Showing papers on "Calorimeter published in 2011"

Measuring the process efficiency of controlled gas metal arc welding processes

Abstract: The thermal or process efficiency in gas metal arc welding (GMAW) is a crucial input to numerical models of the process and requires the use of an accurate welding calorimeter. In this paper, the authors compare a liquid nitrogen calorimeter with an insulated box calorimeter for measuring the process efficiency of Fronius cold metal transfer, Lincoln surface tension transfer and RapidArc, Kemppi FastRoot and standard pulsed GMAW. All of the controlled dip transfer processes had a process efficiency of ∼85% when measured with the liquid nitrogen calorimeter. This value was slightly higher when welding in a groove and slightly lower for the RapidArc and pulsed GMAW. The efficiency measured with the insulated box calorimeter was slightly lower, but it had the advantage of a much smaller random error.

SKIROC2, front end chip designed to readout the Electromagnetic CALorimeter at the ILC

Abstract: SKIROC (Silicon Kalorimeter Integrated ReadOut Chip) is the front end chip designed for the readout of the Silicon PIN diodes foreseen for the Electromagnetic CALorimeter (ECAL) at the future International Linear Collider. The fine granularity of the ILC calorimeters implies an extremely large number of electronics channels (82 millions) which is a new feature of ``imaging'' calorimetry. Moreover, for compactness, the chips must be embedded inside the detector without any external component making essential the reduction of the power consumption to 25 μWatt per channel. This is achieved using power pulsing, made possible by the ILC bunch pattern (1 ms of acquisition data for 199 ms of dead time).

Invited Review Article: Photopyroelectric calorimeter for the simultaneous thermal, optical, and structural characterization of samples over phase transitions

Abstract: The study of thermophysical properties is of great importance in several scientific fields. Among them, the heat capacity, for example, is related to the microscopic structure of condensed matter and plays an important role in monitoring the changes in the energy content of a system. Calorimetric techniques are thus of fundamental importance for characterizing physical systems, particularly in the vicinity of phase transitions where energy fluctuations can play an important role. In this work, the ability of the Photopyroelctric calorimetry to study the versus temperature behaviour of the specific heat and of the other thermal parameters in the vicinity of phase transitions is outlined. The working principle, the theoretical basis, the experimental configurations, and the advantages of this technique, with respect to the more conventional ones, have been described and discussed in detail. The integrations in the calorimetric setup giving the possibility to perform, simultaneously with the calorimetric studies, complementary kind of characterizations of optical, structural, and electrical properties are also described. A review of the results obtained with this technique, in all its possible configurations, for the high temperature resolution studies of the thermal parameters over several kinds of phase transitions occurring in different systems is presented and discussed.

Combining cone calorimeter and PCFC to determine the mode of action of flame‐retardant additives

Abstract: The flammability of various flame-retarded formulations containing different hydrated mineral fillers and/or phosphorous compounds and/or carbon nanotubes has been investigated using both a cone calorimeter and a pyrolysis combustion flow calorimeter (PCFC). A method was proposed to evaluate the barrier effect of the flame-retardant additives. This method is based on the fact that the PCFC is non-sensitive to physical flame-retardant effects whereas both chemical and physical phenomena have a great effect on cone calorimeter results. Therefore, normalized peak of heat release rate (pHRR) values obtained with both techniques do not always show a good correlation. It was highlighted that the mismatch between both pHRR results was related to the formation of a protective layer during combustion. Protective layers have been evidenced independently by visual observations. Thus, it is proposed that the magnitude of the deviation from a perfect correlation between cone calorimeter and PCFC pHRRs could be used to quantify the magnitude of barrier effect. Although the results obtained from different fire tests are generally not correlated, such an approach based on the complementarity of different techniques appears more relevant despite of its empirical nature. Copyright © 2011 John Wiley & Sons, Ltd.

