Dry air equivalent

Tray, Truck, and Tunnel Driers In order to accelerate drying, the closet is factory-built with tight walls. It forms a box, and the air is passed by means of a fan over a radiator or over finned tubes and then over the trays. A portion of the air escapes at the discharge opening the remainder is reheated and recirculated. An amount of new air equivalent to the volume discharged is admitted at the fan. Secondary heating tubes are placed in the path of the air to restore their temperature and heat content. In the tray drier, shallow pans 2 ft by 3 ft by 2 in. deep, for example, are placed on a rack, forming part of the drier. In the truck drier, the rack is on wheels, and the whole may be wheeled in and out of the drier. There may be one or several trucks to each drier, and each truck may have twelve, sixteen or more levels for trays. 

Total hold-up, ft3 liquid/ft packing volume Enthalpy of air at any temperature higher than inlet, Btu/lb dry air note hj = exit air Enthalpy of inlet air to tower, equivalent to enthalpy of saturated air at wet bulb temperature, Btu/lb dry air from Moist Air Tables, ASHVTE Guide... 

For combustion calculations, it is acceptable to take the average molecular weight of dry air to be 28.97, and to assume a simplified composition of 79.0 niole% nitrogen and 21.0 mole% oxygen (or equivalently, 76.8 wt% nitrogen and 23.2 wt% oxygen). 

Transfer an aliquot of the sample extract equivalent to 0.5-g of crop (5 mL) into a disposable test-tube (10-mL) and evaporate the sample in a heating block at 50 °C under a stream of dry air to < 1 mL. Add 5 mL of acetonitrile-water (3 7, v/v) to the sample and ultrasonicate the solution to ensure that the sample is fully dissolved. 

Water levels Volume of air (mL) V Hg equivalent of water column (torr) Corrected pressure of dry air (torr) P PV for dry gas (torr x mL)... 

Dilute the TNT and wax filtrate obtd in 4.4.3.3.1 to 100ml with benzene satd with RDX. Transfer a 10-ml aliquot of the TNT soln which contns 35—40mg of TNT to a 300-ml reduction flask (Scientific Glass Apparatus Co JD2776 or equivalent is satisfactory). Evaporate the benzene to dryness with a slow stream of dry air (connect a drying tube between wir supply and inlet tube of flask). 

A stream of dry air blows across the open top of the tube. Thereby the concentrations (or equivalently the mole fractions) of HC1 and H2O at the z = Z are assumed to drop to zero. For this example, assume a tube height of Z = 0.1 m, open to atmospheric pressure (i.e, p = 101325 Pa). The mole fractions of HC1 and H2O at the liquid-vapor interface are assumed to be at their equilibrium values, 0j01395, and 0.00712, respectively [312]. 

Although recycling of moist air does reduce the drying time because of the increased linear velocity, an equivalent amount of fresh air is much more effective because of its lower humidity. The points in favor of moist air recycle, however, are saving in fuel when the fresh air is much colder than 170°F and possible avoidance of case hardening or other undesirable phenomena resulting from contact with very dry air. 

Apparatus Use a Fourier transform infrared spectrometer (FTIR), with its associated computer and peripherals, capable of measuring from 4500 to 500 cm-1 and of acquiring data with a resolution of at least 2 cm-1. The optics of the instmment must be sealed and desiccated, or, like the sample chamber, must be under continuous dry air or nitrogen gas purge. The spectrometer is equipped with software capable of multicomponent analysis using the partial least squares method (PLS-1, or equivalent). This software is commercially available as an accessory to the spectrometer or as an external software package. 

Dry air at 80°F (300 K) and 150 psia (1034 kPa) flows at the rate of 500 ft3/min (0.24 m3/s) through a 4-in schedule 40 pipe from the discharge of an air compressor. What is the flow rate in pounds per hour and the air velocity in feet per second Using the Fanning formula, determine the pressure loss if the total equivalent length of the pipe is 500 ft (153 m). 

In the laboratory it is prepared by the action of methanol on chlorosulphonic acid. According to Claesson, the chlorosulphonic acid is placed in a small flask, which is fitted with a tap-funnel and externally cooled with ice. Water-free methyl alcohol, previously distilled from lime, is slowly introduced in quantity stoichiometrically equivalent to the chlorosulphonic acid. As each drop of alcohol comes into contact with the chlorosulphonic acid, hydrochloric acid is evolved. At the end of addition of the alcohol the flask is heated gently while a current of dry air is passed through in order to remove the hydrochloric acid dissolved in the mixture. The product obtained contains about 90% methyl sulphuric acid. 

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