Showing papers on "Calorimeter published in 1983"
TL;DR: In this article, an adiabatic scanning calorimeter has been used in a calorimetric investigation of alkyl-cyanobiphenyl (nCB) liquid crystals.
Abstract: An adiabatic scanning calorimeter has been used in a calorimetric investigation of alkyl-cyanobiphenyl (nCB) liquid crystals. Measurements near solid to smectic (KA), smectic A to nematic (AN) and nematic to isotropic (NI) or smectic A to isotropic (AI) phase transitions have been carried out for scanning rates as low as a few μKs−1. Results for the temperature dependence of the heat capacity as well as for the enthalpy (including latent heats) have been obtained for 8CB, 9CB, 10CB and 11CB. Latent heat values are reported for the different KA, NI and AI transitions. For the two compounds 8CB and 9CB, which show a AN transition, it was found that, within the resolution of the experiments, these transitions are second-order. The anomalous heat capacity observed near the AN transition is much larger for 9CB than for 8CB. The critical exponent α obtained from power law fits to the heat capacity data is 0.31 ± 0.03 for 8CB and 0.50 ± 0.05 for 9CB. It is suggested that the AN transition in 9CB must be...
70 citations
TL;DR: Regional and total body heat loss rates of human subjects at rest were measured simultaneously by means of an array of heat flux transducers and with a tube suit calorimeter.
Abstract: Regional and total body heat loss rates of human subjects at rest were measured simultaneously by means of an array of heat flux transducers and with a tube suit calorimeter. Conditions ranged from thermal comfort to strong cooling. A high degree of correlation was found between heat loss rates determined by the two independent techniques. For the head and arms, the transducer array system measured less heat loss than the suit. For the torso and legs, measurements by the two methods were equivalent. For the whole body, the transducer system yielded a heat loss rate 87% of the suit calorimeter value.
64 citations
TL;DR: In this article, a new instrument, termed a furniture calorimeter, has been constructed and placed into operation for measuring furniture heat release rates based on oxygen consumption, which has been obtained on a series of 13 chairs, loveseats and sofas, most of them specially built to permit direct comparisons of construction features.
Abstract: A new instrument, termed a furniture calorimeter, has been constructed and placed into operation for measuring furniture heat release rates based on oxygen consumption. Using the furniture calorimeter, burning rate information has been obtained on a series of 13 chairs, loveseats, and sofas, most of them specially built to permit direct comparisons of construction features. A quantitative assessment is made of the effect of fabric types, padding types (cotton batting, ordinary polyurethane foam, and California-requirements foam), and frame types. The advantages of furniture calorimeter testing over normal room fire testing are discussed. Based on these measurements, a rule is presented for estimating the heat release rate based on design factors. Finally, implications for achieving both good flame resistance and good cigarette ignition resistance are discussed.
44 citations
TL;DR: In this article, a flow mixing calorimeter was used to make measurements of the excess enthalpy of (water + nitrogen) at temperatures up to 698.2 K and pressures up to 12.6 MPa.
44 citations
TL;DR: The heat capacity of a sample of zone-refined, high-purity pterphenyl has been determined from 4 to 370 K in a fully automated high-resolution vacuum adiabatic calorimeter and from 320 to 580 K in differential scanning calorimeters.
Abstract: The heat capacity of a sample of zone‐refined, high‐purity p‐terphenyl has been determined from 4 to 370 K in a fully automated high‐resolution vacuum adiabatic calorimeter and from 320 to 580 K in a differential scanning calorimeter. The melting point of p‐terphenyl is 487.0 K and the enthalpy of fusion is 35.3 kJ/mol. A λ‐type solid–solid transition occurs with a peak temperature of 193.55 K. The transition is highly reproducible without observable hysteresis, even after various thermal treatments. In the transition region which spans from 140 to 240 K, the sample reaches a state of thermal equilibrium within a period of one‐half to one hour, as normally required in adiabatic calorimetry. These characteristics are desirable for the application of the equilibrium λ transitions as a calibration standard for use in dynamic calorimetry. The behavior of the λ transition at equilibrium is mapped in high temperature resolution, with small temperature increments of measurement down to 0.01 K by adiabatic calori...
