Pad Temperature Research Articles

Thermal Modelling of a Disc Brake System at Different Vehicle Weights and Constant Speeds

In this study, three-dimensional thermal modelling has been made for a disc brake mechanism of an automobile by using the COMSOL Multiphysics programme. Frictional heat has been calculated by means of multibody dynamic module, and heat distribution has been calculated by means of heat transfer module. In such model, an automobile with an initial speed of 25 m⁄s and 35 m⁄s has been decelerated by -10 m⁄s^2 braking speed, and the braking state has been realised at time interval of 2-4 s. Thermal analysis has been made for two different vehicle weights (1200 kg-1500 kg) under the same braking scenario. The results obtained from the thermal analysis have shown similarity to various studies carried out within the literature. An increase of 300 kg in vehicle weight has resulted in a temperature increase by 3.33% during motion at 25 m⁄s vehicle speed, and by 6.03% during motion at 35 m⁄s vehicle speed. According to temporal temperature change, maximum pad temperature has been obtained at the 4th second; and in the case that the vehicle with a weight of 1500 kg and moving at 35 m⁄s speed has braked, maximum pad temperature has been obtained as 450 K.

A Model for Tilting Pad Thrust Bearings Operating With Reduced Flow Rate—Do Benefits Outweigh Risks?

Abstract The literature on tilting pad thrust bearings (TPTB) calls for flow reduction as an effective means to reduce drag power losses as well as oil pumping costs. However, the highest level of flow reduction a bearing can undergo while maintaining reliable operation is a key question that demands comprehensive analysis. This paper implements a model into an existing thermo-elasto-hydrodynamic (TEHD) computational analysis tool to deliver load performance predictions for TPTBs operating with reduced flow rates. For bearings supplied with either a reduced flow or an overflow conditions, a sound model for the flow and thermal energy mixing in a feed groove determines the temperature of the lubricant entering a thrust pad. Under a reduced flow condition, the analysis reduces the effective arc length of a wetted pad until matching the available flow. Predicted discharge flow temperature rise and pad subsurface temperature rise from the present model match measurements in the archival literature for an eight-pad bearing supplied with 150% to 25% of the nominal flow rate, i.e., the minimum flow that fully lubricates the bearing pads. A supply flow above nominal rate increases the bearing drag power because the lubricant enters a pad at a lower temperature, and yet has little effect on a thrust pad peak temperature rise or its minimum film thickness. A reduced flow below nominal produces areas lubricant starvation zones, and thus the minimum film thickness substantially decreases while the film and pad's surface temperature rapidly increase to produce significant thermal crowning of the pad surface. Compared to the bearing lubricated with a nominal rate, a starved flow bearing produces a larger axial stiffness and a lesser damping coefficient. A reduction in drag power with less lubricant supplied brings an immediate energy efficiency improvement to bearing operation. However, sustained long-term operation with overly warm pad temperatures could reduce the reliability of the mechanical element and its ultimate failure.

Measurements to Quantify the Effect of a Reduced Flow Rate on the Performance of a Tilting Pad Journal Bearing With Flooded Ends

Abstract Operation of tilting pad journal bearings (TPJBs) with a reduced flow decreases pumping costs and oil sump storage. A low supplied oil flow improves system energy efficiency by reducing drag power losses, albeit the temperature rise in both the bearing pads and the lubricating oil become a concern. This paper presents measurements of the static and dynamic load performance of a flooded ends TPJB lubricated with an ISO VG 46 oil supplied at 60 °C, and with a flow rate ranging from 150% to just ∼5% of a nominal supply condition. The flow range covers both over-flooded and starved flow conditions. The test bearing is a four-pad, 102 mm diameter, center pivot, with single orifice feeds, and configured with end seals to flood the bearing housing. The experiments include operation at two shaft speeds = 6 krpm and 12 krpm (= 64 m/s surface speed) and under three specific loads = 0.345 MPa, 1.03 MPa, and 2.07 MPa applied in between pads (LBP). The measurements show the bearing drag power loss decreases by nearly 20% when the flow rate drops to 50% of nominal. However, halving the flow produces a raise in pad subsurface temperatures, ∼7 °C for operation at 12 krpm. Flow reduction below 50% does result in even more substantial power savings; however, it also produces too hot pad temperatures that approach 130 °C, a known limit for Babbitt material safe operation. The bearing static eccentricity (e) and direct stiffnesses Kxx < Kyy (load direction) do not show a significant dependency on the supplied flow, either above or below the nominal condition. A minor stiffness hardening does occur for very low flow conditions, 5% or so of nominal. Damping coefficients (Cxx ∼ Cyy) decrease by ∼30% as the flow rate decreases from 150% to just a few % of the nominal flow. The experimental results are first to quantify the operation of a TPJB supplied with minute amounts of lubricant flow. A test with a very low flow rate at ∼2% of nominal and under a light load produced the emergence of a broadband subsynchronous vibration (SSV) frequency, albeit with a very small amplitude.

