Properties of Air and Water Vapor

This is the state equation of an ideal gas, where p is pressure, v is specific volume, p is density, R is the gas constant, and T is absolute temperature. In an airflow there is a transfer of heat from one layer to another. This change of 

State is adiabatic and reversible. Such an adiabatic reversible process is called an isentropic state change one in which the entropy remains constant. 

When dT is eliminated from this equation, the following differential equation results  

When Cp and R can be treated as constants, the equation is usually written as 

In this section incompressible liquid flow is dealt with, and the effect of compressibility is ignored. 

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FIG. 12-36 Psychrometric chart properties of air and water-vapor mixtures from 20 to 120 C, Catrier Corp. )... 

The key properties of mixtures of air and water vapor are described in Section 9.1. Here the interactions of air and water in packed towers under steady flow conditions will be analyzed. The primary objectives of such operations may be to humidify or dehumidify the ait as needed for particular drying processes or other processes, or to cool process water used for heat transfer elsewhere in the plant. Humidification-dehumidification usually is accomplished in spray towers, whereas cooling towers almost invariably are filled with seme type of packing of open structure to improve contacting but with minimum pressure drop of air. 

Psychrometrics. Psychrometrics is the branch of thermodynamics that deals specifically with moist air, a biaary mixture of dry air and water vapor. The properties of moist air are frequentiy presented on psychrometric charts such as that shown ia Figure 2 for the normal air conditioning range at atmospheric pressure. Similar charts exist for temperatures below 0°C and above 50°C as well as for other barometric pressures. AH mass properties ate related to the mass of the dry air. 

Wire cords are particularly subject to degradation of their adhesion values by moisture. To combat this, halogenated butyl (HIIR) is used in tire innerliners because of its property of low air and water vapor diffusion rates. Moisture is present in most air pumps and many tires are mounted with water left in the tire on mounting. For these reasons tires and tire compounds are tested extensively at simulated aging conditions in the laboratory and on test vehicles before they are sold to the customer. 

HUMIDITY CHART. A convenient diagram showing the properties of mixtures of a permanent gas and a condensable vapor is the humidity chart. A chart for mixtures of air and water at 1 atm is shown in Fig. 23.2. Many forms of such charts have been proposed. Figure 23.2 is based on the Grosvenor chart. 

Enthaipy - A thermodynamic property of a substance, defined as the sum of its internal energy plus the pressure of the substance times its volume, divided by the mechanical equivalent of heat. The total heat content of air the sum of the enthalpies of dry air and water vapor, per unit weight of dry air measured in Btu per pound (or calories per kilogram). 

The interrelationships between air and water vapor are called psychrometric properties [3]. Changes in these properties are shown by a psychrometric chart. A sample of the chart is given in Figure 24.2. The psychrometric terms given in the chart are defined as follows. 

An optimal protective cloth should be able to preveut infiltratiou of aerosols (e.g., chemical/biochemical agent microdroplets, bacteria, virus, radioactive dust, etc.) and at the same time must be highly permeable to the air and water vapor to improve wearer comfort. Nonwoven polymeric nanofibers are a natural fit for this application due to their enormous surface area and microscale pore size. By physical absorption and exclusion, the nanofiber mat can provide an impermeable barrier to toxic chemical agents, that is lightweight with remarkable breathing properties [17,18]. 

Films or membranes of silkworm silk have been produced by air-drying aqueous solutions prepared from the concentrated salts, followed by dialysis (11,28). The films, which are water soluble, generally contain silk in the silk I conformation with a significant content of random coil. Many different treatments have been used to modify these films to decrease their water solubiUty by converting silk I to silk II in a process found usehil for enzyme entrapment (28). Silk membranes have also been cast from fibroin solutions and characterized for permeation properties. Oxygen and water vapor transmission rates were dependent on the exposure conditions to methanol to faciUtate the conversion to silk II (29). Thin monolayer films have been formed from solubilized silkworm silk using Langmuir techniques to faciUtate stmctural characterization of the protein (30). ResolubiLized silkworm cocoon silk has been spun into fibers (31), as have recombinant silkworm silks (32). 

Computes thermodynamic properties of air, argon, carbon monoxide, carbon dioxide, hydrogen, nitrogen, oxygen, water vapor, and products of combustion for hydrocarbons. Computes all properties from any two independent properties. 

Computes properties of air-water vapor mixtures for HVAC, combustion, aerodynamic, and meteorological applications. Any two independent properties may be inpuicd by... 

The introduction of estrogens and progestogens into the environment is a function of the way several factors are combined. The manufactured quantity and the dosage applied (amount, frequency, and duration) combined with the excretion efficiency of the compound and its metabolites, the capability of adsorption and desorption on soil, and the metabolic decomposition in sewage treatment are examples of necessary factors to assess environmental exposure. In general the fate and effect of a substance in the environment is dependent on the distribution into the different natural systems, such as air, water, and solids (soil, particles, sediment, and biota). Information on the physical and chemical properties (Ku, Kd, and Kim vapor pressure) of a compound may help determine whether it is likely to concentrate in the aquatic, terrestrial, or atmospheric... 

By controlling the structural and electronic properties of sNPS which are related to the nanocrystallite dimensions and porosity, their surface selectivity and sensitivity to different gases (nitrogen and carbon oxide, vapors of water and organic substances) can be adjusted. This approach for the effective detection of acetone, methanol and water vapor in air was described in [13-15].The minimal detectable acetone concentration was reported to be 12 pg/mL. Silicon sensors for detection of SO2 and some medicines such as penicillin were created [16-18]. sNPS were used for the development of a number of immune biosensors, particularly using the photoluminescence detection. Earlier we developed similar immune biosensors for the control of the myoglobin level in blood and for monitoring of bacterial proteins in air [19-23]. 

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