Ultrasonic agitation and mixing

Discussion in 'Physics' started by EatingSnakes, Oct 14, 2016.

  1. EatingSnakes

    Thread Starter New Member

    Oct 14, 2016
    Hey guys

    I'm an amateur biodiesel enthusiast
    I want to increase the agitation between triglycerides and methanol to produce fatty acid methyl esters and want to use an ultrasonic transducer to do this.
    I have seen successful test batch reactions in ultrasonic cleaners and wanted some advice on optimising the process.
    Does the frequency/wattage need to be optimised to the size of the vessel in which the reactants are mixed?
    Does the frequency/wattage need to be optimised to the viscocity (or other properties) of the reactants?
    or is it as simple as increasing the frequency/wattage will increase agitation?

    Thanks in advance for all the help

  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
    Mostly a function of wattage and viscosity. Lower viscosity materials are more easily mixed. Google "mixing energy".

    Also, if two phases are present, (oil and methanol, for example) the rate of the reaction will be dependent on the rate of mixing - specifically, the shear or turnover at the liquid-liquid interface to remove product from the interface and replace with raw materials.
  3. Paul van den Bergen

    New Member

    Dec 15, 2016
    I think you have got the right idea - that improved mixing is required to improve reaction rate. The problem I can forsee is scale - you might not be able to move enough material at scale to make a difference. This is down to power. Power needs to scale with the volume of material being agitated.

    I'm going to preface this with, I don't know what I'm talking about... - but - IIUC, in terms of the circuit design, the resonance frequency of the circuit depends in part on the mechanical load/response from the material in the bath - increased viscosity will increase the load and change the resonance frequency (and current drawn - which is where trouble might arise).

    Personally I'd try a mixing pump first and if that doesn't work, perhaps you can bolt on a "closed bath" that the pump pumps through... YMMV...
  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010