INFLUENCE OF AMBIENT TEMPERATURE AND TYPE OF WORKING FLUID ON THERMODYNAMIC EQUILIBRIUM OF HYDRAULIC SYSTEM OF EXCAVATORS

Introduction. The article discusses the climatic conditions of Yakutia, as well as the cooling process of the hydraulic system of DZ-98 motor grader in order to prevent violation of the thermal regime of hydraulic units under the influence of low temperatures, taking into account the wind blowing and operating conditions. The surface temperature of the hydraulic units was measured on January 16, 2018 in the city of Yakutsk on the basis of Yakutdorstroi joint-stock company at an ambient temperature of -42 ° С.Materials and methods. To ensure a reliable operation of the hydraulic system at low temperatures, hydraulic units must provide a supply of working fluid under pressure, regardless of changes in ambient temperature. The thermal regime of hydraulic units is characterized by three main parameters: pressure, temperature and volume. In the North, where the ambient winter temperature varies from -27 ° С to -49 ° С, the absolute temperature is the determining parameter. Studying the problem, theories of heat conduction and heat transfer in solids, hydrodynamics, and differential equations were used.Results. Natural and climatic data, as well as the recorded surface temperature of hydraulic units, allow to determine the number of days with a critically negative temperature, the heat transfer of hydraulic units and the regularity of its change depending on the operating mode.

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Calculation of a closed hydraulic volumetric system

10.36652/0042-4633-2021-5-27-30 ◽

2021 ◽

pp. 27-30

Author(s):

Keyword(s):

Power Plant ◽

Wind Power ◽

Hydraulic System ◽

Working Fluid ◽

Wind Power Plant ◽

Hydraulic Systems ◽

Hydraulic Motor ◽

Hydraulic Pump ◽

Oil Pump ◽

Selection Of

An algorithm is proposed for calculating a closed volumetric hydraulic pump-hydraulic motor system using the example of the hydraulic system of a wind power plant, based on the calculation of the hydraulic systems of mobile machines. The main characteristics of the system components, the selection of initial data for the calculation, working fluid and diameters of hydraulic lines are analyzed. Keywords: hydraulic system, energy, fluid, oil, pump, motor, renewable energy source, wind power plant, machine. [email protected]

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ENERGY-EFFICIENT TECHNICAL SOLUTIONS FOR THE OPERATIONAL CHARACTERISTICS OF THE HYDRAULIC DRIVE OF THE TRACTOR

10.34220/itrt2021_59-63 ◽

2021 ◽

Author(s):

R.V. Yudin ◽

◽

R.N. Puzakov ◽

Keyword(s):

Energy Saving ◽

Energy Efficient ◽

Hydraulic System ◽

Hydraulic Drive ◽

Working Fluid ◽

Uneven Terrain ◽

Operational Characteristics ◽

High Dynamic ◽

Hydraulic Accumulator ◽

Technical Solutions

During the movement of the tractor on the uneven terrain, there are fluctuations that cause jumps of the working fluid in the hydraulic system and high dynamic loads. The solution to this problem is the use of an energy-saving hydraulic drive with a hydraulic accumulator and a system of aggregates this leads to increased efficiency and increased productivity of skidding grippers. A mathematical model of working processes with an energy-saving hydraulic drive is compiled.

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Exergetic and Economic Evaluation of a Transcritical Heat-Driven Compression Refrigeration System with CO2 as the Working Fluid under Hot Climatic Conditions

Entropy ◽

10.3390/e21121164 ◽

2019 ◽

Vol 21 (12) ◽

pp. 1164 ◽

Cited By ~ 1

Author(s):

Jing Luo ◽

Tatiana Morosuk ◽

George Tsatsaronis ◽

Bourhan Tashtoush

Keyword(s):

