Replacing ice blocks, the chiller, with 20lbs of ammonia, improves the freshness of the catch.
Isotherm's low-charge-ammonia RSW (Refrigerated Seawater) chiller
Isotherm, Inc., an Arlington, Texas (U.S.)-based manufacturer of specialized heat exchangers, pressure vessels, and packaged systems, has equipped a small fishing boat in Pakistan with what it calls the first low-charge ammonia (R717)-based RSW (Refrigerated Seawater) chiller package to be used in that country.
Fishing boats in Pakistan have traditionally used blocks of ice to cool fish, though this approach has not been effective “due to expedited spoiling rates,” explained Adnan H. Ayub, General Manager of Isotherm.
“Our goal with our ammonia package,” he added, “is to pave the way for the country to improve the fish quality and eventually become a market for overseas customers.”
This RSW package consists of Isotherm’s DX evaporator, condenser, and receiver, along with a Bitzer compressor; less than 20lbs (9.1kg) of ammonia refrigerant is used. The nominal cooling capacity of the system at 23°F (-5°C) ammonia saturated temperature is 10TR (35.2kW).
The system cools seawater, which recirculates through the fish-holding tanks (with a capacity of 90,000lbs/40,823kg) and maintains a temperature of 32°F (0°C).
Isotherm recently completed successful tests on the system and the boat “is ready to sail,” the company said in a LinkedIn post.
Carrying ice by the tons
Isotherm has, for decades, been directly and indirectly involved in the installation around the world of hundreds of RSW and brine-cooling systems – all with ammonia systems and recently with CO2 (R744) as well. While it is very common for large fishing fleets to use ammonia refrigeration, “we want to get low-charge ammonia systems on board smaller fishing vessels such as this one in Pakistan,” said Zahid Ayub, Technical Director at Isotherm.
In developing countries local fishermen have been making and using indigenous wooden boats for centuries, and there are thousands of such boats in each major coastline country on all continents. In Pakistan alone, there are more than 20,000 such fishing vessels sized between 10 to 20m (32.8 to 65.6ft) in length, said Zahid Ayub.
The small boats carry ice “by the tons,” noted Zahid Ayub. The drawbacks of this arrangement include extra fuel consumption; melting ice, which results in spoiled fish; and dependency on ice suppliers. “Introducing small compact [ammonia refrigeration] systems would certainly change the business model for them,” he said.
“We want to get low-charge ammonia systems on board smaller fishing vessels such as this one in Pakistan.”
– Zahid Ayub, Isotherm