###### Abstract  
This paper presents the results of numerical and experimental studies of wind action on longitudinal finned tubes of LNG ambient air vaporizers. The main objective of the study was to determine the aerodynamic drag coefficients for longitudinal finned tubes with different number of fins considering various directions of wind action. Numerical calculations were performed using CFD analysis, while experimental tests were carried out in a wind tunnel test stand. The obtained results indicate the variation of tube loads depending on the number of fins and the direction of wind action and can be used in the design of ambient air vaporizers. longitudinal finned tubes; LNG ambient air vaporizers; aerodynamic drag coefficients; CFD analysis; wind tunnel tests +
Footnote †: journal: Applied Sciences  
values of the heat transfer coefficients at the outer surface of the longitudinal finned tube for free and mixed convection conditions. In turn, [PERSON] and [PERSON] (2021) [7] presented the optimization results of the geometric parameters of longitudinal finned tubes under mixed convection conditions. The tubes with fins of wavy shapes were intended to use in a heat pump evaporator. [PERSON] et al. (2018) [8] studied the heat transfer between ambient air and LNG under supercritical conditions. The CFD modeling was proposed to investigate the supercritical flow of liquefied natural gas inside the ambient air vaporizer. In addition, the results of longitudinal finned tube geometry optimization were delivered. [PERSON] et al. (2022) [9] proposed a calculation model of coupled heat and mass transfer from ambient air to LNG inside the tube. The model was intended to analyze the heat transfer process in ambient air vaporizers including LNG phase change inside longitudinal finned tubes. Another issue raised in publications was the problem of longitudinal finned tubes frosting during ambient air vaporizer operation. [PERSON] et al. (2009) [10] presented a study on the optimum design of AAV longitudinal finned tube geometry by applying numerical and experimental analyses. As a result, the recommended relations of the fins' dimensions were proposed for optimal heat transfer both with and without frosting. [PERSON] et al. (2013) [11] presented a study on the thermal conductivity of frost accumulated on the finned tube of cryogenic vaporizers using a fractal method. In turn, studies presented by [PERSON] et al. (2015) [12], [PERSON] et al. (2016) [13], [PERSON] et al. (2017) [14], [PERSON] et al. (2018) [15], and [PERSON] et al. (2021) [16] were concerned with the analysis of ambient air vaporizer operation, including frosting conditions and their influence on heat transfer efficiency. Ambient air vaporizers can be large, even reaching several meters in height, due to the need to obtain a sufficiently high efficiency. The large size causes AVVs to be subjected to significant wind exposure. A study on the wind action on ambient air vaporizer structures was presented by [PERSON] and [PERSON] (2022) [17]. CFD analysis was applied to investigate the influence of a longitudinally finned tube arrangement on the wind load. In addition, the effect of various spacing pitches of the tubes and different wind directions were analyzed. It was noticed that, depending on the above parameters, individual tubes can be significantly overloaded compared to other tubes in the AVV structure. There are several methods to evaluate and compare the effect of wind action on ambient air vaporizer structures. The essential quantity to be determined for the further  
Figure 1: Ambient air vaporizer (**a**) general view; (**b**) detailed view on the aluminum finned tube. estimation of finned tube strength, as well as that of the entire AAV structure, is the wind force. In general, calculation procedures in accordance with the relevant wind standards can be used or CFD analysis can be applied.