Thermal Environment of Launch Pads During Rocket Launching

This paper investigates the thermal environment of launch pads during rocket takeoff. The rocket plume model is set up using the three-dimensional Navier–Stokes equations and realizable turbulence model. The aluminium oxide particles in the plume are considered by the Eulerian dispersed phase model. Comparing with the experimental data, the accuracy of the numerical model can be verified. On this basis, in total 16 numerical cases are performed to analyze the influence of the rocket flight altitude and lateral drift on the temperature of the launch pad. The results show that the launch pad has a more severe thermal environment at the flight altitudes from 3 to 20 m. Because of the rocket drift, a high-temperature gas flow layer is formed on the launch pad, which results in a dramatic increase in the temperature of the cross beam. At this location, the maximum temperature can reach up to 3900 K, 30% higher than the value without rocket drift. The method in this paper can provide an effective way to evaluate the thermal environment of the launch pad during rocket launching and have a great value on the thermal protection system design.

Thermal imaging evaluation of the felines paw pad temperature before and after walking: A pilot study

The purposes of this pilot study were to explore the temperature changes of the paw pads in healthy cats before and after a 6-min walking test (6MWT), and to further compare the accuracy of the point and line region of interest (ROI) selection methods of the thermal imaging. Five healthy intact cats were recruited and trained to run on the treadmill, and to keep still during the standing phase on a glass panel when capturing thermographic imaging data. The paw pad temperature was recorded using a thermal camera and then analysed using both the point and line ROI before and after the 6MWT. The symmetry index (SI) between the limbs (left and right) was further calculated. Compared to the baseline, there were significant increases in the paw pad temperature of the forelimbs (point of left P < 0.001, point of right P = 0.048, point of average P = 0.002, line of left P < 0.001, line of right P = 0.007, line of average P < 0.001), hindlimbs (point of left P < 0.001, point of right P < 0.001, point of average P < 0.001, line of left P < 0.001, line of right P < 0.001, line of average P < 0.001), and average value after the 6MWT both using the point and line ROI selection methods. However, there is no temperature difference between the point and line ROI either before or after the 6MWT. In addition, no difference in the SI was found between the baseline and post-test or between the point and line ROI. These results preliminarily indicated that a 6WMT and thermal imaging could be a good combination for further clinical practices to recognise lameness or any other gait disabilities in cats, and both the point and line ROI selection methods can be considered when analysing thermographic data.

Development of a Resting Energy Expenditure Estimation in Patients Undergoing Targeted Temperature Management with a Surface Gel Pad Temperature Modulating Device.

