Results 1 to 13 of 13

Thread: Design Help

  1. #1
    Join Date
    Oct 2008
    Location
    Dallas, Texas
    Posts
    8
    Rep Power
    0

    Design Help



    I am very green to this and have been thrown into something that I have to figure out.

    I had a manufacturer build a custom flushing stand for aircraft oil coolers. The fluid being flushed through the hot side will be mineral spirits @ 60GPM with 86Deg temp going into an American Industrial 4 Pass Heat Exchanger, P/N AB1002C6FP. The specs I have for the pump that is pumping this fluid- 7.5HP @ 60GPM/150psi. I need to find a chiller system that will work with the Industrial Heat Exchanger buit into the stand and take the 86Deg Minerial Spirits at the inlet of the heat exchanger and deliver 70Deg going out. I want to use water or a 50/50 mixture to achive this.

    When I do the equation, it comes to around 50Tons of cooling which has to be too much. The inlet and outlet of the cold side of the Heat Exchanger is only 3/4" and a 50ton chilling system is 5 times that or more.

    I know this may require more information than what I can give in the first port, ask what information you could need to help me and I will provide what I possibly understand or can provide.

    Thanks for any help with this.

    Eric



  2. #2
    Join Date
    Mar 2005
    Location
    USA
    Age
    76
    Posts
    639
    Rep Power
    20

    Re: Design Help

    First thing you need to do is give us the properties off your minerla spirits. Specifically, I'd need the specific heat (at conditions) and the desity of the product at conditions.

    Then on the mineral spitrits side, the equation is
    Q (heat load) = (mass flow) x (specific heat) x (Tin-Tout)

    ken

  3. #3
    Join Date
    Oct 2008
    Location
    Dallas, Texas
    Posts
    8
    Rep Power
    0

    Re: Design Help

    The density of mineral spirits is .78 but I have nothing on specific heat. I called our supplier and they said they had never even been asked that questions before. I searched the end of the earth on google and found nothing as well.

    Any other way I can get this info?

    Thanks for your help!

    Eric

  4. #4
    Join Date
    Oct 2008
    Location
    Dallas, Texas
    Posts
    8
    Rep Power
    0

    Re: Design Help

    I think I found that the Specific Heat is around .48 to.50 at the conditions I will be using it at.

  5. #5
    Join Date
    Oct 2008
    Location
    Dallas, Texas
    Posts
    8
    Rep Power
    0

    Re: Design Help

    Alos the mass flow will be around 450lbs per minute

  6. #6
    Join Date
    Mar 2005
    Location
    USA
    Age
    76
    Posts
    639
    Rep Power
    20

    Re: Design Help

    You have the answer at hand....

    BTUH = (250 x 60) x 0.49 x 16

    I don't have a calculator at hand... multiply it out.

    Ken

  7. #7
    Join Date
    Oct 2008
    Location
    Dallas, Texas
    Posts
    8
    Rep Power
    0

    Re: Design Help

    THANK YOU SO MUCH!!!

    I had guessed 10 toms before but that was a complete guess! Now you have given the exact calculation... I am getting 9.8 toms.

    I really appreciate your help with this!!!!!!!! YOU ROCK!

    Eric

  8. #8
    Join Date
    Oct 2008
    Location
    Dallas, Texas
    Posts
    8
    Rep Power
    0

    Re: Design Help

    That was 10 tons not toms... hahahaha

  9. #9
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,326
    Rep Power
    25

    Re: Design Help

    whoops. The mass flow you stated was 450 lbs per minute, so that would make the load:

    (450 X 60) X 0.49 X 16 = 211,680Btu/hr or about 17.6 Tons.

    The 9.8 Tons is correct if the mass flow is 250 lbs per minute.
    If all else fails, ask for help.


  10. #10
    Join Date
    Oct 2008
    Location
    Dallas, Texas
    Posts
    8
    Rep Power
    0

    Re: Design Help

    Thanks for your help!

    Now how do you get roughly 18 tons of chilling go through the 3/4 inlet and outlet of the heat exchanger cooling side efficiently. Does it matter if the exchanger is a 4 pass system?

  11. #11
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,326
    Rep Power
    25

    Re: Design Help

    Generally, you can the number of passes controls the pressure loss in the heat exchanger. 4-passes will have a higher pressure loss than 2-pass for the same flow volume and fluid mixture.

    My suggestion is to use water for cooling the mineral spirits since the fluid temperatures are certainly above 32°F. If the chiller is located indoors and above freezing temperature all of the time, why would you need a 50/50 mix of glycol?

    Another suggestion is to use this process as a DX evaporator cooling the mineral spirits directly. Refrigerant on one side of the heat exchanger and the mineral spirits being pumped through the other side. This would be simpler than chilling water or glycol and then using the water or glycol to cool the mineral spirits.
    If all else fails, ask for help.


  12. #12
    Join Date
    Mar 2005
    Location
    USA
    Age
    76
    Posts
    639
    Rep Power
    20

    Re: Design Help

    My boo-boo, if your flow is 450 #/minute, use 450, in the calculation. That is what happens when you are trying to type on a lap top in your lap in a semi-dark room.

    If you use plain water on the other side, and a 20 df range, your water flow would be 21.6 GPM from 45 to 65 dF or 40 to 60 dF.

    If you used water from 40 to 65 dF, your flow would be 17.28 GPM.

    For a 3/4" pipe, 14 GPM put you at 8.4 fps line velocity and 70.5 ft of head loss per 100' of pipe. This is a bit on the high side.

    Do you know why you are limited to a 3/4" connection?

    You may need to look at replacing the HX on the unit if that is what is limiting your connecton. Look at a brazed plate cooler such as manufactured by Flate Plate.

    You have a good source of information for this type application in the DFW area. Look for BruceBoldy on this forum.

    Ken

  13. #13
    Join Date
    Oct 2008
    Location
    Dallas, Texas
    Posts
    8
    Rep Power
    0

    Re: Design Help

    Thanks Ken,

    The 3/4in line is what is on the heat exchanger that is sized from my system. The actual inlet and outlet on the Heat Exchanger is 3/4. I was told I need 70 Deg process fluid for my application but after looking at the aircraft manuals, it does give me a requirement for low or high temperature. I am using mineral spirits so my only restriction is to keep the fluid low enough to not allow excess vapors to build up. The boiling point of the Type II fluid I am using is 174C and the flash point some place around 40C. I think I just need to size my chilling system to maintain ambient or keep it just below that without it rising.

    Eric

Similar Threads

  1. Replies: 3
    Last Post: 28-01-2008, 09:29 PM
  2. Efficient Water-Source Condenser Design?
    By Enginerd in forum Fundamentals
    Replies: 4
    Last Post: 28-05-2007, 05:11 AM
  3. Replies: 31
    Last Post: 28-11-2006, 11:32 PM
  4. How to Design Refrigerated Cabinets
    By Rayin in forum Fundamentals
    Replies: 5
    Last Post: 26-11-2006, 09:27 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •