Chapter 4, Problem 4.23P

A stream of humid air containing 1.50 mole% H₂O(v) and the balance dry air is to be humidified to a water content of 10.0mole% H?O. For this purpose, liquid water is fed through a flowmeter and evaporated into the air stream. The flowmeter reading, R, is 95. The only available calibration data for the flowmeter are two points scribbled on a sheet of paper, indicating that readings R = 15 and R = 50 correspond to flow rates V = 40.0 ft³/h and V = 96.9 fP/h, respectively.

(a) Assuming that the process is working as intended, draw and label the flowchart, do the degree-of- freedom analysis, and estimate the molar flow rate (lb-mole/h) of the humidified (outlet) air if (i) the volumetric flow rate is a linear function of R and (ii) the reading R is a linear function of V .

(h) Suppose the outlet air is analyzed and found to contain only 7% water instead of the desired 10%. List as many possible reasons as you can think of for the discrepancy, concentrating on assumptions made in the calculation of Part (a) that might be violated in the real process.