Comparative study of a novel liquid–vapour separator incorporated gravitational loop heat pipe against the conventional gravitational straight and loop heat pipes – Part I: Conceptual development and theoretical analyses. (15th January 2015)

• Record Type: Journal Article
• Authors: Zhang, Xingxing; Shen, Jingchun; He, Wei; Xu, Peng; Zhao, Xudong; Tan, Junyi
• Is Part Of: Energy conversion and management. Volume 90(2015)
• Page Start: 409
• Page End: 426
• Publication Date: 2015-01-15
• Subjects: Gravity -- Heat pipe -- Composite wick -- Heat transfer -- Mass -- Theoretical model; Direct energy conversion -- Periodicals; Energy storage -- Periodicals; Energy transfer -- Periodicals; Énergie -- Conversion directe -- Périodiques; Direct energy conversion; Periodicals; 621.3105
• DOI: 10.1016/j.enconman.2014.11.041
• Languages: English
• ISSNs: 0196-8904

Abstract

Highlights: We proposed a liquid–vapour separator incorporated gravity-assisted loop heat pipe. Comparative study of the thermal performance of three heat pipes were conducted. A dedicated steady-state thermal model of three heat pipes were developed. Optimum operational settings of the new loop heat pipe were recommended. The new loop heat pipe could achieve a significantly enhanced heat transfer effect. Abstract: Aim of the paper is to investigate the thermal performance of a novel liquid–vapour separator incorporated gravity-assisted loop heat pipe (GALHP) (T1), against a conventional GALHP (T2) and a gravitational straight heat pipe (T3), from the conceptual and theoretical aspects. This involved a dedicated conceptual formation, thermo-fluid analyses, and computer modelling and results discussion. The innovative feature of the new GALHP lies in the integration of a dedicated liquid–vapour separator on top of its evaporator section, which removes the potential entrainment between the heat pipe liquid and vapour flows and meanwhile, resolves the inherent 'dry-out' problem exhibited in the conventional GALHP. Based on this recognised novelty, a dedicated steady-state thermal model covering the mass continuity, energy conservation and Darcy equations was established. The model was operated at different sets of conditions, thus generating the temperature/pressure contours of the vapour and liquid flows at the evaporator section, the overall thermal resistance, the effective thermal conductivity, and the flow resistances across entire loop. Comparison among these results led to determination of the optimum operational settings of the new GALHP and assessment of the heat-transfer enhancement rate of the new GALHP against the conventional heat pipes. It was suggested that the overall thermal resistance of the three heat pipes (T1, T2, and T3) were 0.10 °C/W, 0.49 °C/W and 0.22 °C/W, while their effective thermal conductivities were 31, 365 W/°C m, 9, 648 W/°C m and 5, 042 W/°C m, respectively. This indicated that the novel heat pipe (T1) could achieve a significantly enhanced heat transport effect, relative to T2 and T3. Compared to a typical cooper rod, T1 has around 78 times higher effective thermal conductivity, indicating that T1 has the tremendous competence compared to other heat transfer components. It should be noted that this paper only reported the theoretical outcomes of the research and the second paper would report the follow-on experimental study and model validation. The research results could be directly used for design, optimisation and analyses of the new GALHP, thus promoting its wide applications in various situations to enable the enhanced thermal performance to be achieved.