Determination of Ability of Hydrotronic Systems to Start in Low Ambient Temperatures

2010 ◽  
Vol 164 ◽  
pp. 31-36 ◽  
Author(s):  
Ryszard Jasiński
Keyword(s):  
Thermal Shock ◽  
Hydraulic System ◽  
Transfer Coefficients ◽  
Warm Up ◽  
Ambient Temperatures ◽  
Heat Transfer Coefficients ◽  
Electric Control ◽  
Start Up ◽  
Working Medium

During start-up of hydrotronic system (hydraulic system with electric control) in low ambient temperatures a faulty operation may occur. The principles and conditions of safe operation of hydraulically (hydrotronically) driven machines and devices is essential for their designers and operators. For these reasons the author did a series of tests of hydraulic (hydrotronic) components and systems under thermal shock conditions (cooled-down components were supplied with hot working medium). In such conditions starting parameters of the selected hydrotronic components and systems, which secured safety of their operation, were determined. During start-up of a hydrotronic system under thermal shock conditions elements of hydraulic components warm up in a non-uniform way, due to varying material and shape properties. This causes change of clearances between the cooperating elements and may lead to faulty performance of hydraulic components and result in machine break-down. Heat transfer coefficients between oil and swilled element were determined and used for a calculation method developed by the author. The method enables to predict correct or incorrect operation of hydrotronic system.

Influence of Type of Material on Performance of Hydraulic Components in Thermal Shock Conditions

2011 ◽  
Vol 183 ◽  
pp. 95-100 ◽  
Author(s):  
Ryszard Jasiński
Keyword(s):  
Thermal Shock ◽  
Material Properties ◽  
Hydraulic System ◽  
Correct Operation ◽  
Warm Up ◽  
Ambient Temperatures ◽  
Start Up ◽  
Working Medium ◽  
Machine Safety ◽  
Selection Of

During the start-up of a hydraulic system in low ambient temperatures an incorrect operation may occur. The principles and conditions of safely operating hydraulic driven machines and devices are essential to designers and operators. For this reason the author of this article has conducted a series of tests on hydraulic components and systems in thermal shock conditions (cooled-down components were supplied with hot working medium). In such conditions, the initial parameters of the hydraulic components and systems determine their correct operation. During the start-up of a hydraulic system in thermal shock conditions, elements of hydraulic components warm up in a non-uniform way, due to various material properties and shapes of parts. Differences in clearances between elements and may lead to the faulty performance of hydraulic components and machine break-down. The selection of appropriate materials for various hydraulic component parts should increase machine safety during start-up in thermal shock conditions.

scholarly journals Analysis of the Heating Process of Hydraulic Motors during Start-Up in Thermal Shock Conditions

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 55
Author(s):  
Ryszard Jasiński
Keyword(s):  
Pressure Drop ◽  
Thermal Shock ◽  
Hydraulic Drive ◽  
Experimental Tests ◽  
Temperature Fields ◽  
Heating Process ◽  
Ambient Temperatures ◽  
Start Up ◽  
Working Medium ◽  
Hydraulic Motors

Conditions that prevail during harsh winters and hot summers pose a serious challenge for machine designers building devices suitable for operation in extreme weather. It is essential for the designers and the users to define the principles and conditions for the safe operation of machines and devices with hydraulic drive in low ambient temperatures. Bearing in mind the above, the author tested the hydraulic motors in thermal shock conditions (cold motors were fed with a hot working medium). This enterprise required the design and construction of a specialized stand for testing hydraulic motors, including satellite motors, in thermal shock conditions. The stand was equipped with the apparatus and a system for measuring the temperature of the moving parts of the satellite motor. The experimental tests were conducted in the laboratory of the Faculty of Mechanical Engineering and Ship Technology at Gdańsk University of Technology. The paper presents the results of tests of a correctly and incorrectly operating satellite motor during start-up in thermal shock conditions. The results concerned the course of oil temperatures, temperatures of heated elements, oil pressures, and the pressure drop in the motor. The influence of the oil pressure drop in the motor on its temperature increase was determined. The distributions of the temperature fields of the heated elements of the satellite motor during start-up in thermal shock conditions were derived by means of computer simulation. The utilization of the distribution of the temperature fields of the motor elements enables the evaluation and analysis of the work of this unit. The conducted tests may determine the conditions for the proper operation of hydraulic motors started in thermal shock conditions.

