Showing papers on "Calorimeter published in 1979"
TL;DR: Current procedures for calibrating subjects may lead to large errors which could be reduced by using a respiratory chamber, particularly during the night when the mean (±SD) difference between the actual and predicted HP was −66±38±6%.
Abstract: 1. The heart-rate (HR) method for determining the energy expenditure of free-living subjects has been evaluated using a whole-body calorimeter in which individuals lived continuously for 27 h while carrying out normal daily activities. Eight male volunteers each occupied the calorimeter on at least two occasions when HR and energy expenditure were measured continuously. 2. After each session in the calorimeter a calibration was obtained using standard techniques by determining HR and heat production (HP) over periods of 10-15 min at several levels of activity. Energy expenditure in the calorimeter was then predicted, by each of five methods, from the mean HR in the calorimeter. Additionally, one session in the calorimeter was used to obtain a calibration and was used for predicting the subject's energy expenditure while in the calorimeter on other occasions. 3. Standard methods of prediction using one calibration point at rest and several points during activity were unreliable for predicting the energy expenditure of an individual. The 24 h HR was at the lower end of the calibration scale and there were considerable over-estimates or underestimates of energy expenditure, particularly during the night when the mean (+/- SD) difference between the actual and predicted HP was -66 +/- 38.6%. A linear regression fitted to points at the lower levels of activity improved the prediction of 24 h HP while a logistic plot reduced the error even further. The best estimate of energy expenditure was that obtained from a calibration over 24 h within the calorimeter; the mean (+/- SD) difference between the actual and predicted 24 h HP was +3 +/- 10.5% for light activity and -3 +/- 6.7% for moderate activity. Thus current procedures for calibrating subjects may lead to large errors which could be reduced by using a respiratory chamber.
102 citations
TL;DR: The thermal relaxation method is used to measure heat capacities of small samples in the temperature range around room temperature by using a calorimeter to measure under heat exchange gas.
Abstract: The thermal relaxation method is used to measure heat capacities of small samples in the temperature range around room temperature. The calorimeter is designed to measure under heat exchange gas and a steplike excess heat is applied to the sample by irradiation from a lamp.
60 citations
TL;DR: This chapter discusses the design of specific types of calorimetric experiments, including the isoperibol and isothermal calorimeters, which consist of mixing two solutions that contain reactive components.
Abstract: Publisher Summary This chapter discusses the design of specific types of calorimetric experiments The basic calorimetric experiment consists of mixing two solutions that contain reactive components The success of a calorimetric experiment depends upon a number of factors, but perhaps the most commonly ignored is the achievement of thermal equilibrium of the solutions prior to mixing It is important to realize that during the calorimetric experiment temperature changes on the order of l0 –4 degree or less are being measured In the batch-type calorimeter, the loading of the solutions into the reaction vessels requires that the calorimetric heat sink and air bath be exposed to the environment, thus disturbing the existing equilibrium among the cells, heat sink, and bath The time required to achieve satisfactory thermal equilibrium after the calorimeter is loaded depends upon the magnitude of the heat effect being measured In the flow calorimeter, thermal equilibrium between the solutions and the calorimeter heat sink is achieved by flowing the solution through one or more heat exchangers that are in equilibrium with the heat sink In the isoperibol and isothermal calorimeters, the solutions are equilibrated within the calorimeter prior to mixing
53 citations
TL;DR: In this paper, the formation enthalpies of solid alloys in the Fe, Co, Ni, and Ni binary systems have been determined with the aid of a solution calorimeter using liquid tin as solvent.
52 citations
TL;DR: In this article, a new procedure was developed to determine the specific heat of food products by using a calorimeter which was prepared through the proper modification of a household vacuum jar.
Abstract: A new procedure was developed to determine the specific heat of food products by using a calorimeter which was prepared through the proper modification of a household vacuum jar. Since there was no direct contact between food and heat exchange medium in the calorimeter, the evaluation of heat of solution for dissolvable chemical entities in the food was eliminated and also this new method is readily applicable to food whose temperature is higher than 100°C. The reproducibility and reliability of the developed procedure were carefully examined by using several materials whose specific heat values were well documented. This procedure was utilized to determine specific heat values of four cookies, wheat flour and one fresh produce. The agreement between the experimental and literature values was found to be excellent. The standard deviations of replicated experiments were less than 2%.
