The number of papers about carbon dioxide has reduced not only in percentage of the number of papers but also in absolute numbers: from 71 in 2006 to 66 in 2008, 41 in 2010 and 57 in 2012. The research on CO2 is now mainly focused on the improvement of the cycle by among others the inclusion of ejectors to recover part of the expansion losses. The use of ejectors in transcritical CO2 heat pumps systems has shown to improve the cycle efficiency by 7 to 14%. For refrigeration cycles a maximum improvement of 7% has been reported. The operating range of compressors has being extended to higher pressures and higher temperatures making high temperature heat pumps feasible, also with other fluids. The performance of CO2 secondary systems both with forced circulation and natural gravity circulation has been the topic of some of the papers. The impact of circulation flow rate was, among others, one of the topics studied.
The sorption papers were very well represented. Figure 1 indicates an increase in the interest in sorption related topics. Solar assisted sorption systems were the topics of some of the papers while others were dedicated to heat and mass transfer phenomena in sorption systems. A number of prototypes in under development and the progress has been reported by the authors. Most of the sorption papers concerned absorption cycles although a few of the papers were dedicated to adsorption processes. Experimental data have been presented about solar systems from which it was concluded that the auxiliary systems represent a large share of the energy needs of the solar systems. One of the papers concerned double-output, double-effect chillers with a total COP of 3.3. These machines have not only been tested in the laboratory but have also been implemented in district heating systems. One of the proposed systems concerned seasonal storage of solar heat which, taking the seasonal behavior of solar energy into account, may become quite relevant.
Hydrocarbons have been extensively discussed in the 2002 and 2004 Conferences. Their interest has stabilized and has remained practically constant in the last 4 Conferences. Operating maps of compressors for hydrocarbons have been presented allowing identification of possible operating conditions. Compressor designs have been improved for hydrocarbon operation allowing for higher isentropic efficiencies. Charge reduction and safety concepts for hydrocarbon systems have also been discussed.
The low number of papers dealing with ammonia is comparable to previous Conferences. For years ammonia has been the topic of specialized conferences with very limited number of papers in Gustav Lorentzen Conferences. However specifically in the field of compressors new developments related to high pressure and high temperature applications have been reported. Also the application of ammonia in a small heat pump with extremely low charge has been reported.
Compressors have not been a significant topic in previous conferences but with 10% of the Delft Conference being dedicated to compressors was now an important topic. Developments related to carbon dioxide compressors are mainly related with two stage operation. This allows for an economizer or intermediate pressure separator connected at an intermediate pressure, improving the system performance. The discharge temperature of hydrocarbon compressors is significantly lower than for HFC’s. This allows for an extended operating range. Design modifications allow for higher efficiency. Combination of Vi control with rotational speed control allow for part load operation of screw compressors with very high isentropic efficiency.
The percentage of papers with heat pumps as topic is slightly lower than in previous conferences. Industrial heat pumps but also heat pumps for applications in renovated buildings require high heat rejection temperatures. Several papers propose selection methods for these applications for what concerns best fluids and best working principles taking the operating conditions into account. New compressor designs which allow higher operating pressures and temperatures have significantly enlarged the working range maps of the compressors allowing for more applications at higher rejection temperatures.
In the past Conferences the use of CO2 in supermarkets has been mainly concerned with the CO2 systems. In the present conference the integration of the several energy systems in supermarkets has been the focus of most supermarket papers. System integration appears to deliver significant energy advantages.
The following event, the 11th IIR International Gustav Lorentzen Conference on Natural Working Fluids, will be held in Hangzhou, China, in 2014. But before that, the 4th IIR International Conference on Thermophysical Properties and Transfer Processes of Refrigerants will be held in Delft, the Netherlands, on June 17-19, 2013 (see www.tptpr2013.nl): don’t miss it - many papers will deal with natural refrigerants.
A CD-ROM with all presentations on the Delft Conference is available via www.iifiir.org.
Carlos Infante Ferreira
Delft University of Technology
Process & Energy
E-mail address: firstname.lastname@example.org
01 July 2012
Figure 1 gives an overview of the most discussed topics during the last 6 Gustav Lorentzen Conferences (Guangzhou, Glasgow, Trondheim, Copenhagen, Sydney and Delft). The Conference in Asia has attracted a smaller number of papers. This might indicate that natural working fluids still have a low priority in this region. The papers have been subdivided in the categories: Carbon Dioxide, Sorption, Hydrocarbons (HC) and Ammonia for what concerns the fluids. Major topics as compressors, heat pumps, ejectors (including expanders) and supermarkets have also been included since these topics have been represented in all the 6 conferences.
Table 2 indicates the best represented countries for what concerns the origin of the first author and for what concerns the country of the participants. Most authors and participants came from central Europe but also Asia was well represented.
The Delft Conference, following the Sydney Conference in April 2010 (Paul, 2011), was organized under the governance of KNVvK (Dutch Refrigeration Association) in close cooperation with the Delft University of Technology. Table 1 gives some statistical data in comparison with the two previous Gustav Lorentzen Conferences. The Copenhagen Conference clearly beats all other Conferences for what concerns the number of participants. However, the Delft Conference had the largest number of papers and represented countries.
March 15, 2012 Registration open
March 31, 2012 Final manuscripts submitted
April 15, 2012 Deadline early registration
May 15, 2012 Deadline for registration
of at least one author
June 24, 2012 Welcome reception
June 25, 2012 Conference opening
June 27, 2012 Conference closing
June 28, 2012 Technical tours