The influence of superheated steam on lithium bromide refrigeration machine

The influence of superheated steam on lithium bromide refrigeration machine

In the operation of lithium bromide absorption refrigeration units, steam quality is a key factor determining their performance and lifespan. Although superheated steam has a higher thermodynamic enthalpy, it is an important hazard source for bromine chillers designed specifically for saturated steam. This article aims to explore in depth the impact mechanism of superheated steam, clarify common cognitive misconceptions, and propose fundamental solutions.

Taking the common 6kgf/cm ² (gauge pressure, absolute pressure about 0.688 MPa) steam as an example:
Saturated steam: At this pressure, the saturation temperature of water is approximately 158.08 ℃. At this point, steam and liquid water are in a phase transition equilibrium state, and their heat content includes sensible heat and enormous latent heat of vaporization.
Overheated steam: If the saturated steam is further heated to increase its temperature to 208.08 ℃ (superheat degree of 50 ℃), superheated steam is obtained. It is a single gas phase without liquid droplets, and the added heat is sensible heat.
The fundamental difference in this physical state lays the foundation for the vastly different performance of the two in terms of heat transfer efficiency.

The high-pressure generator of lithium bromide unit is essentially a condensing heat exchanger, designed based on the phase change heat transfer principle of saturated steam.
The heat transfer advantage of saturated steam: When saturated steam condenses inside the generator tube, its latent heat of vaporization is released at a constant temperature. This is a highly efficient heat transfer method (with a very high heat transfer coefficient), which makes the heat transfer process smooth and controllable, and can transfer huge amounts of heat with a small heat transfer area.
The heat transfer disadvantage of superheated steam: The heat release of superheated steam is convective heat transfer of single-phase gas, and its heat transfer coefficient is usually one to two orders of magnitude lower than that of condensation heat transfer. Even at high temperatures, its ability to transfer heat to the pipe wall is extremely poor. In order to transfer the same amount of heat, a larger heat transfer temperature difference is required, resulting in a significant decrease in overall heat transfer efficiency.

The hazards of superheated steam have the characteristic of multiple time scales, and understanding the dialectical relationship between its "instantaneous" and "long-term" is the key to resolving cognitive contradictions.
1. Instantaneous hazards: severe disturbances and dangerous peaks
The hazards of superheated steam erupt in a violent and localized manner during the initial introduction, causing instantaneous impact on the system.
Instantaneous overload of condenser: In the inlet section of superheated steam, the extremely high wall temperature causes the solution to flash or boil, resulting in excessive and potentially overheated refrigerant vapor. This steam flow causes the condenser's heat load to momentarily exceed its design capacity, resulting in a sharp increase in pressure and temperature. Although the overall cooling capacity has decreased in the long run, the instantaneous overload shock has seriously disrupted the system balance.
Instantaneous triggering of crystallization risk: "Flash evaporation" causes the solution moisture in the inlet area of the generator to evaporate instantly, and the local concentration reaches a dangerous peak in a very short time, easily exceeding the crystallization line. Crystallization is often triggered by local concentration spikes rather than the overall average concentration of the unit.
2. Long term impact: continuous decline in efficiency and irreversible damage
After instantaneous impact, superheated steam will cause long-term and irreversible degradation of unit performance.
Irreversible decrease in overall efficiency: Due to low heat transfer efficiency, the effective driving heat source obtained by the unit is continuously insufficient, resulting in long-term low refrigeration capacity and permanent increase in energy consumption.
Corrosion exacerbation and permanent damage: Local high temperatures can decompose corrosion inhibitors, damage metal protective films, and rapidly accelerate corrosion. Corrosion products (such as rust, copper rust) can have two major consequences:
Forming crystal nuclei: significantly narrowing the metastable region of the solution, allowing crystallization to occur below theoretical temperature.
Blocking pipelines and nozzles: contaminating the solution, forming flow dead zones, further deteriorating heat transfer and creating new crystallization beds, forming a vicious cycle.

In summary, the harm of superheated steam to lithium bromide units is comprehensive. It disrupts the stable condensation heat transfer mechanism, not only causing instantaneous shock threats to operational safety, but also leading to long-term performance degradation and shortened equipment life. The essence of its harm lies in the disruption of the stability and uniformity of the system.
Therefore, the most fundamental and necessary response strategy is to strictly treat the superheated steam to the saturated steam state required by the unit design through reliable temperature and pressure reduction devices. This is the only correct prerequisite for ensuring efficient, stable, and long-lasting operation of lithium bromide refrigeration machines. Any operation that allows superheated steam to directly enter the unit is a short-term behavior that sacrifices equipment health and safety.

Lithium bromide solution manufacturer

Flier Refrigeration Engineering Technology Co., Ltd is a professional technical service enterprise integrating central air-conditioning host sales, spare parts sales, unit repair and maintenance.

Factory located in Zhenjiang, Jiangsu, covering an area of 25,000 square meters ,and has been built with 1 R&D center, 1 pilot plant, 3 An innovative production, learning, and research base composed of a professional production workshop and its corresponding infrastructure. At present, the company has become a well-known technical service provider in the field of central air conditioning in China.

The company's main business scope includes: central air-conditioning maintenance, cleaning and technical services; cooling tower and fan coil cleaning and maintenance services; custom processing of lithium bromide solution; sales of lithium bromide solution special impurity separators; central air-conditioning host and various zero Sales of accessories; installation and sales of central air conditioning systems, etc.

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