Re: How Many Fresh Overhead Air Vents Do You Have?
Posted: Sun Sep 17, 2023 2:50 pm
OK, I guess I need to describe my heating, ventilation and A/C systems. Being pressured, bleed air mixes with outside air, and is then either cooled (in the summer) by routing through the "Flow Pack" or kept warm with routing directly into the cabin (by passing the Flow Pack). My heat is delivered through vents under the instrument panel and at the feet of the rear seat passengers. (Well, the heat duct to the right back seat has a selectable valve to direct air to Beth's window to de-fog in the FL's in the winter when she desires to see outside).
My ventilation system, used only when NOT Pressurized (below 12K), is air routed from the NACA vent in the vertical tail, through a formed fiberglass tube (no flexible hose with the inherent drag and resistance) to a purpose built "VALVE" at the aft side of the upper seat close out panel. This valve will 100% close off ventilation air from the NACA Vent, which is absolutely necessary to allow pressurization. On the interior cab side of that "Vent System" is a gravity door that is top hinged to open with air flow from the NACA Vent, but close once my special purpose vent system "VALVE" is closed. This allows pressurization in spite of an outside air vent system.
The interior portion of A/C (Evaporator, & fan) is in the same "box" as the above stated Gravity door. On the ground, whether the engine is running or the plane is moving, I have the ability for all fan speeds including "high" when the Master Switch is on. The air flow I see from this fan is virtually identical in every phases of operation of my plane! That said, until I have started the engine, I have no actual A/C. My A/C system has an engine drive compressor. But, once running, with a turbine my A/C compressor speed is very high due to turbine idle being 70% of actual full power.
My system is likely much more complex than most, especially non-pressurized planes. But the point of my original submission was, if you have sufficient "fan volume", your vent size "COULD" be limiting the VOLUME of air you are getting out of your system.
A final note on "MY A/C". I was hearing a lot of complaints on the effectiveness of the typical IVP A/C in truly cooling the cabin down in hot weather, especially on the ground. The common system being used was 10k BTU. I spent my life working on commercial heavy vehicle A/C systems and decided I would build my own. I bought a commercial (Red Dot, a big supplier of Heavy Truck HVAC Systems) 16K BTU roof mount A/C unit. I removed all the critical components, built all the essential enclosures, mounts, attachments, etc. to install it in an efficient manner in my IVPT. I had an aeronautical engineer review and approve my inlet scoop to cool my condenser (for size, wind drag, flow, and structural integrity) which opens into the airstream for ground and climb out operations, and then can be closed during cruise for zero drag. I have no exit scoop because, after hearing Lance speak at a Lancair Banquette back in early 2000's, it was clear everything not tied down in the aft area's of the plane will find it's way out the tail surface gaps. I had many pilots, including Chris Rust, comment my A/C was the most effective they have seen in a IVP or IVPT. Chris would routinely ask me to turn it down because he was getting cold.
Tom
My ventilation system, used only when NOT Pressurized (below 12K), is air routed from the NACA vent in the vertical tail, through a formed fiberglass tube (no flexible hose with the inherent drag and resistance) to a purpose built "VALVE" at the aft side of the upper seat close out panel. This valve will 100% close off ventilation air from the NACA Vent, which is absolutely necessary to allow pressurization. On the interior cab side of that "Vent System" is a gravity door that is top hinged to open with air flow from the NACA Vent, but close once my special purpose vent system "VALVE" is closed. This allows pressurization in spite of an outside air vent system.
The interior portion of A/C (Evaporator, & fan) is in the same "box" as the above stated Gravity door. On the ground, whether the engine is running or the plane is moving, I have the ability for all fan speeds including "high" when the Master Switch is on. The air flow I see from this fan is virtually identical in every phases of operation of my plane! That said, until I have started the engine, I have no actual A/C. My A/C system has an engine drive compressor. But, once running, with a turbine my A/C compressor speed is very high due to turbine idle being 70% of actual full power.
My system is likely much more complex than most, especially non-pressurized planes. But the point of my original submission was, if you have sufficient "fan volume", your vent size "COULD" be limiting the VOLUME of air you are getting out of your system.
A final note on "MY A/C". I was hearing a lot of complaints on the effectiveness of the typical IVP A/C in truly cooling the cabin down in hot weather, especially on the ground. The common system being used was 10k BTU. I spent my life working on commercial heavy vehicle A/C systems and decided I would build my own. I bought a commercial (Red Dot, a big supplier of Heavy Truck HVAC Systems) 16K BTU roof mount A/C unit. I removed all the critical components, built all the essential enclosures, mounts, attachments, etc. to install it in an efficient manner in my IVPT. I had an aeronautical engineer review and approve my inlet scoop to cool my condenser (for size, wind drag, flow, and structural integrity) which opens into the airstream for ground and climb out operations, and then can be closed during cruise for zero drag. I have no exit scoop because, after hearing Lance speak at a Lancair Banquette back in early 2000's, it was clear everything not tied down in the aft area's of the plane will find it's way out the tail surface gaps. I had many pilots, including Chris Rust, comment my A/C was the most effective they have seen in a IVP or IVPT. Chris would routinely ask me to turn it down because he was getting cold.
Tom