# What is Mass transfer: Definition and 40 Discussions

Mass transfer is the net movement of mass from one location, usually meaning stream, phase, fraction or component, to another. Mass transfer occurs in many processes, such as absorption, evaporation, drying, precipitation, membrane filtration, and distillation. Mass transfer is used by different scientific disciplines for different processes and mechanisms. The phrase is commonly used in engineering for physical processes that involve diffusive and convective transport of chemical species within physical systems.
Some common examples of mass transfer processes are the evaporation of water from a pond to the atmosphere, the purification of blood in the kidneys and liver, and the distillation of alcohol. In industrial processes, mass transfer operations include separation of chemical components in distillation columns, absorbers such as scrubbers or stripping, adsorbers such as activated carbon beds, and liquid-liquid extraction. Mass transfer is often coupled to additional transport processes, for instance in industrial cooling towers. These towers couple heat transfer to mass transfer by allowing hot water to flow in contact with air. The water is cooled by expelling some of its content in the form of water vapour.

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1. ### B Mass transfer between neutron stars in a binary pair

When we read about the mass transfer between neutron star pairs in a binary system, how is it that the one receiving the matter can increase its spin rate. Adding mass to a spinning object ought to slow due to conservation of momentum. Where does the energy come from?
2. ### Engineering Mass Transfer in a wetted-wall column

Please can someone assist me as this particular question seems to have me completely confounded?
3. ### Boundary conditions for convective heat and mass transfer + wall Temperature

I am operating via finite differences. Say for example, I have this pipe that contains a fluid. I have the boundary condition at x = x1: k is the effective thermal conductivity of the fluid, T is the temperature of the fluid at any point x, hw is the wall heat transfer coefficient, and Tw is...
4. ### Mass Transfer in a Binary Star System

Homework Statement: A binary star system consists of M1 and M2 separated by a distance D. M1 and M2 are revolving with an angular velocity w in circular orbits about their common center of mass. Mass is continuously being transferred from one star to the other. This transfer of mass causes...
5. ### Mass transfer coefficient from a numerical model

Dear all, For an assignment, I am trying to find the relationship between the Sherwood number and the Reynolds number in a channel for different laminar velocity profiles, where there is a concentration of a species at both the top and bottom wall which is transported to the fluid. For this, I...
6. ### Mass Transfer: are both convective mass transfer and eddy diffusion the same?

I have studied that mass transfer is of two types Molecular mass transfer(diffusion) Eddy diffusion then in later portion of the book I found that there is convective mass transfer too, I wanted to ask if both convective mass transfer and eddy diffusion are same ? I read this equation N_i =...
7. ### Mass transfer and absorption

A gas stream containing 3% A is passed through a packed column to remove 99% of A by absorption in the water . The absorber operates at 25 degree Celsius and 1atm and the gas and liquid rates are to be ##20\frac{mol}{hr ft^2}## and ##100\frac{mol}{hr ft^2}##. Find the ##(NTU)_{OG}## ...
8. ### Various Pressures in mass transfer

I'm confused between partial pressure, total pressure, boiling point , vapour pressure , saturation pressure and saturation temperature.These things haunt me in my subject mass transfer. I get really confused when this words come in a liquid - vapour system, I cannot identify what these pressure...
9. ### Transport Phenomenon: Drag Coefficient & Friction Factor

My book states that when a flow around object is considered, Non dimensional momentum flux is defined as the drag coefficient In case of flow through tubes it states The non dimensional momentum flux is defined as the friction factor What do these statements mean? What do they practically...
10. ### Engineering Heat and Mass Transfer: Thermal Radiation Circuit

Homework Statement 1.) A piece of bread (ε = 0.85) is being toasted in a toaster, as shown below. The heating element of the toaster consists of a wire 2 mm in diameter that is wound to approximate cylinders spaced 2 cm apart. This element acts as a blackbody. The housing for the toaster is...
11. ### Heat and Mass Transfer: Nodal Networks

Homework Statement So this is more of a really vague conceptual question, I'm sorry if it doesn't really make sense. I'm in the stage of learning this where I don't quite understand things well enough to form a proper question. I'm a little bit confused about nodal networks in heat and mass...
12. ### Heat and Mass Transfer: Heat Out

Homework Statement The temperature distribution across a wall 0.3m thick at a certain instant of time is T(x)=a+bx+cx2, where T is in degrees Celsius and x is in meters, a = 200°C, b = -200°C/m, and c=30°C/m2. The wall has a thermal conductivity of 1W/m2K. (a) On a unit surface area basis...
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### A Questions about Taylor dispersion in laminar pipeflow