An improved single crystal adsorption calorimeter for determining gas adsorption and reaction energies on complex model catalysts

Abstract: A new ultrahigh vacuum microcalorimeter for measuring heats of adsorption and adsorption-induced surface reactions on complex single crystal-based model surfaces is described. It has been specifically designed to study the interaction of gaseous molecules with well-defined model catalysts consisting of metal nanoparticles supported on single crystal surfaces or epitaxial thin oxide films grown on single crystals. The detection principle is based on the previously described measurement of the temperature rise upon adsorption of gaseous molecules by use of a pyroelectric polymer ribbon, which is brought into mechanical/thermal contact with the back side of the thin single crystal. The instrument includes (i) a preparation chamber providing the required equipment to prepare supported model catalysts involving well-defined nanoparticles on clean single crystal surfaces and to characterize them using surface analysis techniques andin situreflectivity measurements and (ii) the adsorption/reaction chamber containing a molecular beam, a pyroelectric heat detector, and calibration tools for determining the absolute reactant fluxes and adsorption heats. The molecular beam is produced by a differentially pumped source based on a multichannel array capable of providing variable fluxes of both high and low vapor pressure gaseous molecules in the range of 0.005‐1.5 × 10 15 moleculescm −2 s −1 and is modulated by means of the computer-controlled chopper with the shortest pulse length of 150 ms. The calorimetric measurements of adsorption and reaction heats can be performed in a broad temperature range from 100 to 300 K. A novel vibrational isolation method for the pyroelectric detector is introduced for the reduction of acoustic noise. The detector shows a pulse-to-pulse standard deviation ≤15 nJ when heat pulses in the range of 190‐3600 nJ are applied to the sample surface with a chopped laser. Particularly for CO adsorption on Pt(111), the energy input of 15 nJ (or 120 nJcm −2 ) corresponds to the detection limit for adsorption of less than 1.5 × 10 12 CO moleculescm −2 or less than 0.1% of the monolayer coverage (with respect to the 1.5 × 10 15 surface Pt atomscm −2 ). The absolute accuracy in energy is within ∼7%‐9%. As a test of the new calorimeter, the adsorption heats of CO on Pt(111) at different temperatures were measured and compared to previously obtained calorimetric data at 300 K. © 2011 American Institute of Physics.

Influence of physical properties on polymer flammability in the cone calorimeter

Abstract: The relationship between physical properties and fire performance as measured in the cone calorimeter is not well understood. A number of studies have identified relationships between the physical and chemical properties of polymeric materials and their gasification behaviour which can be determined through numerical pyrolysis models. ThermaKin, a one-dimensional pyrolysis model, has recently been employed to predict the burning behaviour in fire calorimetry experiments. The range of thermal, chemical and optical properties of various polymers have been utilised to simulate the processes occurring within a polymer exposed to a uniform heat flux, such as in a cone calorimeter. ThermaKin uses these material properties to predict the mass flux history in a cone calorimeter. Multiplying the mass flux history by the heat of combustion of the fuel gases gives the HRR history and these have been calculated for cone calorimeter experiments at 50 kW m-2 incident heat flux for the lowest, average and highest values of physical parameters exhibited by common polymers. In contrast with actual experiments in fire retardancy, where several parameters change on incorporation of an additive, this study allows for the effect of each parameter to be seen in isolation. The parameters used in this study are grouped into physical properties (density, heat capacity and thermal conductivity), optical properties (absorption and reflectivity), and chemical properties (heat of decomposition, kinetic parameter and heat of combustion). The study shows how the thermal decomposition kinetic parameters effect the surface burning (pyrolysis) temperature and resulting heat release rate history, as well as the relative importance of other properties directly related to the chemical composition. It also illustrates the effect of thermal inertia (the product of density, heat capacity and thermal conductivity) and of the samples’ ability to absorb radiant heat.

Performance of glass resistive plate chambers for a high-granularity semi-digital calorimeter

Abstract: A new design of highly granular hadronic calorimeter using Glass Resistive Plate Chambers (GRPCs) with embedded electronics has been proposed for the future International Linear Collider (ILC) experiments. It features a 2-bit threshold semi-digital read-out. Several GRPC prototypes with their electronics have been successfully built and tested in pion beams. The design of these detectors is presented along with the test results on efficiency, pad multiplicity, stability and reproducibility.

Electromagnetic response of a highly granular hadronic calorimeter

Abstract: The CALICE collaboration is studying the design of high performance electromagnetic and hadronic calorimeters for future International Linear Collider detectors. For the hadronic calorimeter, one option is a highly granular sampling calorimeter with steel as absorber and scintillator layers as active material. High granularity is obtained by segmenting the scintillator into small tiles individually read out via silicon photo-multipliers (SiPM). A prototype has been built, consisting of thirty-eight sensitive layers, segmented into about eight thousand channels. In 2007 the prototype was exposed to positrons and hadrons using the CERN SPS beam, covering a wide range of beam energies and angles of incidence. The challenge of cell equalization and calibration of such a large number of channels is best validated using electromagnetic processes. The response of the prototype steel-scintillator calorimeter, including linearity and uniformity, to electrons is investigated and described.

