Performance simulation on unilateral ladder type helical baffle heat exchanger in half cylindrical space

A unilateral ladder type helical baffle heat exchanger (ULHBHX) which is a novel countercurrent U-tube heat exchanger was proposed and investigated for better characteristics of high heat transfer coefficient, low resistance, anti-vibration and anti-fouling with a spiral flow pattern than those of the conventional segment one. The numerical model of ULHBHX was established and simulated by CFD software with 38 heat transfer tubes and 2 rod and spacing tube assemblies in the lower half cylindrical space under the parameters of subcooling of a high pressure feedwater heater in power plants. Different views such as on baffle-parallel slices and polygonal slices were presented to show the flow patterns of the main helical flow, secondary vortex flow and the leakage flow. The influences of geometrical parameters of baffle pitch and projection length of the inclined section on heat transfer and pressure drop were discussed quantitatively. The results show that the shell-side heat transfer coefficient ho of the ULHBHXs is 13.2%-18.2%, with an average of 16.0%, higher than those of the corresponding segment schemes, and the comprehensive index hoΔpo−1/3 is 15.7%-46.4%, with an average of 28.3%, higher than those of the corresponding segment schemes with identical baffle pitches in the discussed range.