In the period of sharp warming conditions can occur in which the temperature of the outer surface for some time will be below the ambient air temperature. While warmer ambient air, not in contact with the heated surface of the wall may cause condensation on the surface. The article discusses some of the exterior building envelope, in conditions of rapid warming and condensation process of moisture on the outer surface of the walls. With the help of finite difference method numerical modeling of the thermal regime of the outer surface.
Keywords: Exterior walls, non-stationary conditions, moisture condensation, winter
The article considers a method for optimizing circular ducts for ventilation and air conditioning systems. Universal dependencies are given to determine the diameters of the cross-sections of the air ducts and the air velocities in them that are technically and economically optimal. It is shown that the optimum air velocity in the section of the ventilation network does not depend on the site location relative to the fan of the system. Specific examples of determining the optimum diameters of air ducts and air velocities in them with the use of the dependences obtained are given in the technical and economic sense.
Keywords: Аir duct, aerodynamic calculation, ventilation system, air conditioning system, techno-economic optimization, optimal diameter, optimal air speed, energy saving, energy efficiency, aerodynamic efficiency
The aim of this work is determination of regularities that determine the operation parameters of the fan in a thermally non-stationary ventilation system contains a heater located along the air flow after the fan. It is established that the ventilation system, containing the heater, has two characteristics aerodynamic resistance related to the volumetric air flow at the sections of the network before and after the heater. It is proved that when using the superposition method, P-L characteristics to determine the parameters of the fan in the system, you must apply the P-L characteristic of the network is related to the volumetric air flow to the heater. The obtained dependences determine the parameters of the fan depending on its aerodynamic characteristics and the location of the heater in the system.
Keywords: the ventilation system is in a thermally transient mode, fan, heater, energy efficiency, energy conservation
With the aim of obtaining objective data about the energy potential of the air flow in the ventilation system proposed to use the parameter "local mechanical power flow". The formulas describing the change of this parameter in different parts of the ventilation system. Describes the author's method of graphic representation of the processes of change of flow parameters in the coordinate axes L - Pn, allowing enough just to determine the change in local mechanical power on isothermal and non-isothermal sections of the ventilation system.
Keywords: ventilation system, fan, mechanical power, heat exchanger, energy efficiency, energy conservation
The results of the analysis of the energy efficiency of water heating's accession to the heat network. Introduced the concept of the coefficient of the hydropower efficiency. Discusses the features of its calculation in the dependent scheme of attaching the water heating system of consumers to the heat network and the independent circuit.
Keywords: Heat supply network, individual heating unit, water heating system, energy efficiency, hydropower efficiency ratio