Experimental Investigation and CFD Modelling of a Thermosyphon-equipped Heat Exchanger used in Low-grade Waste Heat Recovery

    Student thesis: Doctoral Thesis


    Energy lost in the form of heat is reported to account for more than 50% of the total energy waste in industry. Due to renewed environmental policies with focus on promoting sustainability and reducing wasted energy, new measures have been put in place to reduce these energy losses. In industry, waste heat is recovered through the use of heat exchangers installed at the outlets of high temperature exhausts, recovering heat energy and meanwhile helping reduce the overall exhaust temperature with the objective of increasing the overall efficiency of the process.

    The heat exchanger under study is equipped with wickless heat pipes, tubular devices filled with a working fluid and sealed in vacuum. Heat pipes are commonly found in modern electrical equipment due to their high rate of heat transfer per unit area and lack of outer energy source. Wickless heat pipes, also known as two-phase closed thermosyphons, lack a sintered wick structure within and are therefore easier to manufacture in large quantities making them ideal heat sinks in macroscopic applications such as industrial waste heat recovery.

    The subject of this work is the creation of an analytical prediction model to predict the thermal behaviour of heat exchangers equipped with heat pipes. To that end, three tests were conducted, one on a single thermosyphon, another on a heat exchanger equipped with thermosyphons and the last one on a heat exchanger with returned flow on a second pass over the thermosyphons. CFD is also used using data from the prediction model in order to obtain a visualisation of the results.

    The results of the analytical and CFD models were found to be in good agreement with the experimental results and a recommendation is made to implement the same model to larger heat exchangers equipped with more thermosyphons. The model will benefit the company partner, Econotherm, who shall use it in the modelling of future heat exchangers.
    Date of Award14 Aug 2017
    Original languageEnglish
    SupervisorAlex Chong (Supervisor), CK Tan (Supervisor) & Jason Matthews (Supervisor)


    • Thermodynamics
    • Heat Transfer
    • Conduction
    • Convection
    • Heat Pipe

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