Background. Thermal calculations of heat exchangers designed to ensure comfortable indoor conditions must account for both convective and radiative components of the total heat flux. This approach enables the rational selection of geometric parameters of apparatuses to maximize the total heat output. Accurate calculation of the radiative heat flux emitted by a heat exchanger requires knowledge of the directional emissivity of the material coating its convective surfaces. Unfortunately, the scientific literature contains no works devoted to either experimental or theoretical determination of the directional emissivity of paint coatings applied to convective surfaces of heat exchanger apparatuses. Since the shape, size, and spacing of the fins on the heat exchange surface of the apparatus, in combination with its directional emissivity, can affect the magnitude of the radiant convective heat flux emanating from it, it is important to know, at what parameters of the heat exchange surface the heat flux reaches an extreme value; what proportion each heat transfer component contributes to this flux. Thus, research devoted to the development of an experimental setup and a method to determine the directional emissivity of paint coatings is relevant both from the perspective of acquiring new knowledge and from the standpoint of improving the calculation method, the implementation of which leads to the development of heat exchange equipment with high energy efficiency.
Materials and methods. The study of the directional emissivity of paint coating has been carried out experimentally on a specially designed experimental setup.
Results. An experimental setup has been developed, along with a method to evaluate the magnitude of directional emissivity of paint coatings used on convective surfaces of heat exchanger apparatuses.
Conclusions. Experimental results of directional emissivity of paint coatings show that the influence of coating color on directional emissivity is negligible. Specifically, paint coatings of different colors but identical chemical composition exhibit closely similar directional emissivity values.