Showing papers on "Calorimeter published in 2001"

The RHIC zero-degree calorimeters

Abstract: The RHIC zero-degree calorimeters provide common event characterization in the four heavy ion experiments which recently completed their first data taking run. Here, we describe simulations which lead to the design of these devices, teastbeam performance and initial experience at RHIC.

Enhancement of Molar Heat Capacity of Nanostructured Al2O3

Abstract: The nanosized alumina prepared by the hydrolysis method with an average particle size of 20 nm was characterized by X-ray diffraction. The heat capacity measurements of the prepared sample were carried out using an adiabatic calorimeter in the temperature range from 78 to 370 K. Enhancement of heat capacity was observed in the nanostructured materials as the heat capacity data were compared with those of the corresponding coarse-grained materials. The enhanced heat capacity was discussed on the basis of experiments. Differential scanning calorimetry and thermogravimetry were used to determine the thermal stability of the nanostructured alumina.

Test of Reaction Kinetics Using Both Differential Scanning and Accelerating Rate Calorimetries As Applied to the Reaction of LixCoO2 in Non-aqueous Electrolyte

Abstract: Extracting reliable reaction kinetics from nonisothermal calorimetric results can be difficult. The reaction model, activation energy, and frequency factor make up a “kinetic triplet” for a particular reaction and define the reaction kinetics. One expects a good correlation between data and the predictions of the reaction model for a variety of experiments, provided the reaction triplet has been well determined. Such a correlation is expected for the results of accelerating rate calorimeter (ARC) and differential scanning calorimeter (DSC) experiments. As an example, the reaction of LixCoO2 in nonaqueous electrolyte (as is important in Li-ion battery safety) has been studied with both DSC and ARC. Comparing the shape of ARC profiles to those predicted theoretically limits the choice of reaction model. The activation energy is determined from the shift of the DSC profile with heating rate or from the change in the initial self-heating rate of ARC samples as a function of temperature. The frequency factor i...

The CLAS Forward Electromagnetic Calorimeter

Abstract: The CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab utilizes six iron-free superconducting coils to provide an approximately toroidal magnetic field. The six sectors are instrumented individually to form six independent spectrometers. The forward region (8deg < (theta) < 45deg) of each sector is equipped with a lead-scintillator electromagnetic sampling calorimeter (EC), 16 radiation lengths thick, using a novel triangular geometry with stereo readout. With its good energy and position resolution, the EC is used to provide the primary electron trigger for CLAS. It is also used to reject pions, reconstruct pi-0 and eta decays and detect neutrons, This paper treats the design, construction and performance of the calorimeter.

Liquid−Liquid−Vapor, Liquid−Liquid, and Liquid−Vapor Phase Transitions in Aqueous n-Hexane Mixtures from Isochoric Heat Capacity Measurements

Abstract: The constant volume and constant composition heat capacity CVX data for aqueous n-hexane mixtures are reported for seven compositions, (0.6146, 0.7965, 0.9349, 0.9775, 0.9858, 0.9892, and 0.9940) mol fraction of n-hexane, along seven near-critical isochores between 259.34 and 312.50 kg·m-3 in the temperature range from 463 to 522 K at pressures up to 6 MPa. All of these isochores display two features in the heat capacity as a function of temperature: the first peak appears when one of the liquid phases disappears, and the second peak appears when the vapor or liquid phase disappears. These features are interpreted in terms of the liquid−liquid−vapor, liquid−liquid, and liquid−vapor phase diagram, and their consistency is shown with earlier PTx measurements on the three-phase (L-L-G) boundary. Measurements of the isochoric heat capacity (CVVTx) of water + n-hexane mixtures were made in a spherical high-temperature, high-pressure nearly constant volume adiabatic calorimeter. The calorimeter was also used a...

Specific Heat Capacity at Constant Volume for Water, Methanol, and Their Mixtures at Temperatures from 300 K to 400 K and Pressures to 20 MPa†

Abstract: Specific heat capacities at constant volume (cv) of water, methanol, and their mixtures were measured with a new adiabatic calorimeter. Temperatures ranged from 300 K to 400 K, and pressures ranged to 20 MPa. Densities were determined at the initial and final end points during each calorimetric experiment. The calorimeter is a twin-cell type whose sample and reference cells (33 cm3) and their shields are heated by electric power. The cells are surrounded by a high vacuum. During the experiment, the heating power was carefully controlled so that the cell temperature increased uniformly. The reference cell was always evacuated and was heated with a constant current. The temperature of the sample cell tracked that of the reference cell temperature by means an automatic control system. Automated sample pressure measurements were made with a crystal quartz transducer. The expanded relative uncertainty for cv is estimated to be 1% for liquid-phase measurements, and for density it is about 0.2%.

Calorimeter and manufacturing method thereof

Abstract: It is an object to obtain a calorimeter characterized by excellent mechanical strength, and a manufacturing method thereof, when a plurality of calorimeters are arranged inside a single substrate The calorimeter has an absorbent for converting energy of radioactive rays into heat and a resistor for converting heat into an electrical signal using superconductive transition are arranged on a membrane for determining thermal conductivity with the membrane being attached to a substrate, the substrate having a tri-layer structure comprising an etching layer, an etching stop layer and a support substrate, the membrane being arranged separated by the thickness of the etching stop layer and the etching layer

Direct Determination of Equilibrium Thermodynamic and Kinetic Parameters from Isothermal Heat Conduction Microcalorimetry

Abstract: Calorimetry is recognized1-8 as a noninvasive, nondestructive method for the determination of both the thermodynamic and the kinetic parameters associated with chemical reactions. The most immediate applications of the technique have been found in the determination of long-term stability data particularly for pharmaceuticals. However, the methods proposed required that calorimetric data (thermal power, Φ, watts recorded as a function of time) be analyzed iteratively to obtain the order of the reaction n, the rate constant k, and the enthalpy change of reaction ΔRH. A necessary assumption in this process was that all of the sample placed into the calorimeter would react. This is obviously a severe constraint for the flexibility and application of the method. This paper reports a significant extension of the procedure that allows direct calculation of all of the above parameters. Moreover, the equations that are developed permit the determination of the actual quantity of the sample placed into the calorime...

Dynamic Characteristics of a R-410A Split Air Conditioning System

Abstract: This paper presents experimental results on the shut-down and start-up characteristics of a residential split system R-410A air-conditioner with a capillary tube. During shut-down, the transient characteristics are evaluated by measuring the high and low side pressures and temperatures of the system. The dynamic behavior of the system after start-up is also investigated at the standard cooling capacity rating condition of which the dry and wet bulb temperatures for the indoor and outdoor are 27/19.5 and 35/24°C, respectively. All experiments are performed in a psychrometric calorimeter. The cooling capacity, power consumption, dehumidification capacity and cycle characteristics after start-up are analyzed. The test results show that the cooling capacity and the coefficient of performance (COP) after start-up can be expressed as the combination of two exponential functions of time, approaching the cooling capacity of steady-state.

Calorimetry as a routine dosimeter at an electron beam processing facility

Abstract: The invention is generally directed to methods of radiation processing and methods for routine dosimetry, such as for the measurement of radiation dosages delivered to items to be processed by the application of radiation. Radiation-induced heat in an irradiated item is measured with a calorimeter and used to determine the dose of radiation received by the item. Resistive elements such as thermistors may be used in calorimeters to measure the change in temperature of an item receiving radiation, such as in electron beam radiation. Calorimeters exposed to irradiation in the same manner as irradiated items provide routine dosimetry for radiation processing.

The Isothermal Heat Conduction Calorimeter: A Versatile Instrument for Studying Processes in Physics, Chemistry, and Biology

Abstract: An approach to teaching calorimetry is offered through practical, versatile undergraduate experiments using an isothermal heat conduction calorimeter, which measures a variety of heat changes--enthalpies of phase changes, hydration, dissolution, adsorption and desorption, and reaction--as well as the metabolic rate of living organisms. Isothermal heat-conduction calorimetry is contrasted with adiabatic calorimetry. The general design and calibration of an instrument is discussed and five student experiments are described: heat capacity of solids, enthalpy of acid-base reaction, enthalpy of vaporization, hydration of cement, and metabolic rates of insects.

Equilibrium melting curves of silver using high-temperature calorimeters

Abstract: A high-temperature calorimeter has been developed for studying the equilibrium melting behaviour of substances used for realizing the thermometric fixed points. Conventional cells of either 5 cm or 2.5 cm diameter can be accommodated. Using the calorimeter, the equilibrium melting curves of three high-purity silver samples were measured. The samples have narrow melting ranges: two of 1.5 mK and one of about 0.5 mK from 10 % liquid sample fraction to the last measured point near 70 % liquid, yet their liquidus points differ by nearly 5 mK. It was found that 1/F plots cannot be used to determine the deviation of the melting point of real silver samples from that of ideally pure silver.

