Study On Heat Transfer And Flow Characteristics For Water Flowing In Spiral Coil

Spiral coil heat exchangers are usually used in heat pump, petrochemical engineering,nuclear reactor, refrigeration and conditioning, etc by its higher transfer efficiency, compact instructure and easy to manufacture. Study on convective heat transfer process and the pressuredrop characteristics of the water in the helical tubes have very important practical value.The experimental facilities for the water flowing in the spiral coils is established and theheat transfer and flow characteristics is studied. The spiral coils are made by the brass whoseouter diameter is16mm. The experimental condition: Re:4000-9000, the current speed:0.276—0.483m/s, the volume flow rate:200—350L/h, heating power:80—350w. The experimenton the four different spiral coils is carried out, the experimental data at the variousexperimental conditions is acquired and the error analysis is done.The experiment results show: the Nu increases with increasing Re for all test tubes, andfor the same Re, the greatest average heat transfer coefficient appears in SC-type spiral coil.The heat transfer coefficient of SC-type spiral coil is more14.86%to20.35%than BC-typespiral coil. The heat transfer coefficient of BE-type spiral coil is more15.51%to23.11%thanthe SE-type spiral coil. The heat transfer coefficient is mainly affected by the fluid velocity,the shape of the spiral coils and the heating power; the pressures increase with increasing Refor all test spiral coils, the pressure drop of BE-type spiral coil is the biggest. The pressuredrop of BE-type spiral coil is16%larger than SC-type spiral coil. The pressure drop is mainlyaffected by frictional resistance, spiral coil length and the average velocity; the flowingresistance coefficient decreases with increasing Re for all test tubes, the drag coefficient ofSC-type spiral coil is the biggest in all spiral coils. Heat transfer correlations were developedfor the elliptical spiral coil and the circular spiral coil by fitting the present experimental data in the condition of the experiment.This paper provides the reference for the optimization and design of the spiral coil heatexchangers, and also has a certain guiding significance on the energy-saving for the operationof the air conditioning and the heat pump system. The study has reference significance forspiral coil heat exchangers when they are under the same or similar conditions.