Q-value Formula:
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Definition: The Q-value in mass transfer represents the moles of liquid flow in the stripping section that results from the introduction of each mole of feed.
Purpose: It helps chemical engineers determine the thermal condition of the feed entering a distillation column.
The calculator uses the formula:
Where:
Explanation: The heat required to vaporize the feed is divided by the latent heat of vaporization to determine the Q-value.
Details: The Q-value determines whether the feed is:
Tips: Enter the heat required to convert feed to saturated vapor and the molal latent heat of vaporization. Both values must be positive.
Q1: What does the Q-value indicate?
A: It indicates the thermal condition of the feed entering the distillation column.
Q2: How do I determine Hv-f?
A: It's the difference between the saturated vapor enthalpy of the feed and the feed enthalpy at inlet conditions.
Q3: Where can I find λ values?
A: Latent heat values are typically available in chemical engineering handbooks or thermodynamic tables.
Q4: What's a typical range for q?
A: Most industrial distillation columns operate with q-values between 0 (saturated vapor) and 1 (saturated liquid).
Q5: How does q affect column operation?
A: The q-value affects the slopes of the operating lines and thus the number of theoretical stages required.