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Communication Dans Un Congrès Année : 2007

Modelling of an innovative defrosting system of a heating and cooling plant using a HFC or CO2 as a working fluid

Résumé

HFCs are the most common working fluids in refrigeration devices. However, these greenhouse gases are responsible for global warming and are likely to be banned by European directives. Some interest is now turned towards fluids with low global warming potential (GWP) like carbon dioxide. The performances of CO2 can be interesting in transcritical cycles, particularly for domestic hot water (DHW) production. However, this cycle requires the use of devices operating under high pressures. The Heating and Cooling Plant (HCP) is intended to produce domestic hot water and to heat and cool residential and small office buildings. The HCP presents an innovative design of the refrigeration circuit and an innovative defrosting system. It is equipped with three heat exchangers: a water condenser (or gas cooler for transcritical CO2) and a water evaporator linked to three tanks and an air heat exchanger that can be either condenser or evaporator in order to balance productions and needs. When operating with the air evaporator under frosting conditions, some heat is gained by subcooling the refrigerant and stored in the cooling tank. When the cold tank is hot enough the HCP mode changes, to work with the water evaporator while the air evaporator is being defrosted. Two HCPs (CO2 and HFC) have been modelled using TRNSYS and EXCEL. The simulations enable to estimate the performances of both machines and to construct a frosting - defrosting sequence. The results show that both machines see their average COP increasing but that CO2 is 50% less efficient. However, the amount of heat recoverable by subcooling is nearly as high as for R134a and leads to a relatively more efficient defrosting system.
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Dates et versions

hal-00728348 , version 1 (05-09-2012)

Identifiants

  • HAL Id : hal-00728348 , version 1

Citer

Paul Byrne, Jacques Miriel, Yves Lénat. Modelling of an innovative defrosting system of a heating and cooling plant using a HFC or CO2 as a working fluid. Heat SET : Heat Transfer in Components and Systems for Sustainable Energy Technologies, 2007, Chambéry, France. ⟨hal-00728348⟩
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