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Pre-compressor evaporative cooling -- a theoretical discussion
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Don't have to close the books.
Don't have to close the books. There is obviously a few that are interested in how you come up with the values. I was only implying that there are others that are saying :shrug: ....
I work in the Semiconductor Industry on the Photolithography side [imaging IC (computer chip) patterns] and I showed a few the thread and even though most are degreed, they went :shrug: ..... and talked about where to look up the info.
Your last post made the concept more easy to grasp.
4wheeln
killerbee said:
Don't have to close the books. There is obviously a few that are interested in how you come up with the values. I was only implying that there are others that are saying :shrug: ....
I work in the Semiconductor Industry on the Photolithography side [imaging IC (computer chip) patterns] and I showed a few the thread and even though most are degreed, they went :shrug: ..... and talked about where to look up the info.
Your last post made the concept more easy to grasp.
4wheeln
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The idea of water is nothing new as has been stated, it's affect on removing heat are also good and well agreed upon. What is the problem then........... well the theory being looked at here is not looking at the full system that is being used and that has to be done for it to work with out breaking something. This exact theory has been used for years on motorhomes that over heat with one major exception. The water is sprayed as a fine mist just in front of the radiator. There is mixes with the air then contacts the radiator where it changes state removing maximum heat from the radiator there by reducing the ECT's by as much as 50 degrees. The beauty of these systems is that they cost a few hundred dollars and do not damage the rest of the system. In an RV you already have a large water reserve so it's good to go but in this application it would be necessary to install a 50 gallon tank somewhere to hold the water. You could run a smaller tank if you do not mind stopping much more often. If you spray the water into the motor you would still need this size tank.
Don't laugh at me guys, I'm a business administration major... 
ointlaugh
What if...
Would installation of a water injection sytem post turbo, pre CAC provide a ECT decrease? I suspect not; if I understand correctly, the majority of the cooling effect results from water evaporation. :idea:
ointlaugh What if...
Would installation of a water injection sytem post turbo, pre CAC provide a ECT decrease? I suspect not; if I understand correctly, the majority of the cooling effect results from water evaporation. :idea:
To me, what I have noticed, grain of salt:stevebos said:
The attempts to get water to evaporate fail miserably, when attempted in the conventional way, meaning one nozzle, aimed across a small cylindrical conduit. The water simple pools, and becomes impossible to evaporate in the .1 secs that it exists in the stream.
The time factor has to be the biggest issue, along with the fact that this confined environment is not helpful to resisting agglomeration.
However Steve, IF an adequate amount of 20 micron fog could be injected post turbo, I think there would be very good evaporation. Enter the logistics problems. To produce 1 gpm (probably less) of 20 micron fog, requires about 1000 psi, and 5-10 (est) .008 orifice nozzles. Can't do it with one or 2 nozzles.
As a comparison, the typical shurflow pump plus one or 2 nozzles, produces droplets with sauder mean diameter in excess of 100 micron. And the nozzles get worse with age and contaminants
Diesel Techs idea is very effective. It doesn't require ultrafine atomization, is easy to implement, and as long as you have an unlimited supply of de-ionized water, it is the way to go. We should remember that the stack passes 5000-10,000 cfm that needs to be treated. The intake tract is limited to about 1000 cfm. In my mind, internal injection is the water miser method, using one-fifth of the external spray method. I could be wrong. But to give it creedence:
I got into a rain storm when I took my son up to Flagstaff. I mean rain heavy! My ECT gauge dipped down to 170-180, I think actual was around 160. I couldn't keep it warm. Mind you I had no load, and the pure volume of water was staggering (IMO) compared to what we can supply with mist.
As a side note, regarding the CAI that I made for this vehicle: I did pull over to check the condition of my filter element. It was dry.:Thumbup:
Something else that I thought might be interesting to discuss. Air quality. What is a better air for combustion, air with 10% humidity, or air with 80% humidity? I don't know the answer, but it fits the topic.
I will start some testing soon. If anyone has a good suggestion for sampling 500 degree air temps, I need to modify the CAC-in tube to accomodate a thermocouple. Something I can cap off when not in use.
