Characterization and numerical simulation of liquid refrigerant R-134a flow emerging from a flooded evaporator tube bundle

Asher, William; Eckels, Steven J.

doi:10.1016/j.ijrefrig.2019.07.001

Cited by 1 publication

(3 citation statements)

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“…Under the shear entrainment of the vapor flow inside the tube bundle, liquid droplets can enter a higher position in the headspace above the bundle with a certain initial velocity, making it easier to be drawn into the compressor to form the liquid carryover. On the other hand, when the liquid level exceeds the bundle, a layer of liquid will be formed on the bundle, which reduces the height of the space above the bundle and the wave action of the liquid layer will entrain more large droplets into the headspace, further increasing the amount of liquid entrainment [13]. The reason for the close calculation results of the two methods is that the thermal balance at each experimental point is within 1% as mentioned before.…”

Section: Resultsmentioning

confidence: 63%

“…However, there is only limited research on liquid entrainment in the evaporator with refrigerant. Using a laser and camera system and shadow graphic technique, Asher and Eckels investigated the distribution characteristics of droplets generated by the evaporation of refrigerant in the headspace of a rectangular tube bundle with R123 [12], R134a [13], respectively. The effects of heat flux, mass flow rate, evaporation temperature and refrigerant level on the liquid distribution generated in the headspace were investigated and the refrigerant level, mass flow rate and evaporation temperature were found to have the greatest influence.…”

Section: Introductionmentioning

confidence: 99%

“…The effects of heat flux, mass flow rate, evaporation temperature and refrigerant level on the liquid distribution generated in the headspace were investigated and the refrigerant level, mass flow rate and evaporation temperature were found to have the greatest influence. For the R134a refrigerant, computational fluid dynamic (CFD) simulation using Lagrange discrete phase model was also applied to evaluate and validate the liquid distribution in the headspace using experimentally fitted droplet velocity and diameter parameters as the setting conditions for the discrete phase [13]. For the actual evaporator of a water-cooled centrifugal chiller, no research work on the liquid entrainment has been reported to the best of the authors' knowledge.…”

Section: Introductionmentioning

confidence: 99%

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

Huang

Zhang

et al. 2021

Applied Sciences

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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%.

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Section: Resultsmentioning

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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