42 citations
TL;DR: A technical description, constructional details and performance characteristics are presented for a whole-body calorimeter, which with the equipment metabolic heat production, sensible (radiative and convective) and insensible heat exchange of a subject during rest and exercise can be monitored continuously.
Abstract: A technical description, constructional details and performance characteristics are presented for a whole-body calorimeter. With the equipment metabolic heat production (oxygen consumption), sensible (radiative and convective) and insensible heat exchange (water vapour loss) of a subject during rest and exercise can be monitored continuously. The basic principle of the construction is to prevent any heat transfer across the wall of a well ventilated cylinder, so that all heat exchange by the subject can be measured by differential thermometry and hygrometry between inlet air and outlet air. The air flow through the calorimeter itself is more than 12·5 m3 min−1, which makes its response to changes in heat dissipation of the subject fast. The time constant for evaporative water loss is 1·5 min. There are two time constants for sensible heat exchange: 0·86 min and 7·4 min. The calorimeter inlet air temperature is controlled to within 0·03°C and dewpoint temperature to within 0·15°C. Changes in sensible heat exchange can be measured with an accuracy of 1 W. Changes in water vapour loss can be detected within 100 mg min−1; consequently, changes in insensible heat exchange can be assessed to about 4W. There is no heat loss through the wall of the calorimeter, even at a temperature difference between calorimeter temperature and laboratory temperature close to 30°C, and the calibrations are correct. This has been verified by measuring water vapour losses from a water tray at various calorimeter temperatures and the heat required for this evaporation. The latter can be measured as sensible heat exchange. The quotient of the two gives the heat of vaporisation of water, which can be compared favourably with the values from steam tables. Particular emphasis has been given to the subject's safety and comfort.
42 citations
TL;DR: In this article, an approximate correction for the smearing in a differential heat flux calorimeter is presented. But the correction is based on a simple equivalent circuit diagram, which eliminates the greatest part of the distortion.
31 citations
TL;DR: In this paper, the uncertainty of the calibration factor for heat-flux-calorimeters due to variation of sample parameters is estimated to be 1 to 5 percent depending on temperature and on the properties of the calorimeter in question.
30 citations
TL;DR: The heat capacity of pure plutonium metal has been determined from 330 to 700 K by adiabatic calorimetry as mentioned in this paper, including measurements on the α-, β-, γ-, and δ-phases.
30 citations
TL;DR: In this article, the heat capacity of aqueous suspensions of dipalmitoylphosphatidylcholine has been measured near the pretransition and main transition.
Abstract: By an ac calorimeter the heat capacity of aqueous suspensions of dipalmitoylphosphatidylcholine has been measured near the pretransition and main transition. The anomaly at the main transition exhibits a sharp divergence, i.e., the fluctuation at the transition is certainly dominant, although they undergo first-order transition. The pseudo-critical behavior is analyzed in terms of critical-exponent expressions: α and α' are 0.40±0.05 and 0.4±0.1, respectively. Using Pippard's relation, the dependence of the transition temperature on pressure is discussed, which is almost consistent with that of the direct experiments. The anomaly at the pretransition observed by a differential scanning calorimeter is extremely reduced in ac calorimetry. This is due to the frequency dispersion of the heat capacity, since the relaxation at this transition is very long.
28 citations
TL;DR: In this article, body heat storage changes of cattle were measured by means of simultaneous direct and indirect calorimetry and by thermometry in an environment that alternated in temperature between 12 and 25 °C.
Abstract: Body heat storage changes of cattle were measured by means of simultaneous direct and indirect calorimetry and by thermometry in an environment that alternated in temperature between 12 and 25 °C. When the calorimeter temperature was increased deep body temperature (Tc) increased by approximately 0–5 °C, mean surface temperature (Ts) by 3 °C and mean body temperature (determined from calorimetry, Tb) by 1 °C, but these increases were not fully sustained during the next 24 h. Changes in the three temperatures were related by the equation: δTb = αδTc+(1-α) δTs where a was found to be 0·89±0·027 (S.E.).
