Experimental determination of the heat transfer coefficients of shell-and-tube heat exchangers with different hollow fiber arrangements

journal article in Web of Science

en

To maximize heat transfer in heat exchangers (HEs), it is important to enlarge the active surface area and to ensure that the whole surface is in contact with continuously flowing fluids on both sides. Progress in the last two decades led to the creation of polymeric hollow-fiber HEs (PHFHEs) that have an extensive active surface area to volume ratio. Compared to conventional metal HEs, polymeric HEs are lighter and more chemically resistant. Furthermore, the fibers PHFHEs can be organized in a specific arrangement that guarantees high heat transfer efficiency. Six shell-and-tube HEs with three different types of fiber arrangements (parallel fibers, coils, and chaotization) were compared by calculating the heat transfers and the heat transfer coefficients. Pressure drops were also measured. The experiments were conducted with a counter-current mode of operation with constant laminar flow in the fibers and gradually increased flow in the shell. The experiments proved that if the fibers are arranged in a way that secures spacing heat transfer is boosted. Compared to parallel fibers, slight improvements are seen if the fibers are shaped into coils. However, complete chaotization of the fibers is far superior. Chaotized HEs demonstrate a fourfold increase in heat flux and a twofold increase in heat transfer coefficient while reducing the pressure drop by two-thirds compared to similarly sized HEs with parallel fibers.

To maximize heat transfer in heat exchangers (HEs), it is important to enlarge the active surface area and to ensure that the whole surface is in contact with continuously flowing fluids on both sides. Progress in the last two decades led to the creation of polymeric hollow-fiber HEs (PHFHEs) that have an extensive active surface area to volume ratio. Compared to conventional metal HEs, polymeric HEs are lighter and more chemically resistant. Furthermore, the fibers PHFHEs can be organized in a specific arrangement that guarantees high heat transfer efficiency. Six shell-and-tube HEs with three different types of fiber arrangements (parallel fibers, coils, and chaotization) were compared by calculating the heat transfers and the heat transfer coefficients. Pressure drops were also measured. The experiments were conducted with a counter-current mode of operation with constant laminar flow in the fibers and gradually increased flow in the shell. The experiments proved that if the fibers are arranged in a way that secures spacing heat transfer is boosted. Compared to parallel fibers, slight improvements are seen if the fibers are shaped into coils. However, complete chaotization of the fibers is far superior. Chaotized HEs demonstrate a fourfold increase in heat flux and a twofold increase in heat transfer coefficient while reducing the pressure drop by two-thirds compared to similarly sized HEs with parallel fibers.

Polymeric heat exchangers; Shell-and-tube heat exchangers; Hollow fiber arrangement; Heat transfer coefficient; Thermal performance

12.09.2022

SPRINGER

DORDRECHT

1588-2926

147

12.9.2022

14787–14796

10