Relationship between inclination angle and friction factor of chevron-type plate heat exchangers

The inclination angle is a key design parameter of chevron-type plate heat exchangers. An increase of the inclination angle can possibly raise the flow friction by two orders of magnitude. According to our review, previous works concerning experimental measurements and correlations of the friction factor in plate heat exchangers are highly inconsistent. In order to establish a benchmark, we use the Large Eddy Simulation to model the fully-developed flow in cross-corrugated channels of the plate heat exchanger, and then calculate the friction factor for various conditions with the inclination angle ranging from 18^∘ to 72^∘, and the Reynolds number varying from 10 to 6000. Based on the numerical data, well-defined equations are derived to correlate the friction factor with the inclination angle in a general way for both laminar and turbulent flow regimes. Moreover, we derive novel correlations to predict the critical point of laminar-to-turbulent transition in the plate heat exchanger. Then we use these established correlations to draw a friction factor diagram for plate heat exchangers. The diagram maps the relationship between the friction factor and the inclination angle for a wide Re range, which resembles the Moody diagram. Furthermore, the vortex structure and the mean flow properties for different inclination angles are analysed. The results suggest that a larger inclination angle leads to more intensified vortexes and span-wise secondary flows in the channel, resulting in a larger friction factor.