Veggie Experience #5 - IP Fuel Heating

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iPupGary
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Veggie Experience #5 - IP Fuel Heating

Postby iPupGary » Sun Jan 22, 2012 6:28 pm

Veggie Experience #5 – IP Fuel Heating

After completing the Veggie Purge Time test, I decided to measure the temperature of the fuel in the return line. It was a simple exchange of the fuel return view glass for another Autometer 2252 temperature sensor. Now I have the ability to measure the temperature of the fuel at the input of the injection pump and the temperature of the fuel in the return line after it has gone through the injection pump and associated fuel lines and hoses.


Test Purpose

The primary reason for measuring the return temperature is to determine how much the fuel temperature is raised by the heat of the injection pump (IP) and fuel lines. It’s my understanding that one of the reasons for returning the fuel back to the fuel tank, in a loop system, is to cool the injection pump. Some of the veggie folks have considered using the heat generated by the injection pump to aid in heating the veggie fuel. This could be done by re-routing at least some of the fuel returning to the fuel tank back to the input of the injection pump. I want to determine if there is enough heat generated by the IP to actually aid in the heating process. The ideal veggie temperature at the input of the IP is >160 degrees F.


Test Setup

I used one Autometer digital temperature gauge to measure the fuel temperature at the input of the IP and another Autometer gauge to measure the fuel temperature in the return fuel line. The ambient air temperature at the time of the test was 42 degrees F.

Test 1: measure the temperature of the incoming diesel fuel at the input of the IP and compare it to the returning fuel temperature.

Test 2: measure the temperature of the incoming heated veggie fuel at the input of the IP and compare it to the returning fuel temperature. The veggie is heated by a coolant heated heat exchanger.

The 1982 LUV diesel was brought up to normal operating coolant temperature of 200 to 205F before any temperature measurements where performed. I’m currently using a 205 degree F thermostat.


Results

Test 1: the temperature of the diesel fuel at the input of the injection was 53 F and the temperature of the return fuel was 76 F. That is a 23 degree F rise in temperature.

Test 2: the temperature of the veggie fuel at the input of the injection was 167 F and the temperature of the return veggie fuel was 144 F. That is a 23 degree F drop in temperature.


Conclusions

While the heat of the injection pump and fuel lines were able to raise the diesel temperature from 53 F to 76 F, it actually reduced the temperature of the heated veggie fuel from 167 F to 144 F. It’s my opinion that looping your veggie fuel back to the input of the injection pump would actually reduce the veggie temperature rather than raising the temperature. Routing the return fuel to the input of the heat exchanger rather than the input of the injection pump may aid in heating the veggie fuel provided that the temperature of the veggie fuel from the fuel tank is colder than the returning veggie fuel.
1982 Chevy Luv 2wd short bed diesel w/ veggie conversion (under construction)
1999 Isuzu Trooper 3.5L Gas

kravdraa
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Re: Veggie Experience #5 - IP Fuel Heating

Postby kravdraa » Mon Jan 23, 2012 7:33 am

Gary, Very interesting results with the temperature rise on DF and drop on WVO. I would have not guessed that would happen. Maybe a function of the viscosity?
Thanks!
Eric
81 Long bed PuP 2.2 Diesel
Using Bio-D

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iPupGary
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Re: Veggie Experience #5 - IP Fuel Heating

Postby iPupGary » Mon Jan 23, 2012 11:45 am

Eric,

I think I have the answer. The IP does heat the fuel but not enough to increase temperature above 167F. The veggie is pretty hot going in the IP, so it would take a significant amount of heat to raise the temperature or even keep it the same.

During my in-truck veggie testing, veggie looses about 4.2 degrees for every foot of veggie hose (5/16” dia.). My bench testing during the “Veggie Heat Experiment” series, I was loosing about 5 degrees per foot; pretty close agreement. I measured the total length of the hosing between the two sensors, including the valve path and the IP path. The total length was 11.6 feet! If you do the math, 11.6 ft X 4.2 degrees F, you get a total heat loss between the two sensors of 48.7 degrees F.

If it wasn’t for the IP heating the return line veggie, the temperature drop would have been even more. If you figure the IP input temperature was 167 F and the path loss drop would have been 48.7 degrees (11.6 ft X 4.2 F/ft), then the temperature at the return line temperature sensor would have been 118 degrees F, if the IP provided no heat. Since the IP was providing a certain amount of heat, it kept the temperature at the return line sensor at 144F. 144 F minus 118 F is 26 degrees increase if the IP provided no heat. This agrees very closely with the diesel rise in temperature of 23 degrees F.

My hose lengths on the return side have not been optimized. You could raise the veggie temperature at the return line sensor by reducing some of the hose length. But I personally don’t care because my return line veggie goes directly back to the veggie fuel tank. I need the veggie hot enough to keep the veggie flowing well, nothing more.

I think the bottom line is the IP can only raise the veggie temperature about 23 to 26 degrees or in this case, keeping it from dropping by the same amount.

If you had a small heat exchanger that wasn't providing enough heat at the input of the IP, and your temperature of your veggie was say 80 F at the input of the heat exchanger, mixing some of the returning veggie with the veggie from the veggie tank would make sense. I'm running a large and efficient heat exchanger that is meeting my veggie temperature goals, so for my situation I don’t really need to make this modification.

I hope this makes sense.


-Gary
1982 Chevy Luv 2wd short bed diesel w/ veggie conversion (under construction)
1999 Isuzu Trooper 3.5L Gas

hjalbert
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Re: Veggie Experience #5 - IP Fuel Heating

Postby hjalbert » Wed Apr 03, 2013 5:47 pm

I don't think of it as the IP heating the diesel, I think of it as the Diesel cooling the IP. From what I understand that is one of the reasons behind the design of the entire system with a return. the excess fuel helps to cool the injectors and the injection pump. I have never had a problem from running hot vegetable oil, but I think there is a trade off in the long run.
1986 Samurai with C223
1988 Samurai
1981 Pup 4x4 R.I.P.
1986 Isuzu Trooper 2.3
1989 Isuzu trooper 2.8
2007 Toyota Yaris
Vw dasher 2 door diesel
1972 Chevy C10 long bes stepside
John Deere 5210