The Experts below are selected from a list of 279669 Experts worldwide ranked by ideXlab platform
J C Ordonez - One of the best experts on this subject based on the ideXlab platform.
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integrative thermodynamic optimization of a vapor compression refrigeration system based on dynamic system responses
Applied Thermal Engineering, 2018Co-Authors: Sam Yang, J C OrdonezAbstract:Abstract We optimized the internal structure (heat exchanger areas) of a dynamic vapor compression refrigeration system for maximum global system performance described by the coefficient of performance (COP), refrigeration rate, second law efficiency, and pull-down time. The numerical optimization was subjected to fixed system heat transfer surface, and the relative sizes of condenser and evaporator were selected optimally via parametric sweeps. Optimization results demonstrated the existence of distinct optimal area allocation for each objective function considered herein while higher evaporator to condenser global heat transfer ratio was preferred in all cases. Maximum COP was achieved, for instance, with smaller evaporator area than maximum second law efficiency that yielded shorter pull-down time and lower refrigerated Space Temperature in exchange for slightly higher compressor power and total exergy destruction. In summary, this work provides insights into the selection of an optimal refrigeration system design based on its dynamic responses and physical implications.
Murat Hosoz - One of the best experts on this subject based on the ideXlab platform.
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energy and irreversibility analysis of a cascade refrigeration system for various refrigerant couples
Energy Conversion and Management, 2010Co-Authors: Murat HosozAbstract:Abstract This study deals with energy and irreversibility analysis of a cascade refrigeration system employing various refrigerant couples, namely R152a–R23, R290–R23, R507–R23, R234a–R23, R717–R23 and R404a–R23, using a computer code developed for this aim. It is assumed that the refrigeration load is 1 kW, the refrigerated Space Temperature is −40 °C, and the environment Temperature is 300 K, while the degrees of condenser subcooling and evaporator superheat are 5 and 7 °C, respectively, for all cases. Furthermore, the polytropic efficiencies of the compressors are assumed to be equal. It has been determined that the COP of the cascade refrigeration system increases and the irreversibility decreases with rising evaporator Temperature and polytropic efficiency for all studied refrigerant couples. On the other hand, the COP of the cascade refrigeration system decreases and the irreversibility increases on increasing the condenser Temperature and the difference between the saturation Temperatures of the lower and higher Temperature systems in the heat exchanger (ΔT). In all cases, the refrigerant couple R717–R23 has the highest COP and lowest irreversibility except for the limited ranges of polytropic efficiency (50–60%) and ΔT (13 K–16 K), while R507–R23 has the lowest COP and highest irreversibility. The refrigerant couple R152a–R23 has been found to be an alternative couple to R717–R23 for the above mentioned ranges of polytropic efficiency and ΔT. The refrigerant couples R134a–R23 and R290–R23 have placed in the middle range, and R404a–R23 can be considered as a replacement couple for R507–R23 in all cases.
A Zorin - One of the best experts on this subject based on the ideXlab platform.
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magnetic measurements of superconducting insertion devices by stretched wire with direct current
Physics Procedia, 2016Co-Authors: N A Mezentsev, V M Tsukanov, A ZorinAbstract:Abstract The main characteristics of multipole insertion devices (ID) are the first and second field integrals along an orbit trajectory in an accelerator. Such integrals of permanent magnets or traditional electromagnets insertion devices can be obtained by means of longitudinal scanning by Hall probes. Measurements of the magnetic field by Hall probes in superconducting IDs have obvious difficulties because of limited Space, Temperature deviation along the path, etc. Measurements of the integrals by Hall probes, especially when the integrals has to be equal to zero, it is very difficult to make with a necessary accuracy. At Budker INP along with Hall probes the system of magnetic measurements on the basis of the tense wire with a direct current is used. The method is based on similarity of interaction of a direct current in a stretched wire and an electron beam in an accelerator with magnetic field. The stretched wire with current is a good model to describe behavior of an electron beam when passing through a magnet. Especially the method is useful at measurement of superconducting IDs where it isn’t enough Space for other probes. The method provides a dynamic control of the field integrals in different modes of a magnet operation (field ramp up or down), allows to measure the integrals quickly and rather precisely.
