The objective of the assignment is to provide design calculations that will provide preferred parameter values satisfying extremes of ECS requirements, for a 490 seat, ten-abreast, long range civil transport.
The following parameters should be evaluated:
1) the pack mass flow rate,
2) the pack outlet temperature,
3) the percentage re-circulation rate.
Any other parameter values used in the calculations should also be reported.
The ECS pack must be capable of providing passenger comfort and safety in cruise conditions and under the following two extreme conditions, both referred to a prolonged ground-holding period at an airport.
a) very hot climate, with and without strong winds, air temperature, ISA +25oC.
b) very cold climate, with and without strong winds, air temperature, ISA - 40oC.
It is expected that you will provide calculations of skin temperatures, ECS mass flow rates and recirculation flow rates. You should provide reasoned arguments for any parameter values selected, and use accepted targets of cabin temperatures and fresh air requirements.
Cruise conditions considered should be relevant to a typical aircraft role, and should be stated clearly in your report. However, typically, the cruise Mach number will be M = 0.85, with cruise in the stratosphere.
A fuselage length in the region of 70m is practical. You may select an existing aircraft type in order to derive cruise data and fuselage length. A table of atmospheric properties is provided.
You should state any assumptions made, provide a discussion of the results you obtain, and identify any design compromises and worst case conditions.
Standard project report structure should be used. Marks will be awarded for clarity of style, application of design method, accuracy of calculations, demonstration of physical insight, and standard of presentation.
This material may consist of step-by-step explanations on how to solve a problem or examples of proper writing, including the use of citations, references, bibliographies, and formatting. This material is made available for the sole purpose of studying and learning - misuse is strictly forbidden.Target fresh air = 0.005793 kg/s
Hence, our first estimate is not sufficient. Reduce Tecs to -20oC using a sub-zero bootstrap system, to give
mecs/Np = ( + 307.25 )/(1005*(22 + 20) = 0.00728 kg/s/Pax
This is bigger than minimum requirements but must remain as Tecs is low enough.
Use re-circ to reduce cold air shock to passengers – raise Tin to 5oC.
mr Tc + mecs Tecs = ( mr + mecs ) Tin
mr 22 + 0.00728*(- 20) = ( mr + 0.00728 ) 5
mr = 0.01 kg/s
re-circ = 0.01/( 0.01 + 0.00728 ) = 0.59 = 59 %
This is satisfactory for a short period.
If we reduce re-circ to 50%, Tin = 1oC - this is too low....