IIR document

Low-grade industrial waste heat recovery with CO2 transcritical heat pumps in cold climates.

Number: pap. n. 167

Author(s) : MINEA V.


Low-grade heat losses in form of liquid effluents at temperatures between 7°C and 45°C represent more than 24% of total losses of the Canadian manufacturing industry. On the other hand, process hot water up to 85°C is simultaneously or intermittently required, for example, in dairy plants and slaughterhouses. By recovering energy from low-grade waste heat effluents, the incoming cold water can be heated up to such relatively high-temperatures by using two-stage heat recovery systems including preheating heat exchangers and CO2 trans-critical heat pumps as first and second stages, respectively. This paper presents a number of key operating parameters and energy performances achieved by a 7 kW (compressor nominal power input) transcritical CO2 heat pump prototype. It recovers heat from industrial low-grade effluents entering the system at temperatures of 7°C, 10°C and 12°C in the winter conditions, and at 7°C and 15°C, in the summer conditions of operation. On the other hand, the cold water enters the heat recovery system at temperatures varying from minimum 7°C (in the winter) to maximum 17°C (in the summer). The inlet temperatures of both heat source and heat sink fluids are considered in this paper as “extreme” because they are among the lowest encountered in cold climates and they allow the cold water by-passing the preheating heat exchanger in both winter and summer operating conditions. However, at higher waste heat source inlet temperatures, the preheating heat exchanger must be activated, but this paper doesn’t cover this field of operation.

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Pages: 8 p.


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  • Original title: Low-grade industrial waste heat recovery with CO2 transcritical heat pumps in cold climates.
  • Record ID : 30004298
  • Languages: English
  • Source: 10th IIR-Gustav Lorentzen Conference on Natural Working Fluids (GL2012). Proceedings. Delft, The Netherlands, June 25-27, 2012.
  • Publication date: 2012/06/25


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