The Experts below are selected from a list of 11439 Experts worldwide ranked by ideXlab platform

Juha Honkatukia - One of the best experts on this subject based on the ideXlab platform.

  • predicting off design range and performance of Refrigeration cycle with two stage centrifugal compressor and flash intercooler
    International Journal of Refrigeration-revue Internationale Du Froid, 2010
    Co-Authors: Teemu Turunensaaresti, Juha Honkatukia, Pekka Röyttä, Jari Backman
    Abstract:

    A modern Refrigeration Process requires constant control to provide required cooling for the user. To properly and economically accommodate this need, a wide operation range of the compressor is necessary. Therefore, it is of interest to investigate the off-design operation of a cooling cycle and compressor. The Refrigeration cycle equipped with a two-stage centrifugal compressor and a flash intercooler is studied. The compressor operation maps are generated with two different design codes and the operation values of the compressors are interpolated from the compressor maps in the simulation of the entire cooling cycle. Based on the previous studies of the utilised Refrigeration cycle, R245fa is selected as coolant. The aim of this study is to demonstrate the control capacity of the centrifugal compressor and the performance of the cooling loop in off-design conditions. This configuration provides better and wider control over the cooling range than the traditional on-off control of displacement compressors.

  • optimising the Refrigeration cycle with a two stage centrifugal compressor and a flash intercooler
    International Journal of Refrigeration-revue Internationale Du Froid, 2009
    Co-Authors: Pekka Röyttä, Teemu Turunensaaresti, Juha Honkatukia
    Abstract:

    The optimisation of a Refrigeration Process with a two-stage centrifugal compressor and flash intercooler is presented in this paper. The two-stage centrifugal compressor stages are on the same shaft and the electric motor is cooled with the refrigerant. The performance of the centrifugal compressor is evaluated based on semi-empirical specific-speed curves and the effect of the Reynolds number, surface roughness and tip clearance have also been taken into account. The thermodynamic and transport properties of the working fluids are modelled with a real-gas model. The condensing and evaporation temperatures, the temperature after the flash intercooler, and cooling power have been chosen as fixed values in the Process. The aim is to gain a maximum coefficient of performance (COP). The method of optimisation, the operation of the compressor and flash intercooler, and the method for estimating the electric motor cooling are also discussed in the article.

  • Refrigeration Process With High Speed Technology
    Volume 3: Coal Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 1998
    Co-Authors: Maunu Kuosa, Jari Backman, Timo Talonpoika, Petri Sallinen, Jaakko Larjola, Juha Honkatukia
    Abstract:

    The aim of this study was to make a computer program that simulates a standard Refrigeration Process, and a Process provided with a bubble intercooler. A further object of the study was to establish the suitability of a turbocompressor for small Refrigeration plants.Firstly the fundamentals of Refrigeration machines and industrial Refrigeration systems are discussed. An iteration procedure of steady state Refrigeration Process calculation is introduced. Fluid properties are calculated with the program units created for the modelling of an ORC power plant. Specific input files were made for 6 Process fluids R134a, R123, isopentane, isobutane, toluene and ammonia. The compressor program is linked to the Refrigeration Process simulation program in order to model single stage and two stage radial compressors. The Turbo Pascal program made for microcomputers is modular, which makes it possible to develop and test the program unit by unit. The maximum deviations of fluid properties from those in tables was found to be less than 1 per cent.To simulate tailor-made Refrigeration plants, a simple model is required. On nominal loads the program estimates an optimum intermediate pressure for the bubble Process and optimum rotational speed for the radial compressor(s). The lowering of the rotational speed by an inverter gives high COP-values on partial loads of the plant. Based on the example calculation, a two stage turbocompressor calculated with isopentane as the working fluid, a cooling capacity of 1200 W seems to be feasible.Copyright © 1998 by ASME

Pekka Röyttä - One of the best experts on this subject based on the ideXlab platform.

  • predicting off design range and performance of Refrigeration cycle with two stage centrifugal compressor and flash intercooler
    International Journal of Refrigeration-revue Internationale Du Froid, 2010
    Co-Authors: Teemu Turunensaaresti, Juha Honkatukia, Pekka Röyttä, Jari Backman
    Abstract:

    A modern Refrigeration Process requires constant control to provide required cooling for the user. To properly and economically accommodate this need, a wide operation range of the compressor is necessary. Therefore, it is of interest to investigate the off-design operation of a cooling cycle and compressor. The Refrigeration cycle equipped with a two-stage centrifugal compressor and a flash intercooler is studied. The compressor operation maps are generated with two different design codes and the operation values of the compressors are interpolated from the compressor maps in the simulation of the entire cooling cycle. Based on the previous studies of the utilised Refrigeration cycle, R245fa is selected as coolant. The aim of this study is to demonstrate the control capacity of the centrifugal compressor and the performance of the cooling loop in off-design conditions. This configuration provides better and wider control over the cooling range than the traditional on-off control of displacement compressors.

