juk
08-02-2014, 10:34 AM
I've got a lotus elise, which has a couple of problems.
1). I filled the engine bay up with a dirty big motor and supercharger, so i can't fit an aircon compressor in there.
2). The engine is in the back, and the radiator in the front, so aluminium pipes full of hot water run from front to back and return inside aluminium channels, these channels get hot, turning into radiators and blast you with heat.
3). The radiator heat soaks and so the front of the car blasts you with heat too.
4). I live in Australia, where the sun is very hot, very very hot, crazy hot and the car doesn't always have the roof on.
All this isn't so bad when you're moving, but stuck in traffic and you begin to regret taking this car.
So i thought i'd add aircon, hence why i'm here.
The current plan of attack is based around an electric compressor running 12 volts. I have a 95 Amp alternator, car will run on 45 amps including all radiator fans including the ones required for aircon, leaving me 50A to play with without having any headlights on. With headlights on, i'll have to turn the aircon down or i'll be depleting the battery.
Compressor is this model: http://www.masterflux.com/products/sierra/?pid=23 which pulls 52 amps at 12 volts. It has a PWM style controller where if you turn it down to half, you get roughly half the amps, so that's a win.
I'm going with generic evaporator about 200mm*200mm *40mm and bolting a 8" radiator fan to it, carbon fibre plenum underneath with a couple of directional vent outlets all under dash. Underdash units won't fit, so this is the current plan.
I'm also going with a generic condenser, chosen from the catalogue to fit in the crash structure along the diagonal line on the left in this pic:11151 with as big a fan as i can fit as the intercooler radiator and radiator sit on the top of this structure. I'm hoping the big fan turns off at least one of my radiator fans saving me 10 amps.
As you can see, i'm up against it. So i'd like some input as to how best to optimise the system so that i can run the aircon as much as possible without running the battery down. Currently my list of questions is this:
1). Given the data sheet for the compressor has max power at 12V, and the car runs at 14.4V, will this drop the amps at max power, or just produce more coolth? Apologies for the use of the word coolth.
2). The compressor is R134a compatible, can i get away with another refrigerant, like the hydrocarbon ones, will this increase efficiency/reduce amps/create more coolth?
3). Given the following chart:11152 obviously the better the evaporator and condenser and associated fans are, then the better off i am. So is there a better type of condenser or evaporator? Is serpentine better than plate and fin or whatever? What should i be looking for? Similarly with fans, is one brand better than the rest? My radiator fans are currently SPAL.
4). Given the above graph, can we go one better. Can we take the evaporator waste gas, which might be ten degrees, can we whack that into a heat exchanger with the condensed high pressure gas at roughly 50 degrees, just prior to the expansion valve? One like this: 11153 This will recycle the coolth left over from the evaporator and run it back into the evaporator. This appears to be the best way to have the condenser and evaporator at the same temperature, thus pushing me up that chart of COP. Problem is, will this end up cooking my compressor, max discharge temp is 130 degrees, but does it rely on some cooling from the evaporator waste? Will it matter if i'm using a better refrigerant? Can we play one off against the other?
5). Any other tips from the gurus, i'm most grateful?
1). I filled the engine bay up with a dirty big motor and supercharger, so i can't fit an aircon compressor in there.
2). The engine is in the back, and the radiator in the front, so aluminium pipes full of hot water run from front to back and return inside aluminium channels, these channels get hot, turning into radiators and blast you with heat.
3). The radiator heat soaks and so the front of the car blasts you with heat too.
4). I live in Australia, where the sun is very hot, very very hot, crazy hot and the car doesn't always have the roof on.
All this isn't so bad when you're moving, but stuck in traffic and you begin to regret taking this car.
So i thought i'd add aircon, hence why i'm here.
The current plan of attack is based around an electric compressor running 12 volts. I have a 95 Amp alternator, car will run on 45 amps including all radiator fans including the ones required for aircon, leaving me 50A to play with without having any headlights on. With headlights on, i'll have to turn the aircon down or i'll be depleting the battery.
Compressor is this model: http://www.masterflux.com/products/sierra/?pid=23 which pulls 52 amps at 12 volts. It has a PWM style controller where if you turn it down to half, you get roughly half the amps, so that's a win.
I'm going with generic evaporator about 200mm*200mm *40mm and bolting a 8" radiator fan to it, carbon fibre plenum underneath with a couple of directional vent outlets all under dash. Underdash units won't fit, so this is the current plan.
I'm also going with a generic condenser, chosen from the catalogue to fit in the crash structure along the diagonal line on the left in this pic:11151 with as big a fan as i can fit as the intercooler radiator and radiator sit on the top of this structure. I'm hoping the big fan turns off at least one of my radiator fans saving me 10 amps.
As you can see, i'm up against it. So i'd like some input as to how best to optimise the system so that i can run the aircon as much as possible without running the battery down. Currently my list of questions is this:
1). Given the data sheet for the compressor has max power at 12V, and the car runs at 14.4V, will this drop the amps at max power, or just produce more coolth? Apologies for the use of the word coolth.
2). The compressor is R134a compatible, can i get away with another refrigerant, like the hydrocarbon ones, will this increase efficiency/reduce amps/create more coolth?
3). Given the following chart:11152 obviously the better the evaporator and condenser and associated fans are, then the better off i am. So is there a better type of condenser or evaporator? Is serpentine better than plate and fin or whatever? What should i be looking for? Similarly with fans, is one brand better than the rest? My radiator fans are currently SPAL.
4). Given the above graph, can we go one better. Can we take the evaporator waste gas, which might be ten degrees, can we whack that into a heat exchanger with the condensed high pressure gas at roughly 50 degrees, just prior to the expansion valve? One like this: 11153 This will recycle the coolth left over from the evaporator and run it back into the evaporator. This appears to be the best way to have the condenser and evaporator at the same temperature, thus pushing me up that chart of COP. Problem is, will this end up cooking my compressor, max discharge temp is 130 degrees, but does it rely on some cooling from the evaporator waste? Will it matter if i'm using a better refrigerant? Can we play one off against the other?
5). Any other tips from the gurus, i'm most grateful?