107.43 %) and specific wear rate (3.46×10−8 cm3/N-m) when comparing to 5wt.% pineapple fiber based composites. Finally, the possible wear mechanisms were discussed with the help of composites worn surface morphologies.

Modelling the chlorophenol removal from wastewater via reverse osmosis process using a multilayer artificial neural network with genetic algorithm

Reverse Osmosis (RO) can be considered as one of the most widely used technologies used to abate the existence of highly toxic compounds from wastewater. In this paper, a multilayer artificial neural network (MLANN) with Genetic Algorithm (GA) have been considered to build a comprehensive mathematical model, which can be used to predict the performance of an individual RO process in term of chlorophenol removal from wastewater.The MLANN model has been validated against 70 observational experimental datasets collected from the open literature. The MLANN model predictions have outperformed the predictions of several structures developed for the same chlorophenol removal using RO process based on performance in terms of coefficient of correlation, coefficient determination (R2) and average error (AVE). In this respect, two structures (4-2-2-1) and (4-8-8-1) were also used to study the effect of a number of neurons in the hidden layers based on the difference between the measured and ANN predicted values. The model responses clearly confirm the successfulness of estimating the chlorophenol rejection for network structure 4-8-8-1 based on a wide range of the control variables.This also represents a high consistency between the ANN model predictions and the experimental data.

An overview of experimental studies on nanorefrigerants: Recent research, development and applications

Emergence of nanotechnology opens up new avenues in diverse research frontiers. Nanorefrigerants are nanotechnology based refrigerants, which are stable mixture of nanoparticles of metal, oxide, carbon and its allotropes and refrigerants. Development of nanorefrigerants provides a new research frontier in the heat transfer perspective. The studies on nanorefrigerants are still in its budding stage. The intention of the present paper is to provide a comprehensive overview of experimental studies on thermophysical and rehological properties, boiling and condensation phenomena, pressure drop characteristics, aggregation behaviour, migration and degradation characteristics of different nanorefrigerants and application of nanorefrigerants in HVAC systems. Various outlooks of future scope associated with the studies of nanorefrigerants have also been suggested. It has been recognized that addition of nanoparticles in refrigerants contributes noteworthy augment in the thermal physical and heat transfer characteristics of refrigerants. Furthermore, application of nanorefrigerants in heating, ventilation, and air conditioning systems enhance the overall performance in terms of coefficients of performance (COP) and energy efficiency.

Critique of operating variables importance on chiller energy performance using random forest

Chiller systems take up the major proportion of electricity used in commercial buildings. Their energy performance in terms of coefficient of performance (COP) depends on how the controllable and uncontrollable variables change. The aim of this study is to use the random forest (RF) method to measure variables importance and predict the COP. A sophisticated data trend log was carried out on an air-cooled chiller with advanced heat rejection features. The variables measured are: the flow rate of chilled water; the supply and return temperatures of chilled water; the temperature and relative humidity of outdoor air; the compressor power; the evaporating temperature; the condensing temperature; the number and speed of condenser fans staged; the temperatures of air entering and leaving the condenser. The data were logged at 5-min intervals in Aug 2015–Mar 2016. The RF models for different operating modes were validated, with a robust coefficient of determination of 80.52–96.53% for the testing data set. The chiller part load ratio, the condensing temperature, the chilled water flow rate, the heat rejection airflow rate and the wet-bulb temperature are the top five important variables in the prediction of COP. Yet they are not fully considered in typical regression models. Results of this study provide an insight into which variables are important to predict accurately the COP under different energy efficient features. The need of identifying the changing pattern of important variables is ascertained.

Innovative Approach To Enhance Tribological Performance Of Conveyor Belt System

The present case study reports the development of innovative method to reduce coefficient of friction between the conveyor belt systems against the metallic support. The process involves identification of suitable self-lubricating materials – Polytetrafluoroethylene (PTFE) and nylon in the fibrous form to develop modified conveyor belt with improved frictional performance i.e. reduction of coefficient of friction values. The stitching of PTFE fibers on the conveyor system with varying gauge diameter, spacing distance (pitch) and design to reduce the friction. The incorporation of fluorocarbon and/or nylon fibers with the rubber materials created a robust integrated conveyor system. With the stitching of PTFE fibers the frictional force reduced significantly which further reduces the coefficient of friction against the counter face steel component. The fibers are effectively incorporated with rubber and therefore no peeling or reduction in mechanical performance of conveyor belt system is observed. From the measured values, the frictional force can be lowered as much as 64 % for modified conveyor system. The series of samples were developed based upon the varying fiber gauge diameter and pitch further characterized for tribological performance in terms of coefficient of friction. Reduction in coefficient of friction was observed after incorporation of PTFE fibers. The current method is scalable and can be easily adopted for industrial practice.