  • optimising the Refrigeration cycle with a two stage centrifugal compressor and a flash intercooler
    International Journal of Refrigeration-revue Internationale Du Froid, 2009
    Co-Authors: Pekka Röyttä, Teemu Turunensaaresti, Juha Honkatukia
    Abstract:

    The optimisation of a Refrigeration Process with a two-stage centrifugal compressor and flash intercooler is presented in this paper. The two-stage centrifugal compressor stages are on the same shaft and the electric motor is cooled with the refrigerant. The performance of the centrifugal compressor is evaluated based on semi-empirical specific-speed curves and the effect of the Reynolds number, surface roughness and tip clearance have also been taken into account. The thermodynamic and transport properties of the working fluids are modelled with a real-gas model. The condensing and evaporation temperatures, the temperature after the flash intercooler, and cooling power have been chosen as fixed values in the Process. The aim is to gain a maximum coefficient of performance (COP). The method of optimisation, the operation of the compressor and flash intercooler, and the method for estimating the electric motor cooling are also discussed in the article.

Teemu Turunensaaresti - One of the best experts on this subject based on the ideXlab platform.

  • predicting off design range and performance of Refrigeration cycle with two stage centrifugal compressor and flash intercooler
    International Journal of Refrigeration-revue Internationale Du Froid, 2010
    Co-Authors: Teemu Turunensaaresti, Juha Honkatukia, Pekka Röyttä, Jari Backman
    Abstract:

    A modern Refrigeration Process requires constant control to provide required cooling for the user. To properly and economically accommodate this need, a wide operation range of the compressor is necessary. Therefore, it is of interest to investigate the off-design operation of a cooling cycle and compressor. The Refrigeration cycle equipped with a two-stage centrifugal compressor and a flash intercooler is studied. The compressor operation maps are generated with two different design codes and the operation values of the compressors are interpolated from the compressor maps in the simulation of the entire cooling cycle. Based on the previous studies of the utilised Refrigeration cycle, R245fa is selected as coolant. The aim of this study is to demonstrate the control capacity of the centrifugal compressor and the performance of the cooling loop in off-design conditions. This configuration provides better and wider control over the cooling range than the traditional on-off control of displacement compressors.

  • optimising the Refrigeration cycle with a two stage centrifugal compressor and a flash intercooler
    International Journal of Refrigeration-revue Internationale Du Froid, 2009
    Co-Authors: Pekka Röyttä, Teemu Turunensaaresti, Juha Honkatukia
    Abstract:

    The optimisation of a Refrigeration Process with a two-stage centrifugal compressor and flash intercooler is presented in this paper. The two-stage centrifugal compressor stages are on the same shaft and the electric motor is cooled with the refrigerant. The performance of the centrifugal compressor is evaluated based on semi-empirical specific-speed curves and the effect of the Reynolds number, surface roughness and tip clearance have also been taken into account. The thermodynamic and transport properties of the working fluids are modelled with a real-gas model. The condensing and evaporation temperatures, the temperature after the flash intercooler, and cooling power have been chosen as fixed values in the Process. The aim is to gain a maximum coefficient of performance (COP). The method of optimisation, the operation of the compressor and flash intercooler, and the method for estimating the electric motor cooling are also discussed in the article.

Jari Backman - One of the best experts on this subject based on the ideXlab platform.

  • predicting off design range and performance of Refrigeration cycle with two stage centrifugal compressor and flash intercooler
    International Journal of Refrigeration-revue Internationale Du Froid, 2010
    Co-Authors: Teemu Turunensaaresti, Juha Honkatukia, Pekka Röyttä, Jari Backman
    Abstract:

    A modern Refrigeration Process requires constant control to provide required cooling for the user. To properly and economically accommodate this need, a wide operation range of the compressor is necessary. Therefore, it is of interest to investigate the off-design operation of a cooling cycle and compressor. The Refrigeration cycle equipped with a two-stage centrifugal compressor and a flash intercooler is studied. The compressor operation maps are generated with two different design codes and the operation values of the compressors are interpolated from the compressor maps in the simulation of the entire cooling cycle. Based on the previous studies of the utilised Refrigeration cycle, R245fa is selected as coolant. The aim of this study is to demonstrate the control capacity of the centrifugal compressor and the performance of the cooling loop in off-design conditions. This configuration provides better and wider control over the cooling range than the traditional on-off control of displacement compressors.

