Commercial refrigerant industry is one of the biggest contributing factors toglobal warming according to a study by Mota-Babiloni et al. (2015). Studies have shown that emissions of fluorinated greenhouse gases' effect on global warming can increase from 1.3% (2004) to 7.9% (2050) if no change in behaviour is implemented in the industry (Francis et al., 2017). At present, the F-Gas Ordinance sets requirements for leakage warning systems and periodic leakage detection.The most common leak detection systems consist of sensors locatedoutside the cooling process and measure the amount of coolant in the air. However, there are limitations with sensors, including measuring leaks in engine rooms with high air circulation and that the sensors are unable to measure small leaks and mistake other contaminants for refrigerant leakage (Leonardsson, 2021).The purpose of this study is therefore to investigate where leakage occurs in a refrigerant process, howoperating data changes andto propose an alternative detection method for refrigerant leakage.Johnson Control has other technical solutions such as their Performance Index which compares a cooling process operation in practice compared to the theoretical performance that the unit should deliver. In their own test facility, however, it was discovered that a unit can lose up to 20% of its refrigerantmassbefore a clear reduction in COP was discovered(Thorén, 2021).To discover where the leakage in a cooling process occurs, a field study was conducted on a cruise ship docked in Barcelona. The first field study on leak detection was initially carried out by direct method, with the help of an electronic leak detector. The indirect methodwas also used to complement the direct method, this was doneby ocularly looking for oil stains on and around the cooling process. It showed that leakage almost always occurs on the high-pressure side of gaskets, couplingsand plugs. Similar discoveries were made inthe study byFrancis et al. (2017).The results also showed thatthemore connectionsthere are on a unit, such as plugs or service valves, the greater probability that leakage will occur. A solution to reduce leakage on units with many connections,such as supply systems, couldbe to adjustthe design of the systemsand simply remove plugs for connections that are no longer usedfor different reasons.A second field study was conducted on the same cruise ship to determine what operational data changesdue to refrigerant leakage. The unit was emptied into a service tank for two minutes while operating data was logged. After analysis of the results in 16 different operating data points, three of themwere selected for the alternative leak detection model, the DGS-model.Data for longer operating periods, approximately 5 months, with fault-free operation for the selected parameters Θoutin evaporator, expansion valve opening degree and suction overheating were compared with the operating data from the leakage experiment in field study 2. Thesethree were selected from a total of 14measured operating datapoints. The simultaneous increase ofall three operating data points indicatesrefrigerant leakage. That fact is the major reason for the selection of the three operating data points.Aprobability calculationbased on the three data pointswas created to calculate the probability of thedata points being outside a given range. If the probability calculation says that the chance of the reported value is zero, it is indicated that there is a problem with the process, most likely a refrigerant leak.As a proposal for further work,our proposal is to carry out validation tests of the DGS model on units in operation and a more accurate experiment on refrigerant leakage with operational changes per removed mass.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:mdh-55224 |
| Date | January 2021 |
| Creators | Westerberg, Christian, Gustavsson, Henric |
| Publisher | Mälardalens högskola, Akademin för ekonomi, samhälle och teknik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | Swedish |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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