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Published in Splinter Robert, Illustrated Encyclopedia of Applied and Engineering Physics, 2017
[atomic, biomedical] Standard nitrogen: 714N, discovered by the Scottish physician, chemist, and botanist Daniel Rutherford (1749–1819) in 1772. The Earth’s atmosphere consists of approximately 78% nitrogen as a gas under standard conditions. Nitrogen has a evaporation temperature (boiling point) at 77.355 K = −195.795°C and a solidification temperature (melting point) of 63.15 K = −210.00°C; the triplepoint is at 63.151 K under pressure of 12.52 kPa, and the critical point is at 126.192 at 3.3958 MPa. The heat of fusion for nitrogen is 0.72 kJ/mol and the heat of vaporization for nitrogen is 5.56 kJ/mol. Nitrogen is a popular and effective component of fertilizer. Antoine-Laurent de Lavoisier (1743–1794) named nitrogen “mephitic air” referring to the fact that animals would not survive and flames were extinguished when under the inert 100% concentration, a name that is found to carry through in several languages. Evaporating liquid nitrogen provides low-rolling clouds of nitrogen and condensate water vapor (see Figure N.2).
Fundamentals of Two-Phase Flow in Nuclear Power Plants
Published in Robert E. Masterson, Nuclear Reactor Thermal Hydraulics, 2019
The heat of vaporization depends on the molecular forces that hold the fluid together. The primary difference between the behavior of fluids in nuclear power plants and those in other thermal systems is that they are subjected to much higher pressures in either the reactor core or the nuclear steam supply system (NSSS). Hence, two-phase flows in nuclear power plants do not behave in the same way as flows in low-pressure applications associated with turbo machinery. In pressurized water reactors (PWRs), only a small amount of nucleate boiling is allowed to occur in the core because of the way the NSSS is designed. Hence, nucleate boiling usually occurs in only the hottest fuel assemblies near the top of the core. However, in boiling water reactors (BWRs), a phase change is deliberately introduced into the core about one quarter of the way between the inlet and the outlet. Thus if the inlet to the core is assumed to located at z = 0 and the outlet of the core is assumed to be located at z = H, boiling will begin to occur when z = H/4. This boiling becomes vigorous when z = H/2, and by the time the outlet to the core is reached, most of the space in the coolant channels consists of vaporized water or steam. The void fraction at this time can be about 80%. This phase change can be beneficial as long as the cladding does not melt and the fuel rods do not fail. We will have more to say about this in Chapter 24 when we discuss how two-phase flow can affect the value of the convective heat transfer coefficient. Normally the convective heat transfer coefficients are higher for two-phase flow than they are for single-phase flow. Hence, in water reactors, flow boiling is used to increase the heat transfer rate without necessarily increasing the mass flow rate.
Processing Principles
Published in Arthur J. Kidnay, William R. Parrish, Daniel G. McCartney, Fundamentals of Natural Gas Processing, 2019
Arthur J. Kidnay, William R. Parrish, Daniel G. McCartney
The amount of heat that must be added to a given quantity of liquid to convert a pure component into a vapor at the same temperature and pressure is the heat of vaporization. The units are Btu/lbm or Btu/lb-mol (kJ/kg, kJ/kg-mol). The heat of vaporization is a strong function of temperature and decreases to zero at the critical point. Table 1.4 shows a few representative values.
An experimental study on wear, deposits, performance, and emissions of bio-fueled motorcycle engines
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Tuyen Pham Huu, Khanh Nguyen Duc, Truc Nguyen The, Tien Nguyen Duy, Nguyen The Luong
Ethanol addition to gasoline, also affects deposits on the surface of engine components. The higher latent heat of vaporization of ethanol causes the metal surface to cool relatively, which increases engine deposits (Shirazi et al. 2018). The appearance of ethanol in a blend with gasoline decreases the vapor pressure and increases the heat of vaporization of the mixture. As a result, a liquid fuel layer will form on the spark plug insulator if the activation energy is insufficient to vaporize the fuel completely (Lande and Kongre 2016; Shirazi et al. 2018). These cause deposits on the metal surface as intake valves, valve seats, and spark plug. However, due to the addition of ethanol, the blend’s lower 90% distillation temperature allowed the fuel to vaporize at lower metal surface temperatures and have less chance of condensation (Xu et al. 2015). DuMont et al. (2007) reported that carbon deposits on engine components increase with a small proportion, up to 15%, of ethanol in blends. But in other research by Vilardo et al. (2007), the accumulated deposit decreases at a concentration of ethanol above 25%. It is argued that ethanol is unlikely to be a precursor source due to its single-component nature and lack of aromatic or sulfur content (Taniguchi, Yoshida, and Tsukasaki 2007).
Characterization of flat miniature loop heat pipe using water and methanol at different inclinations
Published in Experimental Heat Transfer, 2021
Sireesha Veeramachaneni, Srinivas Kishore Pisipaty, Dharma Rao Vedula, A. Brusly Solomon
The Merit number is calculated by Equation (21) and a comparison between the performances of water, methanol as working fluids of present work with Tharayil et al. [19] can be viewed in Figure 12. Merit number is a function of the normal boiling point, latent heat of vaporization and surface tension of the working fluid. For efficient loop operation working fluids should possess high surface tension to maximize capillary pumping capabilities, high latent heat of vaporization for more efficient heat transport, high thermal conductivity to minimize temperature drops across wick and low viscosity to minimize pressure losses along fluid flow line. At a heat load of 80 W, the Merit number for methanol (0.46912x1011 W/m2) is less compared to that of water (3.006x1011 W/m2) because of high latent heat of vaporization, high surface tension, and low viscosity of water compared to those of methanol. The Merit number increases with increase in heat load for both the working fluids. The present results are compared with Tharayil et al. [19] and observed that present work showed good results.
Research on emissions controlling of coal-made Fischer–Tropsch process diesel/methanol unconventional pollutants
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Hua Xia, Lian Mei, Yang Jiahui
Aldehyde and ketone pollutants were intermediate products in the low-temperature combustion process of fuel. They were mainly derived from the incomplete oxidation of HC and unburned methanol. The formation temperature in diesel cylinders, which was a low temperature before combustion starts, was 800–950 K (Bermúdez, Luján, and Benjamín 2011). In the reaction and exhaust stages, methanol had a low boiling point and a high latent heat of vaporization. As the methanol blending ratio in the mixed fuel increases, the temperature in the cylinder decreases, and the fuel atomization effect decreases. Methanol was easily evaporated from the spray oil bundle. The periphery of the oil bundle was mixed with air to form a low-temperature, too-lean mixture. The HC from incomplete combustion was increased, and the oxygen content of methanol was high. In the reaction temperature range, unburned methanol and HC were oxidized to form aldehydes and ketones.