  • Refrigeration Process With High Speed Technology
    Volume 3: Coal Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 1998
    Co-Authors: Maunu Kuosa, Jari Backman, Timo Talonpoika, Petri Sallinen, Jaakko Larjola, Juha Honkatukia
    Abstract:

    The aim of this study was to make a computer program that simulates a standard Refrigeration Process, and a Process provided with a bubble intercooler. A further object of the study was to establish the suitability of a turbocompressor for small Refrigeration plants.Firstly the fundamentals of Refrigeration machines and industrial Refrigeration systems are discussed. An iteration procedure of steady state Refrigeration Process calculation is introduced. Fluid properties are calculated with the program units created for the modelling of an ORC power plant. Specific input files were made for 6 Process fluids R134a, R123, isopentane, isobutane, toluene and ammonia. The compressor program is linked to the Refrigeration Process simulation program in order to model single stage and two stage radial compressors. The Turbo Pascal program made for microcomputers is modular, which makes it possible to develop and test the program unit by unit. The maximum deviations of fluid properties from those in tables was found to be less than 1 per cent.To simulate tailor-made Refrigeration plants, a simple model is required. On nominal loads the program estimates an optimum intermediate pressure for the bubble Process and optimum rotational speed for the radial compressor(s). The lowering of the rotational speed by an inverter gives high COP-values on partial loads of the plant. Based on the example calculation, a two stage turbocompressor calculated with isopentane as the working fluid, a cooling capacity of 1200 W seems to be feasible.Copyright © 1998 by ASME

G. Trystram - One of the best experts on this subject based on the ideXlab platform.

  • Nonlinear predictive optimal control of a batch Refrigeration Process
    Journal of Food Process Engineering, 1998
    Co-Authors: I.c. Trelea, G. Alvarez, G. Trystram
    Abstract:

    A predictive optimal control algorithm for a fruit Refrigeration Process is described. The future inlet air temperature profile is optimized on line, taking into account the most recent Process measurements, and thus introducing feedback. The optimality criterion is directly based on economic costs. Technological and product quality constraints are included. The future control profile optimization requires long term predictions of Process variables evolution, achieved using a physical model of the plant. The model is adjusted on line in order to account for unmeasured disturbances and poorly known product properties. Both the optimality criterion and the plant model are nonlinear. The approach is experimentally validated on a pilot scale Refrigeration plant. Economic benefits from using an optimal, rather than a traditional constant temperature profile are discussed, revealing the importance of the Process configuration. Robustness of the control algorithm with respect to modeling errors, measured and unmeasured disturbances, and temporary plant failures is demonstrated.

  • Non linear predictive control of a batch Refrigeration Process
    Journal of Food Process Engineering, 1998
    Co-Authors: I.c. Trelea, G. Alvarez, G. Trystram
    Abstract:

    A predictive optimal control algorithm for a fruit refngeration Process is described. The future inlet air temperature profile is optimized on line, taking into account the most recent Process measurements, and thus introducing feedback. The optimality criterion is directly based on economic costs. Technological and product quality constraints are included. The future control profile optimization requires long term predictions of Process variables evolution, achieved using a physical model of the plant. The model is adjusted on line in order to account for unmeasured disturbances and poorly known product properties. Both the optimality criterion and the plant model are nonlinear. The approach is experimentally validated on a pilot scale refngera- tion plant. Economic benefits from using an optimal, rather than a traditional constant temperature profile are discussed, revealing the importance of the Process configuration. Robustness of the control algorithm with respect to modeling errors, measured and unmeasured disturbances, and temporary plant failures is demonstrated.

  • Design of a new strategy for the control of the Refrigeration Process: fruit and vegetables conditioned in a pallet
    Food Control, 1995
    Co-Authors: G. Alvarez, G. Trystram
    Abstract:

    A heat and mass transfer numerical model is developed to describe the Refrigeration Process between the air and agricultural products packed in bins piled on a pallet. The model includes the local overall average heat transfer coefficients and fitted wall with experimental results. A sensivity parameter study suggests that the air temperature is one of the factors which allows strong variation of the cooling kinetics. The model profiles the local heterogeneity of cooling in terms of a "coldest point" and a "hottest point" inside the bins for the same air flow conditions. This study permits the determination of the best location of sensors in order to prevent the over-treatment of products. Finally this work shows that the use of the model could be integrated in a control strategy for the Refrigeration Process.

  • Control strategy of the Refrigeration Process: fruit and vegetables conditioned in a pallet
    1994
    Co-Authors: G. Alvarez, G. Trystram
    Abstract:

    A digital model of mass and heat transfer has been developed to describe the Refrigeration Process between air and agricultural products conditioned in pallets. A study of the parameters indicates that air temperature is one of the main factors causing large variations in the cooling kinetics. A model was defined to control these temperature variations by placing sensors at critical points.