Use of flat panel microchannel photomultipliers in sampling calorimeters with timing

Abstract: Large-area, flat-panel photo-detectors with sub-nanosecond time resolution based on microchannel plates are provided. The large-area, flat-panel photo-detectors enable the economic construction of sampling calorimeters with, for example, enhanced capability to measure local energy deposition, depth-of-interaction, time-of-flight, and/or directionality of showers. In certain embodiments, sub-nanosecond timing resolution supplies correlated position and time measurements over large areas. The use of thin flat-panel viewing radiators on both sides of a radiation-creating medium allows simultaneous measurement of Cherenkov and scintillation radiation in each layer of the calorimeter. The detectors may be used in a variety of applications including, for example, medical imaging, security, and particle and nuclear physics.

Densities, Viscosities, Heat Capacities, and Vapor–Liquid Equilibria of Ammonia + Sodium Thiocyanate Solutions at Several Temperatures

Abstract: Several thermophysical properties were experimentally measured for the ammonia + sodium thiocyanate mixtures at several temperatures: density from (269.4 to 350.9) K, dynamic viscosity from (269.8 to 369.5) K, and isobaric heat capacity from (304.17 to 364.15) K, all them at a constant pressure of 3 MPa, and vapor–liquid equilibria from (253.1 to 393.1) K. All properties were measured in a range of composition from 0.35 to 0.90 in ammonia mass fraction. The experimental techniques used were a vibrating-tube densimeter, a piston-style viscometer, a heat flux Calvet-type calorimeter, and a static method, respectively. The measured data were correlated as a function of temperature and composition using empirical equations and were compared with literature values.

Effective Heat of Combustion for Flaming Combustion of Mediterranean Forest Fuels

Abstract: An adapted bench-scale Mass Loss Calorimeter (MLC) device is proposed for evaluating effective heat of rapid flaming combustion of fine Mediterranean forest fuels. The MLC apparatus uses a calibrated thermopile to quantify heat release rate (HRR) as an alternative to the classical oxygen consumption measurement. A porous holder was used to simulate rapid flaming combustion. Average effective heat of combustion (AEHC) during the flaming phase was related to the classical measurement of gross heat of combustion (GHC) obtained in oxygen bomb calorimeter. Results showed that the effective heat of combustion (oven-dry basis) was between 18% and 44% lower than the gross heat of combustion. A linear regression was obtained (r2 = 0.48; SEE = 1.25; p < 0.01; n = 26) to relate AEHC and GHC values. The simple model developed (AEHC = GHC − 6.75) suggests the possibility of reducing the heat of combustion values used in forest fire behaviour models for Mediterranean forest fuels.

Potentials and limitations of miniaturized calorimeters for bioprocess monitoring

Abstract: In theory, heat production rates are very well suited for analysing and controlling bioprocesses on different scales from a few nanolitres up to many cubic metres. Any bioconversion is accompanied by a production (exothermic) or consumption (endothermic) of heat. The heat is tightly connected with the stoichiometry of the bioprocess via the law of Hess, and its rate is connected to the kinetics of the process. Heat signals provide real-time information of bioprocesses. The combination of heat measurements with respirometry is theoretically suited for the quantification of the coupling between catabolic and anabolic reactions. Heat measurements have also practical advantages. Unlike most other biochemical sensors, thermal transducers can be mounted in a protected way that prevents fouling, thereby minimizing response drifts. Finally, calorimetry works in optically opaque solutions and does not require labelling or reactants. It is surprising to see that despite all these advantages, calorimetry has rarely been applied to monitor and control bioprocesses with intact cells in the laboratory, industrial bioreactors or ecosystems. This review article analyses the reasons for this omission, discusses the additional information calorimetry can provide in comparison with respirometry and presents miniaturization as a potential way to overcome some inherent weaknesses of conventional calorimetry. It will be discussed for which sample types and scientific question miniaturized calorimeter can be advantageously applied. A few examples from different fields of microbiological and biotechnological research will illustrate the potentials and limitations of chip calorimetry. Finally, the future of chip calorimetry is addressed in an outlook.