50 citations
TL;DR: The suitability of the SETARAM high temperature calorimeter for the determination of mixing enthalpies of liquid metallic alloy systems has been investigated in this article, where several methods of calibration were investigated as well as the dependence of the calibration factor on total mass in the crucible and volume of a crucible occupied.
49 citations
Patent•
17 Oct 1979
TL;DR: In this article, a differential scanning calorimeter based on the heat leak principle has been proposed, with a reference measuring cell and a sample measuring cell symetrically seated within a copper heat sink, where a plurality of resistive heating elements are applied to the several surfaces of the heat sink and the isothermal shield, each heating element having a resistance proportional to the heat capacity of the surface to which it is applied.
Abstract: A differential scanning calorimeter based on the heat leak principle having a reference measuring cell and a sample measuring cell symetrically seated within a copper heat sink. Each measuring cell (10) includes a cylindrical stainless steel ampoule (12) which contains a test substance, a honeycombed aluminum cell frame (14) which supports the ampoule, and a pair of thermopiles (18) which are placed between the aluminum cell frame and the copper heat sink (16) and which measure the temperature difference between the two. The copper heat sink is surrounded by a cylindrical copper isothermal shield (20). A plurality of resistive heating elements (146-150) are applied to the several surfaces of the heat sink and the isothermal shield, each heating element having a resistance proportional to the heat capacity of the surface to which it is applied. The heating elements are wired electrically in series. A common current is then passed through the heating elements. Note The International Application refers to drawings which in fact, were not included in the application at the time of filing. Drawings were submitted after the expiration of the time limit prescribed in Rule 20.2 (a) (iii), accordingly, and reference to the said drawings shall be considered non existent under Article 14 (2).
45 citations
TL;DR: The continuous adiabatic method described in this article yields a graphical representation of the inverse specific heat as a function of temperature, and the principal advantages are simple construction high-level electrical signals, small samples (about 1 g), good behaviour through first-order transitions, low additional masses, low cost and complete automation.
Abstract: The continuous adiabatic method described yields a graphical representation of the inverse specific heat as a function of temperature. The principal advantages are: simple construction high-level electrical signals, small samples (about 1 g), good behaviour through first-order transitions, low additional masses, low cost and complete automation.
39 citations
TL;DR: This chapter provides an overview for establishing the need for a calorimeter, determining which instrument is best suited to the problem, and setting up a Calorimetry laboratory that can operate in the manner necessary to answer thermodynamic and other questions.
Abstract: Publisher Summary This chapter provides an overview for (1) establishing the need for a calorimeter, (2) determining which instrument is best suited to the problem, and (3) setting up a calorimetry laboratory that can operate in the manner necessary to answer thermodynamic and other questions. A calorimeter can measure the quantity of heat associated with a particular process in two distinct ways. The first of these is to measure the temperature rise associated with the heat production. The second method involves the determination of the rate of heat flow resulting from a heat effect. There are two basic procedures to measure this heat flow. The first involves the active use of a Peltier heating-cooling device that is controlled by a feedback system. The second procedure is to use a Peltier device, or other type of differential temperature sensor, in a passive mode. There exist three fundamental types of microcalorimeters. These three types have been designated as batch, flow, and titration calorimeters. The batch calorimeter produces a signal such that the total area under the thermogram is proportional to the heat of the reaction. A flow calorimeter produces a signal that is proportional to the rate of heat production by the reaction. A titration calorimeter is loaded in a manner similar to a batch device with a single concentration of each reagent, but, because addition of the titrant is slow and continuous, the resulting signal is a heat flux.
38 citations
TL;DR: In this article, heat capacities of solutions up to 3 mol kg −1 have been determined with one LKB reaction solution calorimeter and two Picker flow calorimeters.
36 citations
TL;DR: In this paper, a flow calorimeter and a flow densimeter were used for measurements leading to apparent molar heat capacities and apparent volumes of dilute aqueous solutions.
TL;DR: In this article, the heat flow through a silt loam, silty clay, and loamy sand were measured in a calorimeter at 7 and 36°C under matrix potential near -0.3 bars.
