keeping drip/injected oil constant hot temp in heaters

Space Heating with SVO WVO Vegetable Oil Biofuel.

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keeping drip/injected oil constant hot temp in heaters

Postby coachgeo » Wed Apr 16, 2008 12:55 am

this seems to be a problem in all the heaters folk have expermented with where the heat it produces also is used to thin the oil. The heater gets hotter ..... thus the oil gets hotter and thinner thus the flow increases and with out you even touching the flow valve the heater burns hotter, thus the oil flows better, thus the heater burns hotter, etc etc till your reaching Solar Flare heat ranges :D Basically you have no temp control but constant get hotter..

What about not heating the oil with the heat generated by the heater but with something simular to a cars radiator cooling system. Keep constant temp by using an automotive type thermostat.

Plumb coolant thru the heater and then thru a thermostate that either diverts coolant straight to a heated jacket that heats the oil fuel container for injecting/dripping/flowing into the heater. Once coolant reaches a certain max temp the wax based thermostat opens up and flows the water thru a radiator before going on to the jacket that heats the oil.

Now that oil is at a constant temp your fuel oil metering valve will allow you to increase or decrease flow to control temprature output of your heater.

the radiator (FPHE? ) could be placed along with your home hot water heater tank to aid in its heating of that?
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Postby David » Wed Apr 16, 2008 3:28 am

^^^^^^ Sounds complicated!

What about just using something like an electric fish tank heater if you have to heat the oil? That would be thermostatically controlled and once heated would maintain a set viscosity. Of course then the problem would be a diminishing fire as the fuel was used and the tank emptied giving less fuel pressure.

A metering pump that only administers a set amount of fuel by volume not viscosity would also solve the problem.

How about not heating the oil and just pressurizing the container to a set PSI to give a constant flow regardless of the oil level in the tank?

A small pump that lifted the oil to a resiviour that fed the burner and overflowed the excess back to the tank would also maintain a set fuel flow and level.

Just some Idea's........
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Postby coachgeo » Wed Apr 16, 2008 9:24 am

David wrote:^^^^^^ Sounds complicated!
Glad Henry Ford and Rudolph Diesel did not just throw away ideas so easy :roll: :D

What about just using something like an electric fish tank heater if you have to heat the oil? That would be thermostatically controlled and once heated would maintain a set viscosity. Of course then the problem would be a diminishing fire as the fuel was used and the tank emptied giving less fuel pressure.
Don't know anything about them thanks for bringing it up. A discussion on these sounds like it could spawn its own thread

A metering pump that only administers a set amount of fuel by volume not viscosity would also solve the problem.
Yep, been discussed in here. They are rather expensive though. 150 to 300 dollars

How about not heating the oil and just pressurizing the container to a set PSI to give a constant flow regardless of the oil level in the tank?
What do you use to keep the tank at constant pressure?

A small pump that lifted the oil to a resiviour that fed the burner and overflowed the excess back to the tank would also maintain a set fuel flow and level......
Like many of the ones above as the oil feed line gets closer to the heater its feed line will begin to heat up, reducing viscosity in the oil inside it and encouraging faster flow. Same cycle I described in the first post then begins.

Thanx for the ideas.
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Postby David » Wed Apr 16, 2008 8:17 pm

Fish tank heater is a small thermostatically controlled heating element used to keep fish tanks at a constant temp and would be a much easier and simpler solution to the plumbing setup you describe.

[url]http://cgi.ebay.com.au/FISH-TANK-INTERNAL-300W-HEATER-QUARTZ-QUALITY-GLASS_W0QQitemZ370041579408QQihZ024QQcategoryZ20754QQss
PageNameZWDVWQQrdZ1QQcmdZViewItem[/url]

A metering pump that only administers a set amount of fuel by volume not viscosity would also solve the problem.

Yep, been discussed in here. They are rather expensive though. 150 to 300 dollars


I have seen them on ebay for like $10 from time to time but maybe you don't get them over there as much as they come up here. In any event, I suppose it would depend on how much having the heater being able to operate safely and reliably unattended would be worth to you and what the alternative solutions would cost in time, materials and overall effectiveness.


How about not heating the oil and just pressurizing the container to a set PSI to give a constant flow regardless of the oil level in the tank?

What do you use to keep the tank at constant pressure?


In the past I have used a bottle of compressed air with a regulator on it. It can just be an empty LP gas bottle that is pressurised to 100PSI with compressed air. The pressure in the fuel tank would not need to be high and the compressed air is only replacing the fuel used so a BBQ size bottle would have plenty of capacity to do a decent size tank. A bottle of CO2 or nitrogen could also be used with a suitable regulator.

A small pump that lifted the oil to a resiviour that fed the burner and overflowed the excess back to the tank would also maintain a set fuel flow and level......

Like many of the ones above as the oil feed line gets closer to the heater its feed line will begin to heat up, reducing viscosity in the oil inside it and encouraging faster flow. Same cycle I described in the first post then begins.


No, it's nothing like it.
If this was a factor, I don't believe your own original idea of controling the flow would work either.
In the reservoir system I described, the heating in the line would be constant as would the temp of the main reserve of oil. The oil in the line may thin as it gets nearer the fire but as long as the main tank of oil were far enough away so it did not warm and have it's viscosity change, the temp of the fuel fuel entering the line and through the metering valve would maintain a constant flow once set and keep the fire at the same rate providing their temp is more or less constant. If they were in a position to receive increasing radiant heat, some simple modifications to the system could be made to make this system of regulation work properly.

If the oil tank were in the same area as the heater, it may warm over many hours and the oil thin somewhat. Surely though people don't just set one of these primative heaters going and then walk away from them for hours on end without coming back to check on them regularly at which time any minor adjustments could be made??

