Thermal-hydraulic performance of R1234yf in brazed plate heat exchanger at low saturation temperature and mass flux conditions: Experimental investigation
{"title":"Thermal-hydraulic performance of R1234yf in brazed plate heat exchanger at low saturation temperature and mass flux conditions: Experimental investigation","authors":"","doi":"10.1016/j.applthermaleng.2024.124634","DOIUrl":null,"url":null,"abstract":"<div><div>This study investigated the heat transfer coefficient (<em>h<sub>r</sub></em>) and two-phase frictional pressure drop during the evaporation of R1234yf within an offset strip fin (OSF)-structured brazed plate heat exchanger (BPHE). The work is conducted at a saturation temperature (T<sub>s</sub>) of −3 to 3 °C, with mass flux (G) ranging from 25 to 45 kg m<sup>−2</sup> s<sup>−1</sup> and heat flux (q) between 15 and 23 kW m<sup>−2</sup> across a vapor quality (<em>x</em>) range of 0.1–0.8. Understanding these behaviors is critical for optimizing BPHEs in low-temperature applications, such as heat pumps, where energy efficiency is essential. The novelty of this work lies in its exploration of operating conditions that are less studied in the literature, particularly the impact of low T<sub>s</sub>, low G, and high q on <em>h<sub>r</sub></em> and two-phase frictional pressure drop in an OSF-BPHE with R1234yf. Unlike prior studies focusing on convection-dominated boiling, our findings reveal a coexistence of nucleate and convective boiling mechanisms, especially at different vapor qualities. The <em>h<sub>r</sub></em> is significantly influenced by q at <em>x</em> < 0.6, G at <em>x</em> > 0.6, and T<sub>s</sub> across all <em>x</em>. In contrast, evidence of dryout at high <em>x</em> highlights the importance of these parameters in managing heat transfer efficiency. The results indicate a strong correlation between the two-phase frictional pressure drop and G, with a marked increase in it at higher G. Besides, this study reveals flow characteristics commonly linked with both macrochannel and minichannel flows, enhancing novelty by bridging the gap between these two regimes. These findings challenge existing literature correlations that predominantly emphasize convection-dominated behavior and contribute to a better understanding of the dual boiling mechanisms in BPHEs.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":null,"pages":null},"PeriodicalIF":6.1000,"publicationDate":"2024-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Applied Thermal Engineering","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1359431124023020","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
引用次数: 0
Abstract
This study investigated the heat transfer coefficient (hr) and two-phase frictional pressure drop during the evaporation of R1234yf within an offset strip fin (OSF)-structured brazed plate heat exchanger (BPHE). The work is conducted at a saturation temperature (Ts) of −3 to 3 °C, with mass flux (G) ranging from 25 to 45 kg m−2 s−1 and heat flux (q) between 15 and 23 kW m−2 across a vapor quality (x) range of 0.1–0.8. Understanding these behaviors is critical for optimizing BPHEs in low-temperature applications, such as heat pumps, where energy efficiency is essential. The novelty of this work lies in its exploration of operating conditions that are less studied in the literature, particularly the impact of low Ts, low G, and high q on hr and two-phase frictional pressure drop in an OSF-BPHE with R1234yf. Unlike prior studies focusing on convection-dominated boiling, our findings reveal a coexistence of nucleate and convective boiling mechanisms, especially at different vapor qualities. The hr is significantly influenced by q at x < 0.6, G at x > 0.6, and Ts across all x. In contrast, evidence of dryout at high x highlights the importance of these parameters in managing heat transfer efficiency. The results indicate a strong correlation between the two-phase frictional pressure drop and G, with a marked increase in it at higher G. Besides, this study reveals flow characteristics commonly linked with both macrochannel and minichannel flows, enhancing novelty by bridging the gap between these two regimes. These findings challenge existing literature correlations that predominantly emphasize convection-dominated behavior and contribute to a better understanding of the dual boiling mechanisms in BPHEs.
期刊介绍:
Applied Thermal Engineering disseminates novel research related to the design, development and demonstration of components, devices, equipment, technologies and systems involving thermal processes for the production, storage, utilization and conservation of energy, with a focus on engineering application.
The journal publishes high-quality and high-impact Original Research Articles, Review Articles, Short Communications and Letters to the Editor on cutting-edge innovations in research, and recent advances or issues of interest to the thermal engineering community.