Theory and development of position-sensitive quantum calorimeters

Abstract: Quantum calorimeters are being developed as imaging spectrometers for future X-ray astrophysics observatories. Much of the science to be done by these instruments could benefit greatly from larger focal-plane coverage of the detector (without increasing pixel size). An order of magnitude more area will greatly increase the science throughput of these future instruments. One of the main deterrents to achieving this goal is the complexity of the readout schemes involved. We have devised a way to increase the number of pixels from the current baseline designs by an order of magnitude without increasing the number of channels required for readout. The instrument is a high energy resolution, distributed-readout imaging spectrometer called a Position-Sensitive Transition-Edge Sensor (POST). A POST is a quantum calorimeter consisting of two Transition-Edge Sensors (TESS) on the ends of a long absorber capable of one-dimensional imaging spectroscopy. Comparing rise time and energy information from the two TESS, the position of the event in the POST is determined. The energy of the event is inferred from the sum of the two pulses. We have developed a generalized theoretical formalism for distributed-readout calorimeters and apply it to our devices. We derive the noise theory and calculate the theoretical energy resolution of a POST. Our calculations show that a 7-pixel POST with 6 keV saturation energy can achieve 2.3 eV resolution, making this a competitive design for future quantum calorimeter instruments. For this thesis we fabricated 7- and 15-pixel POSTS using Mo/Au TESs and gold absorbers, and moved from concept drawings on scraps of napkins to a 32 eV energy resolution at 1.5 keV, 7-pixel POST calorimeter.

A self-correcting indirect calorimeter system for the measurement of energy balance in small animals

Abstract: Indirect calorimetry involves measurement of CO2 produced and O2 consumed by an organism. These measurements are then used to calculate energy output, metabolic rate (MR), and respiratory quotient ...

Hydration Heats of Zeolites For Evaluation of Heat Exchangers

Abstract: The enthalpy of hydration of purified clinoptilolite from Beli Plast, Bulgaria, and various cation-exchanged types such as Na-, K-, Ca- and Mg-clinoptilolite was determined by the adiabatic water-vapor absorption calorimeter. The hydration enthalpy becomes more exothermic in the sequence K, Na, Ca, Mg depending on hydration energy values of exchanged cations. Na-clinoptilolite would be an efficient heat exchanger in a wide temperature range of dehydration, 180–300°C, while Mg-clinoptilolite in higher temperatures, 300–350°C.

A Study on Heat Flux Measurements in High Enthalpy Flows

Abstract: Comparative heat flux measurements were performed in a high enthalpy flow field. Five different heat flux sensors were compared: a Garden gauge, a so-called "heat flux microsensor" HFM, a calorimeter probe, a transient probe and a sensor of tile material. Tests were carried out at two flow conditions with different specific enthalpies and for two model configurations. For stagnation point tests the model geometry was varied between a sphere of 100 mm diameter and flat faced cylinders of 50 mm and 100 mm in diameter with different edge radii. In addition to the stagnation point test configuration some flat plate tests were performed to extract the influence of extraneous radiation from the convective heating. Therefore the sensors were integrated in an insulation material to avoid any heat conduction to the water cooled flat plate model holder. Using the tile sensor heat flux rates were measured at surface temperatures up to 1500 K. The influence of the temperature and pressure dependency of the tile material properties on the heat flux rate is demonstrated. The data of the sensors confirm, that the extraneous radiation from the reservoir of high enthalpy facilities or hot surfaces of a re-entry vehicles has an influence on the measurement and has to be considered in the evaluation of measured data.

HIGH PRESSURE CALORIMETRY Comparison of two systems (differential vs. single cell) Application to the phase change of water under pressure

Abstract: In high pressure calorimetry the pressure change is used to obtain the desired phenomenon (i.e. phase change) at constant temperature. Two high pressure calorimeters have been developed to measure the latent heat of fusion of pure water (hexagonal ice-type I) at subzero temperature. Both calorimeters used a constant pressurisation rate produced with a high pressure pump driven by a step motor. The first calorimeter was a single cell calorimeter where mercury acted as the pressurisation fluid, while the second one was differential (two cells) and was pressurised with pentane. Both calorimeters gave high accuracy data of latent heat of fusion of pure water, which were determined taking into account that either the fluid used to pressurise or the pressurisation rate affected the calorimetric signal.

