Absorption chillers are critical components in central air conditioning systems, especially in large buildings where efficient cooling is necessary. However, one of the common challenges faced in maintaining these systems is the leakage of cooling water tubes. This issue can lead to severe disruptions, compromising the overall efficiency of the chiller. The root causes of these leakages often include scale buildup, electrochemical corrosion, scour corrosion, unprofessional tube cleaning, and stress corrosion cracking in stainless steel (SS) tubes due to chlorine exposure. To address these challenges, BROAD has introduced an innovative solution: using titanium tubing in BROAD absorption chillers.
Understanding the Causes of Leakage
- Scale and Electrochemical Corrosion
Scale formation occurs when mineral deposits accumulate on the inner surfaces of the tubes, reducing heat transfer efficiency and creating an environment conducive to corrosion. Electrochemical corrosion, often exacerbated by scale, occurs when two dissimilar metals in contact with water undergo an electrochemical reaction, accelerating corrosion and leading to tube leaks.
2. Scour Corrosion
High-velocity water flow can cause scour corrosion, where the protective oxide layer on the surface of the metal is worn away. Once this layer is removed, the underlying metal is exposed to further corrosion, leading to tube damage.
3. Unprofessional Tube Cleaning
Inadequate or improper tube cleaning techniques can damage the tubes, removing protective coatings or even scratching the metal surface. Such damage makes the tubes more susceptible to corrosion and leakage.
4. SS Tube Crack Due to Chlorine
Stainless steel tubes, while generally resistant to corrosion, can crack when exposed to chlorine, a common disinfectant in cooling water systems. Stress corrosion cracking (SCC) occurs under the combined influence of tensile stress and a corrosive environment, leading to the failure of SS tubes.
Basic information of titanium
- The global reserves of titanium is 61 times more than copper, China has the largest titanium reserves and production in the world. While the cost of titanium is reducing because of the improvement of smelting technology.
- Except for hydrofluoric acid, concentrated hydrochloric acid, hot sulfuric acid, etc., there will be almost no corrosion in titanium. The corrosion rate of titanium under sea water is about 1mm/1,000 years, can be compare to platinum.
- Titanium is the metal with highest specific strength, and has excellent ductility.
- Titanium requires high techniques in smelting, machining, welding and tube expanding, has low resistance in high temperature flame. However, by using titanium, there is almost no corrosion in chiller cooling water and chilled water system
Evolutions of tubing in BROAD Absorption Chiller
- Titanium Known as the best corrosion-resistance metal, titanium was previously only used in aviation and aerospace industry, human dental implant and bone transplant.
- Central air conditioning is the heart of a building, and any corrosion or leakage in one of thousands of heat-exchange tubes may cause a complete shutdown of the entire building’s air conditioning system.
- To achieve “zero fault” and “the same lifespan as the building” for central air conditioning, BROAD has over come challenges of skyrocketing cost and complicated technologies by developing titanium-tubed air conditioning, extending the designed lifespan to 60 years, which has created an unparalleled value for customers.
Why Titanium?
| Copper | Stainless Steel | Titanium | |
| (Chlorine) Cl | Anti-corrosion only at low temp. and low concentration | Anti-corrosion level is different | No Corrosion |
| Seawater scour | Less than 1.2m/s | 5-7m/s | No Limitation |
| Ammonia, Amine | Serious corrosion | No corrosion | No Corrosion |
| Polluted air and water | Corrosion | Light corrosion, Chlorine corrosion | No Corrosion |
- Under normal condition, there is almost no corrosion in titanium, which can expand chiller life span to 60 years.
- Coefficient of heat transfer of titanium is similar to SS 316L, lower than copper, however the largest area of heat transfer resistance is at critical layer of tube, not at the performance of tube.
- Chiller can be used for seawater directly cooling
Advantages of titanium chiller tubing
- Titanium is well known as super corrosion resistant material. No corrosion from titanium tubing in different absorption chiller applications.
- Copper is very sensitive to ammonia & sulfide, and cannot resist with acid cooling water due to air pollution. While stainless steel cannot resist with Chlorine.
- Since the heat exchange tubing is the weakest part of a chiller, to use titanium tube can increase chiller life span to 60 years decisively. Titanium chiller can be used in any environment except for fluoride and strong acid