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Monobloc vs. split-design of heat pumps: fluid selection and thermodynamic analysis.

Number: 0018

Author(s) : HÖGES C., VENZIK V., MÜLLER D.

Summary

Due to current regulations, alternative working fluids for heat pump systems have to be identified. Thereby, hydrocarbons (HC) and hydrofluoroolefins (HFO) are possible solutions. However, both fluid categories are at least mildly flammable and thus, result in additional safety regulations. In particular, regulations includes refrigerant charge limits for defined applications. For HFOs higher charge limits are allowed compared to HCs. Due to these restrictions, heat pumps with HCs have to be built in monobloc design, while the application of HFOs is also possible in split designs. In general, monobloc design leads to lower heat pump efficiencies because of an additional heat exchanger for similar operating conditions. In this work, HCs are compared to HFOs while including the influence of an adjusted heat pump cycle (construction type: monobloc vs. split-design). Thereby, HCs have to deal with higher minimum approach temperature differences in the condenser, penalizing HCs and reducing the overall cycle efficiency. Additionally, we investigate a simple cooling cycle and a cycle with an internal heat exchanger (ihx) due to their wide application range. Despite the penalty, HCs lead to higher seasonal coefficients of performance (SCOP) with a maximum increase of up to 16 % in the simple cycle. Thereby, propane reaches a break-even point with R454C for a penalty of 8 K. In the ihx cycle, the difference between HCs and R454C diminishes, resulting in a break-even penalty at 2 K. Overall, the investigation shows that both the construction type and the cycle design have a significant influence on fluid ranking and thus, has to be kept in mind when selecting a proper working fluid.

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Pages: 10 p.

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Details

  • Original title: Monobloc vs. split-design of heat pumps: fluid selection and thermodynamic analysis.
  • Record ID : 30029658
  • Languages: English
  • Subject: Technology
  • Source: 15th IIR-Gustav Lorentzen Conference on Natural Refrigerants (GL2022). Proceedings. Trondheim, Norway, June 13-15th 2022.
  • Publication date: 2022/06/13
  • DOI: http://dx.doi.org/10.18462/iir.gl2022.0018
  • Document available for consultation in the library of the IIR headquarters only.

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