Refrigeration engineering and technology

4-11

Authors: O. Ostapenko; O. Yakovleva; M. Khmelniuk; O. Zimin

Design of modern high-efficient systems is a key priority for the Energy Sector of Ukraine. The cooling technological streams of gas and oil refineries, including air coolers, water cooling and refrigeration systems for specific refrigerants are the objectives of the present study. Improvement of the refrigeration unit with refrigerant separation into fractions is mandatory in order to increase cooling capacity, lowering the boiling point of coolant and increasing the coefficient of target hydrocarbons extraction from the associated gas flow. In this paper it is shown that cooling temperature plays significant role in low-temperature condensation process. Two operation modes for refrigeration unit were proposed: permanent, in which the concentration of the refrigerant mixture does not change and dynamic, in which the concentration of refrigerant mixtures depends on the ambient temperature. Based on the analysis of exergy losses the optimal concentration of refrigerant mixtures propane/ethane for both modes of operation of the refrigeration unit has been determined. On the basis of the conducted pinch-analysis the modification of refrigeration unit with refrigerant separation into fractions was developed. Additional recuperative heat exchangers for utilization heat were added to the scheme. Several important measures to increase the mass flow rate of refrigerant through the second section of the refrigeration centrifugal compressor from 22.5 to 25 kg/s without violating the agreed operational mode of the compressor sections were implemented.

20-26

Authors: L. I. Morosuk

The perspectives in the field of heat pumps and refrigeration systems are associated with implementing new working fluids as well as developing the schematics of the machines working on novel thermody-namic cycles. One of the promising approaches is the development of the cogeneration machines (for different industrial technological processes) with multi thermal effects. In this paper, the principles of the machines working on inverse thermodynamic cycles with four temperature levels (two high-temperature and two low-temperature) have been evaluated. The synthesis of the generalized schemat-ic and corresponding thermodynamic cycle for the mixtures of insoluble components as the working fluid has been carried out based on the “cycle method” of the thermodynamic analysis. The thermody-namic modeling is proposed using the principle of equivalent replacement of complex processes asso-ciated with the mixture by simple processes associated with the one-component working fluids. As an example, the machine with the mixture of R717 / R123 is analyzed.

35-46

Authors: A. Doroshenko; V. Kirillov; K. Lyudnitskij

The developed schematics for the solar refrigeration systems, based on the use of absorbing cycle and solar energy for the regeneration of absorbent solution are presented in the article. Cascade (two-stage) principle of construction of contours is used with growth of concentration of absorbent on the stages of cascade. The solar absorbing systems in the basic variants of cooling and air-conditioning are developed. Heat-mass-transfer apparatus of film-type, entering in the complement of contours compatible and executed on the basis of multichannel compositions from polymeric ma-terials. The features of film-type flows in the heat-mass-transfer apparatus of the basic solar systems are considered theoretically. Experimental research of processes of heat and mass transfer in the apparatuses of drying (absorber) and cooling (evaporated coolers of air and water of direct and in-direct types) contours of the solar system is executed. On the basis of findings on efficiency of pro-cesses the comparative analysis of the solar refrigeration and air-conditioning systems possibilities is carried out. Positive influence of growth of concentration of absorbent from the first to the second stage of cooling is shown. The preliminary comparative analysis of the solar refrigeration systems possibilities is proposed.

52-58

Authors: T. V. Diachenko; A. O. Kolesnik

The paper is devoted to research of different types of isolation which is applied in the production process of tanks for methane carriers. The calculations technique is developed and settlement re-searches of a daily evaporability and metal consumption for five types of isolation are conducted: the powder and vacuum; the screen and vacuum; the polyurethane foam; the glass foam and the aer-ogel. The analysis of results has shown that the aerogel is a perspective view of thermal isolation for use in cryogenic capacities for liquefied natural gas transportation.

67-79

Authors: Y. D. Kotukov; V. I. Levchenko; O. V. Rogankov; M. V. Shvets; V. B. Rogankov

There are two main obstacles to perform the objective comparison and choice of preferable variant within the set of ap-propriate textile materials (TM), related to the thin permeable media: 1) the different experimental methodologies and tools usable by different authors for an estimate of water-vapor-transmission rate; 2) the different ambient conditions of such measurements and a variety of experimental means proposed, at present, for an estimate of TM-porosity. Recently we have studied, in detail, the former factor [V.B. Rogankov et al, Refrigeration Engineering and Technology, 51(1), 2015, pp.47-54] and pointed out the possible strategy to overcome this obstacle. In this work we will pay the main atten-tion to the latter factor. The novel concept of mesoscopic (nano-) porosity of threads is formulated for any woven and non-woven TMS. The resulting alternate basic (AB-) model for theoretical estimate of effective (observable) porosity in hydrophilic and hydrophobic permeable media is developed. It is based, exclusively, on the standard (but the measuring-laboratory-condition’s-dependent) measurements of so-called square mass and thickness for the wide set of 41 samples taken from 5 different experimental works. The proposed treatment of such data leads to the simple, well-founded rela-tionships of AB-model without any adjustable coefficients. They provide a possibility to obtain the reliable estimates for the following fundamental TM-characteristics: density of moist and/or dry matrix; observable effective porosity at any level of ambient moisture; maximum hygroscopicity without the additional experiments.

88-91

Authors: V .V. Antoniuk; O. V. Drozd; M. O. Drozd; I. M. Nikolenko

А problem of the hidden faults without solving of which the fault tolerant structure of the digi-tal сотponents does not guarantee function safety of the safety­critical systems is considered. The problem is shown in the potentially hazardous circuit points, which in а normal mode сап accumulate the hidden faults reducing the fault tolerance of the digital component at transition to ап emergency mode of the system operation. А model of the activated path for pipeline circuit of the digital component is offered. It allows determining input data for calculation of point ob-servability in modes of the system. А method of potentially hazardous point identification for pipeline circuit of the digital component is developed.