Refrigeration and Air Conditioning
Outdoor climate parameters are always variable, both during the year and in long-term perspective, which leads to uncertain expenses on building microclimate maintenance systems. The great variety of facilities and their initial conditions predetermines a variety of possible technical solutions, and controversy of defining parameters with lack of recommendations on how to evaluate the influence of chosen design parameter on seasonal provision coefficient, and related to this circumstance calculated values of needed resources of heat and cold, makes it difficult to choose. The basis of choosing rational technical solution options is targeted consideration of the facility’s initial conditions with further analysis of alternative technical solution indicators. Due to the dependence of needed resource values both on the technical solution and on the operation mode, it is suggested to evaluate system’s functional indicators by the values of seasonal provision coefficient. The approach is explained on the example of specific facilities.
This article provides overview of scientific works on heat hydrodynamic characteristics during the boiling of refrigerants in mini-(micro) channels. The article shows also the advantages of the mini cannels heat exchanges from the standpoint of energy efficiency, reliability, weight and size characteristics. The article describes methods for carrying out thermophysical experiments in mini (micro) channels with different hydraulic diameters and refrigerants, such as R134a, R410A, water-air mixtures and water. In the article the schemas of the experimental installations with mini channels, also with micro channels to study the boiling regimes and the heat transfer coefficients are presented. The expediency of continuing the study of heat transfer and hydrodynamic in the mini channels is shown, basing on complex approach, including studies of boiling regimes, true vapor content, local heat transfer, and pressure drops. The schema of the experimental stand is presented.
This article is focuses on the one of the major problems of the XXI century – energy efficiency and energysaving of buildings and structures. The considered problem is multifactorial and includes several methods of reducing the cost of resources in heating, ventilation and air conditioning systems: architectural and construction solutions, the use of renewable energy, optimization of microclimate systems. The article compares the classifications of energy efficient buildings in Europe and Russia, provides examples of national experience in the construction of energy efficient buildings, describes methods to improve energy saving through set of architectural and construction solutions, describes the use of renewable energy, presents optimization methods of microclimate systems of buildings and structures. The article gives an example of determine the value of the specific characteristics of the thermal energy consumption for heating and ventilation of the operated building during the heating season.
This paper examines the impact of the scheme of air distribution from ventilation and air conditioning systems on the characteristics of the fields of temperature and humidity over the ice surface areas in the indoor ice rink. Reveals the influence of air movement on the distribution of parameters over the ice, and on the condition of the ice surface. Graphs of air temperature over the ice platform height, formed in the heat exchange process the results of measurements of the author and from other sources. Presents a graph of the moisture content of the air on the basis of data obtained by the author, illustrating the intensity of mass transfer. It is proposed to use the scheme of air distribution, tested on a number of sites, excluding the direct impact of air jets on the ice array. The design procedure of the proposed scheme taking into account ensure the necessary air movement over the ice.