**Nomenclature**

*A*; area, m2 *Aoval;* area of oval cross-section, m2 *cp*; specific heat at constant pressure, J/(kg K) *c*1 - *c*11; coefficients of function *η<sup>f</sup>* (*Rtc*, *ha*) *dh*; hydraulic diameter of narrow air flow passage, m *d*min, *d*max; minor/major oval axes, m *dt* ; hydraulic diameter of oval tube, m *F*; correction factor *h*; heat transfer coefficient, W/(m2 K) *h* ¯ ; enhanced heat transfer coefficient based on tube outer surface *Ao*, W/(m2 K) *j*; Colburn j-factor, Nu/(Re Pr1/3) *k*; thermal conductivity, W/(mK) *Lt* ; tube length in car radiator, m *m*˙ ; mass flow rate, kg/s *N*; number of transfer units Nu; Nusselt number *p*1; pitch of tubes in plane perpendicular to flow, m

*p*2; pitch of tubes in direction of flow, m

*P*; perimeter, m

coefficient and the thermal contact resistance. The air-side heat transfer correlations are determined based on the CFD simulations. The heat transfer coefficients predicted from the CFD simulations were larger than those obtained experimentally, because in the CFD model‐ ing the thermal contact resistance between the fin and tube was neglected. A new procedure for estimating the thermal contact resistance was developed to improve the accuracy of the heat exchanger calculation. When the value of mean thermal contact resistance, determined by the proposed method, is included in the CFD model, then the computed air temperature

The computations presented in this study allows to draw the following conclusions. CFD modeling is an effective tool for flow and thermal design of plate fin-and-tube heat exchangers. and is an effective tool for finding heat transfer correlations in the newly designed heat exchangers. However, to obtain good agreement between the CFD modeling and experimental data, it is necessary to adjust some parameters of the CFD model using the experimental results. An example of such a parameter may be thermal contact resistance between the tube and the

distributions show better agreement with measurements.

fin base.

*A*; area, m2

*dt*

*h*

*Lt*

**Nomenclature**

286 Heat Transfer Studies and Applications

*F*; correction factor

*Aoval;* area of oval cross-section, m2

*c*1 - *c*11; coefficients of function *η<sup>f</sup>*

*d*min, *d*max; minor/major oval axes, m

*h*; heat transfer coefficient, W/(m2

*j*; Colburn j-factor, Nu/(Re Pr1/3) *k*; thermal conductivity, W/(mK)

; tube length in car radiator, m

*m*˙ ; mass flow rate, kg/s

Nu; Nusselt number

*N*; number of transfer units

; hydraulic diameter of oval tube, m

*cp*; specific heat at constant pressure, J/(kg K)

*dh*; hydraulic diameter of narrow air flow passage, m

*p*1; pitch of tubes in plane perpendicular to flow, m

(*Rtc*, *ha*)

K)

¯ ; enhanced heat transfer coefficient based on tube outer surface *Ao*, W/(m2

K)

Pr; Prandtl number

*Rtc*; mean thermal contact resistance between tube and fin, m2 K/W

Re; Reynolds number

*q;* heat flux, W/m2 *q*¯*<sup>I</sup>* , *q*¯*II* average heat flux on the outer surface of tube in the first and second tube row, W/m2 *Q*˙ ; heat flow, W

*s*; thickness of air flow passage, m

*T*; temperature, °C *T*¯ *a*, *T*¯ *<sup>w</sup>* mean temperature of air/water in heat exchanger, °C

*U*; overall heat transfer coefficient, W/(m2 K) *V*˙ ; volumetric flow rate, dm3 /h

*w*; velocity, m/s;

*w*0; air inlet velocity, m/s;

*w*max; maximum air velocity in narrow flow passage, m/s;

*x*, *y*, *z*; Cartesian coordinates, m

*y*¯ distance, measured along the flow direction, between the oval gravity center and the point located at the outer surface of tube wall, m

xi ; unknown coefficient
