Purdue papers address HC alternatives

A series of papers on hydrocarbon-based technology, including research on the use of alternative refrigerants R600 (n-butane, also known as butane) and R1270 (propene), were presented at the Purdue series of conferences, held at West Lafayette, Ind.-based Purdue University July 9-12.

The conferences include the 24th International Compressor Engineering Conference, the 17th International Refrigeration and Air Conditioning Conference and the 5th International High Performance Building Conference. Here is a sampling of the papers.

Liebherr challenges isobutane in domestic fridges

Mario Straub of German manufacturer Liebherr presented “Alternative Refrigerants For Household Refrigerators,” which aims to challenge the domination of R600a (isobutane) in household refrigerators.

“Since the beginning of the 1990s it is common in Europe to use R600a (isobutane) as a refrigerant in household appliances,” Straub notes in the paper “It is worth to evaluate if R600a is still the most suited refrigerant.”

After testing over 100 refrigerants, the paper found two candidates – R600 and R290 (propane) that could be suitable to replace R600a in household fridges and freezers.

According to the paper, with R600 instead of R600a, the energy consumption of mainly small domestic refrigerators – which have a low heat load and high evaporating temperatures – can be reduced by 5%.

However, small freezers with propane were found to be less efficient “due to the higher specific cooling capacity of R290 compared to R600a and the resulting increase in temperature difference in the heat exchangers,” the paper explains. 

High-temp heat pumps with R600 and R290 

The paper “Experimental Investigation of a Hydrocarbon Piston Compressor for High Temperature Heat Pumps,” by Bamigbetan et al, also concerns using n-butane as a refrigerant. 

“This study experimentally investigates the performance of a prototype butane compressor adapted for high-temperature heat pumps,” which was installed In the high-temperature cycle in a 20 kW cascade heat pump, with propane on the low-temperature cycle, the researchers state. 

The paper concludes that at a heat sink outlet temperature of 115^oC, the discharge temperature of the compressor would be 127^oC on average, demonstrating an average of “74 % for the total compression efficiency (suction head) across all operating conditions tested.” 

A cocktail of CO₂ and propene

The paper “Parametric Analysis and Optimization of a Cascade Refrigeration System using a CO₂/Propene Mixed Refrigerant,” by Massuchetto et al, looks into the effects of mixing the refrigerants R744 (CO₂) and R1270.

The analysis was done by theoretical simulations and a parametric analysis, which compared the CO₂/propene mixture to the use of the refrigerants in their pure forms in cascade systems.

The paper concludes that mixing natural refrigerants might yield efficiency gains.

Other hydrocarbon papers at the conference include:

• Optimization of MicroGroove Copper Tube Coil Designs for Flammable Refrigerants, by Cotton et al.

• A Theoretical and Experimental Analysis of a Self-contained R-290 Refrigeration Unit Applied to a Glass Door Reach-in Supermarket Display Case, by Ronzoni et al.

• Charge Equation For Small Charge Hydrocarbon Based Commercial Refrigeration Appliances, by van Beek and van Gorp.

• A Numerical Study on the Temperature Field of a R290 Hermetic Reciprocating Compressor with Experimental Validation, by Wu et al.

• An Experimental Study of HC-600a Flow Through Variable Expansion Devices for Household Refrigerators, by Knabben and Melo.

• Theoretical study on a modified subcooling vapor-compression refrigeration cycle using hydrocarbon mixture R290/R600a, by Chen et al.