A thermal model of a flow calorimeter

Abstract: This work shows the difference between the results obtained in the electrical calibration and those corresponding to the chemical calibration in a TAM2277-204 flow-calorimeter by Thermometric. This difference is due to the fact that the mixture and the electrical dissipation do not occur in the same place. There are other additional aspects inherent to the mixture dissipation: the mixture does not take place instantaneously and extends in space. The physical model that has been calculated in this work explains the characteristics that are proper to a mixture dissipation and the effects of the injection in a qualitative and quantitative way.

A Novel Single-pan Scanning Calorimeter. Measurement of thermophysical properties of metallic alloys

Abstract: In this paper problems associated with a conventional heat-flux DSC are discussed. A single pan calorimeter has been designed and built which eliminates many of the errors that occur in a conventional DSC. It was found that: enthalpy changes and heat capacity were repeatable to better than 1%; the apparent latent heat and heat capacity did not depend on specimen size or significantly on rate of heating as often occurs in a two-pan heat-flux DSC; during the melting of pure Al, more than 80% of the latent heat was evolved over a temperature of 0.04 K; in alloys, separate heat capacity peaks for different reaction less than 1 K apart were resolved.

The Dose mapping system for the electromagnetic calorimeter of the BaBar experiment at SLAC

Abstract: An array of 116 p-channel radiation-sensitive MOSFET transistors (RadFETs) has been commissioned for the BaBar experiment at the PEP-II accelerator at the Stanford Linear Accelerator Center (SLAC). The aim of this system is to map the integrated dose absorbed by different regions of the calorimeter during the course of the experiment. This paper reports the design, characterization and installation of the sensors and briefly describes the readout system designed by co-workers. The response at low doses and the temperature coefficient for 130 RadFETs has been determined. At a “read” current of 160 μA an average shift in voltage of 51±4 mV was measured at an integrated dose of 30 rad with a temperature coefficient of 2.3±0.3 mV/°C. Calibration for high doses is also described. The system provides a novel method for real-time measurements of the spatial distribution of ionizing radiation dose within a large particle physics experiment.

Measurements of heat transfer to a massive cylindrical object engulfed in a regulatory pool fire

Abstract: A series of large-scale experiments were performed to measure heat transfer to a massive cylindrical calorimeter engulfed in a 30-minute circular-pool fire. The calorimeter inner surface temperature and the flame black body emissive power were measured at several locations as functions of time. An inverse conduction technique was used to determine the net heat flux to the calorimeter. Light winds of around 1 m/s tilted the fire so that the windward side of the calorimeter was only intermittently engulfed. As a result the flame temperatures on the windward side were substantially less than the leeward surface. The variation of calorimeter temperature and heat flux with time was closely correlated with the flame emissive power. The current data set is well suited for benchmarking computer codes that simulate heat transfer from large-scale fires to massive engulfed objects.

Thermodynamic Properties of Liquid n-Pentadecane

Abstract: This paper reports experimental results concerning the isobaric heat capacity Cp of Liquid n-pentadecane as a function of pressure (up to 100 MPa) and temperature (313.15 to 373.15 K). The measurements were performed with a modified C80 SETARAM calorimeter based on the Calvet principle. These calorimetric data, combined with density data, were used to evaluate derived thermophysical properties such as the isochoric heat capacity Cv , the isentropic compressibility ks and the speed of sound u in the same ranges of pressure and temperature. The pressure-temperature behaviour of these properties was then discussed as a model for simple organic liquids.

Thermodynamic properties of the MZr2(PO4)3 (M=Na, K, Rb or Cs) compounds

Abstract: The enthalpies of the solution of MZr2(PO4)3(M=Na, K, Rb or Cs) compounds have been measured by the help of a differential automatic isothermal Calvet calorimeter and the standard enthalpies of formation have been derived. The temperature dependencies of the standard heat capacity of the samples of crystalline NaZr2(PO4)3 and CsZr2(PO4)3 were studied between 7 and 340 K in an automatic adiabatic vacuum calorimeter. The main thermodynamic functions H0(T)–H0(0), S0(T) andG0(T)–H0(0) have been determined. The Gibbs energies of formation of the NaZr2(PO4)3and CsZr2(PO4)3 at 298.15 K were calculated on the basis of these experimental data and the enthalpy of formation data. Qualitative explanations for the results observed were presented.