Targeted temperature management (TTM) directly impacts energy expenditure via temperature modulation and shivering associated with temperature modulating devices. We hypothesized that resting energy expenditure (REE) can be accurately estimated utilizing data obtained from a surface gel pad temperature modulating device (TMD) and demographic factors. Baseline demographic data, along with concurrent temperature, sedation, and shivering data, and indirect calorimetry (IDC) were collected from patients undergoing TTM. The data from the IDC and temperature modulation device (TMD) were synchronized and averaged over 60-second intervals to provide simultaneous comparisons. Heat transfer (calories) was calculated from the TMD by an equation that assessed water temperature from the TMD to the patient, water temperature returning to the TMD, water flow rates, and device mode. A linear regression model was used to determine factors associated with REE as measured by IDC. A difference in the mean between REE and estimated REE was used to assess accuracy. There were 48 assessments conducted in 40 subjects [mean (standard deviation)] age: 58 (14) years, 60% female, body surface area (BSA): 2.0 ± 0.3 who underwent simultaneous assessments. Target temperature was 36-37°C in 75%, with a median Bedside Shivering Assessment Score of 0 (range 0-2). Factors associated with REE on multivariable linear regression included older age (p < 0.001), male sex (p = 0.004), higher BSA (p < 0.001), higher patient temperature (p < 0.001), and lower heat transfer (p = 0.003). Adjusted prediction coefficients from this model were then tested against REE by a Bland-Altman analysis. The difference between difference in resting energy estimation (REEdiff) and measured REE by IDC was 6.2 calories/min (REEdiff: 95% confidence interval: -14.1 calories, 26.5 calories, p = 0.5). We believe that the heat transfer data from the TMD coupled with clinical characteristics of patients can be utilized to calculate the REE for every minute of TTM. These data can be utilized to mitigate the consequences of shivering and malnutrition during TTM.

Insights into Underrail Rubber Pad’s Effect on Vehicle-Track-Viaduct System Dynamics

To scientifically characterize the dynamic mechanical characteristics of the rubber pad under the rail of fasteners and its influence on the dynamic response of the vehicle-rail-viaduct system, taking the rubber pad under the rail of WJ-7B high-speed railway (HSR) with constant resistance as an example, a TFDV model was applied to characterize the viscoelasticity of the rubber pad and the theoretical model in the dynamic coupling of vehicle-rail-bridge was also studied. The results show that the energy storage modulus and loss factor of rubber pad under rail show a curved surface relation versus the change of frequency-temperature. In a certain frequency/temperature range, the energy storage modulus and loss factor of rubber pad under rail increase with the decrease of temperature and the increase of frequency, and the influence of low temperature on dynamic parameters is more significant. With the decrease of temperature, the minimum value of total dynamic flexibility decreases, and the corresponding extreme frequency shifts to high frequency. Viscoelastic dynamic features of rubber pad under rail mainly affect the dynamic response of vehicle subsystem and rail-bridge subsystem. With the decrease of ambient temperature of rubber pad, the dominant frequency band of power spectrum curve of each structure shifts to high frequency.

Power loss reduction for tilt pad journal bearings utilizing pad pockets and steps

Tilting Pad Journal Bearing (TPJB) are ubiquitous in turbomachinery from small high speed compressors to large turbine generator sets. The TPJB's power losses increase with machine size and speed, reaching as high as 1–2 MW loss (equivalent power for about 1000 homes) per bearing, in a large turbine generator. This study presents a novel power loss reduction technique, inserting a pocket and step in the pads, to activate cavitation in the pocket while maintaining pad stability. The benefits are demonstrated via Thermo-Elasto-Hydrodynamic (TEHD) CFD simulations comparing results with and without these modifications. The novel approach shows power loss reductions up to −27% without a load capacity loss, while reducing required supply oil flow, and peak pad temperature.

Influence of Active Cooling at the Trailing Edge on the Thermal Behavior of a Tilting-Pad Journal Bearing

In tilting-pad journal bearings (TPJB) with a non-flooded lubrication concept, higher maximum pad temperatures occur than with a flooded bearing design due to the lower convective heat transfer at the pad edges. In this paper, we present an approach to influence the thermal behavior of a five-pad TPJB by active cooling. The aim of this research is to investigate the influence of additional oil supply grooves at the trailing edge of the two loaded pads on the maximum pad temperature of a large TPJB in non-flooded design. We carry out experimental and numerical investigations for a redesigned test bearing. Within the experimental analysis, the reduction in pad temperature is quantified. A simulation model of the bearing is synthesized with respect to the additional oil supply grooves. The simulation results are compared with the experimental data to derive heat transfer coefficients for the pad surfaces. The experimental results indicate a considerable reduction of the maximum pad temperatures. An overall lower temperature level is observed for the rear pad in circumferential direction (pad 4). The authors attribute this effect by a cooling oil carry-over from the previous pad (3). Within the model limits, a good agreement of the simulation and experimental results can be found.

