The Experts below are selected from a list of 51 Experts worldwide ranked by ideXlab platform
Y.w. Wong - One of the best experts on this subject based on the ideXlab platform.
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Distributed steady and dynamic modelling of Dry-Expansion evaporators
International Journal of Refrigeration-revue Internationale Du Froid, 1999Co-Authors: P.g. Jolly, Y.w. WongAbstract:Abstract A general distributed parameter model is presented to describe both steady and dynamic behaviors of Dry-Expansion evaporators. The homogeneous and three different non-homogeneous two-phase flow models are used to evaluate the impact of different flow models on the accuracy of the simulation. The experimental work was carried out on a full-scale refrigeration system with R-134a as the working fluid and without frost formation at the evaporator. Comparison between the modelling and experimental measurements shows that the drift flux flow models give satisfactory predictions. The simulation results indicate that an even air temperature distribution off the evaporator may be obtained by controlling liquid Dry-out point at the two ends of the coil. The study also indicates that the counterflow configuration provides a higher heat exchange efficiency with a slower transient response compared with the cocurrent-flow configuration. A general distributed parameter model is presented to describe both steady and dynamic behaviors of Dry-Expansion evaporators. The homogeneous and three different non-homogeneous two-phase flow models are used to evaluate the impact of different flow models on the accuracy of the simulation. The experimental work was carried out on a full-scale refrigeration system with R-134a as the working fluid and without frost formation at the evaporator. Comparison between the modelling and experimental measurements shows that the drift flux flow models give satisfactory predictions. The simulation results indicate that an even air temperature distribution off the evaporator may be obtained by controlling liquid Dry-out point at the two ends of the coil. The study also indicates that the counterflow configuration provides a higher heat exchange efficiency with a slower transient response compared with the cocurrent-flow configuration.
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distributed study of air temperature inside a Dry Expansion evaporator
Applied Thermal Engineering, 1996Co-Authors: X Jia, P.g. Jolly, C P Tso, Y.w. WongAbstract:A distributed steady and transient model is presented for studying air temperature distribution inside Dry-Expansion evaporators. The evaporating two-phase flow inside coils is described by a drift-flux flow. The model is capable of predicting distributions of refrigerant velocity, void fraction, temperature, tube wall temperature, air temperature and humidity, in both position and time domains. Comparison between the prediction and experimental measurements on a commercial evaporator is satisfactory for both steady and transient responses. The results indicate that an even air temperature distribution off the evaporator may be obtained by controlling liquid Dry-out point at the two ends of the coil.
P.g. Jolly - One of the best experts on this subject based on the ideXlab platform.
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Distributed steady and dynamic modelling of Dry-Expansion evaporators
International Journal of Refrigeration-revue Internationale Du Froid, 1999Co-Authors: P.g. Jolly, Y.w. WongAbstract:Abstract A general distributed parameter model is presented to describe both steady and dynamic behaviors of Dry-Expansion evaporators. The homogeneous and three different non-homogeneous two-phase flow models are used to evaluate the impact of different flow models on the accuracy of the simulation. The experimental work was carried out on a full-scale refrigeration system with R-134a as the working fluid and without frost formation at the evaporator. Comparison between the modelling and experimental measurements shows that the drift flux flow models give satisfactory predictions. The simulation results indicate that an even air temperature distribution off the evaporator may be obtained by controlling liquid Dry-out point at the two ends of the coil. The study also indicates that the counterflow configuration provides a higher heat exchange efficiency with a slower transient response compared with the cocurrent-flow configuration. A general distributed parameter model is presented to describe both steady and dynamic behaviors of Dry-Expansion evaporators. The homogeneous and three different non-homogeneous two-phase flow models are used to evaluate the impact of different flow models on the accuracy of the simulation. The experimental work was carried out on a full-scale refrigeration system with R-134a as the working fluid and without frost formation at the evaporator. Comparison between the modelling and experimental measurements shows that the drift flux flow models give satisfactory predictions. The simulation results indicate that an even air temperature distribution off the evaporator may be obtained by controlling liquid Dry-out point at the two ends of the coil. The study also indicates that the counterflow configuration provides a higher heat exchange efficiency with a slower transient response compared with the cocurrent-flow configuration.
