Engine Room ventilation - Air out issue

Discussion in 'Boat Design' started by Lucya, May 20, 2018.

  1. Ad Hoc
    Joined: Oct 2008
    Posts: 5,752
    Likes: 265, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Correct :)

    Ok..what engines do you have in the ER..and do you have any generators too?
     
  2. Lucya
    Joined: May 2018
    Posts: 24
    Likes: 0, Points: 1
    Location: Croatia

    Lucya Junior Member

    The grill is to be horizontally orientated.
     
  3. Heimfried
    Joined: Apr 2015
    Posts: 258
    Likes: 18, Points: 18, Legacy Rep: 37
    Location: Berlin, Germany

    Heimfried Senior Member

    I don't know anything about the intended fans, but just to give an example of a fan, which is able to deliver 19,650 m³/h (page 247 at the linked booklet): if you look at the graph it shows the nearly 20,000 m³/h are for "free discharge" (without any flow resistance). If the fan has to work against a pressure loss of e.g. 300 Pa, it delivers only 16,000 m³/h.
     
  4. Lucya
    Joined: May 2018
    Posts: 24
    Likes: 0, Points: 1
    Location: Croatia

    Lucya Junior Member

    :( At least something I said is correct.

    So, there are two diesel generators. each 65 kW

    Edit: to be less confusional, it is a barge.
     
  5. Ad Hoc
    Joined: Oct 2008
    Posts: 5,752
    Likes: 265, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Need make model number and tech data to get the spec's....since this give the heat rejection etc.
     
  6. Lucya
    Joined: May 2018
    Posts: 24
    Likes: 0, Points: 1
    Location: Croatia

    Lucya Junior Member

    Scania Diesel Gen OL 621 C / HCM 534 C - 265 kW
    (I missed "2" in post above regarding kWs)
     
  7. Heimfried
    Joined: Apr 2015
    Posts: 258
    Likes: 18, Points: 18, Legacy Rep: 37
    Location: Berlin, Germany

    Heimfried Senior Member

    You will not achieve this exhaust rate in the outlet duct without using the pressure created by the intake fans. That means, if the ER door is open, the air takes a different path. May be, this would also be sufficient for required cooling - maybe not.

    Assumed, the ER is closed, the 2 fans are able to deliver an intake of 11 m³/s against a pressure of say 300 Pa, then the 2 ducts will pass this flow rate to outside. But note that air velocities over (5 to) 7 m/s are tending to be noisy. Therefore in buildings they are unwanted. A ship is different, an ER is noisy too, but 20 m/s is a lot and pressure loss increases with air velocity.
     
  8. Lucya
    Joined: May 2018
    Posts: 24
    Likes: 0, Points: 1
    Location: Croatia

    Lucya Junior Member

    There are two ducts, so 2 x 0,3 m2 - resulting 10 m/s each? (Sum of Air-out cross section is 0,6 m2 - 6/0,6=10)... or I am doing it wrong, again?
     
  9. Ad Hoc
    Joined: Oct 2008
    Posts: 5,752
    Likes: 265, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

  10. Lucya
    Joined: May 2018
    Posts: 24
    Likes: 0, Points: 1
    Location: Croatia

    Lucya Junior Member

    40000 m3/h (around 11 m3/s), is the result I have for required ER airflow, since there are other equipment in the ER, not only generators.
    Are the 0,3 x 2 PCS outlet ducts cross section resulting sum of 0,6 m2 sufficient to exhaust ER air of 6 m3/s (this value should maintain the ER temperature at max. delta T of 10C) without using the fan assistance (fan is only in the Air-in duct, pushing the air into ER)? And if yes, what is the calc which (theoretically) proves it?
     
  11. Ad Hoc
    Joined: Oct 2008
    Posts: 5,752
    Likes: 265, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Sorry Lucya

    You're not reading correctly.

    So...please list AL THE ITEM OF COMBUSTION..in the ER.....and you replied:

    Just 2 gennies. But now you say:

    I have asked what is in the ER...you said 2 gennies..now you say there is more.?????????????!!!!!!!!!!!!!!

    Can't help you if you don't answer the questions.
     
  12. Lucya
    Joined: May 2018
    Posts: 24
    Likes: 0, Points: 1
    Location: Croatia

    Lucya Junior Member

    Yes, only two of generators which requires airflow for combustion + airflow for evacuation of heat emission from all of the ER equipment including gensets, exhaust pipes, other pipes in ER, electro cabinets incl. main switchboard, boiler for FW, pumps - of which I do not have at the moment asked data, only gensets).

    The result was 11m3/s airflow needed, taking into account the needed airflow for combustion for gensets and needed airflow for evacuation of all equipment and pipes heat emission included other parameters (air density, specific heat capacity of air and temp difference).

    But please, do not bother.
    Thank you anyway, appreciate your efforts so far very much.
     
  13. Ad Hoc
    Joined: Oct 2008
    Posts: 5,752
    Likes: 265, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    You are over thinking this, it is not a university exam question.

    What sources of combustion do you have inside the ER..in TOTAL....for get pipes/cabinets etc.

    You will have engines....yes???...if so..what size type and how many...do you have gensets...yes??..if so what size and how many.....any other major sources such as steering gear etc etc?

    That's it.

    You only need to focus on the major heat sources.
     
  14. Lucya
    Joined: May 2018
    Posts: 24
    Likes: 0, Points: 1
    Location: Croatia

    Lucya Junior Member

    I have edit my post before adding info that this is a barge, to make it less confusional, so only 2 gensets and already mentioned equipment/pipes are in ER. No propulsion.
     

  15. Ad Hoc
    Joined: Oct 2008
    Posts: 5,752
    Likes: 265, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    The skill of the engineer is to be factual no more no less and to have no ambiguity, and to comprehend the task at hand.

    So, if ONLY 2 genset as noted, the required air is 6.8m3/s (if i use the stand by power heat) so call it 7.0m3/s.

    This would give you something like:

    upload_2018-5-21_10-22-39.png

    With a pressure rise of no more than 250-300Pa.

    So this gives you an ELTA fan of 800 model:

    upload_2018-5-21_10-24-24.png

    From this you can work the rest out, as Hiemfried notes. But this is for a pressurised ER and the air-in and air-out will be noisy. Thus to avoid the noise path you should cite the air-in and air-out away from the main structure and these should be insulated too.

    Ideally, these fans should be controlled at 2 speeds so that in harbour (if noise control) or at cooler conditions the fan can be set at the lower speed to reduce noise and power consumption.
     
    Lucya likes this.
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.