Interest in indirect (secondary) refrigeration systems has grown since the discovery of the negative effect of environmentally hazardous refrigerants and leakage problems from direct expansion systems. Among the positive effects of indirect systems are: decreased quantities of primary refrigerant, factory built units and confinement of refrigerant to the machine room. Ground source heat pumps, ice rink and indirect system solutions for supermarket refrigeration are examples where indirect refrigeration systems are being used in Sweden. The secondary fluids circulating in the secondary systems are of great interest as its choice can affect heat transfer process; the overall performance of system; corrosion problems and maintenance costs as well as acceptable risks for the environment in case of leakage from the secondary system. A secondary fluid should have low viscosity, high thermal conductivity, high volumetric heat capacity, low freezing point, be non-corrosive, non-explosive, non-flammable, environmentally friendly, non-toxic, give low pressure drop in the system, have good material compatibility, chemically stable and have low cost. The market for secondary fluids worldwide and in Sweden is complex and a comprehensive overview of the available secondary fluids has not been available. The purpose of this thesis is to compile most of the existing secondary fluids on the Swedish market and present them briefly in this report. Different brands of secondary fluids on the Swedish market based on ethylene and propylene glycol, ethyl alcohol, potassium formate, potassium acetate, calcium chloride and other blends are presented in the thesis. Some of the most common brands are: Eco MPG, Dowcal 200, Dowcal N, Zitrec FC, Zitrec LC, Antifrogen L, Frigogel Neo, Heliogel CS80, Brineol MPG, Glytherm 20, Zitre MC, Dowcal 100, Antifrogen N, Neutragel Neo, Brineol MEG, Glytherm 10, Antifrogen Sol HT, Freezium, Hycool, Antifrogen KF, Brine 25, Swedbrine 25, Brenntag KBS, Brineol Bioethanol, E-Therm KBS Bio, Thermol, Zitrec S, Temper, Pekasol 50, Pekasol 2000, Greenway RTU, Greenway Heat Pump -30, greenway Solar -30, Thermera R and Thermera AC. Additionally, it is important to underline that a permit for installation of ground source heat pumps in Sweden is required. Swedish laws and regulations regarding secondary fluids and ground source heat pumps are complex and difficult to overview on municipalities’ levels.

Ethyl alcohol (ethanol) as secondary fluids is very popular as heat transfer fluid for indirect refrigeration system with ground source heat pump systems (GSHP) in several countries such as Sweden, Norway, Switzerland, Finland and other European countries. There have been several researches about the future ofthe refrigeration sector, refrigerants and refrigeration systems. Moreover, strict regulations such as F-gasregulation and Kigali Amendment forcing a phase down of many current widely used high global warming potential (GWP) refrigerants, i.e. R134a or R410A. Therefore, secondary refrigeration systems and their working fluids are expected to play a key role in order to minimize the refrigerant charge in the systems, reduce the indirect refrigerant leakages as well as increase the safety during operation. The aim of this thesis is to investigate the effect different additives to increase the flame point together with ethanol-based secondary fluids and validate their thermophysical properties by comparing them with reference values for pure ethanol water solutions. The study aims to design a new commercial ethyl alcohol-based product for GSHP system that could replace existing ones in the Swedish market and could workwith natural or flammable low GWP refrigerants. Different high flash point additives were tested such as 1-propyl alcohol, n-butyl alcohol, glycerol andpropylene carbonate. Thermophysical properties were investigated and a GSHP model in Excel was created in order to assess the energy performance of the resulted blends. After screening different blends and assessing the energy performance, glycerol as additive in low concentration seems to be the future for the ethyl alcohol-based secondary fluids because of its high flashpoint (160ºC) that will reduce the flammability risk associated to ethyl alcohol blends, the low viscosity (by 12% lower compared to pure ethyl alcohol blends) that help reduce pumping power by 4.5% compared topure ethyl alcohol blends. Moreover, ethyl alcohol and glycerol blend showed the lost in heat transfer coefficient by 4% lower compared to pure ethyl alcohol blends due to lower thermal conductivity compared to pure ethyl alcohol blends. Finally, it is a rather cheap and natural product which has no problem related to corrosion since ethyl alcohol and glycerol are less corrosive than water. Although, flash point test was not conducted so there is no data regarding the flash point, it is expected the flash point is increased due to the high flash point of glycerol compared to ethyl alcohol or other possible additives. Therefore, it is expected that the flammability risk associated to ethyl alcohol-based secondary fluids is reduced. / Etylalkohol (etanol) som köldbärare är mycket populärt som värmeöverföringsvätska för indirekt kylsystemmed bergvärmepumpsystem (BVP) i Sverige, Norge, Schweiz, Finland och andra europeiska länder. Fleraundersökningar har gjorts om kylsektorns framtid, köldmedier och kylsystem. Dessutom strängaförordningar som F-gas förordning och Kigali- förordning tvingar en utfasning av många nuvarande allmäntanvända köldmedier med den höga globala uppvärmningspotentialen (GWP), dvs. R134a eller R410A. Därför förväntas det att kylsystem och deras köldbärare spela en nyckelroll för att minimera köldmediumsmängd i systemen, minska de indirekta köldmedieläckage och öka säkerheten under drift. Syftet med detta examensarbete är att undersöka effekten av olika tillsatser för att öka flammanpunkten tillsammans med etanolbaserade köldbärare och validera deras termofysikaliska egenskaper genom att jämföra dem med referensvärden för rena etanolvattenlösningar. Studien syftar till att utforma en nykommersiell etylalkoholbaserad produkt för BVP-system som skulle kunna ersätta befintliga produkter på den svenska marknaden och kan arbeta med naturliga eller brandfarliga köldmedier med låg GWP. Olika tillsatser med hög flampunkt testades såsom 1-propylalkohol, n-butylalkohol, glycerol och propylenkarbonat. Termofysikaliska egenskaper undersöktes och en BVP-modell i Excel skapades för att bedöma energiprestanda för olika blandningarna. De erhållna resultaten för olika blandningar visar att glycerol i en låg koncentration som tillsats kan vara framtidens additiv för de etylalkoholbaserade köldbärare på grund av dess höga flampunkt (160 ºC) som förmodligen kan minska brandrisken för etylalkoholblandningar. Dessutom hade glycerol och etanolblandningar den lägsta viskositeten (c.a.12% lägre jämfört med ren etylalkoholblandningar) som bidrar tillen minskning av pumpeffekten med c.a. 4,5% jämfört med rena etylalkoholblandningar. Däremot visade etylalkohol och glycerol blandningen c.a. 4% lägre värmeöverövergångstal jämfört med de rena etylalkoholblandningar på grund av lägre värmeledningsförmåga jämfört med ren etylalkoholblandningar. Slutligen är glycerol en ganska billig och naturlig produkt som inte har några korrosionsproblem eftersom etylalkohol och glycerol är mindre frätande än vatten. Även om flampunkttest inte genomfördes i projektet, förväntas det att flampunkten ökas lite på grund av den höga flampunkten av glycerol jämfört med etylalkohol och andra tillsatser. Därför förväntas det att brännbarhetsrisken förknippad med etylalkoholbaserade köldbärare reduceras.