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distributed study of air temperature inside a Dry Expansion evaporator
Applied Thermal Engineering, 1996Co-Authors: X Jia, P.g. Jolly, C P Tso, Y.w. WongAbstract:A distributed steady and transient model is presented for studying air temperature distribution inside Dry-Expansion evaporators. The evaporating two-phase flow inside coils is described by a drift-flux flow. The model is capable of predicting distributions of refrigerant velocity, void fraction, temperature, tube wall temperature, air temperature and humidity, in both position and time domains. Comparison between the prediction and experimental measurements on a commercial evaporator is satisfactory for both steady and transient responses. The results indicate that an even air temperature distribution off the evaporator may be obtained by controlling liquid Dry-out point at the two ends of the coil.
Chunlu Zhang - One of the best experts on this subject based on the ideXlab platform.
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a generalized moving boundary model for transient simulation of Dry Expansion evaporators under larger disturbances
International Journal of Refrigeration-revue Internationale Du Froid, 2006Co-Authors: Weijiang Zhang, Chunlu ZhangAbstract:A generalized model based on the moving-boundary approach is developed to describe the transient behavior of Dry-Expansion evaporators in the vapor-compression refrigeration system. To improve the robustness of the traditional moving-boundary model under larger disturbances, the time-variant mean void fraction is employed instead of the constant. Numerical integration is applied to get the mean properties in the two-phase region and the superheated region. The interface wall temperature between the two-phase and the superheated regions is also evaluated by a new weighted mean. Qualitative case study shows that the present model can well predict the transient behaviors of evaporators under larger disturbances and keep the robustness whenever superheated region appears or disappears.
Luca Cecchinato - One of the best experts on this subject based on the ideXlab platform.
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A simulation environment for Dry-Expansion evaporators with application to the design of autotuning control algorithms for electronic Expansion valves
International Journal of Refrigeration-revue Internationale Du Froid, 2009Co-Authors: Alessandro Beghi, Luca CecchinatoAbstract:In this paper some results of a research project aimed at deriving high-performance, adaptive control algorithms for electronic Expansion valves (EEVs) to be used in finned-coiled, Dry-Expansion evaporators for refrigeration systems are reported. With the aim of developing a software environment that can be used for controller design, rapid prototyping, optimization of data collection and test design, virtual prototyping approach to design was adopted. The development of a distributed dynamic simulation model of the evaporator coupled with an electronic Expansion valve, and its use for deriving autotuning PID control algorithms is described. Experimental results confirm the effectiveness of this kind of approach.
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A simulation environment for Dry-Expansion evaporators with application to the design of autotuning control algorithms for electronic
2008 IEEE International Conference on Automation Science and Engineering, 2008Co-Authors: Alessandro Beghi, Umberto Bianchini, Cristian Bodo, Luca CecchinatoAbstract:In this paper we report some results of a research project aimed at deriving high-performance, adaptive control algorithms for electronic Expansion valves (EEVs) to be used in finned-coiled, Dry-Expansion evaporators for refrigeration systems. The approach we use in the design is that of virtual prototyping, with the aim of developing a software environment that can be used for controller design, rapid prototyping, optimization of data collection, and test design. We describe the development of a simulation model of the evaporator, and its use for deriving autotuning PID control algorithms. Experimental results confirm the effectiveness of the approach.
Denis Clodic - One of the best experts on this subject based on the ideXlab platform.
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modelica based modelling and simulation of Dry Expansion shell and tube evaporators working with alternative refrigerant mixtures
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Khattar Assaf, Assaad Zoughaib, Denis ClodicAbstract:Abstract A new methodology of intermediate complexity level is developed to model the Dry-Expansion shell and U-tube evaporators. The model has a reasonable level of accuracy and uses fundamental physical principles in a distributed parameters approach capable of detecting the complex circuit of the shell-side flow. This level of details is necessary to simulate accurately the zeotropic refrigerant mixtures evaporation. Using Modelica language gives a heat exchanger model with a generic flow arrangement. The model is experimentally validated using a standard shell-and-tube evaporator working with HFC-134a. Three distinct working fluids, pure HFC-134a, R-407C, and a specially selected glide matching refrigerant mixture are simulated in the same heat source duty with different shell-and-tube configurations. Three different gas superheat values are also taken into account. The total amount of irreversibility is considered by calculating the total exergy losses. It is concluded that the effect of the temperature profile of any refrigerant mixture can be substantial on the relative performance of a particular heat exchanger configuration compared to counter-flow configuration.
