STIRLING HEAT ENGINE & PELTIER DEVICE
Hello class, I am actually looking forward to learning about the Stirling heat engine and the peltier device. I blog will be outlined in the following manner, first I will describe what a stirling heat engine is and what purpose it serves. I will continue by doing the same for the peltier device. I will then conclude my blog by stating interesting facts or links that will benefit you.
The diagram above is a stirling heat engine.
Invented by Robert Stirling in 1816, the Stirling engine does not allow gasses used to leave the engine. Unlike gasoline or diesel engines, no combustion takes place inside the cylinders of the engine. Stirling engines are very quiet because of the Stirling cycle.
My curiosity led me to learn more about the Stirling cylinder and how it works. The key principle of a Stirling engine is that a fixed amount of gas is sealed inside the engine.
There are several properties of gasses that are critical to the operation of Stirling engines:
If you have a fixed amount of gas in a fixed volume of space and you raise the temperature of that gas, the pressure will increase.
If you have a fixed amount of gas and you compress it (decrease the volume of its space), the temperature of that gas will increase.
Let’s go through each part of the Stirling cycle while looking at a simplified Stirling engine. Our simplified engine uses two cylinders. One cylinder is heated by an external heat source (such as fire), and the other is cooled by an external cooling source (such as ice). The gas chambers of the two cylinders are connected, and the pistons are connected to each other mechanically by a linkage that determines how they will move in relation to one another.
The diagram above is a picture illustrating a Stirling cycle.
http://www.youtube.com/watch?v=NvKbPEuMRy4
The link above provides a video explaining how a Stirling engine works.
There are four parts to the Stirling cycle.
- Heat is added to the gas inside the heated cylinder (left), causing pressure to build. This forces the piston to move down. This is the part of the Stirling cycle that does the work.
- The left piston moves up while the right piston moves down. This pushes the hot gas into the cooled cylinder, which quickly cools the gas to the temperature of the cooling source, lowering its pressure. This makes it easier to compress the gas in the next part of the cycle.
- The piston in the cooled cylinder (right) starts to compress the gas. Heat generated by this compression is removed by the cooling source.
- The right piston moves up while the left piston moves down. This forces the gas into the heated cylinder, where it quickly heats up, building pressure, at which point the cycle repeats.
Now that you have a clear understanding of a Stirling engine let’s move on to explaining a peltier device.
Peltier Device – cooler, heater, or thermoelectric heat pump is a solid-state active heat pump, which transfers heat from one side of the device to the other, with consumption of electrical energy, depending on the direction of the current.
http://www.youtube.com/watch?v=Ipt8xqKbCSw
Please take a look at the link provided above to view how to make a peltier device on your own.
A phenomenon first discovered in the early 19th century. The Peltier effect occurs whenever electrical current flows through two dissimilar conductors. Depending on the direction of current flow, the junction of the two conductors will either absorb or release heat.
Peltier devices are literally heat pumps, which have two sides a hot side, and a cold side. When a voltage is applied (around 12V), heat is ‘magically’ pumped from the cold side to the hot side through the semiconductor junction.
Peltier devices have different power ratings, corresponding to how fast the cold side is able to cool down an object. Another factor is generally specified, the delta-T, which is the maximum thermal difference in temperature between both sides.
Lets now conclude the blog with purposes for each device. The Stirling engine can be used in each of the following devices:
- Automotive engines – although unlikely, recently scientist have found a way to mitigate all the difficulties and implement the engine in autos (patent 7,387,093)
- Electric Vehicles – Stirling engines are part of hybrid vehicles
- Pump engines
- Solar power generation
Peltier devices are used for heating, cooling or generating electricity. They are flexible in that they can be used to do things such as but not limited too, charging batteries, running small electrical devices such as led’s, as well as heating and cooling. Your imagination and the number of peltier elements are the only limitations you have.
References:
http://auto.howstuffworks.com/stirling-engine.htm
http://www.penguinslab.com/peltier.htm
http://www.dansdata.com/peltprac.htm
http://www.survival-manual.com/electricity/peltier-elements.php