Document 0Ljbwb90oyL8OpD17qO9qbJVM

f DESCRIPTION OF THE BULKELEY PSYCMROMETRIC CHART* Vapor pressures at different temperatures are plotted on the vertical ordinate in millimeters of mercury to logarithmic scale. The saturation line is the upper diagonal straight line running between lower left and upper right hand corners of the chart. The relative humidity lines are those parallel to and below the saturation line. All vertical lines on the chart are dry-bulb temperatures. All horizontal lines to the right of satura tion line are dew-point temperatures. For the convenience of any who may prefer it, the equivalent centigrade temperatures are given at bottom and right side of chart. The wet-bulb lines are those curving downward to right of saturation line. A is the total heat in Btu contained in the mixture above 0 F, and is to be referred to the column of figures at the left sideof the chart. Heat of the liquid is not included. B is the grains of moisture of water vapor contained in each pound of the saturated mixture and is to be referred to the figures at the left side of the chart. C is the grains of moisture of water vapor per cubic foot of saturated mixture, and is to be referred to the figures at the left side of the chart which are to be divided by 10. D is the weight in decimal fractions of a pound, of one cubic foot of'the saturated mixture, and is referred to the first column of figures to the right of the saturation line between the vertical dry-bulb temperature lines 170 and 180 F- The relative density of. ...the mixture is read in a .similar manner from the same curve by the column of figures between the vertical dry-bulb temperature lines 180 and 190 F. E is similar to D but is for dry air, devoid of all moisture or water vapor. For con venience, the approximate absolute temperature of 500 F is given at 40 F oh the satura tion line for the purpose of calculating volume, weight per cubic foot, and relative density at partial saturation^ See Chapter 1 Fundamentals of Heating and Air Conditioning, A.S.H.V.E. Guidb 1935. Also A.S.H.V.E. Transactions, Vol. 32,1926. JVB'OW Directrix Line* DJIL" Or} Bulb l/ne D.P.I." Dew WrrtLine_____ tP.U.'&xum Moisture perIbJJryAirSaturated IH.oMdfWperlb.pn4tf5oturaW HP.8VaporPressure in Mm.Mercury 6J,.C.F.ie6ritira Moisture perOiFflSahmifedAir RJLL.=Re!ative HumWftj Line W&L.'ffetBdbline S,L Saturation Line tiBC/.&*ttgrfjtpcrCuf}.tn lbs.Saturated RJXS*Relaftve density perCu.FfcSaturated' . IP.CJJLsfieiatTveOensirrper&i.Ft^ry * RJ)JX8Retotiw DensityperCu.Ft.P17 6 P rrV Abs-Temp. of Abs-Temp.at D.P.. OB. 6.P.C-F.at Partial Saturation wPf-F i Abs-Tcmp.atO.P. r* ' Abs.Tertjp.otaB. W.P.CF. at Partial Saturation bn x Abs-Temp. at OR Abs-Temp. at aa . R.D.atPartiat Saturation - Diagrams Showing Procedure to Follow in Using Bulkeley Chart Example 1. Relative Humidity: At the intersection of the 78 F wet-bulb line and the 65 F dry-bulb line, the relative humidity is read directly on the straight diagonal lines as 46 per cent. Example 2. Dew Point: At the intersection of the 78 F wet-bulb line, the dew-point temperature is read directly on the horizontal temperature lines as 70.9 F. Example 3. Vapor Pressure: At the intersection of the 78 F wet-bulb line and the 95 F dry-bulb line, pass in a horizontal direction to the left of the chart and on the logarithmic scale read the vapor pressure as 19.4 millimeters of mercury. (Divide by 25.4 for inches.) Example 4- Total Heat Above 0 F in Mixture per Pound of Dry Air Saturated with Moisture: From where the wet-bulb line joins the saturation line, pass in a vertical direction on the 78 F dry-bulb line to its intersection with curve A and on the logarithmic scale at the left of the chart read 40.6 Btu per pound of mixture. The use of this curve to obtain the total heat in the mixture at any wet-bulb temperature is a great con venience, as the number of Btu required to heat the mixture and humidify it, as well as the refrigeration required to cool and dehumidify the mixture, can be obtained by taking the difference in total heat before and after treatment of the mixture. Example 6. Grains of Moisture per Pound of Mixture: From 70.9 F dew-point temperature on the saturation line, pass vertically to the intersection with curve B and on the logarithmic scale at the left read 114 grains of moisture per pound. Example 6. Grains of Moisture per Cubic Fool of Mixture, Partially Saturated: From 70.9 F dew-point temperature on the saturation line proceed in a vertical direction to curve C, and on the logarithmic scale to the left read 83.3 which, divided by 10, gives 8.33 grains. A temperature of 70.9 F is equal to an absolute temperature of 530.9, and . 95 F equals 555, absolute temperature. Therefore, 5 30'9 X 8.33 - 7.97 grains per ooo cubic foot of partially saturated mixture. Example 7. Grains of Moisture per Cubic Foot of Dry Air, Saturated: Starting at the saturation line at the desired temperature, pass in a vertical direction to curve C and on the logarithmic scale at the left, read a number which, divided by 10, will give the answer. Example 8. Weight per Cubic Foot of Dry Air and Relative Density: From point where, for example, the 70 F vertical dry-bulb line intersects curve E, pass to right side and read 0.075 lb; if cubic feet per pound are desired, divide 1 by this amount. The relative density is read immediately to the right as 1.00. Example 9. Weight per Cubic Foot of Saturated Air and Relative Density: From the' point where, for example, the 70 F vertical line intersects the curve D, pass to the right and read weight per cubic foot as 0.07316 with a relative density of 0.9755 for saturated air at 70 F. Example 10. Weight per Cubic Foot and Relative Density of Partially Saturated Air: Air at 50 F and a wet-bulb temperature of 46 F is to be heated to 130 F. The wet- and dry-bulb lines intersect at a dew-point temperature of 42 F. Pass to the left where this dew-point line intersects the saturation line and then pass in a vertical direction to where . the 42 F dry-bulb line intersects with curve D. Then pass directly to the right and read ,the weight per cubic foot of saturated air at 42 F as 0.07844 and the relative density as 1.046. The absolute temperature at 42 F is 502, and at 130 F is 590. Therefore, CAQ ggjj = 0.851. The weight of 1 cu ft of air at 50 F dry-bulb and 46 F wet-bulb when heated to 130 F is 0.07844 X 0.851 = 0.06675, and the relative density is 1.046 X 0.851 = 0.89. Copyright 1935, American Society of Heating and Ventilating Engineers, 61 Madison Avenue, New York, N. Y.