Achiro
Mechanical
- May 11, 2018
- 5
Dear all,
would appreciate if anyone is willing to help me with following:
I manage to figured out the ventilation calculation for duct/grilles sizing for E.R. inlet (but need to double check, air-in is not the issue).
Calculated following:
1. Airflow for combustion from engines (Value X - m3/s)
2. Airflow for evacuation of heat emission (Engines, pipes, electro cabinets) (Value Y - m3/s)
3. Total airflow required (Value Q - m3/s) / devided by 2 (two ducts)
4. Maximum airflow velocity shall not exceed (v): 6 m/s
5. Duct sizing (minimum): A = Q/v (m2)
6. Air Inlet grilles have a pressure drop of following: ∆p = 1,4 x v2
7. Calculation of new flow velocity (∆p, ω, where ξ=2,5 (minor loss coef.); ρ=1,13kg/m3 (air density))- v/ω =1,15
Velocity needs to be increased by 15%; Q(1) = Q x 1,15 (m3/s)
8. v(1) = Q(1)/A = 8 m/s
9. Second iteration: ∆p = 1,4 x v(1) ; ω(1)
10. Fan in air out requires minimum of free flow rate of Q(1) - condition satisfied.
(Air density: 1,13 ; Base temperature: 30 degree celsius; Peak temp: 40 degree celsius;
temp. difference: ∆T =10; Minor loss coef: ξ=2,5; Specific heat capacity of air: c=1,01)
My question is following:
How to calculate minimum Air-OUT ducts and Grilles size, in a way to avoid use of fan pushing air out? (natural outlet of air)?
The ducts/grilles must be sufficient to exhaust this amount of air - without creating a large back pressure issue.
Which formula do I need to use?
In attachment preliminary plan and side views.
Thank you very much all in advance.
would appreciate if anyone is willing to help me with following:
I manage to figured out the ventilation calculation for duct/grilles sizing for E.R. inlet (but need to double check, air-in is not the issue).
Calculated following:
1. Airflow for combustion from engines (Value X - m3/s)
2. Airflow for evacuation of heat emission (Engines, pipes, electro cabinets) (Value Y - m3/s)
3. Total airflow required (Value Q - m3/s) / devided by 2 (two ducts)
4. Maximum airflow velocity shall not exceed (v): 6 m/s
5. Duct sizing (minimum): A = Q/v (m2)
6. Air Inlet grilles have a pressure drop of following: ∆p = 1,4 x v2
7. Calculation of new flow velocity (∆p, ω, where ξ=2,5 (minor loss coef.); ρ=1,13kg/m
Velocity needs to be increased by 15%; Q(1) = Q x 1,15 (m3/s)
8. v(1) = Q(1)/A = 8 m/s
9. Second iteration: ∆p = 1,4 x v(1) ; ω(1)
10. Fan in air out requires minimum of free flow rate of Q(1) - condition satisfied.
(Air density: 1,13 ; Base temperature: 30 degree celsius; Peak temp: 40 degree celsius;
temp. difference: ∆T =10; Minor loss coef: ξ=2,5; Specific heat capacity of air: c=1,01)
My question is following:
How to calculate minimum Air-OUT ducts and Grilles size, in a way to avoid use of fan pushing air out? (natural outlet of air)?
The ducts/grilles must be sufficient to exhaust this amount of air - without creating a large back pressure issue.
Which formula do I need to use?
In attachment preliminary plan and side views.
Thank you very much all in advance.