Heat exchangers are unique devices that exchange heat between two different liquids at different temperatures without mixing them. Heat exchangers have a wide range of applications. They range from household heating and air conditioning to utilizations in the oil and gas industry. Among these, heat exchangers differ from mixing chambers in the way that the liquids are not mixed. It is an essential part of different media, such as oil and water. In a heat exchanger, heat transfer occurs by convection in each fluid, and conduction occurs through the wall. The wall is necessary to separate the liquids from each other. To analyze the heat exchanger correctly, many effects need to be considered. An example is the overall heat transfer coefficient U, which plays an important role. The heat transfer rate also depends on the temperature difference at the respective position along the heat exchanger. There are also some different types of heat exchangers. In this thesis, the focus is on a modification of the double-pipe heat exchanger. The modification is done due to a kind of thread along the length of the heat exchanger pipe. This thread allows the mixing of the fluid inside the tube, which results in a better heat transfer coefficient along the pipe. The thread is used to increase the heat transfer coefficient of the cold oil pipe. The water pipe has a smaller diameter than the oil tube and it is located inside the oil pipe. It is used to heat up the cold oil. The performance of the heat exchanger is increasing, and the length of the heat exchanger is decreasing due to a better heating effect. A simulation in OpenFOAM shows the solution of this analysis.