Search Results
Abstract
A new-design conduction microcalorimeter is described, which has been used to measure the heat of cement hydration evolved in the initial period of hydration. The calorimeter is 30 cm3 in volume; the heat loss coefficient is 27.2700.015 W V–1, the time constant is 300 s.
Abstract
After the development of differential conduction calorimeters realized by E. Calvet around 1946, the standard equipment always used a differential configuration. In home made systems for special purposes, the instrumentation available nowadays suggests that it is possible to use non-differential conduction calorimeters. In order to prove this, a simple and cheap design was constructed and tested. A sensitivity of 700 mV/W near 298 K (in agreement with the detecting semiconductors), a noise around 0.3 W and a long time fluctuation of the base line lower than 1 W were obtained. The reliability of the system was evaluated by analyzing the changes of single crystals of Cu-Zn-Al Shape Memory Alloys after different thermal treatments. The calorimeter allowed the determination of a reproducible set of time constants related to the heat treatments and to the mass (or shape) of the sample. It is concluded that the experimental configuration used is suitable for this isothermal analysis.
Abstract
The experimental analysis of conventional conduction calorimeters shows excellent reproducibility and relevant systematic errors in comparison with thermodynamic values established via adiabatic calorimeters. Two examples: a DSC and a liquid flow device are schematically analyzed. When an increased accuracy will be obtained the positional effects on the experimental set-up and on the measurement process need to be modelled. From experimental measurements realized on the Xensor liquid nano-calorimeter representative models can be built. To evaluate the reliability of measurement routines, established from experimental basis, several different dissipation structures inside the working space can be simulated. Two experimental configurations related to drop to drop reaction and to continuous mixing are modelled via RC approach. The RC formalism is extended to evaluate the carried energy effect produced by the continuous inflow/outflow of reactants in the mixing enthalpy chamber.
Introduction Isothermal (heat conduction) calorimeters measure thermal power (heat production rate), P (W), which is proportional to the rate of the process being studied: (1) In this article, Δ H (J mol −1 ) is the
Abstract
Composting technologies rely on standard methods for quality determination. The maturity of a compost is assayed by self-heating experiments in Dewar-vessels. The resulting maximum temperature is classified on a five-level scale. This study demonstrated systematic errors that might occur when assays are performed in Dewars of different size. The vessels were characterized as heat conduction calorimeters and the processes of biochemical decomposition and heat generation and autothermic effects (temperature) were evaluated quantitatively.
Abstract
This paper presents a novel data processing method for thermokinetics of faster first-order reaction on the basis of the double-parameter theoretical model of a conduction calorimeter, in which the rate constant of a first-order reaction can be calculated from only four peak height data from the same thermoanalytical curve without using any peak-area. The saponifications of ethyl acetate and methyl acetate in aqueous solution and ethyl benzoate in aqueous alcohol have been studied to test the validity of this method. The rate constants calculated with this method are in fair agreement with those in literature; hence the validity of this method is demonstrated.
