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4 Row Core? 5 Row Core? Getting the Most out of Radiator Cooling Capacity

     Simply stated, radiators are heat exchangers. In order to cool down the engine, coolant is passed through the engine block where it absorbs heat from the engine. The hot coolant is then fed into the inlet tank of the radiator and distributed across the radiator core. As the coolant is circulated through the radiator tubes on its way to the opposite tank, it cools again. The cold coolant is fed back into the engine, and the cycle repeats. As it circulates through the tubes, the coolant transfers its heat to the tubes which, in turn transfer the heat to the fins which are located between each row of tubes. The fins then release the heat to the ambient air. Fins are used to greatly increase the contact surface of the tubes to the air, thus increasing the exchange efficiency.

     A standard five (5) row radiator core for an over the road truck is made with either 5/8” or ½” tubes on 5/8” centers making up the overall core depth of 3 1/16” or 3 5/8”. Because of size limitations this is typically found in trucks produced prior to the mid 1980’s.

     The standard four (4) row would consist of 3/8” to ¾” tubes on 3/8” to 5/8” centers creating a core depth of 2 ¼” to 2 5/8”. Both normally contain 10 to 14 fins per each inch (FPI) of the core.

     One thing to keep in mind when determining how much overall capacity is needed is that 70% of the cooling is accomplished in the first and second rows of tubes. Also, there are exceptions to the standards when horsepower exceeds 700hp or when hauling loads of over 80,000 pounds. The solution can be found in using a dimpled, rather than a flat, tube when manufacturing the core. Dimples are stamped within the tubes which will cause the coolant to swirl, thereby increasing the heat transfer ability. This type of core is normally referred to as a “high efficiency” (HE) with 5/8” tubes on 3/8” centers and an increased fin count of 14 to 16 FPI.

     Other factors such as the fan, shrouds, and hubs must be considered, however, a well-engineered 4 row radiator will provide as much cooling as an original 5 row using less space. The HE core, therefore, is ideal for trucks from the mid 1980’s and newer. Over the road, heavy duty trucks such as Kenworth, Peterbilt, Freightliner, International, and Volvo have gone through many design and engineering changes over the years to create more efficiency. Keeping up with the cooling needs of these trucks is important to Truck Radiators, Home of West Side Radiator Works and, of course, the customers we serve every day!