INTERNATIONAL NEWS |
INCORPORATING COLD CHAIN |
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REFRIGERANTS AND HEAT PUMPS FOR EFFICIENT USE OF LOW-GRADE THERMAL EFFICIENCY
Thanks to heat pumps , low-grade thermal
energy , such as solar energy , waste heat from industries , and geothermal energy , can be upgraded into high-temperature heat for central heating or industrial manufacturing processes .
The selection of suitable cycles and refrigerants is important for getting good performance of heat pumps . In their paper presented at the 5th IIR Conference on Thermodynamic Properties and Transfer Processes of Refrigerants , R . Z . Wang et al . analysed the performance of typical refrigerants — such as R152a , R1233zd ( E ), R1234yf , R1234ze , R134a , R245fa , R717 , R718 , and R744 — and various thermodynamic cycles for vapour compression , absorption , solid sorption and chemical HPs . A broad-spectrum diagram of HP applications is provided for different working modes .
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system and component design is helping to reduce charge sizes by more than 70 % when compared with pumped circulation . Developments in evaporator technology and the use of variable speed drive technology are ensuring that reduction in charge doesn ’ t come at the expense of efficiency . The introduction of packaged systems enables refrigeration plants to be located adjacent or close to evaporators , reducing pipework length and sizing .
• R . Lamb . Low charge packaged ammonia refrigeration systems .
ADVANCEMENT IN INTEGRATED CO 2
SYSTEMS
This was also widely discussed at the IIR Ohrid
Conference . A . Hafner highlighted that integrated CO 2 systems can simultaneously provide refrigeration capacities at various temperature levels as low as -50 ° C , air conditioning ( AC ), heating , and even sanitary hot water at adequate temperature levels . A further integration of advanced thermal storage devices will enable these systems to become a valuable element within smart ( thermal ) grids .
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to their fast recovery times , low jitter , and low dark count rates .
SNSPDs operate at extremely low temperatures , only a few degrees above absolute zero ( -273.15 ° C ). Until now , that level of cooling was achieved with liquid-helium systems , which present a few disadvantages : they are large , expensive , complicated , and demand considerable expertise to operate safely .
NIST recently found an alternative and created a very small prototype , adapted to the size of SNSPDs since it measures 0.31m high and 0.61m long . Its power demand is about 250W , whereas the previous best alternative drew 1.5kW of power . The prototype device relies on a hybrid cooling system comprised of a Joule-Thomson cryocooler and a pulse-tube refrigerator that can reach
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temperatures as low as 10K . It precools the cryocooler that can reach below 2K , which is an almost adequate temperature for SNSPDs operating at temperatures between 1K and 2K .
The NSA supported the initial planning and asked NIST to write a paper . The project is currently receiving funding under a cooperative research and development agreement .
• Kotsubo V . et al . Compact 2.2K cooling system for superconducting nanowire single photon detectors .
GEOTHERMAL ENERGY TO POWER A COLD STORAGE FACILITY
In Fiji , two remote villages located on the
tiny island of Vanua Levu do not have
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