In addition to sweeping measurements during heating, DSC enables cooling in a wide range of cooling rates. Depending on the instrument and temperature range, cooling rates of up to 750 K min−1 can be achieved (HyperDSC™ PerkinElmer, USA).20,37–39 In general, however, the temperature range for controlled cooling with the highest speeds is limited. Measurements carried out in a wide range of heating or cooling rates require optimization of experimental conditions. The mass of the sample shall be scaled inversely with the sampling frequency. At low flow rates, when thermal delay is not an issue, the mass of the sample must be high to have a good signal-to-noise ratio. At high rates, when signals are large, the mass of the sample should be low to minimize heat flow to the sample, which is proportional to the rate and causes thermal retardation. Issues related to thermal retardation, temperature calibration and reproducibility in rapid scan NSC experiments have been thoroughly investigated and appropriate recommendations have been made.37,40,41 Figure 4 shows the cooling curves in the crystallization region of low-density polyethylene (PE). At speeds greater than 200 K min−1, controlled cooling to 100 °C was not possible due to the limited cooling capacity of the mechanical intercooler used. If higher cooling rates are required, liquid nitrogen should be used.

For the lower sampling rates in Figure 4, the sampling mass shall be large enough to provide a good signal-to-noise ratio. At higher rates, the large sample (4 mg) causes some thermal delay, as described in manuals and references 37, 40 and 42. It is also reflected in the widening of the crystallization peak to 20 K min−1 compared to the 0.4 mg sample at the same cooling rate. The data presented in Figure 4 provide information on crystallization kinetics and can be analyzed with various kinetic models.43–48 This becomes clear. Imagine splitting twice the mass of water into two bodies of water smaller than the original mass, and then heating both simultaneously with two immersion heaters. The two immersion heaters would therefore transfer twice as much heat in total. In the article Specific heat capacity of the selected substances, the specific heat capacity is explained in more detail with regard to the different behaviour of the substances during heating or cooling. Due to the complexity of this topic, other important notes on specific heat capacity are explained in more detail in the linked article. The specific heat capacity at constant volume and pressure of a uniform compressible system can be defined as [20, 21] respectively, for example, if a pot of water is kept boiling, the temperature remains at 100°C (212°F) until the last drop evaporates, because all the heat supplied to the liquid is absorbed as latent heat of vaporization and carried away by the escaping vapor molecules. Another influencing factor is the mass of the substance to be heated.

It can be assumed that the greater the mass to be heated, the more heat must be absorbed by the substance. This is also demonstrated by the daily experience of heating water on a griddle. Heating a large amount of water takes much longer than heating a smaller amount of water, that is, with large amounts of water, more heat must be transferred to achieve the same temperature change as with a small amount. Specific heat capacity is the amount of heat energy required to increase the temperature of a substance per unit mass. The specific heat capacity of a material is a physical property. It is also an example of an extended property, as its value is proportional to the size of the system being studied. Latent heat of vaporization is the amount of thermal energy that must be added to a liquid at the boiling point to evaporate it. The heat is said to be latent because it does not heat the liquid. 23 Mar 2018 Specific thermal efficiency is measured by the amount of thermal energy needed to increase a product by one gram of one degree Celsius. The specific heat output of water is 4.2 joules per gram per degree Celsius or 1 calorie per gram per degree Celsius. Specific heat is directly proportional to heat capacity The most common mode of operation in DSC is constant speed heating or cooling.

The main result of such an experiment is a graph of heat flow over time. If the temperature of the sample location is known, the data can also be represented as the heat flow rate relative to the temperature. (Note that usually a temperature is measured near the sample and not the temperature of the sample itself.) Figure 2 shows a typical example. Specific heat is measured in BTU/lb°F in imperial units and J/kg K in SI units. As the pressure increases, the pressure action helps bind the molecules, so even removing less heat would be sufficient. Thus, with the temperature increase to 100 degrees of latent heat of vaporization, the latent heat of condensation also decreases, while with the increase in pressure, the latent heat of condensation also decreases. The latent heat of vaporization is a physical property of a substance. It is defined as the heat required to change one mole of liquid to its boiling point under standard atmospheric pressure. The heat of evaporation of water is about 2,260 kJ/kg, which corresponds to 40.8 kJ/mol, where Cpw, o = 1.4 kJ kg−1 K−1 and Cpw,m = 3.0 × 10−4 kJ kg−1 K−2. However, it should be noted that a constant specific heat capacity for dry fresh wood, regardless of temperature, has also been assumed by a number of researchers such as Kanury and Blackshear (1970a), Kung (1972), Kung and Kalelkar (1973), Chan et al. (1985), Alves and Figueiredo (1989), Bonnefoy et al.

(1993) and Di Blasi (1994a). In general, values of 1.386 kJ kg−1 K−1 to 2.52 kJ kg−1 K−1 were used, most of which were greater than 2.0 kJ kg−1 K−1. The specific heat of copper is 385 J/kg K. With this value, you can estimate the energy required to heat 100 g of copper to 5 °C, i.e. Q = m x Cp x ΔT = 0.1 * 385 * 5 = 192.5 J. The specific heat of water is greater than that of dry soil, so water absorbs and releases heat more slowly than land.