Pin Temperature Research Articles

An experimental method for evaluating the heat transfer coefficient of liquid-cooled short pin fins using infrared thermography

The aim of this research is to evaluate the convective heat transfer coefficient of liquid cooled short pin fins by means of the infrared thermography. An experimental apparatus was set-up to analyze single, in-line and staggered array configurations of short pin fins. In this work the attention is focused on single pins having different shapes: circular, square, triangular and rhomboidal. The infrared thermography is used to indirectly measure the lateral pin temperature by observing the upper surface temperature of radially heated pins; these are placed in a test section chamber equipped with a Zinc Selenide infrared window. Flow visualizations by means of ink tracers are also carried out to relate the thermal behavior with the flow field. Regressions by the Zukauskas correlation were performed for each shape and new coefficients were carried out; a comparison among the different pin geometries underlines a better thermal exchange for the triangular and rhomboidal pins.

Wear Behaviour of C/C–SiC Composites Sliding against High-Cr Steel Discs

Abstract An experimental investigation was conducted to examine the wear behaviour of cross-ply carbon–carbon–silicon carbide composites (C/C–SiC) under dry sliding against a chromium steel disc at various speeds and loads. Results indicated that under identical conditions, C/C–SiC composites with weak fibre resin interfaces at all times had a larger weight loss than those with a strong bond. In the first few minutes of wear, weight losses were approximately the same for both types of composites. Also, the wear rates of both the composites decreased sharply with sliding distance up to 7 km, and then gradually tended to become constant. Scanning electron microscopy showed that the graphite film was transferred on the test pin side, which stabilizes the increase in test pin temperature after the formation of a thick film of graphite debris.

TiN coating wear mechanisms in dry sliding contact against high speed steel

Abstract Dry sliding wear experiments at specific loads ranging between 20 and 250 N were conducted on a PVD TiN coating, arc deposited onto an AISI M2 high speed steel substrate. The coating was worn against AISI M2-type high speed steel pins using a pin-on-disc sliding configuration at a constant sliding speed of 0.7 m s −1 . Wear rates, coefficients of friction and temperatures of the pin were measured as a function of load. Three wear regimes were identified: (i) transfer and build up of oxidized pin debris on the coating at a 20-N load, (ii) increased polishing damage and brittle spallation failure of the TiN at loads in the 50–100 N range and (iii) a sharp transition to plastic deformation and microploughing of TiN at loads greater than 100 N, which coincided with the attainment of a critical steady-state pin temperature of approximately 160°C. Softening of the TiN coating above this temperature leads to rapid wear and exposure of the substrate material.

Modeling of LMR fuel pin temperature behavior using water

This paper describes the possibilities for modeling of non-uniform temperature behavior around the metal fuel pins in reactors cooled by liquid metal using water. The temperature non-uniformities arise due to nonsymmetric heat removal from the pin. The data on heat transfer to mercury, sodium-potassium alloy and water in compact pin bundles found in the State Scientific Center of Russian Federation « Institute of Physics & Power Engineering » are analyzed here. The principles of thermal similarity of fuel pins form the basis of the analysis mentioned.

Abstract of a study to measure the possible differences in the perception of pain and temperature in hemiplegic patients

Introduction: The peripheral sensations of pain and temperature are so closely linked anatomically1 that often only one is assessed during the physiotherapy examination of a neurologically impaired patient. The assumption is made that they would either both be affected or both be normal. Usually pain perception is evaluated as it is the quicker and easier of the two tests. However, could it be possible that pain sensibility be normal, yet temperature abnormal? This scenario could have dire consequences for the patient, as the therapist would neglect to warn the patient or his/her care giver of the possibility of burning themselves, for instance, when climbing into too hot a bath, or sitting too close to a heater. A pilot study investigated the validity of this assumption in subjects having sustained a cerebral vascular accident (CVA).Procedure: The pain and temperature perceptions of twenty-two acute (less than three months prior) CVA patients were assessed. Pain was assessed using the pin prick method, and temperature, using hot and cold test-tubes on both sides of the body in thirteen different areas2,3.Results :There were fifteen female and seven male subjects tested, nine of whom had right CVA's, while thirteen had sustained left CVA's. Eight of the subjects had normal sensation, and ten had both pain and temperature decreased. Four of the subjects (all left CVA's) reported a normal perception to pain, but this was decreased as compared to temperature, especially to heat.Discussion: The results were in keeping with those of Samuelsson et al4. However, the study requires more stringent inclusion criteria, for example a smaller age range as the appreciation of sensation may decrease with age, and a larger sample in order to determine the difference between left and right CVA's. Only middle cerebral artery territory strokes should be included. Unfortunately the nature of the assessment of sensation requires that the subject be able to understand the test and be able to communicate their reply, thus aphasic subjects, both receptive and expressive would have to be excluded. Follow-up studies may have to be included, as sensation perception may improve with time following a CVA1.Conclusion: Although there was not conclusive evidence these two sensations may be affected by a CVA, there were examples of when it did occur. perhaps it is incumbent on physiotherapists to warn all their clients of the possibility and consequences of a loss of temperature sensation, even if pain perception appears normal.

