Reversing heat flow curve

The TMDSC plots in Figures 11 and 12 for Nitinol are complex with shallow peaks [36]. Because of the high-sensitivity setting on the vertical axis, the reversing heat flow curve is not a straight line. 

Figure 5. Reversing heat flow curves of PS/P(S-pSF46) (50-50wt%) aged for indicated times at 92 °C.

Figure 9.40 Total, reversing and non-reversing heat flow curves obtained during the heating of a non-annealed 65% w/w sucrose solution. Endothermic changes are in the negativedirection. 7, glass transition ER, enthalpic relaxation D, devitrification ID, ice dissolution. (Taken from [140, Copyright (2001), with kind permission of Springer Science and Business Media.)...

Cp X heating rate) is termed the reversing heat flow component. The non-reversing part is obtained by subtracting this value from the total heat flow curve. It is important to note that all... 

Figure 7. TMDSC reversing and nonreversing heat flow curves for the heating cycle of as-received Nitinol SE [37]. Reproduced with permission from Elsevier Science.

In Fig. 4.101 an abrupt 50% increase in curve C starts at 300 s. An effect on the reversing heat-flow rate occurs only at the time of increase, broadened and smoothed by triple averaging. The constant change does not affect the measurement at a later time. The baseline shifts due to fluctuations in purge-gas flow or changes in temperature of the calorimeter environment are thus minimized. 

The curve is elevated relative to zero by a constant amount (0.125) and has a contribution of 2o), double the modulation frequency (+, second harmonic). Both these contributions are not included in the experimental reversing heat flow which contains only the contribution to the first harmonic ( , see Sect. 4.4.3). Accepting the present analysis, it is possible to determine y and x from the reversing heat capacity by matching the last term of the equation in Figs. 6.118 and 4.131, and then use the paramters describing the match to compute (A), the actual response of the TMDSC to the quasi-isothermal temperature modulation. 

Figure 2.13. Quasi-isothermal cure of an unsaturated polyester at 30, 40, and 50°C (a) non-reversing heat flow (b) heat capacity and heat flow phase the heat flow phase curves were shifted vertically to avoid overlap. The symbols (o) denote the points at maximum auto-acceleration in the non-reversing heat flow.

Fig. 6.11. Temperature change in the total and reversing heat flow observed for the oriented PET annealed at Ta=125°C. The curve (a) corresponds to that of the reversing heat flow (RHF) and the curve (b) does to that of the total heat flow (THE).

Figure 2.100. DSC curves of glass transition of polystyrene on cooling. As with the heating ramp, the glass transition for the reversing heat flow is higher than that on the total heat flow. Underlying cooling rate is 2°C/min, modulation ampUtude 0.21 °C, modulation period 40 s. (Judovits, unpublished results.)...

A simplified version of the model in Table IX, neglecting accumulation of mass and heat as well as dispersion and conduction in the gas phase, predicts dynamic performance of a laboratory S02 converter operating under periodic reversal of flow direction quite well. This is shown by Fig. 13 taken from Wu et al. (1996). Data show the temperature profiles in a 2-m bed of the Chinese S101 catalyst once a stationary cycling state is attained. One set of curves shows the temperature distribution just after switching direction and the second shows the distribution after a further 60 min. Simulated and experimental profiles are close. The surprising result is that the experimental maximum temperatures equal or exceed the simu-... 

Example 2. What is the heat flow for an ideal gas undergoing an expansion by each of the three reversible paths shown in Fig. 2 States i and f are at the same temperature and the curved path is the isotherm between these states. 

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