Cooling
Another design alteration we chose to make was to improve the cooling system on one side of the displacer cylinder. The original design had a series of fins to disperse the heat into the atmosphere. Whilst this is relatively effective, over a long running time it will begin gradually to heat up. This reduces the temperature difference between the hot and cool parts of the engine, hence reducing the efficiency and output power. It is quite a common technique in the construction of Stirling Engines to include a cooling mechanism using a liquid, commonly water. This is a more effective technique for cooling as water can absorb more heat energy than air. The faster the flow of water, the more effective the cooling is. However, this introduces the complications of pumping the water round the cooling system. In fact, the power required to pump the water round the system is likely to be greater than the output power of the engine itself. With a large surface area (such as by the use of fins) the cooling can be improved by the use of a simple water bath. This is the solution we have included in the design; a jacket has been designed to fit around the cold cap and it will be filled with water. It will decrease the speed of the transfer of heat from the hot end of the cylinder, hence allowing the engine to run for longer before the performance begins to drop.