Analysis of hydrocarbons in domestic and commercial refrigeration shows clear energy savings

Amongst the 141 papers presented at the 10^th Gustav Lorentzen Conference on Natural Working Fluids, experimental results analysing the design of hydrocarbon refrigeration systems for supermarkets and domestic refrigerators were discussed. Replacing R22 with R1270 was shown to reduce energy consumption by 38%; sequential dual evaporators can improve COP; an R1270 integral supermarket cabinet design achieved a COP of 3.15.

Attended by 282 participants from 37 countries, the 10^th Gustav Lorentzen conference opened with a Plenary Keynote Lecture by Pega Hrnak, whose presentation “Some technologies needed to advance the position of major natural refrigerants: HC, NH₃, and CO₂” highlighted the work needed to make hydrocarbon refrigeration more competitive. Key areas for further research identified: smaller systems, ultra low charge for even greater safety, sensitivity of propane to oil and oil reduction, and smaller Cp internal volume.

The 27 June session “Hydrocarbon Drop in/Systems” presented results from the latest research into hydrocarbon commercial and domestic applications.

Performance of integral hydrocarbon cabinets for supermarket applications, I. N. Suamir, S. A. Tassou, P. Arrowsmith, M. Bushell

Supermarket chains such as Lidl are investing in integral hydrocarbon cabinets with heat rejection to the air in the supermarket and a combination of heat rejection to the air as well as water in a closed loop system. This paper discusses the design and optimisation of such integral refrigerated food display cabinets based on results of experimental investigations and Computational Fluid Dynamic (CFD) modelling.

A 3.81m display cabinet with integral condensing unit using a horizontal scroll compressor was modified to operate with R1270 hydrocarbon refrigerant. Designed with two completely independent circuits to minimise refrigerant charge, the converted cabinet could satisfy the M0 product temperature requirements when back panel flow was 67% of the total flow rate, which minimised the load. Increasing the air mass flow rate through the perforated back panel from 37% to 67% reduced energy consumption by 4%.

Experimental Analysis of a commercial refrigeration system operating with R22 and the hydrocarbon R1270, E. P. Bandarra Filho, A. H. P. Antunes, L. M. P. Souza, O. S. H. Mendoza, A. Silva

Three different experimental configurations were compared to analyse the effect of replacing R22 with R1270 in a commercial refrigeration system with a maximum refrigerating capacity of 1.5 kW. Parallel to this aim the electricity consumed was quantified to compare a conventional refrigeration system to an automated system. The three systems tested were:

Conventional system with R22: this system consisted of a reciprocating compressor working at nominal frequency, two concentric tube heat exchangers, a thermostatic expansion valve (TEV), R22 working fluid;
Automated system with R22: in this system the compressor speed was controlled by an inverter frequency drive and an electronic expansion valve (EEV), with R22 as the working fluid;
Automated system with R1270: this system had compressor speed controlled by an inverter frequency drive, an electronic expansion valve (EEV), and used R1270 as the working fluid.

According to results from battery of 51 tests replacing the traditional fluid with a natural refrigerant provided a reduction of 38% in average monthly electrical consumption and a reduction in the total damage related to global warming of 39%.

Performance improvement of sequential dual evaporator refrigeration cycle in domestic refrigerator-freezer charged with R600a, M. Visek, C. M. Joppolo, L. Molinaroli, A. Olivani

To investigate the energy saving potential of a sequential dual evaporator (SDE) compared to refrigeration systems with evaporators in series experiments were carried out on a prototype SDE refrigerator-freezer charged with R600a and equipped with a variable speed compressor. The key advantage of the SDE circuit is the ability of the refrigeration compartment evaporator to operate at elevated evaporation temperature compared to a circuit with evaporators in series in the refrigeration compartment with food freezer compartments.

Second law analysis was used to examine the results of various compressor speeds. The experimental results showed significant potential for improving the refrigeration compartment COP. However, important losses over 40% in the compressor and 23% in the fresh food compartment evaporator were observed. A slab with phase-change material in the fresh food compartment evaporator design was suggested to address these losses.