If anyone has done this, I'm interested
If anyone has done this, I'm interested
This is the most accurate and poignant article on evaporation I have seen.
http://www.shorstmeyer.com/wxfaqs/humidity/humidity.html
It points out why pre-CAC evaporation is entirely more effective than post-CAC evaporation, citing relative energy levels of each air mass due to temperature. Also, infer the need for careful dosing, to avoid excess water use, and excess dew point condensation in the CAC.
http://www.shorstmeyer.com/wxfaqs/humidity/humidity.html
It points out why pre-CAC evaporation is entirely more effective than post-CAC evaporation, citing relative energy levels of each air mass due to temperature. Also, infer the need for careful dosing, to avoid excess water use, and excess dew point condensation in the CAC.
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The CAC tanks are plenty thick so you can drill and tap the CAC where the inlet and outlet tubes attach. A simple NPT plug fills the holes afterwards.
Maybe look at the old oil bath air cleaners that drew the air through the oil to collect air born particals , they were rather good at that job , but a pain to service . Perhapes something like that could be used to introduce water vapour into the intake .
I have given some thought to concerns and realities, done more reading about actual cases.
I am considering developing a "cuff" that can be placed in line on the intake tube, pre-turbo, that would house about 8 nozzles. Each providing a small fog mist with little velocity.
I believe it is possible to get a 40 degree reduction in pre-turbo charge (30% evaporation before compressor), a 200 degree total reduction in post turbo charge, and a 5-10% efficiency increase in boost production. 20% more air charge for the same work performed by the turbo.
The water required at current stock levels of 50 lb/minute air intake, would be 0.7 lb/minute, or roughly 450 ml/minute. That is a BTU absorbtion rate of 700 BTU/minute, or only 42000 BTU/hr. (at first glance this is not much) That is nearly 1/5th of the current heat rejection rate of the CAC (200,000 BTU/hr) at WOT. This does not by itself quantify the improvement. The fact that IAT is effectively lowered, means the turbo runs at better efficiency, CREATING LESS HEAT. Much less heat.
Using a compression calculator for the turbo makes this advantage easier to see.
I see the added humidity also effecting a stronger power stroke as well. The total benefit, is a hodgepodge of speculation, combined with some thermo, at this point.
The downside? If a proper fog machine can be created, I don't see any turbo consequences, save for a longer life running cooler. This may be difficult to believe, but fog doesn't harm blades. Large drops and pooling water does. For now, i am abandoning the idea of direct stream spray.
This without condensation, all assuming a 90 degree day with 30% humidity. In this model IAT would be less, since the fan would be off considerably more. This is the cycle breaker. If the fan goes on, water must go on, looped into a boost threshhold of 15 psi. With a mechanical fan there is no electrical signal to monitor. Enter IAT. With my CAI, IAT never rises above 120 unless the fan comes on. So we can use IAT to trigger water with boost series logic.
This is not set in stone, if someone has another thought on logic that is more predictive, chime in.
I am considering developing a "cuff" that can be placed in line on the intake tube, pre-turbo, that would house about 8 nozzles. Each providing a small fog mist with little velocity.
I believe it is possible to get a 40 degree reduction in pre-turbo charge (30% evaporation before compressor), a 200 degree total reduction in post turbo charge, and a 5-10% efficiency increase in boost production. 20% more air charge for the same work performed by the turbo.
The water required at current stock levels of 50 lb/minute air intake, would be 0.7 lb/minute, or roughly 450 ml/minute. That is a BTU absorbtion rate of 700 BTU/minute, or only 42000 BTU/hr. (at first glance this is not much) That is nearly 1/5th of the current heat rejection rate of the CAC (200,000 BTU/hr) at WOT. This does not by itself quantify the improvement. The fact that IAT is effectively lowered, means the turbo runs at better efficiency, CREATING LESS HEAT. Much less heat.
Using a compression calculator for the turbo makes this advantage easier to see.
I see the added humidity also effecting a stronger power stroke as well. The total benefit, is a hodgepodge of speculation, combined with some thermo, at this point.