Abstract: The heat flow through a silt loam, silty clay, and loamy
sand were measured in a calorimeter at 7 and 36°C under matrix
potentials near -0.3 bars. The transient thermal conductivity
probe, the heat flux transducer, and deVries's theoretical method
all gave low values of the apparent thermal conductivity at
36°C. An empirical correction was proposed for deVries's
method that improved its agreement with the observed conductivities.
The thermal vapor diffusion coefficients for the
three soils were then calculated from his equation and compared
with experimental values from the calorimeter. It was
also shown that the thermal water vapor flow can be estimated
if one knows the soil's saturated thermal conductivity, quart/
content, water content, bulk density and temperature distribution.
TL;DR: The average activation enthalpy of the relaxational process was determined to be (26±5) kJ mol−1 as discussed by the authors, and the residual entropies of the crystal were recalculated on the basis of the present heat-capacity data combined with the revised values for enthalphy of vapourization, saturated vapour pressure, and spectroscopic entropy.
Abstract: The heat capacities of quenched and annealed heavy ice Ih were measured in the temperature range 14 to 300 K by an adiabatic calorimeter. A relaxational thermal anomaly was found at around 115K and this phenomenon was ascribed to the onset of deuteron ordering in the crystal. The average activation enthalpy of the relaxational process was determined to be (26±5) kJ mol–1. Residual entropies of the crystal were recalculated on the basis of the present heat-capacity data combined with the revised values for enthalpy of vapourization, saturated vapour pressure, and spectroscopic entropy. They are (3.47±0.41) J K–1 mol–1 for the quenched crystal and (3.44±0.41) J K–1 mol–1 for the crystal annealed at 102–106 K for 264 h. The characteristics and the origin of the anomaly are discussed in comparison with that of ordinary ice.
TL;DR: A new type of whole-body calorimeter was constructed for measuring human energy expenditure in the form of dry heat and evaporative heat and energy output could be measured over 24-hr periods with a mean error of −0.5% and a standard deviation of ± 1.7%.
Abstract: A new type of whole-body calorimeter was constructed for measuring human energy expenditure in the form of dry heat and evaporative heat. Fresh air at a predetermined temperature flows at a constant rate through the measurement chamber, where its energy content is raised to a predetermined level by the heat given off by the subject through convection, radiation, and evaporation, plus a thermostatically controlled compensatory heater. Thus, a constant temperature is maintained. Heat gradients through conduction are avoided by a special shell construction in which used air flows through an exhaust layer surrounding the measurement chamber, which is in turn surrounded by an independently temperature-controlled isolating air layer. Measurement cells register air temperature and humidity at entrance and exit. The dry, evaporative, and total heat output can thus be calculated from the difference between entrance and exit, the amount of air flown through, and the amount of energy produced by the compensatory heater. The system allows measurements for periods over several days for a range of energy expenditure from 20 to 300 W, within a temperature range from 15° to 40° C and humidity from 10% to 90%. Response time was less than 15 min. In a number of calibration trials, in which both dry and evaporative human heat output were simulated, energy output could be measured over 24-hr periods with a mean error of −0.5% and a standard deviation of ± 1.7%;
TL;DR: In this paper, the fluorescent-converter technique was applied to the design and construction of a segmented calorimeter, and detailed measurements were reported on various materials of possible use.
TL;DR: In this paper, a lead-scintillator shower counter using a flourescent radiation converter for collecting scintillation light is described, and the uniformity of energy response and the spatial resolution have been measured.
TL;DR: In this paper, a flow calorimeter and a flow densimeter were used for measurements at 25 °C of heat capacities and densities of aqueous solutions of four electrolytes of high charge type: LaCl3, Cr(NO3)3, K3Fe.
Abstract: We have used a flow calorimeter and a flow densimeter for measurements at 25 °C of heat capacities and densities of aqueous solutions of four electrolytes of high charge type: LaCl3, Cr(NO3)3, K3Fe...
TL;DR: The compact, heat conduction, flow calorimeter, designed and constructed, was used to monitor changes in the steady-state heat production of 250-mg samples of corn coleoptile tissue in response to the plant growth substance, indoleacetic acid.
