Search

The heat transfer and pressure drop characteristics for water flowing in four spiral coils with different shapes and different sizes were experimental studied. Reynolds number range from 4000 to 9000, volume flow rate range from 200 to 350 L/h and heating power range from 80-350 W. Based on the experimental results, the regularity of Reynolds number and heating power influencing on heat transfer and pressure drop characteristics was analyzed and discussed. The results indicate: the Nu increases with increasing Re, the greatest average heat transfer coefficient appears in the smaller circular spiral coil. The heat transfer coefficients increase with increasing heating power, the greatest average heat transfer coefficient also appears in the smaller circular spiral coil. The pressure drops increase with increasing Re, the pressure drop in big ellipse spiral coil is greatest. The resistance coefficients gradually decrease with increasing Re. The resistance coefficient of small circular spiral coil is always greatest, and the resistance coefficient of big circular spiral coil is smallest.

An error compensation method for the single pair-pole encoder has been discussed in this paper. This article analyzed offset, sensitivity error, quadrature error and ferromagnetic interference error of single-pole magnetic encoder to obtain the expression of each error. In order to facilitate error compensation, the common expression for describing the error has been summed up. The process for formatting the error can be assumed as the process of changing from circle to ellipse. Therefore the inverse of this process is the same as the process of error compensation. The experimental results show that the accuracy of magnetic encoder which used this method could reach ±1, thus the error compensation effect is obvious. The magnetic encoder which applied this method has the advantages of low-cost, high-precision and convenient to use.