Calorimetric Measurement of Droplet Temperature in GMAW

Abstract: Average temperature was calculated from calorimetric measurements in free-flight gas metal arc welding (GMAW) for ER70S-6 (carbon steel), ER316L (stainless steel), and ER4030 (aluminum) electrodes. Measurements were conducted using a constant-pressure water calorimeter to capture the droplets and a flow-through copper cathode/calorimeter to carry the arc. Thermocouples were used to monitor the temperature change of the water flowing through the cathode as well as in the constant pressure calorimeter. Results show a local minimum in temperature during the transition from globular to spray transfer modes.

Development of cryogenic alpha spectrometers using metallic magnetic calorimeters

Abstract: Cryogenic particle detectors have recently been adopted in radiation detection and measurement because of their high energy resolution. Many of these detectors have demonstrated energy resolutions better than the theoretical limit of semiconductor detectors. We report the development of a micro-fabricated magnetic calorimeter coupled to a large-area particle absorber. It is based on a planar, 1 mm2 large paramagnetic temperature sensor made of sputtered Au:Er, which covers a superconducting meander-shaped pickup coil coupled to a low-noise dc-SQUID to monitor the magnetization of the sensor. A piece of gold foil of 2.5×2.5×0.07 mm3 was glued to the Au:Er film to serve as an absorber for incident alpha particles. The detector performance was investigated with an 241Am source. The signal size comparison for alpha and gamma peaks with a large difference in energy demonstrated that the detector had good linear behavior. An energy resolution of 2.83±0.05 keV in FWHM was obtained for 5.5 MeV alpha particles.

Isothermal titration calorimetry in nanoliter droplets with subsecond time constants.

Abstract: We reduced the reaction volume in microfabricated suspended-membrane titration calorimeters to nanoliter droplets and improved the sensitivities to below a nanowatt with time constants of around 100 ms. The device performance was characterized using exothermic acid–base neutralizations and a detailed numerical model. The finite element based numerical model allowed us to determine the sensitivities within 1% and the temporal dynamics of the temperature rise in neutralization reactions as a function of droplet size. The model was used to determine the optimum calorimeter design (membrane size and thickness, junction area, and thermopile thickness) and sensitivities for sample volumes of 1 nL for silicon nitride and polymer membranes. We obtained a maximum sensitivity of 153 pW/(Hz)1/2 for a 1 μm SiN membrane and 79 pW/(Hz)1/2 for a 1 μm polymer membrane. The time constant of the calorimeter system was determined experimentally using a pulsed laser to increase the temperature of nanoliter sample volumes. Fo...

Real-time calibration of the A4 electromagnetic lead fluoride (PbF2) calorimeter

Abstract: Sufficient energy resolution is the key issue for the calorimetry in particle and nuclear physics. The calorimeter of the A4 parity violation experiment at MAMI is a segmented calorimeter where the energy of an event is determined by summing the signals of neighboring channels. In this case, the precise matching of the individual modules is crucial to obtain a good energy resolution. We have developed a calibration procedure for our total absorbing electromagnetic calorimeter which consists of 1022 lead fluoride (PbF 2 ) crystals. This procedure reconstructs the single-module contributions to the events by solving a linear system of equations, involving the inversion of a 1022×1022-matrix. The system has shown its functionality at beam energies between 300 and 1500 MeV and represents a new and fast method to keep the calorimeter permanently in a well-calibrated state.

Study of oxidation and hydrolysis of oil impregnated paper insulation for transformers using a microcalorimeter

Abstract: An isothermal microcalorimeter has been used to study ageing of oil impregnated kraft paper. Under the assumption that the heat flow is proportional to the ageing rate of paper it is found that activation energy seems to be lower for oxidation than for hydrolysis. This observation corresponds well with results obtained by traditional ageing methods. The results have also been confirmed by measuring the changes in DP of the samples used in the calorimetric measurements. Comparing degradation of aged and unaged oil impregnated paper in air gave a higher heat flow for the unaged paper, but the activation energy for the processes remained the same. The process was also studied with another cellulosic material and in addition varying size of the sample holder of the calorimeter, giving similar results. Hence, since the microcalorimeter appears to give the same qualitative ageing characteristics for oxidation and hydrolysis as more time consuming methods, calorimeter could be a useful tool for quick ageing investigations.

