Analysis of fluid retention zones in heat exchangers with segmental baffle and helical baffle

By using the residence time distribution method (RTD), the fluid retention zones in the shell and tube heat exchanger with segmental baffle (STHX-SB) and the heat exchanger with helical baffle (STHX-HB) are compared and discussed. The flow pattern and fluid retention zone of the similar double helical flow heat exchanger (STHX-SDH) were analyzed by using the same method. The result shows the spiral flow can reduce the fluid retention zone. The flow pattern in the STHX-SDH likes a double helical shape and leads to a very small fluid retention zone. According to the simulation results, the location of the fluid retention zone of STHX-SDH is determined. The verification line method and the zone assessment method were adopted, to discuss the flow velocity of each point on the verification line and the average flow velocities of the selected zones. The change laws of the flow velocities on the verification lines and the average flow velocities of the selected zones at different Reynolds numbers were compared. The result reveals the distribution of the fluid retention zone of the STHX-SDH and the sensitivity of each fluid retention zone to the Reynolds number. By optimization of the angle of the baffle, the volume fraction of the fluid retention zone is reduced to 1.61%, and the heat transfer performance is improved by 13.23%. It is verified that reducing the fluid retention zone can effectively enhance the heat transfer performance. This research method provides a theoretical basis for reducing the fluid retention zone of the heat exchanger and enhancing heat transfer performance.

Using CFD To Assess The Impact of Helical Baffle On The First- Law And Second-Law Performance of Water-CuO Nanofluid Inside A Hairpin Heat Exchanger

This study is devoted to the numerical assessment of the influence of helical baffle on the hydrothermal aspects and irreversibility behavior of the turbulent forced convection flow of water-CuO nanofluid (NF) inside a hairpin heat exchanger. The variations of the first-law and second-law performance metrics are investigated in terms of Reynolds number (Re), volume concentration of NF (φ) and baffle pitch (B). The results showed that the NF Nusselt number grows the rise of both the Re and φ whereas it declines by boosting with the rise of baffle pitch. In addition, the outcomes depicted that the rise of both the T and φ results in the rise of pressure drop, while it declines with the increase of baffle pitch. Moreover, it was found that the best first-law performance of the NF belongs to the case B=33.3 mm, φ=2% and Renf=10000. Furthermore, it was shown that irreversibilities due to fluid friction and heat transfer augment with the rise of Re while the rise of baffle pitch results in the decrease of frictional irreversibilities. Finally, the outcomes revealed that with the rise of baffle pitch, the heat transfer irreversibilities first intensifies and then diminishes.

Experimental Study of a Concentric Tube Heat Exchanger with Helical Baffle Using CFD

Heat exchangers are the most common equipment used to transfer heat from high-temperature fluid to low-temperature fluid without direct contact. The present study considers the analytical approach on a concentric tube heat exchanger with the helical baffle. The objective of the study is to reduce the size with effect to increase the effectiveness of the heat exchanger. A heat exchanger with 100 mm external diameter and 560 mm length contains a helical baffle with 20 degrees inclination. The designed heat exchanger is analysed by varying the mass flow rate of hot water from 0.25 Kg/s to 2 Kg/s at an interval of 0.25 kg/s at three different temperatures i.e. 363.16 K, 368.16 K, 373.16 K. A nanofluid is applied to cool the hot water without any loss. The mass flow rate of cold fluid is 2 Kg/s at 30 degrees Celsius. The results have displayed that the heat exchanger exhibited appreciable effectiveness at a flow rate of 0.25 Kg/s for hot water at 373.16 K temperature. There by suggesting it as the optimum model of the heat exchanger.