Yazar "Erisen, Ali" seçeneğine göre listele

Listeleniyor 1 - 5 / 5
  • Küçük Resim
    Öğe
    An algorithmic approach towards finding better refrigerant substitutes of CFCs in terms of the second law of thermodynamics
    (Pergamon-Elsevier Science Ltd, 2005) Arcaklıoğlu, Erol; Çavuşoğlu, Abdullah; Erisen, Ali
    In this study, rational efficiency (RE) and component based irreversibility ratios of a cooling system based on the second law of thermodynamics using HFC and HC based pure refrigerants, such as, R32, R125, R134a, R143a, R152a, R290, R600a and their binary and ternary mixtures, along with R12, R22 and R502 (i.e. CFCs) have been numerically calculated. The effect of temperature glide, occurring at the condenser and evaporator, on the RE of the cooling system has been evaluated. The calculations are based on a constant cooling load on a cooling system with suction/line heat exchanger (SLHE). To be able to calculate the performance of the cooling system, an algorithm that uses the state point properties provided by REFPROP has been employed. We have targeted finding better mixture substitutes in terms of rational efficiency. For example, despite the suggestions in the literature; for R22, the mass percentage level of 20/80 of R32/R134a has provided the best RE level. The highest irreversibility (in percentages) is found at the condenser. The results also suggest that for both binary and ternary mixtures, a general trend of increases in RE level is observed against temperature glide increases occurring at this system component. (C) 2004 Elsevier Ltd. All rights reserved.
  • [ X ]
    Öğe
    Improvement of Plate Heat Exchanger Performance Using a New Plate Geometry
    (Springer Heidelberg, 2021) Aboul Khail, Ahmad; Erisen, Ali
    Plate heat exchangers are important tools used in heat transfer. Since they are characterized by a high heat transfer rate, high compactness, as well as easy maintenance, increasing their performance is a major and important objective for many researchers and related industrial manufacturers. Furthermore, it has a positive impact on fuel consumption and environmental protection. In this study, new geometry for the plates used in the plate heat exchanger is proposed in order to increase its performance. A numerical study of a single-phase counter-current flow model, with the new plate, is carried out using ANSYS Fluent software within the working conditions of the condensing combi boiler. The SST k-omega turbulence model is adopted to study the turbulent flow. The study concerns the thermal and hydrodynamic characteristics of the flow in the exchanger (e.g., Nusselt number Nu and coefficient of friction f) and determination of its performance based on the parameter Nu/f(1/3). The results of the numerical study are validated using a new analytical method. The values of Nu number, coefficient friction, and performance are compared with their corresponding values of new types of plate geometry and commercial chevron plates within the range of Reynolds number from 500 to 5000. The comparison shows an improvement in Nu number and overall performance of an average of 28% and 40%, respectively, compared to other commercial and new models.
  • Küçük Resim
    Öğe
    Investigatıon Of Mechanical Properties Of Carbon Fibre/Epoxy Composites Incorporating Nanoclay And Multi Walled Carbon Nanotube
    (Serban Solacolu Foundation, 2017) Ongun, Alemdar; Avci, Ahmet; Erisen, Ali
    This study was conducted for the purpose of examining the mechanical relations of the multi-walled carbon nanotube (MWCNT) and the nanoclay (NC) with each other on the carbon fiber composite materials. Samples were prepared by reinforcing the MWCNT and the NC into the epoxy matrix at various rates to have them absorbed into the carbon fiber laminates via the vacuum infusion method. Carbon nanotube (CNT) was added into all the epoxy samples at a rate of 0.3 wt% of the epoxy weight, while the nanoclay was added at rates of 1 wt%, 3 wt% and 5 wt% of the epoxy weight. Additionally, the only CNT-reinforced samples (also, not reinforced with NC) were also readied in order to observe the difference. Tensile tests and three point bending tests were conducted to determine the mechanical properties. The NC and the CNT were observed to adhere to the carbon fiber filaments in the scanning electron microscope (SEM), and NC-based bridge cracks were noted.
  • [ X ]
    Öğe
    Novel Design and Thermodynamic Analyses of Cascade Refrigeration System at Ultra-Low Temperature
    (Int Center Applied Thermodynamics, 2022) Tan, Husamettin; Erisen, Ali
    In this study, a cascade refrigeration system comprising gas and vapor compression cycles operating at ultra-low temperature was designed. In the thermodynamic analyses, R744, R404A, and R410A refrigerants in the high temperature cycle (HTC), and R1150, R170, and R23 in the low temperature cycle ( LTC) were used. Thermodynamic analyses were carried out using the Engineering Equation Solver package program. Outputs considered were: system performance(COP), compression ratio, mass flow ratio and HTC cascade outlet temperature. Results show that, at different LTC condenser temperature values, R404A/R23 has the highest COP value, in the LTC, R23 has the highest compression ratio, while R1150 has the lowest one, in the HTC, R404A has the highest compression ratio, while R744 has the lowest one, the performance of the system increased with the decrease of the mass flow ratio.
  • Küçük Resim
    Öğe
    Thermodynamic analysis of refrigerant mixtures for possible replacements for CFCs by an algorithm compiling property data
    (Pergamon-Elsevier Science Ltd, 2006) Arcaklıoğlu, Erol; Çavuşoğlu, Abdullah; Erisen, Ali
    In this study, we formed an algorithm to find refrigerant mixtures of equal volumetric cooling capacity (VCC) when compared to CFC based refrigerants in vapor compression refrigeration systems. To achieve this aim the point properties of the refrigerants are obtained from REFPROP where appropriate. We used replacement mixture ratios-of varying mass percentages-suggested by various authors along with our newly formed mixture ratios. In other words, we tried to see the effect of changing mass percentages of the suggested (i.e. in the literature) replacement refrigerants on the VCC of the cooling system. Secondly, we used this algorithm to calculate the coefficient of performance (COP) of the same refrigeration system. This mechanism has provided us the ability to compare the COP of the suggested refrigerant mixtures and our newly formed mixture ratios with the conventional CFC based ones. According to our results, for R12 R290/R600a (56/44) mixture, for R22 R32/R125/R134a (32.5/5/62.5) mixture, and for R502 R32/R125/R134a (43/5/52) mixture are appropriate and can be used as replacements. (c) 2005 Elsevier Ltd. All rights reserved.