9.5 Condenser underperformance

The condensing process is normally stable, and will not cause any major disturbances of the system performance. However, situations that reduce the capacity are possible. A major reduction in capacity is normally related to the evaporator performance. Problems with the condenser are usually manifested as an increased pressure head. Some checkpoints for determining the reason for underperformance are described below.

  • Check the installation. The exchanger should be mounted upright, with the refrigerant circuit connected to the left side when the arrow sticker is pointing upwards. The refrigerant and water circuits should be connected in counter-current mode with the refrigerant inlet at the top. For further information, see chapter 8.2.
  • Check the condenser for temperature variations on the outside If inert gas is trapped, or water channels are obstructed, inside a brazed plate heat exchanger, there will be large surface temperature differences. Fouling can be identified as particles in the port or as general particle fouling on the plates.
  • Check cooling fluid if pure water is not used A glycol solution with the wrong concentration will affect the heat transfer.
  • Check temperatures on the water side Make sure that the entering and leaving water temperatures correspond to the design conditions. If the temperature difference is higher than the design conditions, the water flow rate has been reduced. Try to increase the water flow rate.
  • Check the amount of sub-cooling Too much sub-cooling will block the heat transfer surface from the condensing process and thus increase the condensing pressure. This indicates that the system has been overcharged. Release the refrigerant charge until a reasonable level of sub-cooling (2-5K) has been achieved.
  • Check the compressor The condenser capacity is always set by the compressor. Thus, if the compressor is working improperly, the condenser capacity will be affected. See chapter 3.4.
  • Check the suction pressure at the compressor inlet Use the compressor data to compare the capacity with the design data.
  • Check the pressure drop over the secondary side of the condenser If the pressure drop is higher than the design conditions, fouling could be the reason. Make sure that the pressure drop is read at the design flow rate, because the pressure drop is proportional to the flow rate squared.
  • Check the pressure drop in the discharge line Make sure that none of the components in the discharge line, i.e. between the condenser and compressor, has a pressure drop that is not taken into account. Oil separators, check-valves and mufflers can cause significant pressure drops if they are not correctly sized.
  • Check the discharge temperature If the discharge temperature is significantly higher than in the design conditions, a larger surface is required for the desuperheating before condensing can start. This will reduce the condensing surface and increase the condensing pressure.

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