In the equation characterizing the mass transfer in laminar flow, the radial variation of velocity and concentration can be lumped into the axial dispersion term as below: After reading the original paper about Taylor dispersion, I know how to derive this equation. But I am still not able to...
14. D

### Heat and Mass Transfer Problem

Homework Statement A plastic pipe (k=0.092 W/m.K) of inner and outer radius of 1 and 1.25 cm, respectively. If the inner and outer surfaces are at 60 °C and 30 °C, respectively. The rate of heat transfer per unit length is close to: a) 98 W/m b) 89 W/m c) 78 W/m d) 168 W/m e) 112 W/m...
15. ### Shell balances in cylindrical coordinates

I have a question regarding writing a shell balance for a cylindrical system with transport in one direction (in any area of transport phenomena). When we set up the conservation equation(say steady state), we multiply the flux and the area at the surfaces of our control volume and plug them...
16. ### I What will be the flow direction?

I guess there would be no flow in case 2; case 3 seems easy to me applying fluid mechanics principle; flow will be 1 to 2. But I doubt case 1; it is not in thermal equilibrium ? Pls help
17. ### Heat and mass transfer analogy to find average Nusselt no.

I am trying to find an expression for the average Nusselt number corresponding to heat transfer from an isothermal disk. Given: ShD≡hm(r)D/DAB=Sho[1 + a (r/ro)n] (1) Sho=hm(r=0)D/DAB=0.814ReD1/2Sc0.36 (2) Relevant equations: Average nusselt number is defined as Nuav=havD/k where k...
18. ### Derivation of the Overall Mass Transfer Coefficient

Homework Statement The problem requires me to find the overall mass transfer coefficient or Kg. Homework Equations $$N_{1}=\frac{1}{\frac{1}{k_{p}+\frac{H}{k_{x}}}}(p_{1}-Hx_{1}), (1)$$ $$N_{1}=k_{p}(p_{1}-p_{1i}), (2)$$ $$N_{1}=k_{x}(x_{1i}-x_{1}), (3)$$ The Attempt at a Solution So, I...
19. ### Burning carbon particle -- Boundary conditions

I want to model the diffusion-controlled combustion of a small carbon particle. The system I want to model is similar to this one However, I'm not going to use the stagnant gas film model as shown in the figure, since I lack data for the film thickness, and I want to evaluate the problem...
20. ### Two-bulb experiment for measuring gas diffusivity

Hi, PF! I recently solved a problem from BSL which asked to analyze the following system used for determining the diffusivity of a binary mixture of gases. The left portion of the system, from the left bulb up to the stopcock at the middle of the tube, is filled with gas A. The right portion...
21. ### Diffusion -- Tarnishing of metal surfaces

Homework Statement Problem 18B.13 from Transport Phenomena, BSL. Tarnishing of metal surfaces. In the oxidation of most metals the volume of oxide produced is greater than that of the metal consumed. This oxide thus tends to form a compact film, effectively insulating the oxygen and metal from...
22. ### Difference between Thiele modulus and Damköhler number

Hi, PF! In the study of mass transfer involving chemical reactions, I have seen the use of two different non-dimensional parameters which apparently quantify the same ratio. These are the second Damköhler number and the Thiele modulus, which are defined as \textrm{Da}^{\textrm{II}} =...
23. ### Modeling a tubular reactor

Good evening, PF! I am supposed to model the following system. I will be using the same notation as in BSL. Fluid A enters the reaction zone at z = 0 at a concentration CA0. A reacts to form B in the first order reaction A → B at a rate of R_A = k_1''' C_A. We assume the whole mixture to be...
24. ### Heat and mass transfer -- Boundary conditions & balance terms

Hello, PF! Recently, while reading chapter 10 (microscopic energy balances) of the second edition of BSL, I found a minor discrepancy which is confusing me, especially when considering the mathematical analogies of heat and mass transfer. In section 10.1, the authors introduce Newton's law of...
25. ### Engineering A choice for a Heat and Mass Transfer Reference TextBook

Which of the two books would you pick as an undergraduate engineering student if you were to study the subject of Heat and Mass Transfer entirely on your own? 1. Heat and Mass Transfer: Fundamentals and Applications by Cengel & Ghajar 2. Fundamentals of Heat and Mass Transfer by...
26. ### Question on Mass transfer coefficient (Sc Number)