Influence of Injection Pressure on the Thermohydrodynamic Behavior of Tilting Pad Journal Bearings—Model and Experiment

In rotating machines, tilting pad journal bearings (TPJBs) are widely used because of their enhanced design stability in comparison with alternative bearing configurations. In the present research, a thermohydrodynamic (THD) lubrication model for a tilting pad bearing with injection is developed. Within the THD lubrication model, the lubricant is also fed into each pad through a central injection orifice. The effects on the lubricant oil film pressures and temperatures and subsequent influences on the system dynamic behavior were investigated. Another important factor considered within the THD model is associated with the flexibility of the pivot of each pad and its impact on the behavior of the bearing when subjected to direct lubricant injection. The numerical model results are compared with the measurements of the rotor equilibrium position within the bearing and the pad temperatures obtained from the test rig designed specifically for the TPJB geometry with and without central pad injection. Pad temperatures are measured before the injection orifice position and after it. Agreement between experimental and model-predicted results provides confidence in the model’s ability to evaluate the dynamic behavior of the bearing and its effect on the complete system through the stiffness and damping coefficients.

Analysis of Correlation between Pad Temperature and Asperity Angle in Chemical Mechanical Planarization

Chemical mechanical planarization (CMP) is a technology widely employed in device integration and planarization processes used in semiconductor fabrication. In CMP, the polishing pad plays a key role both mechanically and chemically. The surface of the pad, consisting of asperities and pores, undergoes repeated cycles of glazing induced by polishing followed by the recovery of roughness by a conditioning process applied during CMP. As a polymer material, the pad also experiences thermal expansion from changes in temperature. Such changes can be expressed in terms of surface roughness values, but these do not fully capture the actual changes to the pad surface. In this study, the change in pad temperature occurring during CMP was analyzed with regard to its effect on the asperity angle, and the influence on CMP outcome was assessed. The changes in the surface asperities according to the steady-state pad temperature were evaluated using various measurement methods. The change in pad roughness was characterized in terms of the asperity angle, and the contact state predicted according to temperature were validated by measuring the contact perimeter, the number of contact points, and related values. Through Scanning Electron Microscope (SEM) and micro-CT analysis, it was confirmed that in the continuous polishing process and the conditioning process, the changes in asperity angle due to changes in pad temperature affect the polishing outcome.

4 패드 저널 베어링 2상 유동 2-FSI 해석

A four-pad journal bearing is used to support high-speed, high-load turbine generators. The direct lubrication type has the merits of low power loss, low pad temperature, and high load capacity. Direct lubrication offers the additional advantages of good vibration and anti-shock characteristics. The simulation of bearings of this type requires two-phase fluid analysis because the fluid consists of a mixture of oil and air. Apart from this, because of the movement of the rotor and tilting pad, two-phase two-fluid structure interaction (2-FSI) simulation is required to determine the final locations of the rotor and pads. Finally, based on these locations, a static simulation is conducted to determine the temperature, pressure, and the oil and air distribution. The rotor moves 0.5 mm in the direction of negative gravity and the tilting pad rotates 0.09, 0.035 degrees with a minimum gap of 78 mm and maximum pressure of 10 MPa.

슬러리 공급 조건에 의한 패드 온도 분포의 변화

슬러리 공급 조건에 의한 패드 온도 분포의 변화

On the Effect of Supplied Flow Rate to the Performance of a Tilting-Pad Journal Bearing—Static Load and Dynamic Force Measurements

