How to determine the mass flow rate from the air velocity?
Thread Content
Dear sea friends, I would like to ask how to calculate the mass flow rate from the following data; the key is the steps. The inner diameter of the reaction tube is dt=31.3 mm, the length of the reaction tube is L=7 m, and the volume space velocity is SV=5500 h-1. What is the mass flow rate G? I found in relevant literature that G=7148 kg·m-2·h-1, but I cannot obtain this value through my own calculations; I urgently need everyone’s help! Thank you!
The mass flow rate you are referring to is different from what we understand: the unit of mass flow rate is usually expressed in units such as kg/h or kg/s, and its value is equal to the mass flowing. There is another way to express flow rate, called volumetric flow rate. If the mass flow rate of the fluid is w, in kg/h, and its density is ρ, in kg/m3, then the volume flow rate V is equal to w/ρ, in m3/h.
Air velocity (h-1) multiplied by reactor volume (m3) = volumetric flow rate (m3/h); the volumetric flow rate, when multiplied by density (kg/m3), gives the mass flow rate (kg/h).
Mass flow rate ws (with s as the subscript) refers to the mass of fluid that passes through any cross-section of a pipe per unit of time, and its unit is kg/s. ws = Vs*ρ, where Vs is the volume flow rate, with the unit of m3/s. Mass velocity G, also known as mass flux, represents the mass of fluid that passes through a unit area of the pipe per unit of time, and its unit is kg/(m2·s). G = ws/A = Vs*ρ/A = u*ρ, where u is the average flow velocity, with the unit of m/s. In reaction engineering, mass velocity (as defined in principles of chemical engineering) is often referred to as mass flow rate; in fact, the two terms denote the same concept. Hehe, it’s a bit off-topic. I hope everyone can pay more attention to the main topic; thank you! This post was last edited by wangcg2004 on 2009-4-17 09:59.]
Isn’t it simple then? Just divide the mass flow rate by the cross-sectional area! The 3rd floor has already told you how to calculate the mass flow rate!
Hehe, I tried it, but couldn’t find the answer in any literature~~