Effects of high-energy particle showers on the embedded front-end electronics of an electromagnetic calorimeter for a future lepton collider

Abstract: Application Specific Integrated Circuits, ASICs, similar to those envisaged for the readout electronics of the central calorimeters of detectors for a future lepton collider have been exposed to high-energy electromagnetic showers. A salient feature of these calorimeters is that the readout electronics will be embedded into the calorimeter layers. In this article it is shown that interactions of shower particles in the volume of the readout electronics do not alter the noise pattern of the ASICs. No signal at or above the MIP level has been observed during the exposure. The upper limit at the 95% confidence level on the frequency of fake signals is smaller than 1 × 10 − 5 for a noise threshold of about 60% of a MIP. For ASICs with similar design to those which were tested, it can thus be largely excluded that the embedding of the electronics into the calorimeter layers compromises the performance of the calorimeters.

Measurement of Thermophysical Pure Component Properties for a Few Siloxanes Used as Working Fluids for Organic Rankine Cycles

Abstract: In this work, heat capacities for three linear siloxanes (hexamethyl disiloxane (MM), octamethyltrisiloxane (MDM), and decamethyltetrasiloxane (MD2M)) in the temperature range of 205.15–395.15 K and for two cyclic siloxanes (octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5)) in the temperature range of 288.15–443.15 K have been measured with the help of a Tian–Calvert calorimeter. Furthermore, vapor pressures for the five mentioned compounds in the temperature range of 250–620 K and pressures from 2 mbar to 1 bar have been determined with the help of a Scott ebulliometer. The prediction of the heat capacities using the group contribution equation of state VTPR were improved by fitting the Twu parameters simultaneously to the new vapor pressure and heat capacity data. In addition, melting temperatures and heat of fusions for these five siloxanes have been measured using a differential scanning calorimeter (DSC). Furthermore, density measurements for the three linear siloxanes (MM, MDM...

The NA62 Liquid Krypton calorimeter readout module

Abstract: The NA62 experiment [1] at CERN SPS (Super Proton Synchrotron) accelerator will be focused on precision tests of the Standard Model via studies of ultra-rare decays of charged kaons. The high resolution Liquid Krypton (LKr) calorimeter of the former NA48 experiment [2], together with other detectors, will provide a photon-veto with hermetic coverage from zero out to large angles from the decay region. The old backend electronics [3] does not satisfy the NA62 specifications and the study of a new readout system began in 2008. This paper presents the Calorimeter REAdout Module (CREAM), an upgrade project for the backend part of the LKr data acquisition chain [3]. The CREAMs will provide 40 MHz sampling of 13248 calorimeter channels, data buffering during the SPS spill, zero suppression, and programmable trigger sums for the experiment trigger processor.

Spectral Modeling of Scintillator for the NEMO-3 and SuperNEMO Detectors

Abstract: We have constructed a GEANT4-based detailed software model of photon transport in plastic sontillator blocks and have used it to study the NEMO-3 and SuperNEMO calorimeters employed in experiments designed to search for neutnnoless double beta decay We compare our simulations to measurements using conversion electrons from a calibration source of (BI)-B-207 and show that the agreement is improved if wavelength-dependent properties of the calorimeter are taken into account In this article we briefly describe our modeling approach and results of our studies (C) 2010 Elsevier B V All rights reserved

Thermophysical properties of mate leaves: experimental determination and theoretical effect of moisture content

Abstract: An experimental investigation to determine the specific heat, thermal conductivity and apparent density of mate leaves (Ilex paraguariensis) was carried out. The experimental method of mixtures and a quasi-adiabatic calorimeter were used to obtain a specific heat of dry leaves close to 1780 ± 450 J/kg/K. A thermal conductivity of 0.17 ± 0.01/W/m/K was tuned on transient experimental measurements of temperature in a dry bar of mate leaves. A dynamic one-dimensional heat transfer model was involved in this procedure of tuning. An apparent density equal to 750 ± 40 kg/m was experimentally found. The effect of moisture content on these thermophysical properties was also theoretically investigated by involving simplified models based on properties of only dry matter and water. Analogous results available in the literature support the reliability of all experimental data and equations presented in this investigation. PRACTICAL APPLICATIONS Mate manufacturing basically involves a stage of enzymatic deactivation and a process of drying that are together responsible for almost the full energy consumed in the mate industry. A detailed description of both these processes with mathematical models is a cheap and safe way to process optimization and energy saving. However, the knowledge of the specific heat, thermal conductivity and density of the processed material whose availability is limited in the literature is required for model solution.