The second law of thermodynamics definition

Many thermodynamic processes proceed naturally in one direction but not the opposite. There must be losses in the conversion process. For example, converting all the energy obtained from coal in a coal-fired power plant or from a nuclear reactor in a nuclear power plant into electrical energy is not possible. One of the areas of application of the second law of thermodynamics is the study of energy-conversion systems. It follows perpetual motion machines of the second kind are impossible. From this law, it is impossible to construct a device that operates on a cycle and whose sole effect is the transfer of heat from a cooler body to a hotter body. Reversible processes are a useful and convenient theoretical fiction but do not occur in nature. The second law of thermodynamics law indicates the irreversibility of natural processes. So the second law is directly relevant for many important practical problems. The second law of thermodynamics places constraints upon the direction of heat transfer and sets an upper limit to the efficiency of conversion of heat to work in heat engines. However, no information about the direction of the process can be obtained by applying the first law. The first law is used to relate and evaluate the various energies involved in a process. The second law of thermodynamics is a general principle that goes beyond the limitations imposed by the first law of thermodynamics. Automotive engines are heat engines that can consume primary energy sources. In gasoline cars, energy undergoes the following conversions: from stored chemical energy to thermal energy and from thermal energyВ to mechanical energy. But in this case, most of its chemical energy stored was produced by another heat engine (e.g., coal power plant), and you must include it. In electric cars, energy undergoes the following conversions: from stored chemical energy to electrical energy and from electrical energy to mechanical energy. Sure electric vehicles have an efficiency of about 70%, but in this case, we are not talking about thermal efficiency because an electrical motor is not a heat engine. In these cases, comparisons are often made for incomparable characteristics. Sometimes you can find comparisons between combustion engines and electric motors or conventional power plants and solar power plants. In modern nuclear power plants, the overall thermal efficiency is about one-third (33%), so 3000 MWth of thermal power from the fission reaction is needed to generate 1000 MWe of electrical power.Sub-critical fossil fuel power plants operated under critical pressure (i.e., lower than 22.1 MPa) can achieve 36вЂ“40% efficiency.In general, engines using the Diesel cycle are usually more efficient. A typical diesel automotive engine operates at around 30% to 35%.About 70-75% is rejected as waste heat without being converted into useful work, i.e., work delivered to wheels. A typical gasoline automotive engine operates at around 25% to 30% of thermal efficiency.What are the typical thermal efficiencies of heat engines? This inefficiency can be attributed to three causes. In modern nuclear power plants, the overall thermodynamic efficiency is about one-third (33%), so 3000 MWth of thermal power from the fission reaction is needed to generate 1000 MWe of electrical power. In a natural thermodynamic process, the sum of the entropies of the interacting thermodynamic systems increases.ДЄll conventional thermal power plants are heat engines subject to the efficiency limitations imposed by the second law of thermodynamics.ДЄ typical gasoline automotive engine operates at around 25% to 30% of thermal efficiency. The entropy of any isolated system never decreases. вЂњIt is impossible to construct a device which operates on a cycle and produces no other effect than the production of work and the transfer of heat from a single bodyвЂќ. вЂњIt is impossible to construct a device which operates on a cycle and whose sole effect is the transfer of heat from a cooler body to a hotter bodyвЂќ. Listed below are three that are often encountered. The second law of thermodynamics may be expressed in many specific ways. Key FactsД«efore these statements, we have to remind CarnotвЂ™s rule that specifies limits on the maximum efficiency any heat engine can obtain. In a natural thermodynamic process, the sum of the entropies of the interacting thermodynamic systems increases. Article Summary & FAQs What states the second law of thermodynamics?ДЄccording to the second law of thermodynamics:

The second law of thermodynamics definition