Ambient Temperature ◽

Climatic Conditions ◽

Working Fluid ◽

Refrigeration System ◽

Exergetic Efficiency ◽

Evaporation Temperature ◽

Aspen Hysys ◽

Operation Conditions ◽

Heating Capacity ◽

Refrigeration Machine

The purpose of this research is to evaluate a transcritical heat-driven compression refrigeration machine with CO2 as the working fluid from thermodynamic and economic viewpoints. Particular attention was paid to air-conditioning applications under hot climatic conditions. The system was simulated by Aspen HYSYS® (AspenTech, Bedford, MA, USA) and optimized by automation based on a genetic algorithm for achieving the highest exergetic efficiency. In the case of producing only refrigeration, the scenario with the ambient temperature of 35 °C and the evaporation temperature of 5 °C showed the best performance with 4.7% exergetic efficiency, while the exergetic efficiency can be improved to 22% by operating the system at the ambient temperature of 45 °C and the evaporation temperature of 5 °C if the available heating capacity within the gas cooler is utilized (cogeneration operation conditions). Besides, an economic analysis based on the total revenue requirement method was given in detail.

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Characterisation of a Variable Conductance Heat Pipe Prototype for a Photonic Application

ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference, Volume 3 ◽

10.1115/ht2007-32623 ◽

2007 ◽

Cited By ~ 3

Author(s):

Martin Cleary ◽

Ronan Grimes ◽

Marc Hodes ◽

Mark T. North

Keyword(s):

Ambient Temperature ◽

Active Control ◽

Temperature Control ◽

Passive Control ◽

Working Fluid ◽

Saturation Curve ◽

Evaporator Temperature ◽

Large Reservoir ◽

Ambient Temperatures ◽

Wide Range

Thermoelectric modules (TEMs) consume a large amount of power when used for precision temperature control of high-power photonic devices, particularly when subjected to a wide range of ambient temperatures. The use of variable conductance heat pipes (VCHPs) as a lower power alternative to TEMs is investigated here. The performance of a methanol-argon VCHP with a non-wicked reservoir for both passive and active control is characterized. The concept of an “deal” working fluid for a gas-loaded VCHP is introduced. It has a liquid-vapor saturation curve resulting in perfect passive evaporator temperature control in the limit of an infinitely-large reservoir when the VCHP is subjected to changes in heat load and/or ambient temperature. The saturation curve of this ideal fluid is compared to that of the fluid used here, i.e., methanol, showing why perfect passive control is unrealistic for varying ambient temperature. An experimental prototype was constructed and measurements obtained from it were compared to the predictions of the flat front model. It was found that, even with active control, the evaporator temperature could not be maintained sufficiently at low ambient temperatures due to axial conduction through the adiabatic section of the prototype VCHP. However, excluding these low ambient temperatures, the VCHP provides a significant reduction in power consumption compared to a TEM.

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Justification of the Kinematic Diagrams for the Distribution System of a Planetary Hydraulic Motor

International Journal of Engineering & Technology ◽

10.14419/ijet.v7i4.3.19544 ◽

2018 ◽

Vol 7 (4.3) ◽

pp. 6 ◽

Cited By ~ 10

Author(s):

Angela Voloshina ◽

Anatolii Panchenko ◽

Oleg Boltynskiy ◽

Igor Panchenko ◽

Olena Titova

Keyword(s):

Distribution System ◽

Hydraulic System ◽

Hydraulic Drive ◽

Fluid Distribution ◽

Working Fluid ◽

Hydraulic Motor ◽

Hydraulic Motors ◽

Output Characteristics ◽

Kinematic Diagram ◽

The Impact

The output characteristics of a planetary (orbital) hydraulic motor could be significantly improved if the kinematic diagrams for its working fluid distribution system are chosen correctly and substantiated. Fluctuations in the flow of the power fluid cause pulsation in the cavity of the input pressure of the hydraulic motor. This results to vibration of the hydraulic system elements. Thus, the hydraulic motor can be considered as a source of pulsation which leads to functional failures of the hydraulic system. As they run at low rotational speeds with high torque, planetary hydraulic motors are commonly applied for a hydraulic drive in active working tools of self-propelled machinery. It has been established that one of the main components of a planetary hydraulic motor, which causes pressure pulsations, is its distribution system. The frequency and amplitude of these pulsations depends on the kinematic diagram for the distribution system of the power fluid. Therefore, we studied how the kinematic diagram for the distribution system effects on the output characteristics of a planetary motor. Since the change in the capacity of a distribution system with various kinematic diagrams influences on the output characteristics of a planetary motor, the impact was investigated. The kinematic diagrams, which improve the output characteristics of planetary hydraulic motors, were justified.