Abstract Rotating machinery relies on engineered tilting-pad journal bearings (TPJB) to provide static load support with minimal drag power losses, safe pad temperatures, and ensuring a rotor-dynamic stable rotor operation. End users focus on reducing the supplied oil flow rate into a bearing to both lower operational costs and to increase drive power efficiency. This paper presents measurements of the steady-state and dynamic forced performance of a TPJB whilst focusing on the influence of supplied oil flow rate, below and above a nominal condition (50% and 150%). The test bearing has five pads, slenderness ratio L/D = 0.4, spherical pivots with pad offset = 50%, and a preload –0.40, with a clearance to radius ratio (Cr/R) ≈ 0.001 at room temperature. The bearing is installed under a load-between-pads (LBP) orientation and has a flooded housing with end seals. The test conditions include operation at various shaft surface speeds (32 m/s–85 m/s) and specific static loads from 0.17 MPa to 2.1 MPa. A turbine oil lubricates the bearing with a speed-dependent flow rate delivered at a constant supply temperature. Measurements obtained at a steady thermal equilibrium include the journal static eccentricity and attitude angle, the oil exit temperature rise, and the pads' subsurface temperatures at various locations, circumferential and axial. The rig includes measurement of the drive torque and shaft speed to produce the bearing drag power loss. Dynamic force coefficients include stiffness, damping, and virtual-mass coefficients. As expected, the drag power and the lubricant temperature rise depend mainly on shaft speed rather than on applied load. A reduction in oil flow rate to 50% of its nominal magnitude causes a modest increase in journal eccentricity, a 15% reduction in drag power loss, a moderate raise (6 °C) in pads' subsurface temperatures, a slight increase (up to 6%) in the direct stiffnesses, and a decrease (up to 7%) in direct damping coefficients. Conversely, a 1.5 times increase in oil flow rate causes a slight increase (up to 9%) in drag power loss, a moderate reduction of pads' temperatures (up to 3 °C), a maximum 5% reduction in direct stiffnesses, and a maximum 10% increase in direct damping. The paper also presents comparisons of the test results against predictions from a thermo-elastohydrodynamic (TEHD) lubrication model. In conclusion, a 50% reduced oil flow rate only causes a slight degradation in the test bearing static and dynamic force performance and does not make the bearing operation unsafe for tests with surface speed up to 74 m/s. As an important corollary, the measured bearing drag power differs from the conventional estimate derived from the product of the supplied flow rate, the lubricant-specific heat, and the oil exit temperature rise.

Effect of copper or carbon fiber addition to the 3D printing of polylactid samples

Abstract This paper presents the effect of additives on the quality of a product created by 3D print. The product is created by the most widely used 3D printing method - Fused Deposition Modeling (FDM). Polylactic acid (PLA) filaments are tested without and with the addition of carbon fibers or copper. The specimens are characterized by different methods, such as mechanical testing, measuring roughness by digital microscope with a large depth of field and thermal analysis. In fact, FDM is a problematic process with numerous criterions that affect printing quality. Printing parameters such as print temperature, pad temperature, print speed for 3D printing, printing orientation etc. have an important impact on the performance and quality of FDM components. Due to the correct parameters, the product of the required quality with a longer service life is obtained. The results of testing show that the quantity and choice of the right ingredient has a major impact on the mechanical properties and overall quality of the investigated product.

Effects of solder degradation on the die temperature measurement via internal gate resistance

The virtual junction temperature measurement via internal gate resistance (Tvg) is attractive for the health monitoring of power modules. Using the gate resistance as Temperature Sensitive Electrical parameter (TSEP) permits precise and timely absolute temperature on the die where the gate is located. This paper investigates how this measurement relates to other parts of the power die, inclusive of aging effects such as die attach degradation. Using in-situ measurements and FEM simulations, a method for compensating the gate pad temperature error is proposed.

Precise measurement of junction temperature by thermal analysis of light-emitting diode operated at high environmental temperature

Light-emitting diodes (LEDs) have become a promising solid-state light source in numerous applications. During operation, they are often exposed to high environmental temperatures, resulting in performance and reliability degradation. It is thus important to monitor the temperature at the junction, which is a primary lighting and heat source, especially for an LED operated under a high-temperature environment. In this study, the temperatures at the junction, phosphor, and thermal pad of the LED operated at high temperatures (up to 107.2 °C) are measured and analyzed. The junction temperature is measured by a transient thermal tester at known environmental temperatures and input currents. Moreover, the temperatures at the phosphor and thermal pad are simultaneously measured by using an infrared (IR) thermometer and a thermocouple, respectively. A single highly linear temperature correlation (R2 = 0.997) is found between the junction and phosphor temperatures regardless of the operating conditions. This could aid in precisely estimating the junction temperature by simply measuring the surface temperature of phosphor. On the other hand, the correlation between the junction and thermal pad temperature that is often treated as a single correlation exhibits dependence on the input current over the tested temperature range. The structural thermal analysis on the thermal resistance of the LED package supports the experimental results along with the numerical analysis. The obtained results in this study could provide a set of guidelines for the precise prediction of junction temperature and thermal management of LEDs, which are operated under high-temperature environments.