TL;DR: In this article, the mixing enthalpies of liquid Sb-Sn alloys were measured as a function of the concentration and of the temperature by means of a high-temperature calorimeter.
TL;DR: In this paper, the authors studied the energy resolution, hadron rejection and ability to distinguish overlapped events for a highly segmented electromagnetic calorimeter using unpolished extruded lead glass bars.
TL;DR: An infrared calorimeter system for measuring energy flux in a noisy electromagnetic environment has been developed in this paper, where a thin oxidized stainless steel foil is heated by energy flux and its temperature is determined by measuring the infrared emission from the back surface of the foil.
Abstract: An infrared calorimeter system for measuring energy flux in a noisy electromagnetic environment has been developed. A thin (13 μ) oxidized stainless‐steel foil is heated by energy flux and its temperature is determined by measuring the infrared emission from the back surface of the foil. The radiation is transported to the detector, which is located inside a double‐shielded enclosure, through a nylon‐tube infrared telescope. The calculated response time is 12 μs, and the measured peak‐to‐peak noise is equivalent to 0.4 mJ/cm2 deposited energy.
TL;DR: In this paper, the excess molar enthalpies HmE for {xCO2 + (1 − x)C2H6} were measured from 29315 to 32315 K at 758 MPa by means of an isothermal flow calorimeter.
TL;DR: A semi-micro rotating-bomb combustion calorimeter is described in this paper, which is designed on the model of the Bartlesville stirred-water system, but is built into a Parr 1243 adiabatic calorometer.
Patent•
25 Jul 1983TL;DR: A calorimeter for measuring the thermodynamic and kinetic characteristics of chemical reactions, microbial fermentations, and other processes of industrial importance is described in this article, where the present invention also relates to a method of operation of this apparatus.
Abstract: A calorimeter for measuring the thermodynamic and kinetic characteristics of chemical reactions, microbial fermentations, and other processes of industrial importance is described. The present invention also relates to a method of operation of this apparatus.
TL;DR: In this paper, the construction and performance of two segmented scintillator photon and hadron calorimeters (a ring and a downstream calorimeter) are described.
TL;DR: In this paper, a simple inexpensive microcomputer has been used to control an adiabatic pulse-type calorimeter and the data acquisition control system incorporates a Rockwell AIM65 microcomputer to control all aspects of the thermometry and the injection of the heat pulse into the sample.
Abstract: A simple inexpensive microcomputer has been used to control an adiabatic pulse-type calorimeter. The data acquisition control system incorporates a Rockwell AIM65 microcomputer to control all aspects of the thermometry and the injection of the heat pulse into the sample. Details of the hardware and software requirements are discussed, including the interface of the system with a host computer that uses the UNIX operating system. The performance of the apparatus was evaluated by measuring the heat capacity of 1965 Calorimetry Conference copper between 2 and 20 K. The results show a total r.m.s. deviation of less than 0·4 % and agree well with the copper reference equation (r.m.s. deviation 0·4 %). Measurements are also presented of the heat capacity of Invar (Nilo 36) and RbNiCI3 over the same temperature range. In the case of RbNiCh the heat capacity anomaly associated with the paramagnetic-anti ferromagnetic transition is observed at 11·1 K.
TL;DR: In this article, a method is described in which the ratio of the heat capacities of two samples is measured with an accuracy which approaches 1:104 between 20K and 200K, but which decreases to 1:103 at 15K and 300K.
Abstract: A method is described in which the ratio of the heat capacities of two samples is measured with an accuracy which approaches 1:104 between 20K and 200K, but which decreases to 1:103 at 15K and 300K The resolution of the system is very much higher than this, and may approach 1:106 over a limited temperature range The system is extremely simple to operate being the thermal analogue of a Wheatstone bridge, and measurements may be taken rapidly at closely spaced temperature intervals The construction of the calorimeter, which contains several new features, is also described
TL;DR: In this paper, the fundamental principles of pneumatic calorimetry are presented together with a detailed analysis of an experimental application, and performance, corrections and limitations are studied and discussed.
