Measurement Method and Experimental Analysis of Liquid Entrainment for a Flooded Evaporator of a Water-Cooled Centrifugal Chiller Based on Energy Balance

Liquid entrainment in a flooded evaporator has an important impact on the performance and safety of a water-cooled centrifugal chiller. In this paper, two methods for measuring the liquid entrainment factor in the evaporator of a centrifugal chiller based on energy balance are proposed. Method 1 involves only the heat exchange capacity of the evaporator and Method 2 involves both evaporator and condenser. The applicable conditions of the methods are discussed. Experimental measurements on the flooded evaporator of a single-stage water-cooled centrifugal chiller with refrigerant R134a show that, for a system with good thermal balance, there is little difference in the entrainment factor values obtained by the two methods. Method 2 was found to have slightly higher measurement accuracy, compared to Method 1. The uncertainty propagation analysis shows that for method two, the inlet and outlet water temperatures of the evaporator and condenser, motor input power, motor efficiency, transmission power loss and compressor suction and discharge temperatures are important factors. The experimental results show that the variation of the evaporator entrainment factor with refrigerant charge amount is different for different cooling capacity. At 700 and 800 refrigeration ton (RT), the entrainment factor of the test evaporator increases with the increase of refrigerant charge and the growth rate gradually accelerates. For the chiller tested, when the entrainment factor reaches 0.89% and 1.02%, respectively, at 700 ton and 800 ton, the rapid increase of the entrainment factor leads to a significant decrease in the coefficient of performance (COP) during the charging process. Based on the analysis of the experimental results, it is recommended that the maximum entrainment factor for efficient operation of the centrifugal chiller should be controlled within 1%.

Improving the Gordon-Ng Model and Analyzing Thermodynamic Parameters to Evaluate Performance in a Water-Cooled Centrifugal Chiller

The Gordon-Ng models are tools that have been used to estimate and evaluate the performance of various types of chillers for several years. A 550 TR centrifugal chiller plant facility was available to collect data from July and September 2018. The authors propose rearranging variables of the traditional (GNU) model based on average electric consumption and through a thermodynamic analysis comparable to the original model. Furthermore, assumptions are validated. Then, by estimation of the parameters of the new model using least square fitting with field training data and comparing to the GNU model and Braun model (based on consumption), it was shown that the proposed model provides a better prediction in order to evaluate consumption of a centrifugal chiller in regular operation, by improving the coefficient of variation (CV), CV = 3.24% and R2 = 92.52% for a filtered sub-data. Through an algorithm built from steady-state cycle analysis, physical parameters (Sgen, Qleak,eq, R) were estimated to compare with the same parameters obtained by regression to check the influence of the interception term in the model. It was found that without an interception term, the estimated parameters achieve relative errors (ER) below 20%. Additional comparison between external and internal power prediction is shown, with CV = 3.57 % and mean relative error (MRE) of 2.7%, achieving better accuracy than GNU and Braun model.

Analisis Chiller Dengan Menggunaan R123 Dan R134a Pada Kinerja Pendinginan

AbstrakChiller adalah mesin refrigerasi yang memiliki fungsi utama mendinginkan air pada sisi evaporator, air yang didinginkan selanjutnya didistribusi ke alat penukar kalor (FCU; fan coil unit). Chiller sudah menjadi pilihan dalam pengkondisian udara ruangan dalam skala besar maupun dalam mesin-mesin proses. Penelitian ini bertujuan untuk mengetahui kinerja pendingin chiller centrifugal water cooled (dari beberapa jenis chiller yang tersedia) yang berkapasitas relatif besar, dengan menggunakan refrigeran R-123 dan R-134a sebagai media pendingin. Dari hasil penelitian dan pengolahan data maka untuk chiller yang menggunakan R-123 didapatkan COP = 2.68; GWP = 76; emisi ; CO2= 43.324.512,58 kg; ODP = 0.02 dan untuk chiller yang menggunakan R-134a didapatkan : COP = 5.74; GWP = 1300; emisi ; CO2= 47.953.644 kg; ODP = 0.0. Kata kunci: Chiller centrifugal water cooled, R123,R134a,COP,ODP dan GWP AbstractChiller is a refrigeration machine that has the main function of cooling the air on the evaporator, the cooled air is then distributed to the heat exchanger (FCU; fan coil unit). Chiller has become the choice in room air conditioning on a large scale as well as in process machines. This study aims to determine the performance of centrifugal chiller water cooled chillers (from several types of chillers available) with relatively large capacities, using R-123 and R-134a refrigerants as cooling media. From the results of research and data processing, the chiller using R-123 obtained COP = 2.68; GWP = 76; emissions; CO2 = 43,324,512.58 kg; ODP = 0.02 and for chillers using R-134a obtained: COP = 5.74; GWP = 1300; emissions; CO2 = 47,953,644 kg; ODP = 0.0. Keywords: Chiller centrifugal water cooled, R123,R134a,COP,ODP dan GWP

Research of cooling load & chiller selection in metro station

Air conditioning is of the most energy saving potential system in the metro station. This study analyzes the composition and characteristics of air conditioning cooling load in a metro station. The hourly distribution and the proportion of each cooling load are calculated. The results show that cooling load fluctuation of metro air conditioning is large, and the operating time of different load varies greatly. According to the air conditioning cooling load, the coefficient of performance of the fixed frequency screw, variable frequency screw, series countercurrent screw and magnetic bearing centrifugal chiller under the load of 20–100% are tested. The annual operating cost of four chillers is compared. Test results show that the magnetic bearing centrifugal chiller has a much higher coefficient of performance at part load and lower annual operating cost. Increased initial investment can be recovered in less than 2 years. The magnetic bearing centrifugal chiller is suitable as a cold source of air conditioning system in the metro station.