Refrigeration Laboratory

The Iowa State University Refrigeration Laboratory contains a range of test and research facilities used for cutting edge research on heat transfer and property characteristics of new working refrigerants. These same facilities are also used to characterize unique refrigerant and lubricant mixtures along with refrigerant type nanofluids.

The Refrigerant Laboratory houses two major heat transfer test facilities, namely the Two-phase Refrigerant Heat Transfer Test Facility and the Shell-side Refrigerant Heat Transfer Test Facility. These two test facilities have been used to measure both in-tube and shell-side heat transfer coefficients for evaporation and condensation conditions for a range of alternative refrigerants (e.g. R-134a, R410a, and R-407c) and enhanced tube geometries. They are also used to evaluate the effects of lubricants on refrigerant heat transfer when using enhanced tube technology (i.e. micro-fin tubes). The Shell-side Refrigerant Heat Transfer Test Facility has also been used to evaluate heat transfer in spray evaporators, which has the potential to significantly reduce refrigerant inventory in actual systems.

The Refrigerant Laboratory also houses the Capillary-tube Test Facility. This facility is used to test and evaluate capillary-tube/suction-line heat exchangers for a range of sizes, geometries, refrigerant types and test conditions. Because refrigerant flow in capillary tubes is a complicated phenomenon of a two-phase fluid flashing in a small diameter tube while losing heat to the suction-line under sonic conditions, experimental tests are the predominant method of designing and sizing this important component for real-life refrigeration systems.

The Miscibility Test Facility and the Solubility/Viscosity Test Rig are also located in the Refrigeration Laboratory. These two important test setups are used to characterize refrigerant – lubricant mixtures at conditions similar to those found in operating refrigeration systems. Specifically, the Miscibility Test Facility consists of two different fluid baths, namely a high temperature bath controlled up to 100°C and a low temperature bath controlled down to -40°C, that can be loaded with a rack of test cells containing specified refrigerant and lubricant concentrations. The contents inside the test cells are viewed for phase-changes, hence miscibility, as the bath temperatures are varied. Viewing of test cell contents is facilitated by the fact that test cells are constructed with glass viewing ports and the fluid baths have glass sides.

The Solubility/Viscosity Test Rig is used to measure the solubility and viscosity of refrigerant – oil mixtures at temperatures and pressures similar to those found in the compressor of a typical refrigerant system. Those compressor conditions are high temperatures up to 100°C, and high oil concentrations, up to 60% oil. The solubility of a refrigerant – oil mixture is defined as the relationship among pressure, temperature and oil (refrigerant concentration) with all three parameters along with viscosity being measured in this test facility.

The In-tube Single-phase Heat Transfer and Property Test Loop is the sixth test rig located in the Refrigeration Laboratory. This versatile facility is used to measure in-tube heat transfer coefficients along with a range of fluid properties including viscosities, thermal conductivities, specific heats, and densities. Fluid viscosity and density are measured by using installed sensors, namely a viscometer and a densitometer, while specific heats and thermal conductivities are obtained from energy balances and Nusselt number correlations, respectively. This particular rig has been used extensively in the past to characterize the properties of refrigerant – oil mixtures while ongoing studies are measuring in-tube heat transfer coefficients and properties of refrigerant-type nanofluids.