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Vacuumed Evaporative rates

  1. Aug 6, 2014 #1
    Hello Physics Forum Members,

    I have chosen this particular forum topic area because I was not to sure in which it would belong or if this is the appropriate forum site for such topics at all other than a having a pool of expert on such matters. If a member(s) believes or knows of a more appropriate forum, I would appreciate the direction. I am a budding entrepreneur, and as such I am finding that equipment vendors are either unable to provide full solutions or quite vague - knowledge being proprietary perhaps.

    I am building a proto evaporation tank to evaporate a sugared liquid from 3% to 6%.
    The evaporation tank will send vapour to a shotgun condenser then to a catch tank – I want to save the water for reconstitution- I am formulating a pop/cola.
    A venturi will be installed between the evaporation tank and the condenser to pull a vacuum at 1”HG/25.4 mmHG/0.03 atm – that should allow me to evaporate somewhere around 25 deg C. As well a venturi will be placed between the catch tank and the condenser to pump the condensate into it – 10”HG/254 mmHG/0.33 atm.

    Some specs:

    225 liter round evaporation tank/flat bottom – 45 deg down pumping pitch blade impeller at center bottom – turbulent flow with baffles – top surface area (liquid level full) – 0.292 sq meters
    - turbulent flows should actually help with evaporation.

    Liquid – 3% sugar reduced to 6% sugar - approx. 1 to 150 cP, p ≈ 1 - 1.3 g/cm3 ≈ 1.3 kg/L , μ ≈ 1.14 - 1.19 mPa/s - approximately half/112.5 liters of water to be removed.

    In-tank heaters will be used: not to boiling but rather to 80-90 C to apply a slow pasteurization method. This will take place during evaporation by applying heat to batch contents from the beginning starting at 25 C – with any luck, arriving at this temp by the time the evaporation stage is complete. And of course this will raise pressures.

    I realize that there are a number of variables here. I’ve tried to cover as many specifications as possible – I am not a calculus guy – but can punch numbers in a calculator as good as any. This is where my questions come in;

    Is there a formulation I could use to calculate the evaporation flow rate and the time to spec – 3% to 6% sugar of evaporation tank?

    Is there a formulation I could use to calculate the dew point or points temperature required of the condenser – the required temp of the circulating fluid to allow condensing? It is a shotgun type condenser (tube in shell with cold fluid pumped through it).

    Could you provide an example using the above specs ?

    Do you foresee any problems with this setup or have any recommendations?

    Empirical formulations are fine as from what I’ve been reading it is not an exact science – but close would be nice. My efforts to use equilibrium equations (Clausius–Clapeyron, PV=nRT, etc...) have gotten me no where.

    Well, that’s a mouth full.

    Appreciate any help.


    David S.
  2. jcsd
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