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Units for 4-pipe systems for simultaneous production of heating and cooling energy, designed for dual source applications.

Author(s) : ROSSI L. de, BUSNARDO E.

Summary

The adoption of multi-purpose unit for buildings characterized by simultaneous cooling and heating requests minimizes the use of an external source for heat dissipation (positive or negative) of the thermodynamic cycle. This happens because the two sources coincide with the plant’s circuit to cool or to heat. The benefit of this solution depends on the percentage of time the unit works with a double effect: cooling and heating together. Obviously, the perfect balance of opposite loads it’s very rare; the most of the time an external medium has to be used to reject heat (if chiller mode is prevalent) or to capture heat (if heat pump mode is prevalent). Multi-purpose units are available both air or water cooled. The first one is easier to use and does not have any constraint on the availability of the source, but in extreme climate conditions (at peak summer or winter) has a quite low efficiency; the second one has higher efficiency than the air solution, but it is tied to the availability of water. The possibility to use more than one source could be an interest solution when water availability is limited, inconstant or not guaranteed for the future; but it can even be an energetically convenient choice if the unit is able to switch the source choosing the one that perform best. The paper presents a case study where a multi-purpose unit has been installed; in this specific case a dual-source solution was chosen to meet the customer’s requirement to don’t be bound by the choice of well water’s utilization. The unit is equipped with screw compressors, refrigerant R134a, two high efficiency heat exchangers shell and tubes type for cooling and heating, one auxiliary shell and tubes heat exchanger coupled with the well water circuit, and a condensing coil for air. At present, the air source is used only in mid-seasons when outdoor temperature is not extreme and consequently the unit’s efficiency is interesting. At present, the switch between one source to the other is done manually. In this paper, the authors describe an advanced control to switch between the two sources in order to achieve moment by moment the highest possible efficiency. The building air-conditioning loads have been re-created and various alternative to match the thermal requests have been simulated. It will be demonstrated that the final energy consumption of the advanced dual-source solution is lower than the single source ones and even of the actual dual source solution manually controlled (seasonal switch).

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Pages: 203-214

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Details

  • Original title: Units for 4-pipe systems for simultaneous production of heating and cooling energy, designed for dual source applications.
  • Record ID : 30001152
  • Languages: English
  • Source: Sources/sinks Alternative to the Outside Air for Heat Pump and Air-conditioning Techniques (Alternative Sources - AS), Padua, Italy, April 5-7, 2011. / International Sorption Heat Pump Conference (ISHPC11), Padua, Italy, April 6-8, 2011.
  • Publication date: 2011/04/05

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