Liquid line approach is a reference check of the heat transfer of liquid refrigerant to entering condenser water. Flow has a minimal effect until extreme. Not hardly affected by noncondensables. Primarily affected by tube fouling or under charge.

Cross referenced with condenser approach, dt, sc, noncondensables test & gpm a complete evaluation is possible.

 

Not trying to split hairs here, but I've never heard of "liquid line approach". I could see the relevance, if used on condensers with subcooling sections. If no subcooling sections, then what the Op was asking on drop leg or liquid line temps is essentially the same thing (unless we are talking subcooler designs). That said, JMO, there is no difference in liquid line temp and drop leg temp. If it's a non subcooling condenser, then what's being determined is the condenser approach as EHSX stated. The measured approach (Leaving Condenser water verses the drop leg (condenser drain, liquid line, all same thing) is the approach. The better the heat exchange (HX) the lower the difference, vs the higher the difference the worse the HX. As for flow, correct flow would give you (for example 95° LCWT [not entering] and a saturated condenser temp of 100° would be a 5° approach. If you cut the flow back, you'll be rejecting less heat, less efficiently which would begin to cause your approach to widen some. Same with fouled tube's, less HX = widening approach temps.

 

EHSX, thank you. Actually been contemplating buying a set of the ASHRAE books. Will definitely look into it. Was the assumption that it was related to subcooling condensers correct?

 

Subcooling and condenser fouling.