How to improve AC efficiency

[Occasionally6]

Originally Posted by teoman

Pvc pipe is thermally fairly non conductive

That's not an issue. The heat exchange, in this case between air and PCM, will occur across the walls of the tubes. I'm envisaging the PVC as the shell, not the tubes.

I will measure the on time and the off time of the compressor to get a rough estimate on what it likes and design around that.

That's where I started too. I used the track timing clock on the car's CD/MP3 player - precise to the nearest second - as a stopwatch, on my regular trips.

[hayden55]

Another obscure option: ceramic weave forge insulation. Well kind of.
Imagine a yeti cooler is made of 2 inches of poly foam which equals R-10 value and can hold ice and what not, but has only an R-value of 5 per inch. Move to ceramic fiber insulation: R-10 per inch!
I can think of many uses from exhaust insulation for race cars (reduce heat soak), insulate an existing fridge, or in the case glue it to the roof of your vehicle and possibly the doors.
Similar to the 3m crystalline tint option the goal here is to keep heat out.

Maybe I could try it out in the ranger as the head liner has already failed. Then I could just yank the header and restore it and throw this stuff in behind it. lol

[teoman]

Or one could do exterior insulation.

If you can also spray water over it, the whole car would act like a swamp cooler

[teoman]

From an HVAC forum I read spraying water on to the condenser can cause it to have a premature demise due to corrosion and accumulation of mineral deposits.

One solution could be the use of distilled water. I could collect AC runoff from the house or the place of work. Or a mini exhaust powered still could be created in the car.

Condenser cleaning solution is not that expensive so regular cleaning could get rid of the deposits.

Another solution proposed by the HVAC guys is spraying the water in the opposite direction of the intake so that it has time to evaporate and the minerals fall out as dust before they can accumulate.

I do not know what distance it takes for the droplets to completey vaporize, but assuming they do in short order how much water would be needed to get the maximum cooing of the incoming air.

The condenser is 0.2m^2.
Assume the car is moving at 100km/h -- 28 m/s

The volume of air is roughly 5.6 m^3 which is about 7 kg of air. (density of 1.25 kg/m^3)

If we assume that the air is 30 degC and at the moment the humidity is at %60.

From the chart below:

REF:https://www.engineeringtoolbox.com/m...air-d_281.html

1 kg of air can hold 30ml of water.
But it is already %60 saturated, so 12ml of water evaporation capacity remaining.
( I am neglecting the temperature drop in the air due to the cooling and the consequent reduction in capacity to hold water)

We previously calculated 7kg of air, that makes 84ml of water per second.


Which is 302 liters of water per hour if the system is run full time. For some reason that doesnt look too feasible. If activated only with the AC compressor it should quite a bit less.

That 302 liters of water can absorb 100800000 joules of thermal energy.

Or 95540 BTUs. Not quite sure all this makes sense. But 95k BTUs per hour sounds like a lot more energy than the entire ac system sucks out of the cabin.

[teoman]

1 kg of gasoline has 45 MJ of energy.
100.8 MJ calculated previously calculated equates to 2.25 kg of gasoline.

For 300L/hour there better be an ice storm in the car.


Anyone know of a smart way to detect if the water is completely vaporized before touching the condenser?

[teoman]

Calculator to get maximum cooling possible, also has the formula:

https://www.easycalculation.com/weat...calculator.php

[MeteorGray]

I install hood louvers on my vehicles to extract heat from the engine bay in order to prolong the life of under hood components, such as the battery, rubber components, etc.

I even go to the extent of installing a radiator-type electric fan to push / pull hot air up through the hood louvers when the engine bay temperatures get significantly above ambient, such as in stop-and-go traffic and upon engine shutdown after a trip in hot weather. When running on the highway, I can see via an engine bay temperature probe that the engine bay temperatures in my Mazda3 are the same as outside ambient.

Although I have not tried to quantify any differences in the air conditioner's performance, I suspect a cooler engine bay benefits the air conditioner system as well. Hood louvers certainly help in that regard.

I live in a hot and humid climate in which the air conditioner is operating most of the time.