I want the Specific Heat (Cp) Vs Temperature (T) variation of certain materials. Which DSC is accurate for this - heat flux (or) heat flow? What is the conceptual difference between the both?
Heat Flow is accurate. Which type of materials do you want to use.Please let me know.
Heat Flow and Heat Flux are 2 differents design of instruments and heat calculation.
I've used the 2 instruments (Perkin-Elmer DSC and Mettler Toledo DSC)
In the perkin elmer (Heat Flow) the sample and the reference are in 2 separate furnaces.
In the Mettler-Toledo (Heat Flux) the sample and the reference pan are in the same furnace.
Theoretically heat flux DSC are less sensitive to small transitions but I had a more stable baseline.
Nevertheless the power compensation system (Perkin Elmer) was faster to cool and heat the samples.
Heat flow is Q=m Cp Delta T/t
Heat flux is related to Area too.
I think the answer is Heat flow not heat flux
See
http://www.perkinelmer.com/CMSResources/Images/44-74542GDE_DSCBeginnersGuide.pdf
Because of the direct measurement of heat flow, the heat flow DSC allows for very precise control of temperature, very accurate enthalpy and heat capacity measurements, and true isothermal performance.
If by "Heat Flow" DSC you are referring to a Power Compensation DSC (as opposed to the alternative Heat Flux design), then the main difference simply lies in the construction and prinicple of measurement (independent variable). In a power compensation DSC, the temperature difference between the sample and reference is maintained constant as the sample is scanned. The resulting power difference is proportional to heat flow. In a heat flux design, the temperature difference is allowed to vary, and the signal is converted to heat flow through the equation q = DT/R where R= the well defined thermal resistance of the transducer. The results from both instruments are quantitative, and virtually identical until you look at subtle differences. A power compensation instrument can generally heat or cool faster, and provide better resolution for sharp events, but the signal is inherently less stable as it is comprised of the very small difference between two very large numbers. As a result, the baseline is less flat and stable, and the short-term noise is higher. A heat flux instrument cannot achieve the rapid scan rates of a power compensation design, generally less than 200°C/min. However, the baseline is usually straighter and more repeatable, providing higher sensitivity for subtle events. More instruments used these days are of the heat flux design, as it is generally considered an industry standard and less "finicky".
Regarding Cp accuracy, both instruments can provide this result through a variety of techniques including the ASTM (Three-Run) method, Modulated Temperature DSC, or in the case of Tzero instruments, Direct Cp. As the classical Three-Run method relies on a repeatable baseline, the heat flux instrument would likely give a more precise and accurate result. Cp from MT-DSC experiments should be equivalent for both types.
Differences between various types of calorimeters can be and are stated in a much more precise definitions than the use of synonyms such as "flux" or "flow".
I do not know the actual reason of your question, so I will simply suggest not to get lost in useless discussion and remain focused on your real problem.
There should be no difference between heat "flux"and "flow" the term flow is correct one.The name of other type DSC is Power Compensation
Heat flux and heat flow DSC are the same. In principle, there exist two types of DSC's: (i) heat flux; (ii) power-compensated.
As for heat flux DSC, there is a single furnace. The primary signal measured is the temperature difference between the sample and the reference. If a heat-consuming process takes place in the sample, its temperature is lower than the reference temperature. Heat flow is then calculated from the temperature difference.
Considering power-compensated DSC, there are two independent micro-furnaces. The temperature of the sample and reference are kept at the same value via independent heating. If a heat-consuming process takes place in the sample, the sample furnace increase the heating power to keep the temperature program. The primary signal measured in this type of apparatus is energy (heat).
The heat flux through a homogeneous wall without phase transitions is constant.
the heat flow through a homogeneous wall with phase transitions exhibits a short-term change in the constant heat flux.
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