Thermal and hydraulic performance of a printed circuit heat exchanger using two-phase nitrogen

Abstract Experiments were conducted in an effort to investigate the thermal and hydraulic performance capabilities of a designed and manufactured printed circuit heat exchanger (PCHE). The core of the PCHE was made of stainless steel 316 L plates, and two different types of channels on the plates were prepared: ‘straight’ and ‘N’-shaped types. In total, 40 etched plates were stacked and diffusion-bonded in a vacuum chamber, and the diameter of the semi-circle channels was verified to be 884 μm using a scanning electron microscope (SEM). In experiments using the PCHE, the flow rate of the cold side remained at approximately 300 kg/h (ranging from 303.5 kg/h ~ 315.3 kg/h), while the inlet temperature and pressure were about −170 °C and 0.77 MPa, respectively. On the hot side, the flow rates were varied from 531 to 1002 kg/h and the corresponding inlet conditions were approximately 30 °C and 0.82 MPa. Numerical simulation using ANSYS fluent was also performed for a single channel to calculate the hot side heat transfer coefficient. And the result was used to estimate the averaged heat transfer coefficient for the two- and single-phases transition with experimental results. In order to explain the averaged two- and single-phases heat transfer coefficient, an empirical equation, θ = C(Reh/Rec)a Bob was developed by modifying an existing correlation, and it showed good agreement with R2 = 0.98. In addition, from the pressure drop result on the hot side, the sum of the pressure drop coefficients in the inlet/outlet headers and the minor losses is suggested to be 29.9 with R2 = 0.93.