Numerical and experimental investigation of flow and thermal mixing phenomena of jets at different temperatures

In this study, thermophysical specifications of jets at different temperatures in a confined channel were investigated experimentally and numerically. An experimental setup was produced for experimental part of the study and Large Eddy Simulation turbulence model was used to simulate numerical part of the study. Parallel and Coaxial jet models were used in the analyses that water was used as working fluid. Passive obstacles that have different geometrical specifications were inserted into the channel. Analyses were carried out for six cases which are function of temperature difference between jets and different momentum ratios of the jets. Three approaches were applied while analyzing the experimental and numerical data. Thermal mixing behavior of the jets in the channel were investigated in the first approach. In the second approach, temperature fluctuating phenomena in turbulent region which effective thermal mixing occur were evaluated and it is identified that these fluctuations contain a thermal stress risk for the channel walls or not. In the last approach, flow field phenomena of the jets were evaluated comprehensively. Results showed that mixing performance gets better with increasing temperature differences between jets for all working parameters. Thermal mixing behavior of the jets changes substantially with changing momentum ratios of the jets. Using passive obstacles into the channel lead better mixing performance in general. Mixing performance enhances with increasing porosity values of the passive obstacles. Dominant frequency of temperature fluctuations in the mixing region is captured as 5 Hz for all working cases. These high amplitude temperature fluctuations sometimes reach to the channel walls in obstacle cases and sometimes it dissipates inside bulk temperature before reach the walls. Using obstacles into the channel reduces the turbulent area in general. Experimental and numerical data correspond with each other with a great accuracy.