Air reversing HVAC unit for public trains.

Unidad reversible de aire HVAC para trenes públicos.


Type of article: Article


A possible system for heating and cooling of a train compartment has been modelled and simulated. This system is a turntable HVAC unit developed at SINTEF, which is reversing the airflows to provide either cooling or heating. It has two gascoolers and two evaporators for separate treatment of ambient and recirculated air. The entire HVAC unit is rotated 180° to switch from heating to cooling mode. Carbon dioxide, CO2 (R744) is a sustainable working fluid for such systems. R744 systems have a large potential for expansion work recovery. If unrealized, this results in large throttling losses at high ambient temperature operation. An ejector is therefore added to the heat pumping circuit. In order to simulate the steady state and transient operation mode of the turntable HVAC unit a simulation model was built using Modelica as programming language. The refrigerant cycle including the ejector system was modelled based on the TIL-Library. Main focus of this study is the investigation of the ejector system performance at different ambient conditions and required heat and cooling capacities. Simulations were performed for the air reversing HVAC unit based on the heating and cooling demand when operated in 5 European cities representing a wide climatic diversity. The COP for cooling mode ranges from 2 to 4.5, depending on load and occupancy rate. The COP in heating mode ranges from 6 to 2. The efficiency decreases with reduced occupancy rate. The annual energy saving potential are calculated for all the 5 cities of the study, compared to current HVAC systems for trains.

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Pages: 34-44 (9 p.)


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  • Original title: Unidad reversible de aire HVAC para trenes públicos.
  • Record ID : 30004947
  • Languages: Spanish
  • Source: Frío Calor Aire acondicionado - vol. 40
  • Publication date: 2012/07


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