Calculation of the Product or Reflux Condenser Operation
There are many process variables that are needed to calculate condenser operations, this calculator uses most of them.
A PC product condenser cooling water flow rate and temperature rise is predicted for a given pot ABV % charge, pot heating watts and the expected (calculated) product vapor rate for a stripping operation.
A plate or packed reflux column RC or PC condenser can also be evaluated. You decide what still and condenser you want to evaluate. Condenser information for a RC is calculated using the expected vapor rate up the column minus the take-off product rate. Input data for the product take-off rate and vapor abv % is based on your experience or from what would likely result during the run.
In the input data, the condenser dimensions are specified. You decide if it is a shotgun or dimroth coil condenser. The initial abv % and watts of the pot are specified along with an expected cooling water flow rate and known inlet temperature.
The calculated results first give the temperatures into and out of the condenser, then the vapor rate and the Heat Transfer Required ( Watts ) to do the condensation of the vapor going into the specified
condenser. Next, the heat transfer area ( A ) of the tubes is given. The log mean temperature difference ( LMTD ) between the vapor and cooling water and the Overall Heat Transfer Coefficient ( U ) are calculated and given next, they vary with the cooling water flow rate. The reflux condenser Heat Transfer is calculated as: { Watts = U * A * LMTD * 0.293 }. Then the program gives the cooling water (cw) flow rate and exit cw temperature and you check that it meets or exceeds the required heat transfer.
For a CM deflagmater condenser, you can have the program search for the required cw flow rate or use your input value. For the search option, the program finds the cw flow rate which makes the Condenser Heat Transfer about equal to the Heat Transfer Required. For a VM or CCVM reflux column, the Condenser Heat Transfer should be 10% to 15% higher than the Heat Transfer Required, and the cw exit temperature should be in the range of about 110F to 125F. You can also search for the PC cw flow rate needed for a stripping operation.
An estimate of the total still heat loss is a required input. For very well insulated pot and column, use 20% heat loss. For average insulation or not the pot insulated, use 30% heat loss. For uninsulated stills, use 36% to 40% heat loss.
If during a search procedure to find the best cw flow rate you get a NaN ( not a number ) in the results, lower the input cw flow rate value, run again and the results will come back. If the two heats are not quite equal, input the last cw flow rate from the search. If you are not searching and NaN appears, increase the input cw flow rate value.
For more background information, see the thread "New Condenser Calculator".