Branch-control and phase-change heat exchange system and method based on two-stage steam-liquid heat exchanger

Abstract

The invention relates to a branch-control and phase-change heat exchange system and method based on a two-stage steam-liquid heat exchanger. The system comprises a heat source heat exchanger (2), a cold source heat exchanger (20) and a low temperature liquid tank (23), and the system further comprises a high temperature heat exchanger (14), a low temperature heat exchanger (22) and a high temperature liquid tank (8); a main heat source steam pipe at the top part of the heat source heat exchanger (2) is divided into two branch pipes after passing through a heat source steam exhaust adjusting valve (16), the two branches are respectively communicated with an upper collection tank and a lower collection tank of the cold source heat exchanger (20), and control systems are respectively arranged on the branches; the low temperature liquid tank (23) is communicated with the high temperature heat exchanger (14) through a condensate pipeline, the bottom of the high temperature heat exchanger (14) is communicated with the high temperature liquid tank (8) through a condensate pipeline, and the condensate pipeline at the bottom of the high temperature liquid tank (8) is respectively communicated with the low temperature heat exchanger (22) and the heat source heat exchanger (2). According to the branch-control and phase-change heat exchange system disclosed by the invention, overheat and over-cold phenomenon of steam and condensate are solved, and the heat exchange efficiency is further improved.

Description

technical field [0001] The invention relates to the technical field of safe and controllable enhanced heat transfer, in particular, the invention relates to a separate-controlled phase-change heat system and a heat exchange method based on a two-stage vapor-liquid heat exchanger. Background technique [0002] In terms of flue gas waste heat recovery and utilization, different phase conversion heat technology schemes are used to control the corrosion and ash deposition speed of the heating surface on the flue gas side, and better results have been achieved. Separately controlled phase-change heat technology achieves higher reliability and precision of heat transfer control through independent control of cold source heat transfer and heat source heat transfer, improves the efficiency of waste heat recovery, and improves the adaptability of system applications. Great improvement. [0003] Due to the influence of flow resistance, the phase change pressure of condensation in the...

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Problems solved by technology

Since the steam will form a liquid film on the wall during the condensation process of the cold source heat exchanger, the thermal resistance of the liquid film will make the condensate supercooled unavoidably

In addition, due to the heat exchanger area, heat transfer coefficient and heat transfer temperature difference under the design working conditions are difficult to adapt to the actual phase change heat under changing working conditions and in different seasons, coupled with the influence of factors such as liquid level fluctuations, the phase change The thermal process is always accompanied by supercooling of condensate and superheating of steam; the existence of supercooled liquid and superheated steam will reduce the heat transfer capacity of the phase change heat exchanger, and at the same time, due to the existence of natural circulation, the supercooled liquid enters the heat source for heat exchange The device will also make the temperature of the lower wall surface of the evaporating heat exchange surface lower than the average temperature, and the safety margin is insufficient, which is easy to cause local low-temperature corrosion and reduce the life of the equipment

[0004] Due to the limitation of equipment layout space and the inconsistency of equipment installation elevation, the liquid level and heat exchange control in the phase change heat system are not uniform. The traditional phase change heat system is difficult to adapt to the difficulties in improving the integration of equipment. In an application project, multiple sets of independent phase-change heat devices are often required to work independently

This not only reduces the utilization rate of equipment, but also makes the redundancy of the control system lower; not only the total cost of equipment is higher, but also reduces the reliability of the system

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