Air-Side Heat Transfer and Pressure Drop Characteristics of Peripheral Fin Heat Exchangers

We present an experimental evaluation of the peripheral finned-tube heat exchanger. In this novel compact evaporator geometry, the air-side is composed by an arrangement of open-pore cells formed by radial fins whose bases are attached to the tubes and whose tips are connected to peripheral fins. Each fin arrangement is made up of six radial fins and six peripheral fins forming a hexagon-like structure. The air-side fin configuration is composed of three levels of fin arrangement, each characterized by the length of radial fin and mounted with a 30° offset from its neighboring level. Experimental data on the air-side heat transfer and pressure drop were generated in an open-loop wind tunnel calorimeter. A one-dimensional theoretical model based on the theory of porous media has also been developed to predict the thermal-hydraulic behavior of the heat exchanger. The model incorporates the actual fin geometry into the calculation of the air-side porosity. The air-side permeability is calculated according to the Kozeny-Carman model with the particle diameter definition due to Whitaker and the friction factor correlation due to Ergun. The model overpredicts the air-side thermal conductance by less than 15% for air flow rates higher than 14 L/s. The air-side pressure drop is underpredicted by the model, but still within the limits encountered in the literature. The analysis is complemented with an entropy generation minimization analysis in order to demonstrate the procedure for obtaining an optimized configuration of the heat exchanger.