physics problem around air conditioner

[bebeours]

First of all, I want to apologize to all the users of this forum for putting this topic here, but I don't know where to put it.

I know there are a few guys in the brain here, so I ask my problem.

I live in Guyana and I work for a company specializing in cleaning air conditioners. In recent months, we have received a thermometer anemometer to take before / after readings at the air outlet from the air conditioner.

So that's what's going on with this device. the readings before gives us an insignificant speed at 3,5m / s and a reading after around 4m / s for the most common models. So far so good.

In terms of temperature, we have before 18c ° to 20c °, and after we have a temperature one or two degrees higher than before. Until then, the explanation I gave to my boss is that if the speed increased, it is possible that the air temperature also increases, but that after calculation, we get a drop in temperature compared to the air volume.

What poses a problem for me is that we have received reports from mainland France with results different from ours with a speed increase and a very significant temperature drop of the kind before (3.5m / s 21c °) after (4.4 m / s 16c °). As a result, none of my colleagues have achieved despite relentlessness.

In my opinion, this difference must come from the humidity of the air. After cleaning an air conditioner, the air is so charged with humidity that there is fog in the room. So I can explain the principle literally but without source or mathematical demonstration.

I think that mathematically, we could prove the performance gain despite conflicting figures.

If you have a lead or even the answer, thank you.

[dedeleco]

Physically exact, humidity is likely to explain the difference, but before you have to specify your precise measurement conditions with great care, in particular where you measure, indoor cold or outdoor hot side, fan only, stopped or at start-up or continuously stable, the humidity level, 100% warm in Guyana and 50% less hot in mainland France, etc.
Normally an air conditioner in summer, is cold inside and hot outside, even in mainland France, with heat wave, with intense operation, humid or dry air !!!

The evaporating humidity makes it cold, if there is any at the start of the humidity on the thermometer, or on the heat exchanger in metropolitan France or fine drops of rainwater in the returning air? ?
If the air is 100% humidity, there will be no evaporation and no cold by evaporation of water.
To see closely the exact conditions.

[chatelot16]

depending on what is the circuit of this air conditioner, is it indoor air that gets cooled (closed circuit) or is it outside air that is cooled before being injected inside?

in the second case with a high outside temperature the slightest increase in flow represents a much higher cooling capacity

you would need a more complete description of your system to understand everything

[bebeours]

Mostly, we are working on split type air conditioners which operate in a closed circuit.

For the measurement, we take it in the center of the fresh air outlet in operation for a long time. Indeed, it takes a while before the compressor starts up and the temperature drops. So the measurement is not taken from the start, but often after having stored some of the equipment.

The humidity remains an unknown despite the certainty that it is wetter in Guyana than in mainland France, and that it must certainly be wetter after cleaning than before. But impossible to put a figure currently on it.

Do electronic weather stations give this kind of information in real time?
If not, what do you think would be the most objective way of proving the effectiveness of our work.
Maybe electrically? Or more data?

It going.
Thank you

[dedeleco]

It is necessary to specify much more, the split, the level of fouling, if the fine passages of the exchanger are totally blocked in places, with no air passing through it or not, if the system has a protection reducing its operating power when the exchanger is blocked, etc. ????

[chatelot16]

it is not only necessary to measure the temperature of the air at the outlet, but also at the inlet, and it is the difference which is significant of the performance

can be that during cleaning, air conditioning stopped and door open the temperature rose

if the outlet temperature has risen by 2 ° c while the room temperature has risen by 5 ° c the cooling in the air conditioning has increased

[bebeours]

Indeed, during cleaning, the temperature rises quickly, see very quickly since the houses here have no insulation. I explain, the walls are only made of a block of capped concrete and the roofing of corrugated sheets, the glass wools are almost nonexistent, revolting limit. But that is not the subject at present.

Since we are using a compressor, we close the door as soon as possible. When at the window have the leash as it is. The hole through which the tubes and pipes pass through the wall is often open and therefore allows air to enter.

Indeed, taking the inlet and outlet temperature seems more reasonable.

In terms of humidity, small weather stations provide real-time information.

Then how to organize this data mathematically to provide the client (large client) with objective proof of the efficiency of our work or, if not, review our working method.

Or if you prefer. How to objectively assess the quality of an air conditioner cleaning?

Thank you

[dedeleco]

with:

corrugated iron roofs, glass wools are almost non-existent, a revolting limit.

using air conditioning is throwing money out the window !!

So as the quality of each exchanger is measured by the refrigeration power, inside and the heat rejected outside, equal to the previous one, plus the energy expended to compress, it is enough to measure this power.
Or after a time long enough to reach a steady state the difference of T between inside and outside (time of a few hours, with T ext stable, given the corrugated sheets)
or the product of the air flow (or speed in the exchanger averaged between inlet and outlet multiplied by the real surface with this speed) by the difference DeltaT of T inlet minus T outlet.
This can be done on the cold indoor exchanger or on the hot outdoor one, which is increased by the compression power in the air conditioning.

If the cleaning is effective on almost blocked exchangers, the power measured by these various means must be increased.
To have the real power to compare with that electric (report which gives the COP) it is necessary to multiply the flows x DeltaT by the specific heat of the air: 1,3KJoule / m3 ° C
http://fr.wikipedia.org/wiki/Diffusivit%C3%A9_thermique
So 1m3 / s with 1 ° C of change gives 1,3KW and with 5 ° C gives 5x1,3 = 6,5KW
You have to be careful to measure the effective surface of air for its average speed, sometimes not very easy.

Finally if the exchanger is well obstructed, you can measure its electrical power at the meter (or with a wattmeter) divided by the cooling capacity, difference DeltaT between outside and inside, in stationary mode, before cleaning then after, because this ratio must be '' improve, smaller, more cold for less electrical power.

After cleaning an air conditioner, the air is so charged with humidity that there is fog in the room.

Finally if before cleaning, there was no fog in the house, and if after, after there is fog (dew point, which gives the% humidity with the variation of T), this proves that this cleaned air conditioner cools much better and works much better than before !!
http://fr.wikipedia.org/wiki/Point_de_ros%C3%A9e

[bebeours]

Thank you very much Dédéléco, I'm going to study what you passed me with a rested head and thanks to that, I know that I'm going to be a hit at the next meeting.

The concern with some of our customers is that these are companies that employ a good handful of engineers, so as it is necessary to submit a report after intervention on large construction sites, it is absolutely essential that this be objective because with the usual sales pitch, we would be turned on. And in terms of lighting, our customers know about it ... I work in Kourou ...

As far as throwing money out the window here, it's terrible. The windows are single glazed, often of the jealousy type with lots of air vents everywhere. Some customers are accommodated by the employer and do not pay for electricity, so the air conditioners run 24 hours a day and there it is seriously disgusting when they have passed.

That said, it is still improving. The stores began to offer double stained glass windows and insulation specialists set up shop in Guyana.

In a well insulated building, air conditioning is useless, even in Guyana. My house is made of wood with roof insulation and the air conditioner has never rotated since it was installed. Anyway, working on it and seeing the type of dirt in it, I don't want air conditioning at home.

Thank you