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Steam and Condensate Systems
Published in Stephen A. Roosa, Steve Doty, Wayne C. Turner, Energy Management Handbook, 2020
Boiling point. The boiling point is the temperature at which water begins to boil at any given pressure. The boiling point of water at sea-level atmospheric pressure is about 212°F. At high altitudes where the atmospheric pressure is lower, the boiling point is also lower. Conversely, the boiling point of water is greater as pressure increases. In steam systems, we usually refer to the boiling point as the saturation temperature.
Applied Chemistry and Physics
Published in Robert A. Burke, Applied Chemistry and Physics, 2020
One of the very basic characteristics of a flammable liquid or liquefied gas is its boiling point. Boiling point of a liquid is the temperature at which the vapor pressure of the liquid overcomes the atmospheric pressure. As the atmospheric pressure is overcome, the vapors from a liquid start to move farther away from a spill, or if inside a container, the pressure in the container starts to increase. The boiling point decreases with altitude. The sea-level boiling point of water is 212°F; however, in Denver, the boiling point decreases to about 202°F (Figure 3.141). That decrease is because the atmospheric pressure is lower at higher altitudes; therefore, it is easier for a vapor coming from a liquid to overcome the atmospheric pressure. It also takes less energy.
Terms and Definitions
Published in Rick Houghton, William Bennett, Emergency Characterization of Unknown Materials, 2020
Rick Houghton, William Bennett
Boiling point is the temperature at which a liquid turns to a gas. Condensation point is the temperature at which a gas condenses to a liquid. Both terms indicate the same temperature for a material. Boiling and condensation points assume standard pressure of 1 atmosphere unless otherwise noted.
Mathematical analysis of temperature distribution uniformity of banana dried by vacuum radio frequency treatment
Published in Drying Technology, 2020
Yuxiang Gu, Luyao Zhen, Hao Jiang
The drying curves can be found in Figure 2. It can be observed that after 270 min drying, the moisture content of RF-vacuum dried banana slices were 0.46 g/g d.b. (top), 0.69 g/g d.b. (middle), and 0.97 g/g d.b. (bottom), less than RF drying 1.29 g/g d.b. (top), 1.02 g/g d.b. (middle), and 1.09 g/g d.b. (bottom). The boiling point of water depends on atmospheric pressure, and decreases with the decrease in atmospheric pressure. It can be found easily the boiling point of water in 0.03 MPa was around 70 °C, which can also accelerate the drying rate. It also can be observed that the top layer of samples showed the lowest moisture content, followed by middle layer and bottom layer in RF-vacuum drying, which was fitted with the data obtained from Li et al. (power density: 4.0 W/g).[15] The superficial area of top layer for diffusing of moisture evaporated from banana slices was larger than middle and bottom layer, which is prone to accelerate the drying rate and avoid the over-heating happened during RF-vacuum drying. As a contrast, the banana slices arranged on the top layer during RF drying showed the highest moisture content, which was probably caused by heat loss to ambient air from the equipment. The heating uniformity can be improved after hot air assistance but the drying rate was reduced.
Thermoeconomic analysis of a new waste heat recovery system for large marine diesel engine and comparison with two other configurations
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Yadaleh Aghdoud chaboki, Ahmad Khoshgard, Gholamreza Salehi, Farivar Fazelpour
The selected working fluids, which are using in the systems, must have some appropriate physical characteristics such as high boiling point temperature for increasing the efficiency of the cycle. Refrigerants that are used in the systems are categorized into three groups: dry, isentropic, and wet. In selecting the proper fluid, safety and environmental aspects are also of great importance. Some fluids may have proper characteristics like R123 and R141b (Tian et al. 2012), but use of these fluids is prohibited by the regulations and international laws. Two criteria used for evaluating the suitability of working fluids from the environmental viewpoints are the ozone depletion potential (ODP) and greenhouse warming potential (GWP). Use of the fluids such as R11, R12, or R115 is prohibited due to their high value of ODP and/or GWP. Besides, it is expected that some other fluids such as R124, R22, R123, and R141b will be phased out in the future (Amicabile et al. 2015; Bao and Zhao 2013; Chen, Goswami, and Stefanakos 2010). On the other hand, working fluids should normally have the necessary characteristics, such as non-flammability or instability, needed to ensure safety. It is obvious that a working fluid can hardly fulfill all these conditions, but some of them are closer to the ideal conditions. In the present study, five working fluids have been selected, i.e., R152a, R245fa, R290, R600, and R1234yf. Some properties and characteristics of these substances are summarized in Table 3. Attempts are made to ensure safety measures as much as possible.
Process modeling of an automotive pem fuel cell system
Published in International Journal of Green Energy, 2019
Abdulrazzak Akroot, Özgür Ekici, Murat Köksal
The state of water depends on the operating conditions of fuel cell (air stoichiometric ratio, operating pressure, and temperature). Liquid water is easily separated from the gaseous stream in a condenser. Figure 8 shows the amount of water (liquid and vapor) at the exit of stack and injected water required for humidification process as a function of vehicle speed for 3 atm pressure. The figure shows that, on average, the exit of fuel cell stack consists of 60% liquid water and 40% of water vapor. At high pressures the vapor pressure is high, thus the boiling point of water increases. Therefore, the amount of liquid water increases with increasing operation pressure. It can also be inferred from the figure that the amount of liquid water at the exit of fuel cell is greater than the amount of injected water, therefore, is enough to humidify the reactants without using a condenser.