Cooler as the most common heat exchange equipment in heating systems
As the most common heat exchange equipment in the heating system, the cooler directly affects the external heating quality. It is of great significance to analyze the reasons for the problems in the operation of the cooler and to achieve safe operation and energy saving.
A problem encountered in the operation of the system During the entire heating season, the main problem is that the peak heater heat exchange is insufficient. The cooler is installed in the circulating water supply bypass, adopts double-tube type cooler, and its design parameters: flow rate G=1500t/h, heat exchange area F=170m2, design steam inlet parameter t=180°C, P=0.2MPa , circulating water inlet and outlet design temperature difference △ t = 15 ° C. During the operation of the cooler, the temperature difference Δt between the inlet and outlet water is only about 5 ° C. Although it is adjusted, the effect is not large, and the effect cannot be fully exerted.
(2) The air in the cooler is not discharged. The cooler body is not designed with a tube-passing or shell-side high-point venting valve, which will affect the heat transfer effect to a certain extent. In order to reduce the impact, we have a bleed valve at the highest point of the supply and return pipelines of the entire heating system. During the initial operation of the system, when the system is filled with water and during operation, the steam is not regularly discharged, so as to minimize the air-induced heat transfer in the system. effect.
(3) The scale of the cooler in the cooler is fouled by the cooler, which will have a great influence on the heat exchange effect of the cooler, resulting in a decrease in the heat transfer coefficient, a greatly reduced heat exchange efficiency, and a low outlet water temperature. In order to avoid fouling of the cooler, a double-tube type cooler is selected. The special structure of the heat exchange tube of the cooler makes the water flow in a turbulent state in the tube, and the flow rate is high, and it is not easy to scale. When the system is out of service, we conduct a physical inspection of the heater, and there is basically no scaling inside.
(IV) Insufficient steam volume In the system, the steam metering device uses a vortex flowmeter. Due to the installation conditions, the installation requirements of the steam metering device cannot be met, and accurate data cannot be obtained for the amount of steam entering the cooler.
(5) Blockage of the waterway blockage The blockage of the waterway will reduce the amount of circulating water flowing through the cooler, resulting in a large temperature difference between the outlet water and the inlet water of the cooler, a large pressure difference, and a high hydrophobic temperature. However, in actual operation, the pressure difference between the inlet and outlet of the cooler is △P=0.02MPa, and the resistance provided by the manufacturer is △P=0.04Mpa. From the analysis of the operating conditions, the possibility of blockage of the waterway is not great. Each pipe was inspected during the disassembly inspection of the heater, and no blockage was observed.
(6) Poor hydrophobicity The system has a phenomenon of poor condensate drainage during operation. The water level in the cooler often reaches a high limit, and the bypass must be opened for hydrophobicity. Otherwise, the water level in the cooler rises and the steam pressure on the steam side rises. High, causing the heater steam side safety valve to take off. The existence of this situation allows the operator to reduce the amount of steam entering and open the bypass operation for a long time, which greatly reduces the heat exchange efficiency of the cooler. Initially suspected trapping of the trap, but no abnormalities were found after the disintegration of the trap, which requires a check of the drainage capacity of the trap.
The solution to the problem of insufficient heat exchange in the cooler is as follows:
1. Re-select the steam trap, and install a drain regulating valve in the drain line. The trap is adjusted according to the water level of the heater and regulated by the DDZ-II electronic regulating system. The water level signal of the heater is controlled by the differential pressure transmitter, the proportional integral unit, the operating unit, and finally by the electric actuator, and the size of the water is controlled by adjusting the opening degree of the valve. In this way, the hydrophobicity in the cooler can be discharged in time to ensure the heat exchange effect.
2, daily attention to control the quality of circulating water, strengthen water quality supervision, minimize the occurrence of cooler fouling phenomenon;
3. For the steam metering device of the system, find a method to solve it as soon as possible;
4. Periodically disassemble the heater or perform backwashing to remove debris from the heater to improve the efficiency of the heater. In addition, when the system is filled with water in the initial stage of operation, the air in the heater must be drained to avoid affecting the change. Thermal quality.