TL;DR: In this paper, a twin enthalpy of vaporization calorimeter of the adiabatic isothermal type has been designed, built and tested by measuring the enthalpies of vaporisation of n-tridecane, n-tetradecane and n-pentadecANE.
Abstract: A twin enthalpy of vaporization calorimeter of the adiabatic isothermal type has been designed, built and tested. The substance, 5–20 mg, enclosed in ampoules, is completely vaporized into a vacuum through a small aperture. The vaporization is performed isothermally at preselected temperatures which may vary between room temperature and 420 K. The calorimeter has been tested by measuring the enthalpies of vaporization of n-tridecane, n-tetradecane and n-pentadecane.
TL;DR: In this paper, a direct heating pulse calorimeter was designed and constructed for measuring the heat capacity of semiconducting materials at high temperatures, where an adiabatic shield was used to enclose the sample.
Abstract: A direct heating pulse calorimeter was designed and constructed for measuring the heat capacity of semiconducting materials at high temperatures. Heat leak from the sample to the surroundings due to the increasing radiation at high temperatures was reduced by providing an adiabatic shield to enclose the sample. The error of the method has been analysed, and the condition for measurement of the heat capacity with a limited inaccuracy is discussed. It is shown that a sample with electrical conductivity in the range from 10-1 to 106 Omega -1 m-1 can be measured with an imprecision of less than 0.5% at 1000K.
TL;DR: In this article, a computer-controlled ac calorimeter has been constructed which enables us to determine the absolute value of the specific heat within an accuracy of 2% over a wide range of temperature.
Abstract: A computer-controlled ac calorimeter has been constructed which enables us to determine the absolute value of the specific heat within an accuracy of 2% over a wide range of temperature. The ways in which the calorimeter has been improved are discussed.
TL;DR: In this article, an isoperibolic calorimeter for determining the enthalpies of solution of salts was constructed and an isopibolic approach was used to calculate enthalps of lanthanum ions in water.
TL;DR: A simple photometric calorimeter has been constructed, consisting of a vacuum-jacketed cell equipped with flat quartz windows to admit incident light, a thermistor probe to monitor temperature change, and a resistance heater for calibration.
Abstract: A simple photometric calorimeter has been constructed, consisting of a vacuum‐jacketed cell equipped with flat quartz windows to admit incident light, a thermistor probe to monitor temperature change, and a resistance heater for calibration. An optically dense, photochemically inert solution inside the cell absorbs incident radiation, converting it quantitatively into heat. The calorimeter gives photon flux measurements in agreement with ferrioxalate actinometry at 366 and 436 nm. It has a sensitivity of 2×1015 photons/s and is useful throughout the optical spectral range.
TL;DR: The Constant Heat-Flux Calorimeter as mentioned in this paper was designed for simultaneously measuring the heat of reaction and the heat transfer data in a reaction solution, which is similar to a differential scanning calorimeter in terms of direct calorimetric measurement of the energies of reaction, but differs from conventional calorimeters described in the literature.
Patent•
03 Mar 1979
TL;DR: In this paper, the problem of simultaneous transfer of heat from a fluid of finite extent to the ambient and to a solid of finite thermal conductivity is solved in the form of an infinite series with the Biot number, the thermal extent ratio H, the ambient loss parameter E and the ambient temperature Va as parameters; the series shows strong exponential decay so that a few terms suffice for most applications.
TL;DR: The results of the experimental investigation of the components of complex external heat exchange in a high-temperature fluidized bed, by means of a radiometer and twoα calorimeters with a different degree of surface blackness, are given in this paper.
Abstract: The results of the experimental investigation of the components of complex external heat exchange in a high-temperature fluidized bed, by means of a radiometer and twoα calorimeters with a different degree of surface blackness, are given.
01 May 1979
TL;DR: In this article, a new sensitive heat flow calorimeter combined with a hydrogen reactor was developed for metal-hydrogen reactions in the temperature and pressure ranges 243
Abstract: A new sensitive heat flow calorimeter combined with a hydrogen reactor was developed. Metal-hydrogen reactions can be investigated in the temperature and pressure ranges 243