Study On Heat Transfer And Flow Resistance Of Polymer Helical Coils Applied To Closed-Loop Surface Water Heat Pumps

As for the increasing hindering of the environmental issue and energy crisis on the world economy, the prospect of the application of surface water heat pumps is very promising due to its high efficiency, energy saving and environmental friendliness, with respect to the abundant resources of surface water in China. The surface water heat pumps can be classified into open-loop systems and closed-loop systems according to different heat exchanging modes with the surface water. And the design and application of polymer helical coils are one of critical technologies for the closed-loop systems. After long-term immersion in surface water, metal helical coils will easily scale and rust ending up with short life time, while polymer helical coils have longer life time because of its good corrosion resistance. And polymer helical coils have more application in foreign engineering cases.In recent years, more and more applications of surface water heat pumps have been conducted in China. However, the lack of the knowledge on heat transfer and flow resistance of the polymer helical coils has impeded the applications of closed-loop surface water heat pumps. Therefore, study of the heat transfer and flow resistance characteristics of polymer helical coils is of great importance.In order to provide reference for the design and operation of the polymer helical coils in the closed-loop surface water heat pumps, this dissertation conducted experimental investigation on the heat transfer and flow resistance characteristics of the polymer helical coils. The existing correlations from helical coils have been compared and analyzed with the experimental data, to determine the appropriate correlations for the polymer helical coils operating in surface water heat pumps. Further theoretical analysis of the performance of polymer helical coils basing on the selected correlations has been performed. The research work focuses on the following three aspects:1)Principles and objectives of the study were summarized basing on a review of the experiment schemes in the literatures. Then, an experimental apparatus was designed and built up.2) A series of experiments were conducted in order to observe the heat transfer and flow resistance characteristics of the polymer helical coils. The influence of Reynolds number, the ratio of coil pitch to tube diameter and Rayleigh number on the characteristics of heat transfer and flow resistance have been analyzed. And the experimental data were compared with the calculated data of the straight tube.3) Appropriate correlations were determined by the comparison between experimental data and those from the existing correlations of helical coils. Then, further theoretical analyses of the polymer helical coils were discussed basing on those correlations.