If that were the plan to leave one of these things unattended for long hours (!!!) then using a metering pump which would only dispense a controlled amount of oil no matter what it's temperature variation along with some over temp and flame sensing cutouts would have to be a worthwhile and more than justified investment.
I can't imagine anyone wanting to heat an area that they were also unconcerned if it burnt down!


Having built a range of burners over the years, I have learnt that getting the things to actually burn is the easy part. Putting the heat to useful work and setting systems up so their output is consistent and reliable is where the real engineering comes in! :D
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Postby harry3 » Thu Apr 17, 2008 5:37 am

I use a suntec pump turned by a 12 volt motor it spins from 1 rp/sec to 5rp/sec. perfect controll. Tim Cook talks about this in detail on the other fourm.
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Postby Welder » Thu Apr 17, 2008 5:55 am

This is an interesting thread. I'm glad I found it. I want to build a tiny WVO boiler.
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Postby coachgeo » Thu Apr 17, 2008 11:03 am

Lets just stick for now in reference to this thread.... NO PUMPS.

Gravity flow feed is what were mainly discussing. Sorry for not making that clear earlier.

Gravity fed is where the rising temps in the oil draw line causes problems especially metering problems. For example a simple needle valve can't keep a constant volume of flow if the liquid going thru the valve keeps getting thinner and thinner.

Seems to be that with a little time, tubing and heat exchanger you could make something that could use no power at all.
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Postby David » Thu Apr 17, 2008 9:03 pm

coachgeo wrote: For example a simple needle valve can't keep a constant volume of flow if the liquid going thru the valve keeps getting thinner and thinner.



Exactly! So arrange the tube and valve, insulate it if you have to, so the oil doesn't get thinned at a rising rate. Keep it constant and problem solved! :roll:
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Postby coachgeo » Thu Apr 17, 2008 10:39 pm

David wrote:
coachgeo wrote: For example a simple needle valve can't keep a constant volume of flow if the liquid going thru the valve keeps getting thinner and thinner.



Exactly! So arrange the tube and valve, insulate it if you have to, so the oil doesn't get thinned at a rising rate. Keep it constant and problem solved! :roll:
Yes David that is exactly what the goal is. Keeping a constant temp in an evironment where the temps are variable. Not sure you can do that with just proximity arrangements and/or insulation

How would you propose to insulate/arrange a heater type unit's fuel delivery and tank system when using the heaters variable temprature output as the heat source? Fuel system includes its metering valves. Assuming heaters heat output is needed to:

. warm the fuel system for better automation
. warm the fuel for better flow thru metering valves.
. Warm the surrounding air space to heat a room
. Have control of air space temprature by metering fuel flow.
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Postby Burbarian » Fri Apr 18, 2008 1:00 am

Use the example of an I.V. drip flow regulator. (that thing that measures out intravenously fed liquids a drop at a time if you're flat on your back in a hospital bed) You only need to maintain constant viscosity just prior to the needle valve. Upstream of that it should be the same temperature or cooler. Downstream of that, it could be hotter. The critical area is the drip chamber which isolates the source from the sink. In this case the source is the temperature regulated needle valve, and the sink is a length of tubing that goes to your burner.

A small temperature regulated electrical heater clamped to the needle valve inlet can maintain constant temperature and hence constant viscosity for that batch of vo. It can be a thermostat that turns a relay on or off depending on a setpoint. PID controllers can have arbitrarily narrow setpoints, or proportional current control.

Upstream of the needle valve, it could be hydronically heated via your thermostatic radiator valve if you are using solid fuel (pho/lard). With liquid fuel, it would not be necessary to heat it so long as it can flow to the needle valve.

It would be a good idea to have a small insulated preheat chamber immediately prior to the needle valve holding say a pint of heated fuel. Much easier to regulate the temperature of a small but significant mass than a very tiny flowing mass like a trickle of vo going through a small diameter pipe. The preheat chamber can quickly get up to temperature and start flowing in a regulated manner.

It wouldn't matter if it got hotter downstream of the valve, as the outflow of the valve is a constant.

Once the furnace is operating and generating heat, you can use the same thermostat and switch the output from turning a relay on/off that powers a heater, to a secondary relay that turns a valve on/off. The valve regulates hot water flow that could go to a water jacket or coil of tubing around the preheat chamber.

You could have the heat source switch-over be automatic by using a thermal switch at the hot water source which is heated by the furnace. Once the furnace is up and the water is heated, the thermostat switches from regulating the temperature via electrical resistance heat to hydronic heat.



A completely different method would be to forget about thermal control altogether and use a proportional drip valve.

Again, use the I.V. drip regulator as a basis. You can allow the fuel source to get arbitrarily hot, so long as on startup it is sufficiently liquid to drip through the metering valve. Perhaps use a starter batch of warmed fuel. Say that preheat chamber with a timer controlled electric heater to just get it liquefied on startup. It only needs to flow.

This time the flow is controlled by a drip counter. Just a photocell that detects when a drop of vo falls from the needle valve. A frequency counter can then be used to measure and control your fuel flow in 'drips per second'. It drives a very low RPM DC gearmotor either clockwise or counterclockwise to adjust the drip valve aperture. Something like cruise control for vo droplets.

This way it wouldn't matter if your fuel was getting thinner, the frequency counter will detect this change in flow characteristics and automatically adjust the needle valve for constant DPS (drips per second). This gives you constant (very low) fueling rate regardless of temperature or viscosity changes.
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Postby Burbarian » Tue May 13, 2008 5:00 pm

Coach,

You may want to look into this:

METERING PUMP W/12 VDC STEPPER MOTOR & CONTROLLER $79.95

http://www.surpluscenter.com/item.asp?U ... 1&catname=
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