Homework Statement What is the mass transfer coefficient for natural convection from rock salt (assume flow is over a horizontal cylinder (salt crystal) of length 2cm, diameter 0.5cm). Given: Temperature = 24degrees Density of salt 2165kg/m^3 Density of mixture when salt...
27. ### Mass Transfer (Wetted Column)

Dear all, I am currently doing a lab question. I do not know how to solve a calculation question. Question: Calculate the average flux of the oxygen through the gas-liquid interface in the wetted-wall column. Remember that a more accurate value of the average flux can be calculated by...
28. ### Rotation: mass transfer and angular momentum conservation

Homework Statement a drum of mass M_{a} and radius a rotates freely with initial angular velocity ω_{a}(0). A second drum with mass M_{b} and radius b greater than b is mounted on the same axis and is at rest, although it is free to rotate. a thin layer of sand with mass M_{s} is distributed...
29. ### Mass Transfer - Boundary Conditions

Homework Statement An airborne spherical cellular organism, 0.015 cm in diameter, utilizes 4.5 gmol O2/(hour kg of cell mass). Assume Sh = 4 for external convective resistance to O2 transfer to the cell. (Sh = kd/D is based on diffusivity in the gas phase). Assume zero-order kinetics for...
30. ### Mass Transfer - Need help on setting it up

Homework Statement Not looking for solutions, just confused with the problem set up. Need help with the boundary conditions. Here it is: A porous ceramic sphere of radius R1 is kept saturated with a pure component liquid A. The vapor pressure of A is 50 torr. This sphere is surrounded by a...
31. ### Fundamentals of Heat and Mass Transfer by Bergman, Lavine, Incropera & DeWitt

Author: Theodore L. Bergman (Author), Adrienne S. Lavine (Author), Frank P. Incropera (Author), David P. DeWitt (Author) Title: Fundamentals of Heat and Mass Transfer Amazon Link: https://www.amazon.com/dp/0470501979/?tag=pfamazon01-20 Prerequisities: Contents:
32. ### Mass transfer with with a pressure regulator

Hi all, I am trying to determine what approach to use to solve the following scenario: I have a pressure vessel with pressure P1 and volume V1. I have another vessel of pressure P2 and volume V2. Vessel #1 is supposed to be a high-pressure storage vessel and vessel #2 is supposed to be...
33. ### Mass Transfer Problem question

Consider a chemical species A, which is soluble in water. The equilibrium of this system with A in air is described by the following question: C(air) = HC(water) where C(air) is mass concentration of the species in air C(water) is the mass concentration in water, and the Henrys Law constant...
34. ### Evaporation of Water Mass Transfer

Hi I had a question regarding an example about mass transfer. I already have the solutions to this but there is one thing I am confused about. The problem just asks the rate of evaporation from the water-air surface to the atmosphere at a given temperature, pressure, and relative...
35. ### Heat and Mass Transfer Problem

Hi everyone I've got a problem about the convective heat loss from a spa any help or pointers would be greatly appreciated A person installed a circular outdoor spa bath in the open area. In a typical operating condition, when the spa water is maintained at 37°C, and when the ambient air...
36. ### Momentum problem with mass transfer

Homework Statement (Kleppner & Kolenkow - Introduction to Mechanics - 3.12) A sand-spraying locomotive sprays sand horizontally into a freight car situated ahead of it. The locomotive and freight car are not attached. The engineer in the locomotive maintains his speed so that the distance to...
37. ### Mass Transfer - GAS ABSORPTION help

Homework Statement A Mixture of air and acetone is being vented from a solvent recovery plant. The air has to be scrubbed and this is done by absorbing the acetone into water in an absorption column. The acetone is present in small amounts and its concentration never rises above 4 mol % of the...
38. ### Heat and Mass Transfer - finding surface temp

Homework Statement A wire is conducting electricity, given values of : R' = .4 ohms/m D = .002 m Tinf=300k Tsur=300k k=380W/m*C emissivity = 1 h=10W/m^2*C Ts = Find this sigma=Stefan boltzmann Plot the Temperature of the wire...
39. ### Heat and mass transfer empirical equations

I guess this question applies to deriving empirical equations from any data set but in my engineering studies I've wondered this when working with heat and mass transfer. When you do an experiment and want to identify the governing equation for the process, is it simply a case of bringing...
40. ### Mass transfer between black holes

Hypothetical scenario: A small black hole passes by a much larger black hole at a velocity large enough to avoid capture. Is there any chance that the tidal forces generated by the gravitational field of the larger black hole could cause part of the smaller black hole's mass-energy to...