Delta T refers to the difference in between your vapor temp and evaporation temp doesnt it?
Example above: (tell me if I’m wrong)
If I’m at 130 torr and my ethanol evaporates at 37c, since delta T is 30, I’d be raising the temp of my ethanol vapor to 67c correct?
The reason I’m asking about this is for pre heating, I’m trying to figure out a way to prevent boiling my ethanol in the plate pre heaters when using the hot vapor to pre heat. I think I could do this by using a plate heat exchanger to cool the vapor down into a liquid before running it though the plate pre heaters that pre heat the crude.
“ Delta T ” is the most common use of the word delta in the HVAC industry, meaning temperature difference. If the temperature before a cooling coil is 75F and the temperature after the cooling coil is 55F, subtract 55F from a 75F to find a delta t of 20F.
First, DM me and I’ll give you my phone number and explain.
But let me try to clarify—you need to calculate heat required to raise the temperature of your solvent from T1 to its boiling point T2. This is where heat capacity comes in—heat capacity is a function of temperature, but let’s assume it stays constant for the time being.
T2-T1 is delta T.
HEAT 1 = massheat capacitydelta T
The heat required to boil the ethanol, which is now at its boiling point requires using the “Latent Heat of Vaporization”. Which is a measure of how much energy is required to boil a unit mass of ethanol.
HEAT 2 = Latent Heat of Fusion*mass
Heat 1 + Heat 2 = Total Heat Requirement.
You can get that value in Joules or BTU.
Divide by the efficiency of the heater (safely assume 0.6 - 0.8) and that’s the size of a heater you’ll need.
Edit: I’m a dummy, you’re asking about superheating your vapor and you’ve already calculated what I provided here.
Terp is right, the pressure zones created will greatly complicate those calcs. You need to find how temperature/pressure affect heat capacity of ethanol vapor and then you can start calculating required heat addition/removal based on a more accurate heat capacity.
If I’m running the whole thing under vacuum though then theres only 1 pressure isnt there? As long as I dont have a check valve or a pump to create pressure on the crude side of course, if I put a pump in between the evaporator and pre heaters then I’d have different pressures wouldnt I?
I was told by someone smarter than me that if you want to do the 2 pressure zones youd need to treat them as seperate enteties then integrate them.
If I’m understanding your OP question correctly, you’re asking about how to prevent crude laden ethanol from boiling in your preheater(s), I’ll make an assumption this is regarding the input to the FFE you posted pics of in the “seems to be the cheapest falling film” thread?
Assuming that’s the case, and you are using a spray nozzle on your infeed side you will have two different pressure zones on either side of the spray nozzle as there is a restriction point there. Past the spray nozzle there will be a pressure gradient that is highest near the spray nozzle that gets lower as the vapor cools and finally condenses on your cold side, this pressure gradient is what keeps vapor moving from the evaporation side to the condensing side. This is true regardless of whether or not there is vacuum on the vapor path of the FFE.
IMO the easiest way to keep your input fluid from boiling is to plumb your inlet side like this
holding tank → pump → heat exchanger → spray nozzle.
Probably put a tee at the spray nozzle with a gauge too so you can see what pressure is occurring there
And figure out what your strategy will be to regulate/maintain pressure. A liquid held under positive pressure will take higher temperature in order to reach boiling temps, the reverse is also true (which is why water boils at 95C near Denver and even lower temps at higher altitudes)