A concept of finless heat exchanger, which is composed of micro tubes, is proposed and assessed for achieving higher performance and better compactness. In reality, however, the precise assembly of numerous micro tubes leads to high manufacturing cost, and even small deviation of assembled tubes may cause considerable deterioration in heat exchanger performance. To resolve these issues, the micro tubes are placed in contact each other in the streamwise direction, so that the manufacturability and quality of the micro finless heat exchanger could be drastically improved. In the present study, the basic characteristics of two kinds of new tube arrangements, i.e., side-contacted and wavy extruded tubes, have been invistigated through numerical simulation and experiment. As a result, it is found that the pressure loss for given volume and heat exchange rate is always smaller when the tubes are side-contacted in the streamwise direction. For these tube banks, empirical correlations of heat transfer coefficient and pressure drop are proposed. The correlation equations obtained agree well with the CFD data. The measured pressure drop is by 8% larger than the prediction because of imprecise tube arrangement, while predicted heat exchange rate shows satisfactory agreement with the experimental data.