DIMPLE PLATE HEAT EXCHANGERS FOR A SEA-WATER CHILLER USING CO_2 AS REFRIGERANT, DESIGN AND TESTING

摘要

To ensure proper quality of high value product, cooling is a critical process in the fishing industry.Traditionally, on board pelagic fish cooling is achieved using Refrigerated Sea Water (RSW) refrigerationplants with halocarbon HCFC 22 as working fluid. According to EU-regulations, refilling of this fluid is notallowed from 2015. HFC alternatives have considerable greenhouse warming potential and are heavily taxedin some countries, thus only a short time solution. The main natural alternative, ammonia, has significantdrawbacks that can be unacceptable particularly for smaller vessels and for rebuilding of existing ships.Carbon Dioxide (CO_2) is an environmental friendly, inexpensive, non-toxic, non-flammable alternative. Onedrawback is the high operating pressure which could give heavy, bulky and expensive components.In this project a novel dimple plate type evaporator and condenser were developed and tested in a 300 kWcooling capacity RSW plant using CO_2 as refrigerant. Optimal geometry was simulated and verified inlaboratory tests. Then, new full size heat exchangers and refrigeration racks were mounted in a fishing boatreplacing an existing R22 system. Measurements on-board boat showed promising results and the firstmackerel catch cooling fulfilled the boat owner's expectations.The heat exchangers are smaller, lighter and cheaper than comparable shell and tube units designed for CO_2.Preliminary calculations show that the production cost could be about equal to ammonia units.