Has anyone else 3D printed a custom slim hose for their Midea Duo?

I've spent alot of time messing with the Midea Duo hoses because that stock design is incredibly bulky for anything other than a standard vertical sash window. Using PETG was definitely the right call here. PLA would've turned into a puddle the first time the exhaust hit 120 degrees, and ABS is often too brittle for the constant vibration of a portable unit. The thermal expansion cycles on these units are no joke, especally when you're switching between cooling and the heat pump mode in the winter.

The biggest hurdle with a slim-profile mod is maintaining the **cross-sectional area**. Even if the volume seems the same, rectangular ducts have more surface friction than round ones. You have to be careful not to introduce too much static pressure, or the fan won't be able to push the hot air out fast enugh. That usually leads to the compressor cycling off early because it's overheating. If you kept the internal dimensions wide enough to match the original square inches of the stock hose, you're probably safe, but it's something to monitor during a heatwave. Separating the intake and exhaust directionally is a huge efficiency win. Most people don't realize how much 'short-circuiting' happens with the stock window kit where the unit just sucks back in the hot air it just blew out. That honeycomb grid on the intake is a nice touch for debris, though I'd keep an eye on it for dust buildup. If those holes are too small, they'll clog up faster than a standard filter and starve the condenser. I've seen some people use 6-inch insulated flexible ducting meant for HVAC to solve the hose diameter problem, but it looks terrible in a living room. Your approach of printing custom adapters is really the only way to actually get the blinds to close properly. It’s a lot of work, but the reduction in **radiant heat** coming off the hose makes a massive difference in how hard the AC has to work to keep the room at a steady temperature.

That static pressure stuff has me a bit worried. I'm new to this and just bought a Duo, but I don't own a 3D printer. If I try to build a slimmer window box out of plywood, how do I actually measure if the air is moving fast enugh? I'd hate to burn out the motor just because I wanted my blinds to close. Also, is the radiant heat relly that bad on the stock hose? It feels like a space heater sometimes when it's running full blast, so I'm wondering if just wrapping it in insulation woud be an easier first step for a newbie like me.

To check your airflow without expensive gear, just grab a cheap handheld anemometer. If the wind speed at the exhaust exit is significantly lower than with the stock setup, you're putting too much stress on the fan. Regarding that 'space heater' feeling, it's very real. Even with a custom plywood box, I'd highly recomend wrapping the setup in Reflectix or thin foam insulation. It’s a game changer becuase that thin plastic hose is a massive heat sink. If you can’t keep the heat inside the ducting, your AC is fighting itself. Just make sure your plywood joints are airtight with foil tape so you aren't leaking hot exhaust back into the room.

If you're going the custom route, watch out for the noise levels. When I tried squishing a duct to fit behind my curtains, the air turbulence made it sound like a jet engine was in my bedroom. Round hoses are quiet beacuse the air flows smooth, but those custom sharp angles in 3D prints can create a whistling sound or a deep hum. If you notice it getting louder, you might need to sand down the inside of your printed parts or round off the internal corners to keep the airflow laminar. It’s one of those things you don't think about untill you're trying to sleep through a heatwave.

One thing people overlook with the Duo is the internal divider. Since it's a hose-in-hose design, if your custom adapter doesn't have a perfect airtight seal between the intake and exhaust chambers right at the back of the unit, you'll get internal bypass. This makes the compressor work twice as hard becasue it's essentially breathing its own exhaust before the air even leaves the machine. I used some EPDM weatherstripping on my custom flange to make sure those two channels stay totally isolated. It’s also smart to check the PETG near the coupler after a long run; even PETG can soften if the heat soak gets high enugh during a 100-degree day.