The downside? If a proper fog machine can be created, I don't see any turbo consequences, save for a longer life running cooler. This may be difficult to believe, but fog doesn't harm blades. Large drops and pooling water does. For now, i am abandoning the idea of direct stream spray.
This without condensation, all assuming a 90 degree day with 30% humidity. In this model IAT would be less, since the fan would be off considerably more. This is the cycle breaker. If the fan goes on, water must go on, looped into a boost threshhold of 15 psi. With a mechanical fan there is no electrical signal to monitor. Enter IAT. With my CAI, IAT never rises above 120 unless the fan comes on. So we can use IAT to trigger water with boost series logic.
This is not set in stone, if someone has another thought on logic that is more predictive, chime in.
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Killerbee,
I always notice my truck runs best on mornings with cool, foggy air .... I have a couple of coworkers with diesels and they have noticed the same thing (I was just talking about this a couple of weeks ago.)
Now 450ml/minute would go through a liter of water in a little over 2 minutes, thus 5 gallons of water would be good for 40 minutes of fan operation. My question, what if the fan is coming on a little late? My fan used to come on at the top of hills when towing, usually at this point the OEM gauge is reading 235 degrees (this was pre-EOC - have not heard the fan or seen the OEM gauge go to the right of the 210 mark since installing the EOC)
I always notice my truck runs best on mornings with cool, foggy air .... I have a couple of coworkers with diesels and they have noticed the same thing (I was just talking about this a couple of weeks ago.)
Now 450ml/minute would go through a liter of water in a little over 2 minutes, thus 5 gallons of water would be good for 40 minutes of fan operation. My question, what if the fan is coming on a little late? My fan used to come on at the top of hills when towing, usually at this point the OEM gauge is reading 235 degrees (this was pre-EOC - have not heard the fan or seen the OEM gauge go to the right of the 210 mark since installing the EOC)
Mark, in my concept, the water would be used to keep the fan off, typically on the grades. So I don't think it would use that much water, to keep the fan off. A feedforward mechanism could be used I guess. Mist when a predictive model anticipates the fan, keeping it off. Anyway it's late, I am sick and getting punchy today.
Mark you are an engineer. Does it strike you odd that the LLY piping, pre and post CAC, is the same size? I have spent half this day researching this. This light went on while I was talking to "super diesel". The LLY went to a smaller pipe pre-CAC, and I never knew it. That added restriction. Meaning the turbo must work harder to accomplish the same intake plenum requirements.
Post-CAC, the air has half the speed, so it is is fine. Pre-CAC, at 450 degrees it is still sailing, and needs a bigger conduit to avoid excessive losses.
WI will reduce that velocity substantially, and help this issue, but I am really considering a custom made 2.5" id pipe. Current one looks to be 1.75 id. Does anyone know for sure?
Mark you are an engineer. Does it strike you odd that the LLY piping, pre and post CAC, is the same size? I have spent half this day researching this. This light went on while I was talking to "super diesel". The LLY went to a smaller pipe pre-CAC, and I never knew it. That added restriction. Meaning the turbo must work harder to accomplish the same intake plenum requirements.
Post-CAC, the air has half the speed, so it is is fine. Pre-CAC, at 450 degrees it is still sailing, and needs a bigger conduit to avoid excessive losses.
WI will reduce that velocity substantially, and help this issue, but I am really considering a custom made 2.5" id pipe. Current one looks to be 1.75 id. Does anyone know for sure?
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Michael,
Some random thoughts ....
I think if we could create a good location to store the reserve water and maybe use IAT like you mentioned to trigger the system, this could be very interesting. Would the water temperature play any significant role (assuming a truck sitting in the sun for an afternoon)?
Something that occurred to me yesterday while letting the air out of my compressor tank - one can feel the cool air/water vapor as I loosened the drain and let the air escape at a high rate of speed. Could a pressurized water tank (with a small compressor) be used to allow for cooler water/air? This would eliminate the need for a water pump (would just need air to create pressure when needed.)
I can see where such a system would need to be removed or drained/disabled during freezing conditions.
As for the CAC pipe diameters on the LLY, does the LBZ also use the smaller diameter one?
Some random thoughts ....
