In shell and tube heat exchanger, especially where the cooling media is cooling water, there is higher probability of fouling. Therefore periodic heat exchanger cleaning is required to improve the heat transfer of the heat exchanger.
In general heat exchanger’s are cleaned either chemically or mechanically, both type of cleaning requires shutdown of the heat exchanger. even after cleaning slowly fouling start building in the heat exchanger. As the fouling starts building in the heat exchanger there loss of heat transfer efficiency,
In case of refrigeration condenser even 0.8 mm of deposition can increase power consumption of compressor by 35% (Source : BEE HVAC and refrigeration system)
Sponge ball based inline heat exchanger cleaning system:-
Most common inline heat exchanger system for cooling water application is sponge ball based condenser cleaning system. In this system sponge balls of approx same size of tube ID (heat exchanger) are passed though heat exchanger’s.
Cleaning sponge balls are manufactured with different elasticity and temperature withstanding capacities. commonly available balls can withstand 80 deg C of temperature, Based on application balls are used with different type of sizes, eleaticity, density for better performance.
Balls are also available with abrasive coating for scale removal but special care needs to be taken while using abrasive material coated balls as it may start eating material while cleaning operation. Sponge rubber balls are safer for use.
In cleaning operation balls passes though the tubes while rubbing fouling material as shown in below picture.
In above picture we can see when ball travels it starts rubbing the tube surface and removes fouling material from the tube. Balls are continuously circulated to maintain high heat transfer coefficient across heat exchanger.
It is always believed that balls used may not be entering into each tube, so cleaning shall not be proper. Somewhat it is true that there is no control on insertion of balls in each tube, it is just a probability that with no of circulation it will pass though each tube.
Inline heat exchanger cleaning system can be made with different combination, with or without injection pump.
Basic inline heat exchanger cleaning system will consist :-
- Sponge Balls: For cleaning of tubes generally 30-50% in quantity of one pass tube nos.
- Ball Traps : To prevent balls from going to cooling tower.
- Collection pot : After trapping balls, collection vessel before start of next cycle
- Auto valves: To divert water and flow based on operation requirement.
- Timer / PLC controller : For controlling cleaning operation either timely or with performance of heat exchanger.
Balls are replaced after physical inspection or observing detoriation in the effectiveness of cleaning operation.
Operation of inline condenser cleaning system can be understand from the below video.