Performance improvement of Savonius rotor using multiple quarter blades – A CFD investigation

Savonius rotor is preferred for many power generation applications like tidal, wind and hydro, especially on a small scale by virtue of its simple and inexpensive construction, installation and maintenance. Present study is focussed on the estimation and comparison of the performance in terms of Coefficient of Performance (COP) of a new configuration of Savonius rotor with the conventional one, using numerical simulation approach. New configuration comprises multiple quarter blades added to conventional configuration. A methodology for the numerical simulation of Savonius rotor is developed and validated, that can be employed for comparative study of different design configurations for design based optimization of Savonius rotor. Accuracy of the simulation results, despite of correct methodology, is dependent on accurate estimation of turbulence and meshing parameters. Present work employs Shear Stress Transport (SST) model for modelling turbulence which incorporates the near wall fluctuation capturing capability of k-ω model and robust k-ɛ model for modelling the bulk domain. Meshing parameters include correct estimation of first layer thickness for boundary layer on the blades based on the desired y+ value. An improvement in Coefficient of Performance ranging between 8.89% and 13.69% for different inlet velocities is observed for new configuration over the conventional configuration.

An Experimental Study of Impinging Synthetic Jets for Heat Transfer Augmentation

According to recent trends in the field of miniature electronics, the need for compact cooling solutions compatible with very thin profiles and small footprint areas is inevitable. Impinging synthetic jets are recognized as a promising technique for cooling miniature surfaces like laptops, tablets, smart phones and slim TV systems. Effect of jet to cooled surface spacing is crucial in cooling performance as well as predicting Nusselt number for such spacing. An experimental study has been performed to investigate the cooling performance of two different synthetic jets actuated with piezoelectric actuators cooling over a vertical surface. Results showed that a major degradation of heat transfer when jets are close to the surface is occurred. Slot synthetic jets showed a better performance in terms of coefficient of performance (COP) than semi-confined circular jets for small jet to surface spacing. Later, a correlation is proposed for predicting Nu number for a semi-confined circular synthetic jet accounting the effects of Re number ([Formula: see text]), jet-to-surface spacing ([Formula: see text] and [Formula: see text]) and the stroke length ([Formula: see text] and [Formula: see text]). It is found that correlation can provide predictions with an [Formula: see text] value of over 98%.

Thermal Performance Improvements of Vapour Compression Refrigeration System Using Eco Friendly Based Nanorefrigerants in Primary Circuit

Now a days nano refrigerants are being considered as a most efficient heat transfer fluids having superior heat transfer properties than conventional refrigerants in various thermal applications. Refrigerant based nano fluid termed as “Nanorefrigerant” have the great potential for improve thing first law thermal performance in terms of coefficient of performance in the refrigeration and air conditioning system. The thermo physical properties by addition of different nanoparticle mixed with eco friendly refrigerant are analyzed and their effects on the coefficient of performance (C.O.P.) have been reported in this paper. The thermal modeling have been done for the same cooling load and same geometry parameter for all nanoparticles and refrigerant combination mixture in the vapour compression refrigeration based chiller system having two concentric tube type heat exchanger as evaporator and condenser. The experimental results are indicating the thermal conductivity, dynamic viscosity and density of nanorefrigerant (different nanoparticle i.e. Cu, Al2O3,CuO and TiO2 with eco friendly refrigerant R134a,R407c and R404A) increased about 15 to 94 %, 20% and 12 to 34 % respectively compared to base refrigerant on the other hand specific heat of nanorefrigerant is slightly lower that the base refrigerant. Moreover Al2O3/R134a nanorefrigerant shows highest C.O.P. of 35%. R404A and R407 with different nanoparticle show enhancement in C.O.P. about 3 to 14 % and 3 to 12 % respectively. Therefore application of nanorefrigerant in refrigeration and air conditioning system is most required to improve the performance of the system.