Vintage Air University
Selecting A Condenser
The most difficult challenge in building an efficient system is getting a condenser large enough, in a place where the air is cool enough, and can flow across it well enough, to remove the heat and condense the refrigerant adequately. The condenser has to provide a low resistance path for the condensed liquid to flow so pressure build-up on the system’s refrigerant can be avoided. (Excessive pressure here tends to reduce heat loss which tries to reduce condensation.)
The old vertical vs. horizontal tubes confusion in the condenser comes into play here. On a tube and fin condenser, the tubes must run horizontally. On a parallel flow condenser, the tanks run vertically, but tubes must run horizontal as well. Why? Because lubrication oil flows with the refrigerant in the system and will settle in the lower loops of the condenser, thereby obstructing the flow of liquified refrigerant. We have seen this single factor increase the internal pressure of the high-pressure part of the air conditioner by 50%, reducing its ability to work properly.
With the conversion from R-12 to HFC-134a refrigerants in automotive air conditioning systems, we would have had to increase the surface contact area of conventional tube and fin condensers by about 20% to maintain proper efficiency, but unfortunately many classic car and truck applications just won’t allow that size increase. A new type condenser was the correct solution and Vintage Air pioneered that technology for the performance aftermarket.
Our new design SuperFlowTM condensers, introduced back in 1991, provided that increase in capacity without additional external size! By using flat tubes manifolded together so that the refrigerant flows through multiple tubes on each pass, we get virtually 100% contact of the refrigerant with the condenser tube walls. This design also offers very low restriction in the pathway through the condenser. The SuperFlow condensers actually deliver up to 40% more efficiency than a comparable sized conventional copper tube-and-fin type condenser. This means we can get more capacity with less space, a good thing for smaller vintage cars and trucks!
The condenser has to have good air flow and must be mounted properly. It must be matched to a compressor of approximately nine (9) cubic inches or slightly less, using a standard aftermarket evaporator. Using this as a basic minimum standard, we have tailored each of our systems with a combination of components optimized to deliver the best performance. We always recommend using the largest parallel flow condenser possible. The condenser should cover as much of the radiator core as possible.
Air flow to the condenser is as important as size: the more the better. Ambient air temperature (outside air temp) is more important to an air conditioner condenser than it is to the engine cooling radiator because when the refrigerant is exposed to temperatures above approximately 100°F, the chemical expands at a very rapid and disproportionate rate, affecting system performance. Water/antifreeze expands more proportionately at much greater temperatures than refrigerant because of the higher boiling point. So, we position the condenser in front of the radiator, or in the coolest air stream possible, to keep the ambient air flowing over the condenser below or as near the century mark as possible. More time and consideration should be spent on selecting the condenser than on any other component of your system.