Energy level matching of heat medium and low temperature waste heat in pipe network of heat exchanger unit

Absorption flow chart of heat exchanger unit, which is mainly composed of absorption heat exchanger and conventional plate heat exchanger. The absorption heat exchanger takes the heat of primary network water supply as the driving force to produce heat pump effect, which can absorb the heat of low-temperature heat source. The primary network water supply releases heat to the high-temperature heat source of the absorption heat exchanger, the conventional heat exchanger and the low-temperature heat source of the absorption heat exchanger in turn. After the temperature is reduced below 30 ℃, it returns to the thermal power plant. The return water of the secondary network is supplied to the heat user after being heated and heated by the absorption heat exchanger and the conventional. After the absorption type is adopted, the water supply and return temperature of the primary network is changed from 110 / 70 ℃ to 110 / 25 ℃, and the temperature difference is increased from 40 ℃ to 85 ℃, which means that the heat transmission capacity of the pipe network is increased by about one time. That is, through absorption heat exchange, the temperature of heat medium in the loop of thermal pipe network is greatly reduced and the transmission temperature difference is increased, which can save the investment in pipe network construction and reduce the transmission power consumption of circulating pump.

According to the law of thermodynamics, there is a large irreversible loss in the heat exchange process with mismatched energy levels of heat exchanger units, which will cause a waste of a large amount of available energy. The traditional plate heat transfer connecting primary network and secondary network has large temperature difference and serious irreversible loss. The absorption type makes effective use of the available potential energy contained in the mismatched heat exchange link between the primary and secondary heat supply networks to drive the absorption heat pump, so that the energy can be used step by step and avoid the "overuse" of energy. Since the return water temperature of the heat supply network is reduced below 30 ℃, it is easier to recover the waste heat of the condenser of the power plant, so as to lay a foundation for improving the energy utilization efficiency of the system. With people's attention to waste heat utilization and the continuous improvement of corresponding technologies, most high-grade waste heat (such as high-temperature flue gas) have been effectively utilized. For low-grade and large amount of low-temperature waste heat, such as circulating cooling water waste heat of power plant, flue gas condensation heat of gas or gas turbine and some industrial low-level waste heat, the research and development of effective utilization technology is still an urgent problem to be solved. The fundamental reason why the recovery and utilization of low-grade waste heat is difficult is that these waste heat do not match the taste requirements of heating, and the means to improve the taste of low-temperature waste heat (such as heat pump technology) are often restricted by technology, investment and other factors. Through absorption heat exchange, the temperature of heat medium in the thermal pipe network circuit can be greatly reduced, and the energy level matching of heat medium in the pipe network and low-temperature waste heat can be realized, which is very important for the recovery and utilization of low-temperature waste heat.