University essay from KTH/Tillämpad termodynamik och kylteknik


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. 

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