Correction Factor to Unit Core Heat Transfer Capability of Heat Exchanger Core Due to Variation of Tube Length

In the design and selection of heat exchangers, three basic methods are used; namely Log Mean Temperature Difference Method, e-NTU Method or the Unit Core Heat Transfer Capability Method. In the preliminary analyses of heat exchanger core in automobile industry, the 3rd design method is generally used. The 3rd method relies on the correlation data between unit core heat transfer capability and air flow velocity in front of the core. These correlation data are usually obtained in wind tunnel using 12″ x 12″ or 6″ x 6″ basic core. When the tube length is different from the basic core length, correction of the heat transfer performance of the core should be made.

This paper presents a mathematical formulation of this correction factor. These correction factor are also presented in several graphs and tables using water, 50/50 aqueous ethylene glycol solution, engine oil and hydraulic fluid as the hot side fluid. These correction factor are needed in engineering analyses of various coolers and radiators in automobile cooling system.