Psychometric chart

The work required to drive the turbine eompressor is reduced by lowering the compressor inlet temperature thus increasing the output work of the turbine. Figure 2-35 is a schematic of the evaporative gas turbine and its effect on the Brayton cycle. The volumetric flow of most turbines is constant and therefore by increasing the mass flow, power increases in an inverse proportion to the temperature of the inlet air. The psychometric chart shown shows that the cooling is limited especially in high humid conditions. It is a very low cost option and can be installed very easily. This technique does not however increase the efficiency of the turbine. The turbine inlet temperature is lowered by about 18 °F (10 °C), if the outside temperature is around 90 °F (32 °C). The cost of an evaporative cooling system runs around 50/kw. 

Computerized psychometric chart. User provides two independent properties of moist air and program calculates the remaining properties. 

In these systems, the total collection efficiencies of the dry product are 85 per cent for the drying vessel, 90 per cent for the cyclone collector and 98 per cent for the scrubber-condenser. The net efficiency of the system may be as high as 99.97 per cent if the scrubber effluent is considered as product. All the runs are based on 1.25 kg/s product and 0.75 kg/s evaporation at an elevation of 300 m above sea level. The total air flow is measured at the outlet before the stream is split into the recycle and bleed portions and, for such flows, the design of suitable fans is outlined by Jorgensen164 . The calculations outlined here may be confirmed by the use of psychometric charts, and this procedure has been considered in some detail by Cook and Demount165. ... 

As stated earlier, a typical air velocity used for spray granulation is from 1.0 to 2.0 meters/second. Table 2, which is based upon the psychometric chart, gives a first guess at determining the proper spray rate for a spray granulation process in a fluid bed processor. 

Wet- and dry-bulb temperatures are measured by exposing two temperature-sensitive elements to the atmosphere whose moisture level is to be measured. The wet bulb is wrapped with a wick soaked in water the other element, the dry bulb, is left bare. Water evaporating from the wick lowers its temperature, which is read as the wet-bulb temperature, whereas the other reads the dry-bulb temperature. The relative humidity can be read from a psychometric chart such as the one shown in Figure 3.25. 

Before drying can begin, a wet material must be heated to such a temperature that the vapor pressure of the liquid content exceeds the partial pressure of the corresponding vapor in the surrounding atmosphere. Different devices such as a psychometric chart can conveniently study the effect of the atmospheric vapor content on the rate of the dryer as well as the effect of the material temperature. It plots moisture content dry-bulb, wet-bulb, or saturation temperature, and enthalpy at saturation. 

Steps 1,2,3, and 4 All the data is in the figure above. The data on concentrations comes from the SI psychometric chart. Assume p = 1 atm. 

CHART/PC Engineering Applications Specialists, Inc. 5610 Medical Circle Suite 31 Madison, W1 5371 Computerized psychometric chart. User provides two independent properties of moist air and program calculates the remaining properties. 

Properties such as moisture content, specific volume, and enthalpy are referred to unit mass of dry air. Figures 9.1 and 9.2 are psychometric charts in English units of lb, cuft, F, and Btu. The data are for standard atmospheric pressure. How to correct them for minor deviations from standard pressure is explained for example in Chemical Engineers Handbook (1999). An example of... 

Figure 9.2. Psychometric chart for a wide temperature range, 32-600°F Proctor and Schwartz, Inc., Horsham, PA Walas, 1988).

COMFORT ZONE - (Average) the range of effective temperatures over which the majority (50 percent or more) of adults feels comfortable (extreme) the range of effective temperatures over which one or more adults feel comfortable. An area on the psychometric chart which shows conditions of temperature, humidity and sometimes air movement in which most people are comfortable. 

PSYCHROMETRIC MEASUREMENT - Measurement of temperature pressure and humidity using a psychometric chart. 

Instruments for measuring the filament linear density continuously use capacitance of the filaments to operate the sensor, similar in principle to the Uster and Keisoki cveness testers. The instruments are usually accurate to between 1% and 3%. but as capacitance is affected by relative humidity and temperature, these parameters need to be strictly controlled. Otherwise the accuracy of the results will be somewhat spurious, even when calibration is on line, as the strict control of relative humidity within an environment where the temperature varies by more than 2 C around an ambient temperature of over 2. C is not realistic, as can be seen from any psychometric chart. 

Typical vapor pressure deficits are 2500N/m in an arid environment and ffiOON/m for more humid areas (Sinclair, 2009). Vapor pressure deficits can be obtained from information in psychometric charts (Johnson, 1999). 

ShaUcross D.C., 1994, Construction of psychometric charts for systems other than water vapour in air, Trans. IChemE, 12A, 763-776. 

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