Temperature is the main control process index in heat exchanger operation. Through the on-line instrument detection and inspection of the inlet and outlet temperature change of each fluid in the heat exchanger, the size of the medium flow, the quality of heat transfer and the presence of leakage can be analyzed and judged. It is necessary to prevent sharp changes in temperature, because temperature drastic change will cause that the expansion and contraction of the inner parts of heat exchanger, especially tube bundle and tube plate, are not consistent, resulting in temperature difference stress, which will lead to the separation or local deformation and crack of tube bundle and tube plate, and accelerate the corrosion and produce thermal fatigue crack.

If water is used as a cooling medium, it is better to control the outlet temperature below 38℃ and the temperature should not exceed 45 ℃. If the water temperature exceeds 38℃, the propagation of microorganism will accelerate obviously, and the decomposition of corrosion components will accelerate, which will cause the corrosion and perforation of the pipe. At the same time, the soluble calcium bicarbonate and magnesium bicarbonate will be decomposed by heat to form precipitation, which makes the scale formation of heat exchanger more and more serious and affects the heat transfer capacity of equipment. The heat transfer coefficient can be calculated by measuring and recording the temperature. The heat transfer efficiency is mainly reflected in the heat transfer coefficient, and the reduction of the heat transfer coefficient indicates the reduction of the heat exchanger efficiency. The inlet and outlet temperature and flow rate of two mediums of heat exchanger are measured regularly, the heat transfer coefficient of each period is calculated, and the trend chart of change is made with coordinate paper. It's going to be basically a continuous a gradual downward smooth curve, with smaller slope at the tangent point. When the heat transfer coefficient is too low to meet the process requirements, the mechanical or chemical cleaning should be used to improve the heat transfer coefficient to meet and maintain the process operation needs.