I think if we could create a good location to store the reserve water and maybe use IAT like you mentioned to trigger the system, this could be very interesting. Would the water temperature play any significant role (assuming a truck sitting in the sun for an afternoon)?
Something that occurred to me yesterday while letting the air out of my compressor tank - one can feel the cool air/water vapor as I loosened the drain and let the air escape at a high rate of speed. Could a pressurized water tank (with a small compressor) be used to allow for cooler water/air? This would eliminate the need for a water pump (would just need air to create pressure when needed.)
I can see where such a system would need to be removed or drained/disabled during freezing conditions.
As for the CAC pipe diameters on the LLY, does the LBZ also use the smaller diameter one?
random replies
I think the LBZ uses the same size turbo out pipe.
The compressed air from your tank feels cold. What is happening is the same process that occurs in the turbo, but in reverse.
But you have to go back to when that air was compressed. A fresh tank of compressed air is hot, just like the turbo stream. But after some time has passed, the tank became room temperature with conduction.
By contrast, if you just compressed the air, then immediately let out the air, the air would be a little bit warmer than ambient, due to the compression process being less than 100% efficient. Can't get away from this reality unfortunately, but i think I see where you were going.
Regarding your question on whether the temp of the liquid water makes a difference: Yes, it makes a negligible difference. For practical purposes 50 degree water is not much more useful than 150 degree water, when it is going to be evaporated. Looking at one pound of water at each temp
50 degree: absorbs 1132 BTU's when fully evaporated
150 degree: absorbs 1032 BTU's
I think the LBZ uses the same size turbo out pipe.
The compressed air from your tank feels cold. What is happening is the same process that occurs in the turbo, but in reverse.
But you have to go back to when that air was compressed. A fresh tank of compressed air is hot, just like the turbo stream. But after some time has passed, the tank became room temperature with conduction.
By contrast, if you just compressed the air, then immediately let out the air, the air would be a little bit warmer than ambient, due to the compression process being less than 100% efficient. Can't get away from this reality unfortunately, but i think I see where you were going.
Regarding your question on whether the temp of the liquid water makes a difference: Yes, it makes a negligible difference. For practical purposes 50 degree water is not much more useful than 150 degree water, when it is going to be evaporated. Looking at one pound of water at each temp
50 degree: absorbs 1132 BTU's when fully evaporated
150 degree: absorbs 1032 BTU's
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·KB...one thing to keep in mind is that relative humidity is simply that...relative. It relates more to the temperature of an air parcel than the amount of moisture it contains. An air parcel at 90 degrees with 15% RH will contain more moisture than an air parcel at 40 degrees with 50% RH.killerbee said:
To get an accurate picture of the amount of water vapor in a parcel of air, you either need to gather the wet bulb temperature, the dewpoint temperature, or find a way of measuring the specific humidity (g/kg) of said air parcel.
One other thing to keep in mind is that water vapor is less dense than an equivalent parcel of dry air. The water vapor molecule replaces the Nitrogen, Oxygen and "other" molecules in said air parcel. This is why home run hitters love playing in humid conditions. The higher amount of water vapor makes the air less dense, thus enabling their baseballs to travel farther.
Good information. If you can get your hands on a high temp psychrometric chart, you can see how much water 600 degree air can hold. A 300 degree temp reduction is possible, but the amount of water to do this is enourmous (and impractical)
Recent boost datalogging shows that working the VVT at the edge of its useful output (way off the map) produces efficiencies in the low 50's. The resultant heat is unmanageable.
I am in the middle of writing an article on my findings, this was very enlightening.
Recent boost datalogging shows that working the VVT at the edge of its useful output (way off the map) produces efficiencies in the low 50's. The resultant heat is unmanageable.
I am in the middle of writing an article on my findings, this was very enlightening.
it turns out, this idea has a lot of potential. I think I have a volunteer to test it out.
For every 15 degrees that charge air can be cooled prior to the CAC, that is one ton of cooling that the CAC does not have to do. Cooler radiator in other words.
This is in addition to the other benefits.
For every 15 degrees that charge air can be cooled prior to the CAC, that is one ton of cooling that the CAC does not have to do. Cooler radiator in other words.
This is in addition to the other benefits.
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