The Experts below are selected from a list of 57 Experts worldwide ranked by ideXlab platform

Matevž Dular - One of the best experts on this subject based on the ideXlab platform.

  • Cavitation dynamics in water at elevated temperatures and in liquid nitrogen at an ultrasonic horn tip.
    Ultrasonics sonochemistry, 2019
    Co-Authors: Martin Petkovšek, Matevž Dular
    Abstract:

    Abstract Understanding and predicting thermodynamic effects is crucial when the critical point temperature is close to the operating temperature of the fluid, like in cryogenics. Due to the extreme difficulties of experimental investigation, predicting of thermodynamic effects in cavitation often bases on data in liquids other than cryogenics. Most often used surrogate liquids are hot water or certain refrigerants, which are selected by a single fluid property, most commonly by the thermodynamic parameter ∑. The paper presents a systematic study of the cavitation dynamics in water at 20 °C, 40 °C, 60 °C, 80 °C and 100 °C and in addition in liquid nitrogen (LN2). Cavitation dynamics on a 4.8 mm (tip diameter) ultrasonic horn tip, which oscillated at 20 kHz was investigated by high-speed visualization at 300,000 frames per second (fps). Simultaneously acoustic emissions were recorded by a high frequency pressure transducer. Measurements were performed under variation of the acoustic power in a closed, Insulated Vessel, where pressure could be optionally set. The main purpose of the presented investigation is to determine whether hot water can act as a surrogate liquid to cryogenics. The results may implicate the future investigations and development of a new generation of rocket engines, which also feature the possibility of re-ignition while in orbit – understanding and predicting of cavitation behaviour is becoming a crucial part at the (liquid oxygen – LOX and liquid hydrogen – LH2) turbo-pump design.

Martin Petkovšek - One of the best experts on this subject based on the ideXlab platform.

  • Cavitation dynamics in water at elevated temperatures and in liquid nitrogen at an ultrasonic horn tip.
    Ultrasonics sonochemistry, 2019
    Co-Authors: Martin Petkovšek, Matevž Dular
    Abstract:

    Abstract Understanding and predicting thermodynamic effects is crucial when the critical point temperature is close to the operating temperature of the fluid, like in cryogenics. Due to the extreme difficulties of experimental investigation, predicting of thermodynamic effects in cavitation often bases on data in liquids other than cryogenics. Most often used surrogate liquids are hot water or certain refrigerants, which are selected by a single fluid property, most commonly by the thermodynamic parameter ∑. The paper presents a systematic study of the cavitation dynamics in water at 20 °C, 40 °C, 60 °C, 80 °C and 100 °C and in addition in liquid nitrogen (LN2). Cavitation dynamics on a 4.8 mm (tip diameter) ultrasonic horn tip, which oscillated at 20 kHz was investigated by high-speed visualization at 300,000 frames per second (fps). Simultaneously acoustic emissions were recorded by a high frequency pressure transducer. Measurements were performed under variation of the acoustic power in a closed, Insulated Vessel, where pressure could be optionally set. The main purpose of the presented investigation is to determine whether hot water can act as a surrogate liquid to cryogenics. The results may implicate the future investigations and development of a new generation of rocket engines, which also feature the possibility of re-ignition while in orbit – understanding and predicting of cavitation behaviour is becoming a crucial part at the (liquid oxygen – LOX and liquid hydrogen – LH2) turbo-pump design.

Badr Habeebullah - One of the best experts on this subject based on the ideXlab platform.

  • An experimental study on ice formation around horizontal long tubes
    International Journal of Refrigeration, 2007
    Co-Authors: Badr Habeebullah
    Abstract:

    The results of an experimental study are presented where the growth rate of ice on the outside of cooled copper tubes was studied. The tubes, which were immersed in water in an Insulated Vessel, were internally cooled by circulating glycol through them. It was found that axial growth rate of ice is distinct at low values of the coolant Reynolds number and short freezing times. The slope of the ice thickness with axial distance showed moderate dependency on time but varied with coolant flow rate, and with Stanton and Biot numbers. A key result from the experiments is the abrupt ice thickness enlargements on the surface of tube bends. This anomaly may be attributed to internal flow disturbances of the coolant, and creation of local eddies inside the bends that enhance growth of ice. The effect was evident for a low Reynolds number (Re = 251.9 and Bi < 1), and fades out for large Reynolds number flows.

Barbara Larwa - One of the best experts on this subject based on the ideXlab platform.

  • Thermal destratification in an Insulated Vessel filled with water
    Heat and Mass Transfer, 2016
    Co-Authors: Krzysztof Kupiec, Krzysztof Neupauer, Barbara Larwa
    Abstract:

    Measurements of the water temperature in the vertical tube with the insulation, which was initially filled in the upper half of the hot water and the bottom half—with cold water were carried out. A mathematical model, which takes into account the simultaneous temperature equalization in the pipe and heat losses to the environment, was developed. Heat losses through side wall of the tank can be described by expression characterizing an internal heat source. Comparison the calculation results with the measurements showed the model quality correctness.

Виктор Васильевич Барун - One of the best experts on this subject based on the ideXlab platform.

  • Method for drying solid insulation of transformer windings in Insulated Vessel by cooling device
    2011
    Co-Authors: Ярослав Олегович Кит, Валерий Иванович Пивненко, Виктор Васильевич Барун
    Abstract:

    FIELD: electricity. SUBSTANCE: invention is referred to the sphere of electric engineering, and may be used for drying solid insulation, in particular of transformer windings moistened in process of transformer operation. In order to freeze-out moisture from gas vapour mixture by means of cooling device temperature less than minus 70°C is ensured at surface of the cooling device that contacts gas vapour mixture at total area of the cooling device contact surface capable to contact of at least 5m 2 ; at that by means of the cooling device contact surface and/or using the cooling device contact surface artificial barriers are set in the path of gas vapour mixture, which may be parts of the cooling device contact surface, and by means of the above artificial barriers travelling speed of gas vapour mixture is reduced and using Coanda effect eddy flows of gas vapour mixture are generated thus stimulating condensation of vapour from gas vapour mixture according to Ranque-Hilsch effect, and in the preset time period freeze-out of the cooling device is performed by heating the surface contacting a layer of frozen substances from gas vapour mixture, at atmospheric pressure, at that in order to freeze out moisture from gas vapour mixture double-circuit device is used with common heat exchanger. EFFECT: suggested method for drying solid insulation of transformer windings carried out in Insulated Vessel by cooling device allows accelerated drying for solid insulation of transformer windings, excludes usage of expensive substances for moisture freeze-out from gas vapour mixture in the process of drying solid insulation of transformer windings, increases reliability of drying for solid insulation of transformer windings as well as increases measurement accuracy of volume of moisture extracted and frozen at solid insulation of the transformer windings. 5 cl