Study Of Thermal Resistance Detection And Anti-scaling Experiment Of High-frequency Pulses For Circulating Cooling Water

The scales widespread in a variety of heat transfer equipment, not only reduce theefficiency of heat transfer equipment, wasting energy, but also affect the safety ofequipment, increasing operation and maintenance costs. The harm of scales is variousand great. The traditional chemical water treatment is efficient, but there are somedisadvantages like environment pollution, high cost and so on. The high-frequencyelectromagnetic water treatment is simple, non-polluting, low energy consumption, andhas been widely studied and applied. In the process of water treatment, one set of online,accurate and efficient anti-scaling monitoring system is very significant for searchingthe best scale inhibition method, for revealing the microscopic scale formation andinhibition, and for promoting water treatment industry continues to prosper.Starting from the basic knowledge of scale, this paper introduced the scale basicclassification and formation theory, and made a brief presentation on the non-thermaland thermal scale detection technology and the high-frequency electromagnetic watertreatment. Some mathematical models of thermal resistance monitoring were illustratedand compared, the adoptive model of thermal resistance was derived in detail. Based onthe above theory, the circulating water high-frequency electromagnetic anti-scalingplatform was developed, including micro-circulating cooling water system,high-frequency electromagnetic anti-scaling system (HAS) and thermal resistancemonitoring system. Micro-circulating cooling water system simulated the structure ofindustrial circulating water system, contained the hot water circulation section, thecooling water circulation section and the heat exchanger. The HAS included ahigh-frequency electromagnetic generator and a high-frequency electromagneticprocessing chamber, the coaxially processing chamber as part of a pipe accessed to thecooling water circulation section, by which high-frequency electromagnetic pulses wasapplied to the cooling water. Thermal resistance monitoring section mainly aimed atmonitoring the heat transfer performance of the pipe heat exchanger. The highsensitivity of the PT1000was selected as temperature sensor, the real-time monitoringof thermal resistance included the lower computer based on the8051machine and uppercomputer using LabVIEW.High frequency electromagnetic anti-scaling experiments for circulating coolingwater were designed and completed. In this experiments, solution conductivity, pH value and crystal size were measured, combined with the thermal resistance monitoring,the scale inhibition effect of blank control group and different signal frequencies groupswere analysed. Each test lasted12hours, the waveforms of electromagnetic signalvoltage and current were recorded by oscilloscope. According to saved signalwaveforms, the power consumption of HAS was analysed using the Matlab FFTfunction, the result revealed the power consumption of HAS was very low from0.35Wto0.47W. Therefore, the HAS had the advantage of low power consumption. AndObserve the anti-scaling effect, conductivity, pH value, and the crystallite size detectionindicated that100kHz and200kHz had the best anti-scaling effect in the four sets ofhigh-frequency signals. Moreover the thermal resistance monitoring had the same result.The reason of anti-scaling was that the high-frequency electromagnetic fields activatedthe water to enhance the ability to dissolve calcium carbonate and electromagnetic fieldreduces the viscosity of the calcium carbonate crystals, making it difficult to adhered tothe heat transfer tubes, resulting in decreased thermal resistance.