Refrigeration engineering and technology

12-20

Authors: A. S. Titlov, A. O. Kholodkov

Absorption refrigerators (AR) with absorption cooling units (ACU) have an increased energy consumption during operation due to the thermodynamic imperfection of the absorption refrigeration cycle, the presence of low-intensity diffusion processes of mass transfer in the evaporator and absorber and the losses associated with evaporation and Subsequent transportation of ammonia from the generator unit to the condenser and then the evaporator. The greatest effect in energy saving during the operation of ACU with minimal changes in design can be achieved by improving the operation modes of generating units. The main direction of modern research of AR is aimed at qualitative obtaining of experimental data. The objects of experimental research were modernized models of household absorption single-chamber refrigerators "Kyiv- 410" and "Kristall-408". The modernization consisted in the installation of an additional heat-insulating casing on the generating set in such a way that the entire lifting section of the reflux condenser was closed. The parameters of the heatinsulating casing were chosen taking into account the known recommendations, in particular, the thickness of the thermal insulation made of glass fiber was 4 mm. To estimate the rate of displacement of the inert gas during the starting period, the amount of generated steam was calculated by calculation. For the analysis, the results of known studies and own experience were used. It was shown the expediency of forcing the heat load on the generator - the reduction of energy costs during the start-up period can be from 25 to 35%. Taking into account the calculation results, the original three-position control methods of AXA with the thermal load input to the generator "110 - 70 - 0" and "130 - 70 - 0" were proposed. It is shown that the method of controlling the AR with a constant two-stage supply of heat load and controlling the flow temperature at the outlet of the reflux condenser allows to reduce energy consumption by up to 20 %, in comparison with traditional position control. Despite the constant in time supply of heat load to the generator, the advantage was achieved due to: A) maintaining the elements of the generating set in the "warmed up" state, which makes it possible to minimize the transition time to the mode with the rated refrigerating capacity of the evaporator; B) maintaining the minimum refrigerating capacity of the evaporator in the "waiting" mode. The energy-saving effect of the new control method is largely related to the installation of the heat-insulating casing on the dephlegmator. This allows not only to use the minimum refrigerating capacity of the evaporator (at Q = 40 W), but also to switch to a lower level of rated thermal load (Q = 70 W) compared to the serial version (Q = 110 W). The duration of the working period for absorption refrigerators is related to the inertia of the startup processes, when all the energy input is spent only on the heating of the elements of the generator assembly. In this regard, measures aimed at maintaining energy-efficient operation modes of the generating set, despite the additional energy costs, provide advantages in energy saving. It is possible to achieve a sufficiently significant increase in the efficiency of the ACU operation, taking into account the peculiarities of their operation over a wide range of ambient air temperatures. One of the effective and low-budget methods for increasing the energy efficiency of ACU is the technology to reduce losses when transporting ammonia to the artificial cold zone (evaporator). A key role in this process is performed by the AR reflux condenser, which purifies ammonia vapor by removing the heat of a phase transition into the environment in the temperature range from 10 to 32°C. To reduce losses during the transportation of ammonia through the AR dephlegmator, it is necessary to install a thermal insulation that would efficiently purify ammonia vapor (at high ambient temperatures) within the working temperature range and promote its minimum condensation of ammonia (at low ambient temperatures). An original design of the mobile heat insulation of the dephlegmator transport zone is proposed, which regulates the air supply to the dephlegmator by moving the bellows walls filled with a low-boiling liquid.

29-33

Authors: N. A. Prusenkov

The systems of temperatures regulation on the surfaces of multi-layered enclosing structures (MES), providing the achievement of different and even opposite aims: а) maintenance of the predetermined temperature of MES internal surface, which is bounded by the normalization of losses at constant resistances to the heat transfer through the layers (closed); б) intensification of exchange by heat with space through MES surfaces, by the change of temperature of coolant-moderator during exploitation (movable) are well-known and used in the different processes. At the same time, the acting DBN recommends a replacement in calculating of heat transfer through the MOS for heat exchange in thermal envelope of buildings, that contradicts the postulates of the constancy and exclusivity of enclosed enclosure designs requiring the modernization of the regulatory and theoretical basis for their creation. The regulation of the characteristics of closed (a) and mobile (b) systems components, combined into a single evolutionary one based on the principles of superposition and distribution of their interaction results, ensures the manifestation of the exergic properties of the interaction of heat exchange and heat supplied during the transition, which are absent in systems for the interaction of which conditions are created. This ensures the formation of a new goal that is not achievable at a local operation of each of the interacting systems. The energy balance of the unification of these systems stimulates the evolution of the operational mode, creating an exergic system of closed and mobile flows interaction, achieving the goal of publication. The presented result proves the expediency of supplementing the current standards with instructions governing the elimination of energy release through the outer surfaces of enclosures.

39-44

Authors: K. Smirnova, А. Smirnov, O. Olshevska

The issue of critical importance objects safety, namely in the electric power engineering, is always acute both for the owners of enterprises and for the state. The article considers the features of providing information protection for the electric power engineering. The concept of organization of technological processes automated control systems information security is proposed. The concept touches upon both electric power enterprises and industrial enterprises as a whole.

49-52

Authors: Yu. Zhuravlov

The possibility of rational design of thermoelectric device in systems for providing thermal modes for radioelectronic equipment during operation in various climatic conditions is considered. The aim of the work was to find solutions that allow choosing a variant of thermoelectric device design at a changing temperature of the environment, which ensures a reduction in energy costs and an increase in reliability indicators. The calculations of the basic energy and reliability parameters of thermoelectric devices for various operating modes have been carried out. The influence of the ambient temperature is analyzed and it is shown that the heat load, operating current, power consumption and intensity of failures increase with temperature. The expediency of thermoelectric devices functioning in the mode of minimum failure rate is substantiated, which allows reducing the failure rate by 1.5 times in comparison with the maximum cooling capacity mode.