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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