Showing papers on "Calorimeter published in 1998"

A novel single-crystal adsorption calorimeter and additions for determining metal adsorption and adhesion energies

Abstract: A new microcalorimeter for measuring heats of adsorption on clean single-crystal surfaces is described, and its operational characteristics are presented. The principle is similar to that pioneered by David King’s group: A pulse of gas from a molecular beam adsorbs on an ultrathin single crystal’s surface, causing a measurable transient heat input and temperature rise. Our novel heat detector is a 9 μm thick pyroelectric polymer ribbon, which is mechanically driven to make a gentle mechanical/thermal contact to the back of the single-crystal sample during measurements. Advantages include use of thicker samples (1 μm), sample preparation at very high temperatures, and potential measurements at cryogenic temperatures. A novel chopped molecular beam of metal vapor and a method of correcting for absorbed radiation from the hot effusion cell are also described. This system is applied to study the heats of adsorption of metals on clean, well-defined and single-crystalline surfaces as a detailed function of cove...

Nonadiabatic scanning calorimeter

Abstract: A high-resolution computerized calorimeter capable of fully automatic operation in either ac or relaxation modes is described. Emphasis is given to a new version of the relaxation technique in which the heater power is ramped linearly in time. This improvement results in superior performance and convenience in studying both first- and second-order phase transitions and allows quantitative evaluation of latent heats as well as pretransitional heat capacity variations. Examples are given for the use of this calorimeter in the study of liquid crystal phase transitions.

Energetics of Micellization: Reassessment by a High-Sensitivity Titration Microcalorimeter

Abstract: The critical micellar concentration (cmc) and energetics of surfactant self-organization have been reassessed at 303 K with the help of a high-sensitivity microcalorimeter. The calorimeter can oper...

Application of cone calorimeter for the assessment of class of flame retardants for polypropylene

Abstract: The study presented addresses the fire behaviour of polypropylene compounded with six classes of flame retardants. The application of cone calorimetry for the assessment of the thermal characteristics of the tested materials and their comparison with thermogravimetry are the central point of this research. This study only presents data for 25 kW/m2 of incident heat flux exposure and includes five tests for polypropylene with no additives and five tests for polypropylene with flame retardants based on triglycidylisocyanurate and lignin. The data collected include the rate of heat release, mass loss rate, char yield, time to ignition and time of total combustion. Results represent meaningful comparison between the behaviour of the materials under simulated fire conditions, using the cone calorimeter, and in the slow dynamic environment utilized in thermogravimetric analysis. © 1998 John Wiley & Sons Ltd.

Absolute values of specific heat capacity and thermal conductivity of liquids from different modes of operation of a simple photopyroelectric setup

Abstract: Photothermal techniques offer a nice tool for the determination of changes in thermal parameters of different types of samples. Using a very thin pyroelectric transducer, a very simple and versatile ac calorimeter can be built. The described inverse pyroelectric technique allows high-resolution ac-calorimetric measurements of the temperature dependence of the specific heat capacity. Since measuring frequencies up to a few hertz can be used, which are higher than in most alternative ac-calorimetric setups, noise can be reduced and measuring times shortened. With a small modification of the measurement cell, the determination of absolute specific heat capacity and thermal conductivity values of liquid samples was achieved. Comparison of the frequency response of the system with and without a solid thermal load in the neighborhood of the sample yields data with an accuracy of about 5% and 10% for specific heat capacity and thermal conductivity, respectively. If necessary, absolute values of specific heat cap...

The quartz-fiber Zero-Degree Calorimeter for the NA50 experiment at CERN SPS

Abstract: Quartz-fiber calorimeters have been the object of an intense and fruitful work of research and development in the last few years. In this paper we report about the first application of this technique in an experiment. Namely, we describe the design and performance of the Zero-Degree Calorimeter (ZDC) used in NA50, a heavy-ion experiment at CERN SPS aiming to detect the formation of quark-gluon plasma in Pb–Pb collisions at 158 AGeV by studying the production of the charmonia states J/ψ and ψ′. The unique properties of the quartz-fiber calorimeters turn out to be well suited to match the specific requirements of this experiment that operates at beam intensity of about 10 7 Pb-ion/s: radiation hardness (up to a few Grads), short duration of the signal (∼10 ns), spatial resolution of a few hundreds of μm, small size of the detector (5×5×65 cm 3 ) and energy resolution adequate for providing a precise measurement of the collision centrality.

