Humidity Measurement Gas Flowrate

Experimental Data and Result Sheet Experiment 6 Humidity Measurement and Gas Flowrate Humidity Measurement Room Air Compressed Air Dry bulb temperature (oC) 23.4 22.7 Wet bulb temperature (oC) 17.7 21.8 Relative Humidity 55% 80% Absolute Humidity (Lb/Lb) 0.0103 0.0164 Humid Volume (ft3/lb) 13.6 13.9 Energy required increasing room air percentage relative humidity (1000 ft3) to 100% saturation at the dry bulb temperature: ______435 btu______________ Rotameter reading (nominal value) U-tube manometer reading (cm. WC) Air Flowrate (ft3/min) 40 2.3 0.463 60 5.7 0.730 80 12.5 1.081 Calculations: The Temperature of the Dry and Wet bulb for both room and compressed air had been convert as below: Dry bulb at room temperature: ToF= 1.8 oC+32 = 1.8 * 23.4 +32 = 74.12oF * At room temperature the density of air is air =0.00129 g/cm3 air = 0.081 lb/ft3 gc = 32.2 1ft=12 inch D1= pipe diameter, 0.445 inch = 0.03708 ft D2= orifice diameter, 0.12 inch = 0.01 ft A pipe = (D2/4) = [* (0.03708)2] /4 = 0.0011 ft2 A orifice = (D2/4) = [* (0.01)2] /4 = 0.000079ft2 Conversion of the pressure from in H2O to lbf/ft2 using 1 atm = 33.9 ft H2O (water column, W.C.) = 406.8 in. H2O P= 11.96 lbf/ft2 = 0.000079ft2 / [1-(0.000079ft2 / 0.0011 ft2) 2]1/2 [(2 *32.2 *11.96 lbf/ft2)/0.081 lb/ft3]1/2 =7.7×10-3 ft3/s = 0.463 ft3/min The Energy required to room air to 100% saturation calculated as below: Energy= (room volume/humid volume) x ( absolute humidity of air both compressed and dry) x Hevp = (1000 ft3/ 13.6 ft3/lb) x (0.0164-0.0103) lb/Lb x 970 btu/Lbm = 435 btu Discussion: For this experiment the sources of error can be explained by different factors: instrumental error and human error. Instrumental error can be explained by the instability of the temperature reading from the thermometer for both wet and dry bulb which caused an inaccurate pressure reading difference. Secondly, since the temperature reading for the wet bulb depends on how wet the wick is, incarnate measurement can be taken when the wick is at higher or lower humidity. Human error caused by the inaccurate reading of the u-tube (pressure difference), for example when the measurement was taken from the manometer was not parallel to the level of the manometer. Therefor to improve the results and measurements these source of error should be carefully considered as well as improve the accuracy of the instrument. Graph of the Air Flowrate vs. Rotameter Reading