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Magnetic Measurements of Superconducting Insertion Devices by Stretched Wire with Direct Current
Physics Procedia, 2016Co-Authors: N A Mezentsev, V M Tsukanov, A ZorinAbstract:Abstract The main characteristics of multipole insertion devices (ID) are the first and second field integrals along an orbit trajectory in an accelerator. Such integrals of permanent magnets or traditional electromagnets insertion devices can be obtained by means of longitudinal scanning by Hall probes. Measurements of the magnetic field by Hall probes in superconducting IDs have obvious difficulties because of limited Space, Temperature deviation along the path, etc. Measurements of the integrals by Hall probes, especially when the integrals has to be equal to zero, it is very difficult to make with a necessary accuracy. At Budker INP along with Hall probes the system of magnetic measurements on the basis of the tense wire with a direct current is used. The method is based on similarity of interaction of a direct current in a stretched wire and an electron beam in an accelerator with magnetic field. The stretched wire with current is a good model to describe behavior of an electron beam when passing through a magnet. Especially the method is useful at measurement of superconducting IDs where it isn’t enough Space for other probes. The method provides a dynamic control of the field integrals in different modes of a magnet operation (field ramp up or down), allows to measure the integrals quickly and rather precisely.
Sam Yang - One of the best experts on this subject based on the ideXlab platform.
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integrative thermodynamic optimization of a vapor compression refrigeration system based on dynamic system responses
Applied Thermal Engineering, 2018Co-Authors: Sam Yang, J C OrdonezAbstract:Abstract We optimized the internal structure (heat exchanger areas) of a dynamic vapor compression refrigeration system for maximum global system performance described by the coefficient of performance (COP), refrigeration rate, second law efficiency, and pull-down time. The numerical optimization was subjected to fixed system heat transfer surface, and the relative sizes of condenser and evaporator were selected optimally via parametric sweeps. Optimization results demonstrated the existence of distinct optimal area allocation for each objective function considered herein while higher evaporator to condenser global heat transfer ratio was preferred in all cases. Maximum COP was achieved, for instance, with smaller evaporator area than maximum second law efficiency that yielded shorter pull-down time and lower refrigerated Space Temperature in exchange for slightly higher compressor power and total exergy destruction. In summary, this work provides insights into the selection of an optimal refrigeration system design based on its dynamic responses and physical implications.
Borui Cui - One of the best experts on this subject based on the ideXlab platform.
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Energy and exergy analyses of R513a as a R134a drop-in replacement in a vapor compression refrigeration system.
International Journal of Refrigeration, 2020Co-Authors: Jian Sun, Borui CuiAbstract:Abstract R513a (XP10), a mixer of 56% R1234yf (C3H2F4) and 44% R134a (CH2FCF3), has similar thermophysical characteristics to R134a but only half of its global warming potential (GWP). This paper uses an economized-cycle vaper compression refrigeration system as an example to investigate the energy and exergy performance of R513a used as a drop-in replacement for R134a. Differing from previous research, this study examines the entire system operating zone to identify the performance differences in terms of capacity, COP, exergy destruction rate, and exergy efficiency between R513a and R134a systems. The analysis found that a system with drop-in R513a demonstrates reduced capacity by up to 12% and efficiency (up to 9% with COP and 14% with exergy efficiency) under a majority of operating conditions, while exhibiting less irreversibility (5% to 13%) under high-ambient, high-Space Temperature conditions and better exergy efficiency of 3% in low-ambient conditions. In addition, the contribution of each individual component to the exergy destruction rate at various operating conditions is identified. To improve the energy and exergy efficiency of a R513a system, the analysis results indicate that the compressor is the first component that should be redesigned or reselected, followed by the economizer, valves, and evaporator. The condenser influence is negligible.