Influence of Design of Hydraulic Components on their Operation in Low Ambient Temperatures

2011 ◽  
Vol 490 ◽  
pp. 106-118 ◽  
Author(s):  
Ryszard Jasiński
Keyword(s):  
Computer Simulation ◽  
Thermal Shock ◽  
Thermal State ◽  
Weather Conditions ◽  
Simulation Method ◽  
Large Temperature ◽  
Shock Condition ◽  
Warm Up ◽  
Ambient Temperatures ◽  
Start Up

In many machines and devices there are hydraulic drives. They should operate well in various weather conditions, also in low ambient temperatures. Some malfunctions may occur during operation of hydraulic system in a so called “thermal shock condition”, which happens when frozen hydraulic component (e.g. hydraulic pump, motor or directional spool valve) is suddenly supplied with hot oil. Transient thermal state emerges in these conditions. Particular elements of component warm up differently. This results in different thermal expansion of components during warm up, which is changing the size of clearance between cooperating elements. Experimental tests of hydraulic components in low ambient temperatures were conducted in the hydraulic laboratory of the Faculty of Mechanical Engineering of Gdansk University of Technology. They concerned: orbital motors, satellite motors, gear pumps, spool valves (also proportional), piston pumps, and hydraulic cylinders. It was proved, that in thermal shock conditions some malfunctions may occur, especially with large temperature differences between oil and component. Based on results of the tests of hydraulic components and systems start-up in low ambient temperatures, one can perform a change in components design, change the type of material of components elements, and even prepare a proper procedure to be followed during start-up of cold hydraulic components and systems. In the article discusses some designs of hydraulic components resistant to thermal shock, and how to prepare components to work in low temperatures, e.g. by providing system with an additional heater to ensure uniform heating of elements in components. Change in design of hydraulic components resistant to thermal shock conditions can be obtained through computer simulation method. Analytic and computer simulation methods can be used by engineers who design machines and devices that work in low ambient temperatures.

Using Thermoelectric Cooling With Tourniquets for Nerve Preservation

2016 ◽  
Author(s):  
M. Trupiano ◽  
S. Aarabi ◽  
A. F. Emery
Keyword(s):  
Thermal Conditions ◽  
Ambient Conditions ◽  
Transfer Coefficients ◽  
Thermoelectric Coolers ◽  
Ambient Temperatures ◽  
Nerve Preservation ◽  
Heat Transfer Coefficients ◽  
Surface Temperatures ◽  
Element Simulation ◽  
Free And Forced Convection

The use of a tourniquet leads to nerve damage, even if applied for short periods of time. This damage can be minimized if the limb is cooled. Because of the low conductivities of human tissue, core limb cooling is slow unless the surface temperature is very cool. Subzero surface temperatures can lead to skin injury (i.e., frostbite). Ideally one would adjust the limb surface temperatures as a function of time to maximize the cooling rate while avoiding permanent tissue damage. One possible approach is to use a thermoelectric cooler (TEC) in conjunction with a programmable power supply. TEC performance varies strongly with heat absorption rate, a function of limb thermal properties, and hot side temperatures that are strongly affected by the surface conditions on the hot side, i.e., overall heat transfer coefficients and ambient conditions. The paper describes the use of finite element simulation to predict the usefulness of using thermoelectric coolers applied to the surface of a limb when compared to the standard approach of using ice packs. Since the TEC performance is strongly influenced by its warm side thermal conditions, experimental results are presented for different ambient temperatures, free and forced convection, and evaporation of water from a wickable covering.

Determination of heat transfer coefficients for complex spray cooling arrangements

2016 ◽  
Vol 11 (3/4) ◽  
pp. 229 ◽  
Author(s):  
Sebastian Herbst ◽  
Kim Florian Steinke ◽  
Hans Jürgen Maier ◽  
Andrzej Milenin ◽  
Florian Nürnberger
Keyword(s):  
Heat Transfer ◽  
Spray Cooling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients
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