I have been once again hard at work with simulations, optimizations, and calculations for the perfectly optimized BHO recovery system (okay maybe not perfect).
Has anyone heard of / played around with a high-pressure condensing system? The propane & butane mix is actually very close to what you need in a refrigerant in terms of boiling point and characteristics, I mean other than the explodey bit. Realistically you would need to compress the gas to at least 300 psi and ideally upwards of 500 psi, but there are quite a few compressing systems that would be able to achieve that. If you haven’t picked up on it yet, you could just use forced air to condense your butane back to liquid through a heat exchanger like any old HVAC system. You could use many of the same expansion valves that are used on chillers. I personally would only feel comfortable in a super controlled environment.
Also, I think it goes without saying, guys don’t use high-pressure flammable gasses to speed up recovery rates. This is more of a proof of concept… Lol
Well, your temperature would be related to pressure. Technically you could have whatever recovery rate you wanted you just need enough pressure. If you look at this phase diagram of butane, the boiling point would be 120 C which would have a delta T of 100 degrees. I know that it’s not exactly how it works (you know ideal gas law and all that), but that you should be able to achieve much better recovery rates. You are no longer limited by heat transfer from refrigerant to chiller fluid to butane. Even the 150 MVP recovery pump would work in some sense. The boiling point is close to 75 C at 150 psi.
What you’re asking about is air cooling a compressed gas then expanding it to cool. This is the condenser side of a refrigerant system. It works much more reasonably if you use water to condense it instead of air. Also, for a reasonably sized system, trying to compress your food grade process gas to use it for cooling makes far less sense than using a refrigeration compressor to do essentially the same thing.
Propane is actually superior as a refrigerant to most of the refrigerants used today. It’s just that it’s a flammable gas and I assume companies that manufacture appliances dont use it because it would be a bad look for a company to have its product on the news being attributed to someone’s house burning down if the lines happened to leak.
CO2 actually has higher COPs than 600 series refrigerants but isn’t widely adopted because common refrigeration components are only rated for 700psi and building systems for higher pressure are annoyingly more expensive than they should be. Fun fact I guess lol
Specific heat is more applicable in thermal storage, no? Given high throughput (which is much more achievable in air), you aren’t even hitting very high thermal saturation points so it more or less doesn’t matter.
I’m not really understanding what your contention is, maybe I’m just missing it.
The specific heat of water is substantially higher than air (I assume this is the metric which @cyclopath was using when saying thermal capacity).
Also, specific heat is per unit mass. Getting 10 kg/minute of water is very easy. 10kg/minute of air is more challenging using the same heat exchanger.
All I’m saying is that the cost for a water pump is less than the bank of radiators, and the piping simpler.
You’re probably still better off putting that coil in water. Misting water on the pipe is best but it’ll only get you so cold. The BTU capacity of a single 1/2" tube in air is going to be pretty dismal, just not enough thermal mass
