Thermosyphons :: physics

Tasked with the quest to economically and efficiently extend civilization into the Northern regions, the construction industry has been hindered by the presence of perennially frozen ground. The thermosyphon is a device that facilitates the harmonious union of structure and ice. This paper will serve as a tutorial on thermosyphons, and present an exploration into the physical concepts that allow their operation. The physical concepts and phenomenon that enable the operation of thermosyphons can at times be complex-but don’t be scared. This tutorial will start with the most rudimentary explanation of thermosyphons, and proceed from there to deliver more in depth examinations in a step by step process. Let’s get right down to business. The steps in thermosyphon operation are: STEP 1-Heat flows into the thermosyphon, STEP 2-Heat flows through the thermosyphon tube, and STEP 3-Heat is released into the atmosphere. Simply stated, a thermosyphon is a device which moves heat from one place to another. There are different types of thermosyphons which are used for different applications, but for the purposes of this primer we will concentrate on thermosyphons used by the construction industry to stabilize frozen ground. For example, consider a road built over permafrost.. In this situation it is desirable to keep the ground from thawing, otherwise the road embankment will be destroyed. A thermosyphon â€Å"collects heat† from the frozen ground. This collected heat is brought to the top of the thermosyphon and the cooling fins, where it is released into the atmosphere. In this way, the ground remains frozen. Now, the thought of frozen soil warming the atmosphere may be hard to grasp. This brings us to an important point about the thermosyphon- they only work when the ambient air temperature is below the temperature of the soil (less than 31 degrees Farenheight). With this in mind, we can consider thermosyphons from a different perspective; a thermosyphon increases the exposure of sub-surface soil to freezing temperatures. Another thought, although not totally correct from a physical standpoint, is that the thermosyphon brings cold into the soil. Let’s examine the thermodynamic process by which a thermosyphon operates. This process is outlined below in a step by step chronology. Step 1-There is an accumulation of the working fluid in the bottom of the thermosyphon. The most important factor that governs the choice of a working fluid is that it must have an extremely low boiling point. Permafrost soil is typically at a temperature of 31F and consequently the fluid boiling point should be less than 31F.