The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform

Lixing Zheng - One of the best experts on this subject based on the ideXlab platform.

  • dynamic simulation of an improved transcritical co2 ejector expansion refrigeration cycle
    Energy Conversion and Management, 2016
    Co-Authors: Lixing Zheng, Jianqiang Deng, Zaoxiao Zhang
    Abstract:

    Abstract This paper presents a dynamic model of a transcritical CO 2 ejector expansion refrigeration cycle with two-stage evaporation (EERC-TE), which is deemed to further improve the performance of a basic transcritical CO 2 ejector expansion refrigeration cycle (EERC). The adjustments of compressor speed, the expansion valve opening, the throat area of ejector nozzle and the chilled water flow rate of Evaporators are conducted as the disturbances to investigate the system transient responses. The presented results show the predictions have a good agreement with the experimental data. The change of compressor speed causes larger response of system parameters than that of the other disturbances. The expansion valve opening can result in obvious variation of the Evaporator Pressure and the Pressure lift ratio of ejector, while the throat area of ejector nozzle leads to outstanding change of the gas cooler Pressure and the ejector entrainment ratio. Moreover, these responses are compared with that of EERC and they show the similar change trends. Based on the transient results, the combination adjustment methods are proposed to improve the system performance, and the enhancement of COP of EERC-TE is more distinct and it is 2.58 times than that of EERC under the conditions of this study. In the basis of the transient simulations, flexible and diverse adjustment methods can be applied to improve the system performance and guide the system control.

  • Dynamic simulation on operating modes of ejector in transcritical CO2 ejector expansion refrigeration cycles
    Science and Technology for the Built Environment, 2015
    Co-Authors: Lixing Zheng, Jianqiang Deng, Yang He, Pei-xue Jiang
    Abstract:

    This article proposes an ejector model based on the real properties of CO2, which includes the critical mode and sub-critical mode (the critical mode means the primary and suction flows are both choked, and the sub-critical mode refers to only the primary flow choking). Moreover, a dynamic model of the transcritical CO2 ejector expansion refrigeration cycle is developed to simulate system responses at different ejector operational modes. The prediction results by the ejector model and system model are compared with available experimental data, respectively. Furthermore, the dynamic responses of the ejector expansion refrigeration cycle based on the entire ejector model are compared with those predicted upon the ejector model only with critical mode. The present results show the entrainment ratio provided by the ejector model coincides well with the experimental data, and most data lie within ±10% error. The system model predicts the gas cooler Pressure and Evaporator Pressure with errors of 1.8% and 4.2% ...

Mohammad Saad Salim - One of the best experts on this subject based on the ideXlab platform.

  • multi objective thermo economic optimization of a combined organic rankine cycle and vapour compression refrigeration cycle
    Energy Conversion and Management, 2019
    Co-Authors: Mohammad Saad Salim
    Abstract:

    Abstract This study focuses on the multi-objective optimization of a combined power (organic Rankine cycle) and vapour compression refrigeration cycle based on heat source temperatures ranging from 120 °C to 150 °C. The primary purpose is to achieve an optimal system through the use of efficiency and cost functions. The size of the heat exchangers and turbines (indicated by the total heat transfer coefficient UAtotal and size parameter SPtotal, respectively) used in the system affect the cost function of the system, whereas the efficiency function of the system is affected by the thermal efficiency (ηth) and the irreversibility ratio (IR value, representing the total exergy destruction) of the system. The sensitivity analysis conducted herein revealed that the ηth value increased by 107.9% when the Evaporator Pressure was varied from the minimum to the maximum value within the bound constraints, whereas the UAtotal value increased by 15.5%. The system was optimized based on six input parameters. The optimization results indicated that the system optimized for R236ea provided the lowest cost and the lowest system efficiency, system optimized for R245ca provided the highest cost and the highest system efficiency, and the system optimized for R245fa was between the two above-mentioned extremes in terms of cost and efficiency. At a heat source temperature of 150 °C and with R245fa as the ORC fluid, the optimum UAtotal, ηth, IR, and SPtotal values were 99.6 kW/K, 35.8%, 54.2%, and 0.386 dm, respectively.

Pei-xue Jiang - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic simulation on operating modes of ejector in transcritical CO2 ejector expansion refrigeration cycles
    Science and Technology for the Built Environment, 2015
    Co-Authors: Lixing Zheng, Jianqiang Deng, Yang He, Pei-xue Jiang
    Abstract:

    This article proposes an ejector model based on the real properties of CO2, which includes the critical mode and sub-critical mode (the critical mode means the primary and suction flows are both choked, and the sub-critical mode refers to only the primary flow choking). Moreover, a dynamic model of the transcritical CO2 ejector expansion refrigeration cycle is developed to simulate system responses at different ejector operational modes. The prediction results by the ejector model and system model are compared with available experimental data, respectively. Furthermore, the dynamic responses of the ejector expansion refrigeration cycle based on the entire ejector model are compared with those predicted upon the ejector model only with critical mode. The present results show the entrainment ratio provided by the ejector model coincides well with the experimental data, and most data lie within ±10% error. The system model predicts the gas cooler Pressure and Evaporator Pressure with errors of 1.8% and 4.2% ...

