| Title | High capacity heat pumps development |
|---|---|
| Authors | I.M.Kalnin. A.M.Mass, A.I.Savitsky |
| Year | 2003 |
| Conference | International Geothermal Workshop, Russia |
| Keywords | Heat pumps, capacity, temperature |
| Abstract | The development of heat pumps with the capacity of up to 50 MW and operating on carbon dioxide (CO2, R744) is currently in progress in Russia. The work on this project is carried out by RMC EKIP, MGUIE, NPO ìHeliymashî as well as by other participants co-working on the topic ìDevelopment of technologies and equipment for the use of low-potential heat resources for the purposes of heat supplyî within the framework of the federal program ìResearch and development on the priority directions of science and technology in 2002-2006î. The use of R744 in refrigerators and heat pumps attracts a lot of attention throughout the globe. The main advantage is absolute non-hazardousness of this substance. Being cheap and abundant, carbon dioxide is not flammable, non-toxic, safe for the ozone layer and possesses the lowest global warming potential among all working media. Research works that have been carried out during the last few years, have now reached the stage of practical appliance. R744 possesses a number of unique thermodynamic characteristics the correct use of which allows for achieving of higher energy effectiveness compared to traditional working media and for developing of heat pump systems of quite high single capacity. Heat pumps based on R744 combine the processes of steam-compression and gas-based machines: the low-temperature processes take place in the saturation zone and high-temperature processes in super-critical zone. A significant temperature change when cooling down the gaseous R744 in the super-critical zone allow for heating the heat-carrier to a higher delta of temperatures with the minimum energy loss. High density of the gas and therefore higher volume heat productivity which is 5 ñ 10 times higher than of Freon stipulates for smaller compressor sizes. Small pressures ratio in the cycle is good for effective work of compressors: higher efficiency, only one compression stage is required when using a centrifugal compressor. High pressure level and high density of the gasiform R744 allow to use high mass current speed in the heat exchange devices which increases the heat transfer factor and reduces the mass and the size of the machine. Thermodynamic features of R744 also allow using expander instead of throttle in large capacity machines which additionally increases conversion factor of the heat pump. An optimal choice of working specifications allows the increase of conversion factor by up to 30% in comparison with the Freon heat pump systems. One of the areas where high capacity heat pump systems can be used is central heat supply systems with the low-potential heat source being geothermal water or the heat of technical water used in the cooling systems of heat energy centrals or atomic power plants discharged into the environment. |