Calorimeter

About: Calorimeter is a research topic. Over the lifetime, 5878 publications have been published within this topic receiving 77157 citations.

Differential AC-chip calorimeter for glass transition measurements in ultra thin polymeric films

Abstract: A differential AC-chip calorimeter capable to measure the glass transition in nanometer thin films is described. Due to the differential setup pJ/K sensitivity is achieved. Heat capacity can be measured for sample masses below one nanogram even above room temperature as needed for the study of the glass transition in nanometer thin polymeric films. The calorimeter allows for the frequency dependent measurement of complex heat capacity in the frequency range from 1 Hz to 1 kHz. The glass transition in thin films of polystyrene (PS) (100–4 nm) and polymethylmethacrylate (PMMA) (400–10 nm) was determined at well defined experimental time scales. No thickness dependency of the glass transition temperature was observed within the error limits (±3 K) - neither at constant frequency nor for the traces in the activation diagrams (1 Hz–1 kHz).

A Heat-Loss-Compensated Calorimeter: Theory, Design, and Performance.

Abstract: A new type of 3-body calorimeter for measuring absorbed dose produced by ionizing radiation is described in detail. All three bodies rise in temperature during irradiation, and the heat absorbed by the central core is measured by standard means. Only the central core is heated during electrical calibration, but the increased heat losses are compensated by measuring most of the heat lost to the surrounding jacket and automatically adding it to the heat retained by the core. The third body is a massive, thermally-floating shield, whose presence reduces the heat losses during irradiation, with a consequent increase in sensitivity and stability. A mathematical description of the calorimeter behavior is presented, along with a discussion of control and operation technique. In particular, it is shown how this 3-body calorimeter can be calibrated as a 1-body calorimeter, with large heat losses, or as a 2-body calorimeter, in the quasi-adiabatic mode. This calorimeter design decreases the effects of thermal gradients and at the same time provides the means to test for these effects. The results of these tests show that for this particular model, systematic errors caused by thermal gradients, during electrical measurements, are no larger than 0.1 percent. Errors in comparing an electrical run with an irradiation may be somewhat larger because of different temperature gradients within the system. It is also pointed out that the general design of this calorimeter is not restricted to measuring absorbed dose but can be applied to calorimetry in general.

Measurement of thermophysical properties of molten salts: Mixtures of alkaline carbonate salts

Abstract: The purpose of this study is to develop measuring methods for the thermal diffusivity, the specific heat capacity, and the density of molten salts, as well as to measure these properties of mixtures of alkaline carbonate salts. The thermal diffusivity is measured by the stepwise heating method. The sample salt is poured into a thin container, and as a result, a three-layered cell is formed. The thermal diffusivity is obtained from the ratio of temperature rises at different times measured at the rear surface of the cell when the front surface is heated by the stepwise energy from an iodine lamp. The specific heat capacity is measured using an adiabatic scanning calorimeter. The density is measured by Archimedes' principle. Thermal conductivity is determined from the above properties. Measured samples are Li2CO3-K2CO3 (42.7–57.3, 50.0-50.0, and 62.0-38.0 mol%).

Pico calorimeter for detection of heat produced in an individual brown fat cell

Abstract: A pico calorimeter with a highly sensitive sensor for detecting heat from a biological cell is developed and evaluated, and also the heat detection of a single brown fat cell has been demonstrated. The measurement principle relies on resonant frequency tracking of a resonator in temperature variation due to the heat from the sample; the resonator is placed in vacuum, and heat is conducted from the sample in the microfluidic channel via a heat guide. This configuration can prevent heat loss from the resonator to the surroundings and damping in water. The heat resolution of the fabricated sensor is 5.2 pJ. Heat emissions from single cells are detected as pulsed or continuous in the absence and presence of stimulation, respectively.

A numerical model and associated calorimeter for predicting temperature profiles in mass concrete

Abstract: This paper describes the development and operation of a finite difference heat model for predicting the time-based temperature profiles in mass concrete elements. The model represents a two-dimensional solution to the Fourier heat flow equation and runs on a commercially available spreadsheet package. An important problem facing heat modelling of concrete is that the rate of heat evolution at any point in the concrete element depends on concrete mixture parameters, time and position within the element. The present model resolves much of this complexity by using, as input, the results of a heat rate determination using a low-cost adiabatic calorimeter together with the Arrhenius maturity function to indicate the rate and extent of hydration at any time and position within the structure, based on the time–temperature history at that point. The paper presents a discussion of the structure of the finite difference model and its application to spreadsheet architecture. A brief description of the calorimeter is also presented together with the results of a verification exercise that was carried out to assess the accuracy of the model using a block of concrete instrumented with thermal probes. The results show that the model is able to predict the temperature at any point in the concrete block to within 2 °C of the measured values.