Deriving guidelines for the design of plate evaporators in heat pumps using zeotropic mixtures

Roberta Mancini*, Benjamin Zühlsdorf, Jonas Kjær Jensen, Wiebke Brix Markussen, Brian Elmegaard

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

This paper presents a derivation of design guidelines for plate heat exchangers used for evaporation of zeotropic mixtures in heat pumps. A mapping of combined heat exchanger and cycle calculations for different combinations of geometrical parameters and working fluids allowed estimating the trade-off between heat transfer area and pressure drops on the thermodynamic and economic performance indicators of the cycle. Compressor running costs constituted the largest cost share, and increased due to a steep decrease of the heat pump coefficient of performance at high refrigerant pressure drops. It was found that the pressure drop limit leading to infeasible designs was dependent on the working fluid, thereby making it impossible to define a guideline based on maximum allowable pressure drops. It was found that economically feasible designs could be obtained by correlating the vapour Reynolds number and the Bond number at the evaporator inlet as ReV-0.42Bd0.26≈ 0.040 . The use of the proposed guideline was illustrated for the mixture Propane/Iso-Pentane (0.5/0.5), leading to evaporator designs with net present values deviating maximum −4.4% from the best value found in the mapping. The presented methodology can be applied in different scenarios to develop similar guidelines, thereby decreasing the cost of combined cycle and component optimizations.
Original languageEnglish
JournalEnergy
Volume156
Pages (from-to)492-508
ISSN0360-5442
DOIs
Publication statusPublished - 2018

Keywords

  • Plate heat exchanger
  • Zeotropic mixture
  • Economic analysis
  • Design guideline
  • Dimensionless numbers
  • Pressure drops
  • Heat transfer area

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