Jianqiang Deng - One of the best experts on this subject based on the ideXlab platform.

  • dynamic simulation of an improved transcritical co2 ejector expansion refrigeration cycle
    Energy Conversion and Management, 2016
    Co-Authors: Lixing Zheng, Jianqiang Deng, Zaoxiao Zhang
    Abstract:

    Abstract This paper presents a dynamic model of a transcritical CO 2 ejector expansion refrigeration cycle with two-stage evaporation (EERC-TE), which is deemed to further improve the performance of a basic transcritical CO 2 ejector expansion refrigeration cycle (EERC). The adjustments of compressor speed, the expansion valve opening, the throat area of ejector nozzle and the chilled water flow rate of Evaporators are conducted as the disturbances to investigate the system transient responses. The presented results show the predictions have a good agreement with the experimental data. The change of compressor speed causes larger response of system parameters than that of the other disturbances. The expansion valve opening can result in obvious variation of the Evaporator Pressure and the Pressure lift ratio of ejector, while the throat area of ejector nozzle leads to outstanding change of the gas cooler Pressure and the ejector entrainment ratio. Moreover, these responses are compared with that of EERC and they show the similar change trends. Based on the transient results, the combination adjustment methods are proposed to improve the system performance, and the enhancement of COP of EERC-TE is more distinct and it is 2.58 times than that of EERC under the conditions of this study. In the basis of the transient simulations, flexible and diverse adjustment methods can be applied to improve the system performance and guide the system control.

  • Dynamic simulation on operating modes of ejector in transcritical CO2 ejector expansion refrigeration cycles
    Science and Technology for the Built Environment, 2015
    Co-Authors: Lixing Zheng, Jianqiang Deng, Yang He, Pei-xue Jiang
    Abstract:

    This article proposes an ejector model based on the real properties of CO2, which includes the critical mode and sub-critical mode (the critical mode means the primary and suction flows are both choked, and the sub-critical mode refers to only the primary flow choking). Moreover, a dynamic model of the transcritical CO2 ejector expansion refrigeration cycle is developed to simulate system responses at different ejector operational modes. The prediction results by the ejector model and system model are compared with available experimental data, respectively. Furthermore, the dynamic responses of the ejector expansion refrigeration cycle based on the entire ejector model are compared with those predicted upon the ejector model only with critical mode. The present results show the entrainment ratio provided by the ejector model coincides well with the experimental data, and most data lie within ±10% error. The system model predicts the gas cooler Pressure and Evaporator Pressure with errors of 1.8% and 4.2% ...

Somchai Wongwises - One of the best experts on this subject based on the ideXlab platform.

  • Experimental study on R-134a refrigeration system using a two-phase ejector as an expansion device
    Applied Thermal Engineering, 2008
    Co-Authors: Praitoon Chaiwongsa, Somchai Wongwises
    Abstract:

    This paper is a continuation of the authors previous work. In the present paper, the performance of the refrigeration cycle using a two-phase ejector as an expansion device is experimentally investigated. Refrigerant R-134a is used as working fluid. Motive nozzles having three different outlet diameters are tested. New experimental data that have never been seen before are presented on the effects of the external parameters i.e. heat sink and heat source temperatures on the coefficient of performance and various relevant parameters i.e. primary mass flow rate of the refrigerant, secondary mass flow rate of the refrigerant, recirculation ratio, average Evaporator Pressure, compressor ratio, discharge temperature and cooling capacity. The effects of size of the motive nozzle outlet on the system performance are also discussed. © 2007.

  • effect of throat diameters of the ejector on the performance of the refrigeration cycle using a two phase ejector as an expansion device
    International Journal of Refrigeration-revue Internationale Du Froid, 2007
    Co-Authors: Praitoon Chaiwongsa, Somchai Wongwises
    Abstract:

    This paper is a part in a series that reports on the experimental study of the performance of the two-phase ejector expansion refrigeration cycle. In the present study, three two-phase ejectors are used as an expansion device in the refrigeration cycle. The effects of throat diameter of the motive nozzle, on the coefficient of performance, primary mass flow rate of the refrigerant, secondary mass flow rate of the refrigerant, recirculation ratio, average Evaporator Pressure, compressor Pressure ratio, discharge temperature and cooling capacity, which have never before appeared in open literature, are presented. The effects of the heat sink and heat source temperatures on the system performance are also discussed.