Calorimeter scanning, twin

In the CSM laboratory, Rueff et al. (1988) used a Perkin-Elmer differential scanning calorimeter (DSC-2), with sample containers modified for high pressure, to obtain methane hydrate heat capacity (245-259 K) and heat of dissociation (285 K), which were accurate to within 20%. Rueff (1985) was able to analyze his data to account for the portion of the sample that was ice, in an extension of work done earlier (Rueff and Sloan, 1985) to measure the thermal properties of hydrates in sediments. At Rice University, Lievois (1987) developed a twin-cell heat flux calorimeter and made AH measurements at 278.15 and 283.15 K to within 2.6%. More recently, at CSM a method was developed using the Setaram high pressure (heat-flux) micro-DSC VII (Gupta, 2007) to determine the heat capacity and heats of dissociation of methane hydrate at 277-283 K and at pressures of 5-20 MPa to within 2%. See Section 6.3.2 for gas hydrate heat capacity and heats of dissociation data. Figure 6.6 shows a schematic of the heat flux DSC system. In heat flux DSC, the heat flow necessary to achieve a zero temperature difference between the reference and sample cells is measured through the thermocouples linked to each of the cells. For more details on the principles of calorimetry the reader is referred to Hohne et al. (2003) and Brown (1998). 

Adiabatic Twin Differential Scanning Calorimetry Privalov s calorimeter... 

The construction may have a single measuring system, or a twin or differential measuring system. Simple solution calorimeters have a single cell, while a DSC has twin cells and operates in the scanning mode. The use of twin cells reduces the effects of internal and external noise and transient fluctuations. 

To better assess heat losses, twin calorimeters have been developed that permit measurement in a differential mode. A continuous, usually linear, temperature change of calorimeter or surroundings is used in the scanning mode. The calorimetry, described in Sect. 4.3 is scanning, isoperibol twin-calorimetry, usually less precisely called differential scanning calorimetry (DSC). 

The sample and reference thermometers and heaters are platinum resistance thermometers (see Sect. 4.1). Instead of relying on heat conduction from a single furnace, governed by temperature difference, reference and sample are heated separately as required by their temperature and the temperature difference between the two furnaces. The two calorimeters are each less than one centimeter in diameter and are mounted in a constant temperature block. This instrument is, thus, a scanning, isoperibol twin-calorimeter (see Sect. 4.2). 

Scanning calorimeters, either adiabatic or isoperibol, single or twin design, allow the determination of the heat capacity of the sample as a function of temperature. Consequently, these instruments can be used to determine the temperature of a phase transition. The same holds for calorimeters, with which the temperature of the sample is not increased continuously but stepwise. 

Mathot, V, Pyda, M., Pijpers, T., Vanden Poel, G., van de Kerkhof, E., van Herwaarden, S., van Herwaarden, F., and Leenaers, A. (2011) The Flash DSC 1, a power compensation twin-type, chip-based fast scanning calorimeter (FSC) first findings on polymers. Thermochim. Acta, 522, 36-45. 

Figure 1 Different types of differential scanning calorimeters, (a) Three-dimensional cylindrical calorimeter (Tian-Calvet). (b) Three-dimensional calorimeter with power compensation, (c) Two-dimensional plate-like calorimeter, (d) Scheme of a twin-chip sensor (Mettler Toledo Flash 1 DSC ) for fast scanning calorimetry.

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