Determination of the Absolute Jet Energy Scale in the DZERO Calorimeters

Abstract: The DZERO detector is used to study proton-antiproton collisions at the 1800 GeV and 630 GeV center-of-mass energies available at the Fermilab Tevatron. To measure jets, the detector uses a sampling calorimeter composed of uranium and liquid argon as the passive and active media respectively. Understanding the jet energy calibration is not only crucial for precision tests of QCD, but also for the measurement of particle masses and the determination of physics backgrounds associated with new phenomena. This paper describes the energy calibration of jets observed with the DZERO detector at the two proton-antiproton center-of-mass energies in the transverse energy and pseudorapidity range ET>8 GeV and pseudorapidity<3.

Mass and heat flow measurement sensor

Abstract: Provided are mass and heat flow measurement sensors comprising a microresonator, such as a quartz crystal microbalance; a heat flow sensor (c), such as an isothermal heat conduction calorimeter; and a heat sink (d) coupled thermally to the heat flow sensor. The sensors may be used to measure changes in mass due to a sample (8) on a surface of the microresonator and also to measure heat flow from the sample (8) on the surface of the microresonator by utilizing the heat flow sensor, which is coupled thermally to the microresonator. Also provided are methods for measuring the mass of a sample (8) and the flow of heat from the sample (8) to the heat sink (d) by utilizing such mass and heat flow measurement sensors.

The GRAAL high resolution BGO calorimeter and its energy calibration and monitoring system

Abstract: We describe the electromagnetic calorimeter built for the GRAAL apparatus at the ESRF. Its monitoring system is presented in detail. Results from tests and the performance obtained during the first GRAAL experiments are given. The energy calibration accuracy and stability reached is a small fraction of the intrinsic detector resolution.

The calibration of therapy level electron beam ionization chambers in terms of absorbed dose to water

Abstract: During 1998, NPL plans to introduce the world's first absorbed dose calibration service for electron beam radiotherapy. The service will be based on the primary standard graphite calorimeter, and will enable the direct calibration of electron ionization chambers, without reference to air kerma standards. This calibration is a two-step process. Firstly, a set of NACP-designed parallel-plate reference chambers have been calibrated against the calorimeter over the last few years. These chambers are then used to calibrate user chambers by direct comparison in a water phantom under standard conditions. This paper describes the calibration of the reference chambers against the calorimeter and the derivation of absorbed dose to water calibration factors (with an estimated uncertainty in this calibration of % at the 95% confidence level).

High precision calorimetry for the measurement of the efficiency of induction motors

Abstract: Calorimeters are used to measure directly the loss in electrical machines operating under various load conditions. This paper examines experimental errors resulting from calorimeter design and from operating procedures. The techniques of minimising these errors used by previous researchers are reviewed. An improved technique for obtaining high accuracy in the measurement of power loss is discussed based on two generations of a calorimeter. The performance of these designs is presented with the first providing an accuracy of 0.5% and the second better than 0.2% in measurement of total loss at the 30 kW level.

Mems-based scanning calorimeter for thermodynamic properties of nanostructures

Abstract: Thermodynamic properties of small structures, such as the melting points and the process of mass transport, can be considerably different compared to material in the bulk form. Calorimetry is the standard experimental technique used to measure thermodynamics properties. However, this technique is extremely difficult to use for the study of small structures because the amount of energy exchanged during the measurement is extremely small - proportional to the amount of material. In order to measure small amounts of thermal energy we have scaled down the physical size of the calorimeter using MEMS technology. This thin-film differential scanning calorimeter has extremely high sensitivity, 0.01 mJ cm2, and is capable of measuring the melting phenomenon of 1 A of Sn deposited onto a SiN surface. In this article we investigate the size dependence of both the melting point and the heat of fusion for ultrathin films of Sn nanonstructures using multiple evaporation and thermal annealing cycles.

A portable calorimeter for measuring liquid-water content of wet snow

Abstract: In order to facilitate the measurement of liquid-water content of snow in high mountains, a portable calorimeter named “Endo-type snow-water content meter” was developed. It is composed of a metal-coated container made of insulating materials and a lid of the container with a small-thermistor thermometer. Its strong points are its light weight, small size and easy fabrication with cheap materials. The total weight of the device is as light as 250 g, which is less than 10% of the snow-water content meter widely used in Japan (Akitaya-type snow-water content meter). The results of experiments have revealed that the device is capable of measuring the liquid-water content within 2 minutes with an accuracy of 2% by weight.