Numerical Simulations of Water Spray on Launch Pad During Rocket Launching

This paper compares the cooling effect on the launch pad with two different levels of water cooling system used in the Long March 7. The rocket plume model is set up based on the three-dimensional Navier–Stokes equations solved by the realizable turbulence model. The Eulerian dispersed phase (EDP) model is employed to describe the injected cooling water. Comparing with test data, the validity of the above models is verified, respectively. On this basis, the temperature distributions on the launch pad with two different levels of water spray system are investigated. The results show that the overall temperature of the launch pad drops significantly with the first-level water spray system. However, because the rocket plume blows most of the injected water away, the temperature of the central area barely decreases. When using the second-level water spray system, the central temperature is reduced obviously, but the cooling area of a single water spray nozzle is limited. Under the influence of plume, the closer to the central zone, the smaller the area that each water spray nozzle can cool.

Assessment of direct evaporative cooler performance with a cooling pad made from banana midrib and ramie fiber

PurposeThe paper aims to apply Buckingham Pi dimensional analysis method for assessing direct evaporative cooler performance with a cooling pad made of banana midrib and ramie fiber. The saturation efficiency acted as the indicator performance of the evaporative cooler.Design/methodology/approachThe paper describes an experimental study of the direct evaporative cooler with a cooling pad made of banana midrib and rami fiber. There were six parameters in the experiment: absorbed water as a dependent variable was affected by independent parameters such as air velocity and temperature, cooling pad cross-section area and thickness. Based on these variables, we arranged three dimensionless numbers and their correlation.FindingsThe paper provides three calculated dimensionless numbers plotted on a curve with a specific correlation. The curve trends for 30 mm and 50 mm pad thickness were almost similar. The range of Reynolds number for 10 mm pad was narrower than other pad thicknesses. The thicker the cooling pad, the more extensive was the calculated Reynolds number range. A new curve exhibited the relationship between the evaporation rate with the μA/t number. The broader cooling pad cross-section, the thinner pad thickness, and the lower pad temperature were factors that increased the evaporation rate, even though the increase was less significant.Originality/valueA new material in cooling pad from banana midrib fiber was tested and compared to ramie fiber and conventional cooling pad.

Effects of temperature probe orientation on the Purdue hog cooling pad data acquisition

Heat stress in domestic animal production consistently alters several physiological, growth, and reproductive metrics within the livestock industry. To increase commercial productivity and general animal husbandry, the agricultural research community has been investigating technologies to combat the effects of heat stress for several decades. A hog cooling pad has been developed at Purdue University through a departmental collaboration between Agricultural & Biological Engineering and Animal Sciences. One of the main points of interest in the hog cooling pad research investigation is the accurate expression of the heat transfer from the sow to the copper coil coolant system. It is vital to obtain accurate temperature data in real time to properly manage the coolant flow in the device. This research project investigated the effect of the temperature probe orientation. Several cooling pad temperature probe orientations were proposed, while trying to keep every other operational aspect of the hog cooling pad the same. Temperature data from two separate collection systems were assessed using analyses that document differences in the selected probe’s responsiveness and accuracy. Three placement areas were examined: the blade, center, and ham locations. This research demonstrated conclusively that the type K thermocouple collection system maintained an accurate, rapid, and consistent performance as the calibrated system, and the Hilitchi® digital probes varied substantially in accuracy and responsiveness. Calibration offset values for digital probes were documented in the 4–5 °C range. This was completely unacceptable for the small ranges of interest in the hog cooling pad work. Horizontal orientations were shown to be the most responsive against 45° orientations with: (tH(37.8) = −14.09, p < 0.01), (tC(41.8) = −9.57, p < 0.01), and (tB(44.5) = −15.08, p < 0.01); and against 90° orientations with: (tH(56.0) = −28.46, p < 0.01), (tC(36.9) = −10.14, p < 0.01), and (tB(53.8) = −13.48, p < 0.01). However, none of the test results indicated that the Hilitchi® digital probes performed acceptably enough to be included in any commercial build of the hog cooling units.