Great answears from SNS3Guppy and Old Fella despite my question was not raise up good, I see it now after I have read it. Also I see I have mixed a lot of stuff, but please forgive me for that, as I am not the proffesional, but I am interested in planes since I am playing the Microsoft flight simulator, and I wish to know more about aeronautics and techology of a plane.
I now see that pneumatic system on an airliner isn't that connected as I thought. Based on my understanding of your answers I see that deicing and fuel heating is really separate system from environmental control system.
So if you allow (and I hope others won't get mad) I' ll wish to question (discous) some further into the topic.
I also made a quick schematics (picture says more than a 1000 words) of how I now understand the ECS on an airliner and wish that you either confirm or correct it. Also please show where is the connection for other pneumatics system - braking, water&fuel tanks pressurization, deicing, hydraulic dempand pump (B747)...
And why is there a need for a centrifugal compresor, why bleed air isn't extracted from high pressure compressor stage in an engine - sure there is more than 32 psi of pressure? Than it will be cooled down and depressurised via expansion turbine?
BTW are objects marked red on the picture below air vents for air to air heat exchangers?
simple ECS schematics
The pressure and temperature data of air at different stages is according to wikipedia. I aslo found some equations that describes the connection of temperature and pressure of air during the compression / decompression. Here they are;
These equations should describe air during adiabatic compression and decomression in constant air mass, so we could use it for calculating the temperature and pressure of air durring compression in a piston compressor, but as far as I read this is not so in a radial compressor. Also I don't think that we have constant air mass because we don't have close cylce. But equation that describes the heat power losses over the fuselage walls should be correct. And that was my consideration earlier in the topic. Is it really necesary to maintain inside temperature with an open loop system - energy transsfer between inside and outside of a fuselage isn't done through the heat exchangers but rather directly - warm or cold air is constantly flowing throug fuselage.
Personaly I thinh that safe level of CO2 in cockpit and air pressure could be maintained with little amount of fresh air introduction, but maintaining the desired temperature could be done throug air to air heat exchanger - (similar as in central heating system for houses). Meaning that hot pressurised bleed air directly from engine would warm or cold air directly from ACM would cool the inside of a fuselage through a separate heat exchanger. Well I don't say this will do any better, maybe this extra fuselage heat exchangers and pipes would raise the weight of a plane too much, maybe efficient cooling with cool air and a heat exchanger wouln't even be possible because of a low air density.
But one is for certain, any heat taken from the engine is a loss of energy, so why cargo planes, that don't even need lots of air refreshing don't have this kind of system where bleed air is warming the fuselage via heat exchanger? Maintaining a safe air pressure and CO2 % in the fuselage can be done with a very low air stream from ACM. In this kind of configuration pressurised hot bleed air that will heat up the fuselage will be returned to the engine - to a lower stage compressor so pressure difference will be obtained and less energy will be lost.
And just the last think on my mind, also earlier mentioned in my thread.
Could instead of air to air heat exchangers, cooling of bleed air will be done by liquid to air heat exchanger with fuel as liquid. As I know jet fuel is certified for operating down to -37°C. 30-36,000 feet above is -56°C so is fuel really heated just prior it is injected into the combustion chamber? If the bleed air will be cooled down trough wing's leading edges, (doing usefull job) and fuel, the energy taken away from engine will be renewed throug fuel that is sooner or later injected to the engine. Aslo at plane stationary on the ground with hot outside temperatures, bleed air could be cooled down to temp od a fuel and when decompressed throug expansion turbine it will be cool enough to make its job.