Numerical Simulation Of Flow And Heat Transfer Characteristics In Informal Corrugated Channels Of Plate Heat Exchangers

Plate heat exchangers have been widely used in chemistry,heating and food fields,due to compact structure,high heat transfer efficiency and the ability to flexibly match a variety of operating conditions.Therefore,revealing the internal mechanism of heat transfer in the plate heat exchanger and improving the heat exchange efficiency is of great significance for improving energy utilization and saving resources.Most of the previous researches have focused on analyzing the effect of geometry on the heat transfer performance of plate heat exchangers,while the contacts distribution,flow and heat transfer characteristics in the transverse channel of plate heat exchanger are rarely mentioned.Moreover,the wavy channels of plate heat exchanger are complex and changeable.Most of the previous researches have focused on analyzing normal wavy channels with the same wave amplitudes.However,the researches on informal wavy channels that composed of different wave amplitudes are rarely reported,especially for local flow distribution and heat transfer performance in the flow channel,which has an extremely important effect on improving the heat transfer efficiency of plate heat exchanger.In present study,the M-type and H-type hybrid plate heat exchangers and the informal unit corrugated channel are simulated and analyzed by Computational Fluid Dynamics(CFD).The numerical results are concluded as follows:(1)The distribution of contact points in the transverse channel of various hybrid plate heat exchangers is different,showing a "square-shaped" distribution in the M-type heat exchanger,and a "diamond-shaped" distribution in the H-type heat exchanger.The velocity and temperature are high on both sides of the contact point,and a low-speed wake vortex area with the lowest temperature is easily formed at the tail of the contact point.With the increase of Reynolds number(Re),the heat transfer is enhanced.(2)The average (?)sselt number((?))and pressure drop(△P)of M and H-type plate heat exchangers increase with the increase of Re,and the increment of △P increases.At the same time,the heat transfer performance of the heat exchanger with larger corrugated angle(β)is higher than that of the smaller corrugated angle.The heat transfer performance of H-type heat exchanger is generally greater than that of M-type heat exchanger.The (?) and △P are greater for the heat exchanger with higher corrugated height(η)and smaller the corrugated pitch(λ).(3)The velocity and temperature distribution of fluid in the informal unit wavy channel are different.The high-speed and high-temperature fluid is mainly concentrated in the middle and lower parts of the wavy channel,while a backflow vortex easily appears on the upper concave surface,and the area of the vortex increases with the increase of the upper wall amplitude,and decreases with the increase of the lower wall amplitude.(4)The average (?)sselt number and friction factor(f)increase with the increase of corrugated height or the decrease of corrugated pitch for three kinds of unit wavy channels(A<B,A=B,A>B).The Performance Evaluation Criterion(PEC)reaches maximum for the corrugated channel(A=3mm,B=3mm).The optimal heat transfer performance of three kinds of unit corrugated channels is obtained,when corrugated height is in a range of 2mm≤η≤3mm,and corrugated pitch is in a range of 12mm≤λ≤14mm.The heat transfer performance on the lower wall is always greater than that of the upper wall.(5)The phase shift angle(θ)has a great effect on the flow and heat transfer characteristics of three kinds of wavy channels.For θ = 300°,the heat transfer performance of the wavy channel is the largest,but its friction factor increases correspondingly.It is found that the optimal heat transfer performance of wavy channels is obtained when phase shift angle is 0° or 360°.