Experimental Study on Thermal Striping in Mixing Tees With Hot and Cold Water

Abstract

Thermal striping tests in mixing tees with hot and cold water were conducted for three types of flow conjunctions in order to establish an evaluation method for high-cycle thermal fatigue of piping systems. Two kinds of examinations were planned. The preliminary tests were flow visualization tests carried out using acrylic pipes to obtain flow pattern characteristics and flow temperature fluctuations. The main tests were temperature fluctuation measurement tests carried out using metal pipes to evaluate the unsteady heat transfer coefficient based on measured temperature fluctuations of fluid and pipe wall. This paper reports visualization test results. The flow patterns were visualized by injection of methylene blue and compared with flow analysis results by the k-ε turbulence model. Temperature fluctuations of fluid 3mm from the inner pipe wall were measured with C-A thermocouples. Fundamental features such as locations with a large fluctuating temperature, the fluctuating temperature amplitude and its frequency were identified.

LES benchmark study of high cycle temperature fluctuations caused by thermal striping in a mixing tee

“…The temperatures at each thermocouple location were recorded at a frequency of 25 Hz. Velocities and temperatures at the main and branch pipes were confirmed to be at steady-state before each experiment was performed (Kawamura et al, 2003). striping experiments in tee junction is dubbed collision type.…”

Experimental study on turbulent mixing process in cross-flow type T-junction

“…Moreover, the characteristics of the temperature field have been investigated as well. In particular, the temperature fluctuation near the channel wall has been examined to make clear the mechanism of the thermal striping phenomena that occur in a nuclear power plant (Kawamura et al, 2002;Igarashi et al, 2002;Fukushima et al, 2003;Yuki et al, 2004;Nakajima et al, 2005;Tanaka et al, 2005). In the application to the automobile HVAC unit, the heat transfer between the hot airflow and cold one is important, but few data are available on the detailed mechanism of heat transfer between two flows in a T-junction (Kok and van der Wal, 1996).…”

Promotion of Turbulent Thermal Mixing of Hot and Cold Airflows in T-junction

“…A T-junction in which two fluids with different velocities, temperatures, and/or concentrations are mixed turbulently is encountered in various thermo-fluids equipment: e.g., chemical reactors, combustion chambers, piping systems in power plants [1][2][3][4][5]. One of the typical mixing T-junctions is found in the HVAC (Heating, Ventilating, Air-Conditioning) unit that is used for an automobile air-conditioning system [6].…”