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Some shock tube experiments on the chemical kinetics of air at high temperatures

Journal of Fluid Mechanics ◽

10.1017/s0022112057000609 ◽

1957 ◽

Vol 3 (3) ◽

pp. 225-242 ◽

Cited By ~ 12

Author(s):

Saul Feldman

Keyword(s):

Shock Tube ◽

High Temperatures ◽

Thermodynamic Equilibrium ◽

Blunt Body ◽

The State ◽

The Body ◽

Working Fluid ◽

List Type ◽

Flat Plates ◽

Hypersonic Speeds

This paper is concerned with the rates at which atoms and molecules react in the air that flows over a body flying through the atmosphere at hypersonic speeds. Using air as a working fluid, a series of shock tube experiments were carried out to provide information about these rates. Mach angle measurements were made to determine the state of the gas in three situations of interest.Flow over flat plates was used to determine the state of the gas behind the incident normal shock; temperatures in the gas that passed through the shock varied between 2000 and 6000°:K and densities between standard and 1/80 of standard density.Flow over wedges was employed to decelerate the flow behind the incident shock to a small supersonic Mach number; here temperatures downstream of the oblique shock increased, at most, 2000°:K above the free stream value.A Prandtl-Meyer expansion was used to cool rapidly the dissociated gas, so that the recombination process could be investigated; temperatures dropped at most 2500°:K and the densities varied between standard and 1/200 of the standard value. In some cases, the initial degree of dissociation of air was over 45%.The results (figure 11) indicate that the dissociation and recombination relaxation times of the chemical species found in air are very fast, when compared to the time it takes a particle of gas to flow either around a blunt body in hypersonic flight or past smtill models in shock tubes. Thus the shock tube is shown to be an instrument capable of supplying air at high temperatures in thermodynamic equilibrium (figure 5).In the case of a non-melting blunt body of about 1 ft. diameter flying through the atmosphere at hypersonic speeds, the present results imply that, when the gas behind the detached shock is in thermodynamic equilibrium, the flow will also be in equilibrium as it expands around the body, provided its speed is greater than 10 000 ft./sec at altitudes below 180 000 ft. (figure 12).

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Numerical Analysis of Mass Flow Leakage Through Orifices for Supercritical CO2: Two-Phase Flow Effects

Volume 11: Structures and Dynamics: Structural Mechanics, Vibration, and Damping; Supercritical CO2 ◽

10.1115/gt2020-15927 ◽

2020 ◽

Author(s):

Ladislav Vesely ◽

Akshay Khadse ◽

Andres Curbelo ◽

Jayanta S. Kapat ◽

Luca Petrungaro

Keyword(s):

Mass Flow ◽

Thermodynamic Equilibrium ◽

Supercritical Co2 ◽

Two Phase Flow ◽

Operating Conditions ◽

Working Fluid ◽

Great Promise ◽

Phase Flow ◽

Computational Domain ◽

Two Phase

Abstract Supercritical CO2 (sCO2) holds a great promise as a future working fluid for power generating Brayton cycles. One of the challenging research areas in sCO2 power cycles is flow leakage and the design of seals on the compressor side of the cycle. Given the compact nature of sCO2 turbomachinery, even a minimal amount of leakage can lead to a significant power efficiency loss. Hence accurate prediction of mass flow leakage rate becomes important. However, on the compressor side of the cycle, operating conditions across the seal lead to two-phase flow. This makes flow modeling very challenging because conventional one-phase flow CFD models cannot be used. This paper is an attempt to understand the behavior of two-phase sCO2 flow going through circular and annular orifices. The focus is to utilize commercially available CFD scheme for modeling phase change and two-phase flow through constrictions. Since the pressure loss across constrictions is also accompanied with reduction in temperature, the flow becomes two-phase by entering the saturation dome. CFD simulation is performed using commercially available software STAR CCM+. 2D axisymmetric geometry is considered as the computational domain. Eulerian Multi-phase Mixture model is used in conjunction with the Two-Phase Thermodynamic Equilibrium implementation. This model is intended for applications that involve two phases of the same substance that are in thermodynamic equilibrium. Fluid properties are defined over a large range of temperatures and pressures, including both the liquid and vapor phases.

