الفهرس 
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Abstract
The hydrodynamics and heat transfer through a finned microtube arrangement and microchannel configurations have been investigated numerically in the presence of the solid domain in a conjugated problem feature. As a matter of fact, the study was performed using FLUENT, a well known commercial program. This model is based on the finite volume method. The effects of outer fluid velocity, number of fins, transverse pitch, geometric configuration and diameter on heat transfer rate, heat transfer per unit base area ,heat transfer per unit volume, outer fluid Nusselt number, inner fluid Nusselt number, fin efficiency, pressure drop, and NTU were presented in each case. Throughout the study, with the application of micro finned tube heat exchanger and microchannel heat exchanger, the outer fluid velocity was varied from 1m/sec to 6 m/sec. Furthermore, the number of fins has been changed from 0 to 75 with transverse pitch variation from 2.0 to 3.0 mm and also the diameter of the tube has been varied between 1cm to 0.5mm. While the Prandtl number for the outer fluid was kept constant at 0.72 referring to air and inner fluid-water- is fixed at 1.96. On the other hand, the inner fluid velocity remained constant corresponding to Reynolds number of 1250 in all comparisons the longitudinal pitch is fixed at 2mm with 6 tubes per row and also the point of variation of mass flow rate is taken into consideration in the comparisons. In general, the results indicate that the enhancement of heat transfer per unit base area increases by 21% at a velocity of 6m/sec. In proportion to this velocity, the augmentation in heat transfer per unit volume reaches 11 times the conventional plain-finned tube heat exchangers. In this case, the pressure DROP decreases by 25%, which leads to the enhancement of the heat transfer rate with decreasing the pressure drop. Additionally, regarding the micro-finned tube heat exchanger, the presence of the fins has a minor enhancement with a value of about 8% only at a fixed velocity and 20% for a fixed mass flow rate. Thus, concerning the moderately restricted space, it is preferred to utilize the unfinned micro tube heat exchanger. On the other hand, for highly restricted space limitations, a finned microtube heat exchanger is recommended. In the staggered configuration, the heat transfer is enhanced by 25% for finned microtube. For the microchannel with staggered array has an insignificant effect on average heat transfer coefficient with no effect on the pressure drop.