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Development and evaluation of ammonia vapor compression coupled to a CO₂ convection loop.

Number: 1180

Author(s) : DOMITROVIC R., TORNSTROM E., DAVIS T., AHMED J.

Summary

A novel approach to the application of zero GWP refrigerants for commercial space cooling was demonstrated using ammonia vapor compression chilling coupled to pumped carbon dioxide convection. Following the lead of emerging supermarket refrigeration systems, this approach is both modeled after and meant to substitute halocarbon -based pumped chilled water cooling. Compared to pumped chilled water, the use of CO2 coupled with ammonia-based chilling could provide a system targeting multiple paths of optimization: reduced cost, increased efficiency, lower GWP potential, improved flexibility. Potential cost reduction may come from reduced piping cost, reduced installation cost, reduced physical building load and reduced pumping cost. These are all derivatives of the higher heat capacity of phase-changing CO2 as compared to pumped water. Furthermore, low-charge ammonia provides a cheaper alternative to high GWP refrigerants. Efficiency gains potentially come from the use of ammonia as the vapor compression refrigerant—a fluid with inherently favorable thermodynamic properties as an HVAC refrigerant. Additionally, power may be reduced in pumping liquid CO2 compared to pumping water. GWP reduction potential comes from eliminating the use of halocarbon refrigerants and from higher system efficiency. There is also potential for reduction related to embedded manufacturing cost, though this study did not evaluate those possibilities. In this first prototype system, the concept was proven to be technically feasible. The ability to operate a convection loop at a wide range of temperatures, including below water’s freezing point, allows for design and operational flexibility that isn’t possible with a water loop. Cooling coils may be operated colder in order to adjust the sensible heat ratio (SHR) and thus have flexibility for greater dehumidification without energy intensive re-heat. This paper summarizes the technical approach to design and shares testing results of the prototype 8-ton system.

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Pages: 10 p.

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Details

  • Original title: Development and evaluation of ammonia vapor compression coupled to a CO₂ convection loop.
  • Record ID : 30033570
  • Languages: English
  • Subject: Environment
  • Source: 14th IEA Heat Pump Conference 2023, Chicago, Illinois.
  • Publication date: 2023/05

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