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Effect of Refrigerant on the Exergy Loss and Performance in Air Conditioner Using Ejector as Expansion Device

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1125.531 ◽

2015 ◽

Vol 1125 ◽

pp. 531-535 ◽

Cited By ~ 1

Author(s):

Vina Serevina ◽

Sumeru ◽

Henry Nasution

Keyword(s):

Ambient Temperature ◽

Energy Analysis ◽

Numerical Approach ◽

Cooling Capacity ◽

Exergy Loss ◽

Working Fluid ◽

Air Conditioner ◽

And Performance

This paper presents a numerical approach to determine the exergy loss in an air conditioner using (A/C) R22 and R290 as working fluid. The exergy loss should be minimized in order to increase the performance of the air conditioner. The present study investigates the A/C with cooling capacity of 2.4 kW. The results show that the total exergy loss of R290 is lower than that of R222, viz. 0.667 and 0.857 kW, respectively. This indicates that the use of R290 in the air conditioner using ejector as expansion device will generate a better COP improvement than that of R22. In addition, energy analysis shows that the COP improvements using R290 is higher than that of R22, for instance, 12.24 and 8.15% for R290 and R22, respectively, at the ambient temperature of 35°C.

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Design and Analysis of Ejector Powerplant System

Volume 6A: Energy ◽

10.1115/imece2013-65130 ◽

2013 ◽

Author(s):

Menandro S. Berana ◽

Edward T. Bermido

Keyword(s):

High Pressure ◽

Ambient Temperature ◽

Waste Heat ◽

Temperature Drop ◽

Working Fluid ◽

Low Grade ◽

Heat Sources ◽

Two Phase ◽

Evaporator Temperature ◽

Working Fluids

An ejector is a device with no moving components and is made up of four main parts: converging-diverging nozzle, suction chamber, mixing section and diffuser. It has become popular in refrigeration system as it gives the advantage of recovering expansion energy from high pressure difference into compression energy. In this study, the potential use of ejector in powerplants that use low-grade or low temperature heat sources was conceptualized and analytically investigated. A novel combination of the ejector and the organic Rankine cycle (ORC) was proposed. The driving fluid in the ejector of the proposed powerplant cycle is the high-pressure liquid in the separator that is just circulated back to the evaporator in the ORC. Further increase in turbine temperature drop (TTD), which can increase the power output and efficiency of the plant, can be achieved through expansion, mixing and recompression processes in the ejector. Ocean thermal energy conversion (OTEC), solar-boosted OTEC (SOTEC), solar-thermal, waste-heat driven, biomass and geothermal powerplants were considered in the analysis. Mathematical models in our previous studies were developed and used to calculate for nozzle and ejector parameters. The geometric profile of the ejector for optimization with categorized heat sources was determined. Isentropic, internally reversible, and irreversible two-phase nozzle expansions were analyzed. Two-phase flow calculations were continued in the mixing section. It was assumed that the constant-pressure mixing of the primary and secondary fluids occur at the hypothetical throat inside the constant-area section. Calculation for shock wave in the mixing section was also done. The diffuser was analyzed in a similar manner with the nozzle. Calculation for other components and plant efficiencies was finally conducted. Ammonia and propane which are both natural working fluids were used in the analysis. Evaporator temperature range from 293.15 K to 393.15 K and condenser and ambient temperatures range from 283.15 K to 308.15 K were used in the analysis. The lowest ambient temperature of 283.15 K was used for the OTEC and SOTEC powerplants. It was shown that ammonia and propane can operate up to 11 K and 12 K below the ambient temperature, respectively. Ejector efficiency ranged from 90 to 95% for both working fluids. The maximum efficiencies of the ejector powerplant were 19.2% for ammonia and 14.9% for propane, compared to 11.7% and 9.8% of the conventional ORC. It was analytically determined that the efficiency of the ejector powerplant is higher than that of the ORC powerplant for the same working fluid and conditions of the evaporator, condenser and the ambient.

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