Heat Capacities at Constant Volume of Pure Water in the Temperature Range 412−693 K at Densities from 250 to 925 kg·m-3

Abstract: The heat capacity at constant volume CV of pure water has been measured in the temperature range from 412 K to 693 K at 13 isochores between 250 kg·m-3 and 925 kg·m-3. Measurements cover the critical region and coexistence curve. Measurements have been made in both the one- and two-phase regions near the phase transition points. The measurements were made in a high-temperature, high-pressure adiabatic nearly constant-volume calorimeter. The uncertainty of the heat capacity measurements is estimated to be within ±2.5%. Liquid and vapor one- ( ) and two-phase ( ) heat capacities, temperatures (TS), and densities (ρS) at saturation were obtained by the method of quasi-static thermograms. The parameters (c, T*,V*) of the simplified-perturbed-hard-chain-theory (SPHCT) equation of state have been optimized to allow calculations of heat capacities for water in the vapor and liquid phases. The relative average deviations for H2O were within about ±4.5%, except in the critical region where differences reached 15−2...

Enthalpy Changes upon Partial Evaporation of Aqueous Solutions Containing Ammonia and Carbon Dioxide

Abstract: The enthalpy changes upon partial evaporation of aqueous solutions containing ammonia and of aqueous solutions containing ammonia and carbon dioxide were measured at temperatures from 313 to 393 K with a thin film evaporator flow calorimeter. The molalities of ammonia and carbon dioxide entering the calorimeter ranged up to 12 and 6 mol/kg, respectively. The physicochemical model originally developed by Edwards et al. (1978) and further modified and extended by Kurz et al. (1995) to describe phase equilibria in aqueous systems containing ammonia and carbon dioxide is used to derive a predictive enthalpy model for this complex, chemical reactive system. Comparisons between the new experimental results for the enthalpy change upon partial evaporation and model predictions reveal deviations mostly within the experimental uncertainties.

High-Temperature Adiabatic Calorimeter for Constant-Volume Heat Capacity Measurements of Compressed Gases and Liquids.

Abstract: A high-temperature adiabatic calorimeter has been developed to measure the constant-volume specific heat capacities (cV ) of both gases and liquids, especially fluids of interest to emerging energy technologies. The chief design feature is its nearly identical twin bomb arrangement, which allows accurate measurement of energy differences without large corrections for energy losses due to thermal radiation fluxes. Operating conditions for the calorimeter cover a range of temperatures from 250 K to 700 K and at pressures up to 20 MPa. Performance tests were made with a sample of twice-distilled water. Heat capacities for water were measured from 300 K to 420 K at pressures to 20 MPa. The measured heat capacities differed from those calculated with an independently developed standard reference formulation with a root-mean-square fractional deviation of 0.48 %.

Thermal characterization of a cryogenic radiometer and comparison with a laser calorimeter

Abstract: We have developed a finite-element-analysis thermal model to study the temperature distribution in a laser-optimized cryogenic radiometer (LOCR). Our modelling showed that the worst-case inequivalence between electrical and optical power is 0.0004%. We used the thermal model, empirical testing, and research performed at other laboratories, to conduct a detailed uncertainty analysis for laser power calibrations based on the LOCR. Using photodiode trap detectors at laser wavelengths of 633.0 nm and 1550.4 nm as intermediate standards, we showed that the cryogenic radiometer and the NIST C4 laser calorimeter agree within 0.1%.

A unique calorimeter-cycler for evaluating high-power battery modules

Abstract: Battery thermal management is critical for high-power battery packs commonly used in electric vehicles (EV) and hybrid electric vehicles (HEV). To design battery thermal management systems properly, obtaining accurate heat generation data from battery modules is essential. To measure heat generation from full-size multiple-cell battery modules, we developed and tested a custom-made calorimeter for large modules. Battery modules with dimensions up to 21 cm/spl times/39 cm in cross section and 20 cm in height can be placed in the cavity of the calorimeter for measuring heat generation rates from 1 W to 100 W with the battery operating at -30/spl deg/C to +60/spl deg/C. The instrument is capable of measuring heat effects as small as 10 joules with accuracy of 5%. A state-of-the-art high power battery cycler is used to cycle the modules in the calorimeter. This paper provides a description of the calorimeter, calibration test results on its performance, and test results from a module simulating a HEV lead-acid battery.

Enthalpy relaxation of glassy glycerol prepared by rapid liquid quenching

Abstract: We have studied the enthalpy relaxation of glassy glycerol prepared by quenching of the liquid in a top-loading type adiabatic calorimeter developed by our group. The glassy sample was prepared by plunging the sample cell into liquid nitrogen. The cooling rate, 5 K s −1 , was about 100 times faster than the rate available in ordinary adiabatic calorimeters. The heat capacity of the rapidly quenched glass (RQG) was only slightly different from that of the normally quenched glass (NQG). RQG released much larger enthalpy than NQG and the relaxations started at a much lower temperature than the glass transition temperatures of NQG. We analyzed these data in terms of the Adam–Gibbs theory. We demonstrate that the relaxation is accelerated by the larger configurational entropy (prominent structural disorder).