Abstract: The fundamental principles of pneumatic calorimetry are presented together with a detailed analysis of an experimental application. The apparatus belongs to a new class of instrument based on the reversible liberation of a quantity of heat following a pressure effect exercised on an ideal gas. This device allows the precise measurement of a quantity of heat +q by opposing a known antagonist effect -q determined from the pressure variation. A thermal feedback is realised, wherein the pressure is servocontrolled by a temperature signal. The system allows absolute determinations and is highly accurate and sensitive. Performance, corrections and limitations are studied and discussed.
TL;DR: In this article, a calorimeter was developed to study the heat conduction coefficient of multilayer insulations and optical properties of their shields and spacers, and experimental and theoretical analyses were carried out on radiation and contact components of heat transfer.
TL;DR: In this article, a vacuum adiabatic calorimeter for measurement of heat capacity was constructed, and has been successfully operated over the temperature range from 70 to 700 K. The accuracy was proved to be better than 0.2 per cent, which was comparable with that of the best calorimeters hitherto reported.
TL;DR: In this paper, the enthalpies of seven aliphatic ketones with an adiabatic isothermal calorimeter in the temperature range from 298 up to 368 K were determined.
TL;DR: In this article, a reactor-calorimeter is described which makes it possible to perform accurate measurements of the thermal power (rate of heat evolution) of chemical and physicochemical processes in essentially fluid reaction systems to be carried out continuously under isothermal conditions.
Abstract: A reactor-calorimeter is described which makes it possible to perform accurate measurements of the thermal power (rate of heat evolution) of chemical and physicochemical processes in essentially fluid reaction systems to be carried out a) continuously under isothermal conditions, b) without interfering with the course of the reaction, c) using large quantities of reaction mix, d) allowing for considerable variations in the consistency and/or the volume of the mix during reaction, e) providing for conditions which are very close to those of industrial practice. In addition, the equipment provides information on the heat transmittance of the reactor and the stirring power.
TL;DR: In this article, the authors describe how to obtain an analytic approximation to the transfer function of a conduction calorimeter, namely a procedure to identify the calorimetric system.
TL;DR: In this article, a pressure-scanning calorimeter (PSC) is described for the pressure range 0.1-35 MPa and temperatures up to 473K.
Abstract: A novel pressure-scanning calorimeter (PSC) is described for the pressure range 0.1-35 MPa and temperatures up to 473K. The calorimeter measures directly the thermal power and/or the energy as a continuous function of pressure. Thermal parameters are measured in a differential calorimeter by a power compensation method. The pressure variation is imposed as a linear function of time by a programming system with a feedback loop. The crystallisation and fusion of di-phenyl-ether induced by a linear pressure change are described as an example of application.
TL;DR: In this paper, enthalpy measurements for 2,6-dimethylpyridine and m-cresol were performed in a high-pressure high-temperature flow calorimeter and cover the pressure range 0.34 to 10.3 MPa and temperature range 314 to 669 K.
TL;DR: In this paper, a prototype electrostatic-calorimeter probe is presented to diagnose edge plasma and test it on the PDX and PLT tokamaks, and the probe provides time-resolved measurements of heat flux Q and Langmuir (I-V) characteristics on each of its opposing active elements.
Abstract: Power loading of the limiters in TFTR is a major concern because of problems of impurity generation and thermal stresses. To diagnose this edge plasma we have prepared a prototype electrostatic‐calorimeter probe and tested it on the PDX and PLT tokamaks. The probe provides time‐resolved measurements of heat flux Q and Langmuir (I–V) characteristics on each of its opposing active elements. The present design, employing carbon shields and tantalum elements, is able to withstand ≊5 kW/cm2 for ≊10 ms or 1 kW/cm2 for 500 ms and provides 5–10 ms time resolution of heat flux. This allows simultaneous estimation of time‐resolved radial profiles of ne, Te, and Ti. By fitting the probe with narrow slit apertures and rotating the probe head, the device provides discrimination between particles having different values of Larmor radius and/or ratios of perpendicular to parallel velocities. Calculations required to interpret the results of probe head rotation are also discussed. This information is of interest in the s...
TL;DR: In this article, the Tian equation is used to account for the effects of thermal disequilibrium in flow microcalorimetry, and a composite equation is presented for the correction of heat loss while deconvoluting electrical heat from a heat of reaction.