Technical selection and refrigerants

  • Which fouling factors does Onda suggest for the selection of shell and tube heat exchangers?

    The fouling factor is important for the selection of an evaporator. The value Onda suggest to input in selection software are:

    For evaporators:
    -    Normal water in closed circuit: 0,000043 m2K/W;
    -    Water in open circuit: 0,000086 m2K/W;
    -    Solutions with glycol <40%: 0,000086 m2K/W;
    -    Solutions with glycol >40%: 0,000172 m2K/W.

    For condensers:
    -    Normal city water: 0,000043 m2K/W;
    -    Treated tower water: 0,000043 m2K/W;
    -    River water: 0,000086 m2K/W;
    -    Solutions with glycol <40%: 0,000086 m2K/W;
    -    Solutions with glycol >40%: 0,000172 m2K/W.

  • What does “Approach” mean in heat exchangers?

    This term refers to the difference between the leaving process fluid temperature and the change of state temperature of the refrigerant. For evaporators, if water is cooled from 12°C to 6°C and evaporating temperature is 1°C, the approach is 5K. For condensers, if water is warmed from 30°C to 35°C and condensing temperature is 40°C, the approach is 5K.

  • What does mean “Dew Point”?

    The dew point is the temperature at which a vapour will condense, or when associated with glide, the higher or highest boiling point of the mixture.