Performance comparison for oil-water heat transfer of circumferential overlap trisection helical baffle heat exchanger

The performance tests were conducted on oil–water heat transfer in circumferential overlap trisection helical baffle heat exchangers with incline angles of 12°, 16°, 20°, 24° and 28°, and compared with a segmental baffle heat exchanger. The results show that the shell side heat transfer coefficient h_o and pressure drop Δp_o both increase while the comprehensive index h_o/Δp_o decreases with the increase of the mass flow rate of all schemes. And the shell side heat transfer coefficient, pressure drop and the comprehensive index ho/Δpo decrease with the increase of the baffle incline angle at a certain mass flow rate. The average values of shell side heat transfer coefficient and the comprehensive index h_o/Δp_o of the 12° helical baffled scheme are above 50% higher than those of the segmental one correspondingly, while the pressure drop value is very close and the ratios of the average values are about 1.664 and 1.596, respectively. The shell-side Nusselt number Nu_o and the comprehensive index Nu_o·Eu_(zo)^(-1) increase with the increase of Reynolds number of the shell side axial in all schemes, and the results also demonstrate that the small incline angled helical scheme has better comprehensive performance.

Heat Transfer and Flow Resistance Characteristics of Helical Baffle Heat Exchangers with Twisted Oval Tube

To overcome the defect of the significant increase in pressure drop when the heat transfer performance of helical baffle heat exchanger is improved,a novel helical baffle heat exchanger with twisted oval tube is proposed.Numerical simulation was done to exhibit the shell side heat transfer and flow characteristics with CFD software Fluent.The field synergy principle was used to evaluate the shell side performance.The results show that the flow velocity distribution on the shell side of the spiral baffle heat exchanger is more uniform and the velocity near the tube wall increases in the range of research parameters,as the circular tube is replaced by a twisted elliptical tube with the same perimeter length.Moreover,the helical baffle heat exchanger with twisted oval tube has better field synergy of velocity and temperature gradient,velocity and pressure gradient.The helical baffle heat exchanger with helix angle of 15°has better performance than that of circular tube,and its heat transfer coefficient is improved about 3.3%and pressure drop is reduced by 17.1%–19.1%.Hence,the comprehensive heat transfer performance is improved by 21.5%–22.5%.When the helix angle is 20°,the comprehensive heat transfer performance is increased by 16.1%–18.0%with heat transfer coefficient improvement of 3.6%and pressure drop reduction of 13.9%–16.5%.