Liquid-Metal-Cooled Reactor Thermal-Hydraulic Calculations in the United States

A wide range of thermal-hydraulic computer codes has been developed by various organizations in the United States. These codes cover an extensive range of purposes from within-assembly-wise pin temperature calculations to plantwide transient analysis. The codes are used for static analysis, analysis of protected anticipated transients, and analysis of unprotected transients for the more recent liquid-metal-cooled reactor designs. Some of these codes are plant specific; others are more general and can be applied to a number of plants or designs.

A Model for the Thermal-Mechanical Behavior of Mixed-Carbide Sphere-Pac Fuel Pins

The major components of a numerical model (SPECKLE-III) for the irradiation behavior of mixed-carbide Sphere-Pac fuel are described. Based on user-supplied power and outer cladding temperature history, radial profiles for the pin temperature, restructuring, fission gas behavior, and stress distribution are calculated at several axial locations as a function of irradiation time. Finite difference and finite element methods are used to solve the quasi-steady, axisymmetric governing equations. Axial slip at the fuel cladding interface is also modeled. The effects of temperature and restructuring on the fuel thermal and mechanical properties are included. Representative results are presented for a Sphere-Pac fuel irradiation experiment.

The Suitability of Tungsten Strip Lamps as Secondary Standard Sources below 1064°C

High-stability tungsten strip lamps are assessed as a means of maintaining the International Practical Temperature Scale below 1064.43°C. The variation of spectral radiance temperature with changes in the lamps and their environment is discussed. Factors necessary to correct the spectral radiance temperature for changes in the resistance and pin temperature of two lamps are given. It is shown that applying corrections for changes in lamp resistance reduces the uncertainty in the use of lamps by an order of magnitude. The uncertainties which are to be associated with the use of tungsten strip lamps under practical conditions are 0.015°C at 1064°C and 0.045°C at 770°C (99% confidence limits). These results indicate that the platinum resistance thermometer appears to be a better alternative means of maintaining temperature scales in the range considered.

Temperature change caused by reducing pins in dentin

Pin temperature increases (heat generation) was prevented by an air-water coolant. Pin height adjustment with an ultraspeed instrument using air-water coolant produces no potentially injurious heat generation.

Einfluss von Schwingungen auf die Verschleisseigenschaften eines Reibsystems

The load carrying capacity of a tribological system can be increased by superposition of a dynamic load to a statically applied load. In this note an example of a test result with a pin-on-disk machine is shown which demonstrates the changes of different characteristic parameters (friction coefficient, pin temperature, contact resistance and wear rate) as a result of the induced vibrations.

The Effect of Rate and Temperature of Drawing on the Properties of Nylon 6,6 Fibers

Higher rates and lower temperatures of cold-drawing nylon 6,6 result in both increased fiber strength and an increased amount of the non-recrystallizable Form II endotherm, as measured by differential scanning calorimetry. This may be explained in terms of mobility of the molecular chains in the neck region; long times and high temperature in the neck favor formation of the recrystallizable Form I material, whereas short times and low temperatures, which result in lower mo lecular mobility, favor the non-recrystallizable and stronger Form II. Because of the temperature effect on the drawing a draw pin temperature rise due to friction and work of drawing can have a variable, detrimental effect on yarn strength at a given draw ratio.

The Suitability of Vacuum Tungsten Blackbody Lamps as Secondary Standard Sources in Photoelectric Pyrometry

The suitability of vacuum tungsten blackbody lamps as secondary standard sources in photoelectric pyrometry has been investigated. It has been found that although the sources are stable when operated for long periods at temperatures up to 1625 °C they will not maintain calibration when physical strain is introduced into the tungsten tube or supports, for example, by vibration of the lamp. All changes detected in calibration of lamps have been accompanied by changes in their electrical resistances, and therefore this parameter can be used as a monitor of calibration stability. Variations in resistance at the gold point of 0.1% produce significant changes in calibration. The effect of pin temperature on the lamp resistance and spectral radiance temperature are given. When precautions are taken in handling, mounting and storage to minimise the introduction of strain in the lamps the uncertainty in their calibration at the gold point is less than ±0.1°C.

An Experimental Study of the Thermal Aspects of Sliding Contacts and Their Relation to the Unlubricated Wear of Steel

Experiments are described in which low-alloy, medium-carbon steel (AISI 4340) pins were slid against discs of the same material under various loads, at a speed of 625 cm/s. The bulk temperatures of the pins and discs were measured continuously, as also were the frictional forces and the volumes of wear. Similar experiments were also carried out, at a much lower speed (about 5 cm/s), in which the bulk temperatures of the specimens were due almost entirely to externally supplied heat. As far as possible, the bulk temperatures, and the corresponding loads, were maintained at the same values as for the initial, frictionally heated, experiments. The wear debris produced during both sets of experiments was examined by X-ray diffraction in order to identify the various components and to analyse their relative proportions. The variation of the proportions of α-iron, rhombohedral oxide, and spinel oxide with measured bulk pin temperature was used to give an estimate of the temperatures occurring in the regions of true contact. This estimate was approximately of the same magnitude as those temperatures measured in recent dynamic thermocouple experiments. The wear results are discussed in terms of oxidation of the real areas of contact at the temperatures indicated by the proportional analysis of the wear debris. It is shown that reasonable values of the activation energy can be obtained from a direct comparison between frictionally heated and externally heated experiments carried out under the same load and the same bulk temperatures. It is concluded that the contact temperature is the factor governing the wear behaviour of steels rather than the ambient temperature of the whole surface.