ICR2019: overview of current refrigeration research topics (part IV)

Energy storage, desiccant air conditioning, high-temperature heat pumps and ejector technologies were some of the salient topics of the latest IIR Congress. Continuation of the synthesis of key presentations of ICR2019.
Heat pumps were one of the major themes of this congress (100 communications) and the focus was on high temperature heat pumps (20 papers)

Dereje S. Ayou, José Miguel Corberan and Alberto Coronas [5] stress that high-temperature heat pumps (HTHPs) offer an opportunity to upgrade low-to-medium temperature heat sou]ces to high-temperature useful heat for industrial processes. They can be implemented in a wide range of industries as heat recovery solutions, including beverage, chemical, food, paper, leather, and textile industries. Furthermore, there are ongoing research and development activities to fully utilize the heat recovery potential of HTHPs at a heat supply temperature above 90 °C.

Apart from the vapor compression heat pumps (VCHPs), there are different types of heat pump technologies commercially available for high­temperature applications. The technologies are mainly absorption heat transformer (AHT) and compression-resorption heat pump (CRHP).

The market available HTHPs based on absorption technology are mostly the single-stage water/LiBr AHT with heating capacity between 150 and 10,000 kW. The thermal COPs are in the range of 0.45 to 0.5. The heat supply temperature of these heat pumps can reach up to 160 °C with a temperature lift of up to 50 K. A few heat pump applications are available for high-temperature heat supply, between 90 and 100 °C, using single-effect water/LiBr AHP, while there is no ammonia/water single-effect AHP for supply temperature higher than 90°C due to high operating pressure to use standard components. The current technology based on ammonia/water CRHP delivers heat up to 120 °C. The obtained electrical COPs of the CRHP technology are about 2.4 (at 75 K lift), 4.3 (at 65 K lift) and 6.1 (at 22 K lift). The theoretical and experimental studies carried out by several researchers in the literature have shown that higher temperature lift (above 85 K) could be obtained using double-lift water/LiBr AHT with a potential of converting more than 30% of industrial waste/excess heat at low-to-medium temperatures to a useful high temperature level.

Finally, there is a strong potential for AHT and CRHP technologies for high-temperature lift and heat supply temperature above 160°C, which is the current limit for VCHP technology. Therefore, in order to capitalize on these potentials, further research and development activities are needed.

Cryogenics was another topic of this congress, as illustrated by the keynote [6] of Noburu Motomura on cryopreservation of human cardiovascular tissues. Cryopreservation of human tissues has been performed more than over 30 years in various biomedical applications. In cardiovascular surgery area, cryopreserved human tissues are now used in the tissue infection cases, like cardiac valve endocarditis, cardiac valve prosthetic endocarditis, artificial graft infection, etc. The mortality rate of prosthetic valve endocarditis using cryopreserved allograft cardiac valve is now only about 15%.

See part III

These keynotes are available in the Fridoc database (see links below).

All the other communications of the Montreal congress can be downloaded here.

IIR members benefit from a quota of free downloads.

(5) Dereje S. Ayou, José Miguel Corberan, Alberto Coronas, Current status and new developments on high temperature heat pumps: https://bit.ly/31lsNma

(6) Noboru Motomura, Cryopreservation of human cardiovascular tissues: clinical application and storage devices: https://bit.ly/2MK4hGf