Flow boiling heat transfer and pressure drop characteristics of Isobutane in horizontal channels with twisted tapes. (December 2020)

• Record Type: Journal Article
• Authors: Sarmadian, Alireza; Moghaddam, Hadi Ahmadi; Asnaashari, Amirmasoud; Joushani, Hossein Ahmadi Nejad; Moosavi, Mostafa; Islam, Mohammad S.; Saha, Suvash C.; Shafaee, Maziar
• Is Part Of: International journal of heat and mass transfer. Volume 162(2020)
• Publication Date: 2020-12
• Subjects: Heat transfer -- Isobutane -- Mass velocity -- Pressure drop -- Vapor quality; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2020.120345
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Twisted tapes usage increased the heat transfer and pressure losses. Increasing the vapor quality and mass flux enhanced the heat transfer rate. Pressure drops grew by increasing the vapor quality and mass flux. The system performance factor was between 0.44–1.09 using inserts. Abstract: Using twisted tapes as a passive method for heat transfer improvement in a two-phase flow heat exchanger is experimentally studied. The test evaporator is a copper channel with a length of 1000 mm and an internal diameter of 8.1 mm which is installed horizontally. Three twisted tapes with twist ratios of 4, 10, and 15 are used at refrigerant vapor qualities in the range of 0.1–0.8 and refrigerant mass velocities between 160-350 kgm −2 s −1 . The natural refrigerant Isobutane (R600a) is chosen as the working fluid because it is environmentally friendly. According to the experiments, installing twisted tapes inside the channel augments both heat transfer rate and pressure drops over the plain channel. It is also observed that for both plain and twisted tape inserted channels, the values of heat transfer coefficients and pressure losses grow by giving rise to the refrigerant mass velocity and vapor quality. Results showed that the system performance factor varied between 0.44–1.09 offering that using twisted tapes as a turbulator is beneficial under specific operating conditions. The empirical data showed that there is an optimum value of the working fluid mass velocity at which the performance of twisted tape inserted channels is higher.