Alaska Pipeline - Alyeska - Physics

The designers definitely did a thorough job of researching and protecting the wildlife in the region, and in keeping excessive heat from going DOWNWARD and getting to the delicate permafrost in the soil. (Because environmental activists made so much noise that they had to.) They even installed thousands of "automatic refrigerators" which remove heat from the soil whenever the air temperature is less than the soil temperature, which was brilliant! However, there does not seem to be any evidence at all that anyone considered effects of heat radiated UPWARD, and therefore on the weather, either then or since.

In order to pump the crude oil through the pipeline, the oil needs to be heated so it is less viscous and flows easier. Therefore, the entire Alaska pipeline has always operated with the oil inside at around 140°F, rather warm! This is in an environment where the outdoor temperature can be as low as -90°F The surface of the pipeline is covered by thermal insulation, but there is SO much surface area and the temperature difference between the pipe and the air is often so extreme, that huge amounts of heat are given off by the pipeline. How much? Also, extremely little attention has been paid to the condition of all that insulation, which has been exposed to that very climate for nearly 40 years.

This is a standard and simple Engineering calculation. The total heat loss is simply the product of the temp-differential times the surface area divided by the R-factor of the insulation. The pipeline is almost exactly 800 miles long, which is just over 4,200,000 feet in length. The actual pipe is 48" (four feet) in diameter so its circumference is 12.6 feet, so the total pipe surface area is just over 53 million square feet! In the dead of winter, the air temperature can get down to 90°F below zero, so the temp-difference is then 230°F. And Aleyska gives the thickness of the insulation but not its R-value. However, from the thickness, good polyurethane insulation has an R-factor of about R-18. (Assuming that they have maintained that 53 million square feet of insulation during the past 40 years!)

So we have 53 million times 230 divided by 18 or 680,000,000 Btu/hr of heat loss! That is as much heat that is used up and given off by about 17,000 heated residential homes on the coldest night, a HUGE amount!

It turns out that they do not have to use heaters or heating elements to keep the oil hot. They use aircraft jet engines driving giant pumps, which are so strong, and the viscosity of the oil is so bad, that there is enough friction between the oil and the pipeline to produce this heat completely by friction. Which means that the total pumping work must approximately equal the heat loss from the surface of the pipeline.

Note above that we took an extreme low temperature, and around 450,000,000 Btu/hr is a better average amount of heat given off by the pipeline.

It is also true that only around half of the length is actually supported on posts above ground. The other half is buried in the ground. However, consider what has to happen to the heat given off by that buried pipe. One way or another, it MUST eventually escape, which means upward into the atmosphere. The totals calculated here might be slightly off for the buried portion, but still must be fairly close.

There is a way that we can confirm this! Presently the oil flow is reduced and only 9 of the 48 available giant pumps are operating. The pumps are driven by modified jet aircraft engines! Each (Avon) jet turbine produces 24,600 horsepower. The pump (reaction) turbines are decently efficient and each produces 18,700 brake horsepower. This data is all from Alyeska, the company that operates the pipeline. OK. So 18,700 brake horsepower is added to the oil flow by each of the nine operating pumps (in four of the twelve pumping stations), or a total of a constant 168,300 horsepower. Each horsepower is equivalent to 2544 Btu/hr of heat energy, so the pumps are inserting about 428 million Btus of energy into the oil, PLUS the heat that the oil starts off with as it comes out of the wells at about 160°F. This seems to be in very good agreement that the pipeline dissipates around 450,000,000 Btu/hr of heat to the atmosphere.

Those aircraft engines represent another heat source, as they continuously run at full speed and they have the jet exhaust heat of all airliners. It turns out that gas turbine engines are relatively efficient (as compared to gasoline vehicle engines that are commonly around 21% overall thermal efficiency) at having around 32% thermal efficiency at their operating speed. What this means is that 32% of the energy in the fuel is used "productively" in turning the shaft of the turbine. The other 68% is nearly all given off as wasted heat, primarily in the jet exhaust. Now, each of those jet engines creates 24,600 horsepower of useful output (different than brake horsepower), or 62.6 million Btu/hr. The nine of them that constantly are running therefore create a total of 563 million Btu/hr of useful output, which is that 32% figure of the total fuel energy. That means that the other 68% which is given off as exhaust heat from those engines represents 1200 million Btu/hr given into heating the atmosphere (mostly in the exhaust gases of those jet engines).

We have a way to confirm this value, too. Alyeska says that the pipeline system uses up 210,000 gallons/day of fuel oil (equivalent). A gallon of fuel oil contains around 140,000 Btu of energy, so this means that 29,400 million Btu/day of fuel are consumed, which is 1225 million Btu/hour. Above we have calculated that the jet exhausts plus the energy put into the oil total around 1700 million Btu/hour. Not a really tight confirmation, but an indication that our reasoning and our calculations are generally valid.

Further scientific study seems called for. This seems especially true now that President Bush has gotten his freedom to allow far more prospecting for oil in Alaska. It may be VERY foolish to consider building additional pipelines, and there may even be cause to require Alyeska to install additional insulation on the existing pipeline and to somehow use up some of the jet exhaust heat. A very small part of that jet exhaust heat IS presently used, primarily to drive electric generation stations at each of the pump stations.

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C Johnson, Theoretical Physicist, Physics Degree from Univ of Chicago