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Geothermal Heat Pumps
Published in Vasile Minea, Heating and Cooling with Ground-Source Heat Pumps in Cold and Moderate Climates, 2022
Enounced as the principle of the increase of entropy, the second law of thermodynamics states that in any process, whatever between two equilibrium states of a system, the sum of the increase in entropy of the thermodynamic system and the increase in entropy of its surroundings is equal to or greater than zero. In other words, entropy cannot be destroyed, but it can be created. Therefore, the entropy of any isolated system always increases, and the system spontaneously evolve towards thermal equilibrium, i.e., the state of maximum entropy. In the case of geothermal heat pumps’ closed thermodynamic cycles, the second law of thermodynamics states that, for a given delivered heat (Qwarm), better performance means a smaller input work (W), but the smallest work (W) will never be zero.
Energy and the Environment
Published in Anco S. Blazev, Power Generation and the Environment, 2021
Enthalpy is another important variable, which is basically a measure of the total energy (or thermodynamic potential) of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure. This can be figuratively seen reflected in the behavior of water vapor in a water boiler. As the vapor goes through the boiler’s piping, it carries its energy to another place—be it a space heater or a steam turbine. At this point there are no transfers of energy and no chemical reactions. It is simply a physical transport of a heated mass to a point of use.
Energy Today
Published in Anco S. Blazev, Global Energy Market Trends, 2021
Enthalpy is another important variable, which is basically a measure of the total energy of a thermodynamic system. It is a measure of the thermodynamic potential of the system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure. This can be figuratively seen reflected in the behavior of water vapor in a water boiler. As the vapor goes through the boiler’s piping, it carries its energy to another place; be it a space heater or a steam turbine. At this point there are no transfers of energy and no chemical reactions. It is simply a physical transport of a heated mass to point of use.
Thermal management and develop energy storage in performance improvement of triangular and cubical parabolic collectors
Published in Numerical Heat Transfer, Part A: Applications, 2023
Samaneh Baharloui, Mofid Gorji Bandpy
In thermodynamics, the enthalpy is the measure of energy in a thermodynamic system. It is the thermodynamic quantity equal to the complete heat content of a system. The enthalpy is described to be the sum of the inner energy E plus the product of the stress P and quantity V. In many thermodynamic analyses the sum of the internal strength U and the product of pressure P and quantity V appears, consequently it is handy to supply the combination a name, enthalpy, and an awesome symbol, H. Figure 9, illustrated the maximum enthalpy in triangular collector with water, oil, ethylene glycol, and glycerin fluids are 289,682.97, 280,459.62, 28,115.92, and 279,530.99j/kg, respectively. According to Figure 9, the maximum enthalpy in cubical collector using water, oil, ethylene glycol, and glycerin fluids are 285,160.95, 215,510.97, 224,122.95 and 216,187.99 respectively. Also, Figure 10, illustrated that the enthalpy performance of triangular collector for oil, ethylene glycol, and glycerin fluids are 12%, 26%, and 30%, respectively.
Optimization of Palm Oleic Acid Epoxidation via in Situ Generated Performic Acid Using Taguchi Orthogonal Array Design and the Study of Reaction Kinetics
Published in Smart Science, 2019
The enthalpy of activation, entropy of activation and free energy of activation the epoxidation of oleic acid are summarized in Table 10. The results indicated that the present reaction was endothermic in nature since the enthalpy of activation was positive, hence an increase in the reaction temperature leads to an increased conversion to oxirane. Entropy also calculated to measure of disorder or randomness of the particles in a thermodynamic system. The negative value of entropy change indicated less disorder results due to the reaction is too fast and less reaction time to achieve the maximum yield of epoxide [24]. In addition, the free energy of activation was found to be positive, which indicates that the reaction is non-spontaneous under the present experimental conditions and therefore external energy is needed to induce the reaction. With an increase in temperature, the non-spontaneity of the reaction should increase since free energy activation to be positive.
Pyrolysis kinetics of regional agro-industrial wastes using isoconversional methods
Published in Biofuels, 2019
Alejandra Saffe, Anabel Fernandez, Marcelo Echegaray, Germán Mazza, Rosa Rodriguez
The thermodynamic parameters, ∆H, ∆G and ∆S, were calculated at the temperature that the maximum mass loss rate is produced [16]. Enthalpy is a measurement of the energy in a thermodynamic system. Enthalpy is defined as a state function, and it depends only on the prevailing equilibrium state identified by the internal energy, pressure, and volume. It is an extensive quantity. If ΔH is positive, the reaction is endothermic. The exothermic processes exhibit a negative value of this variation. ΔH is equal to the change in the internal energy of the system, plus the pressure–volume work that the system has done on its surroundings. ΔH, under such conditions, is the heat absorbed (or released) by the material through a chemical reaction or by external heat transfer. The activation ΔH also shows the energy differences between the activated complex and the reagents. If this difference is small, the formation of an activated complex is favored, because the potential energy barrier is low [60].