Refrigeration engineering and technology

11-16

Authors: V. О. Bedrosov, M. G. Khmelniuk, O. Yu. Yakovleva

Nowadays energy efficiency improvement and global warming are issues of current interest because of the natural resources depletion and extreme climate change. Thus, the problem of formation of strict regulations regarding emissions into the air arises. This paper presents the study of cascade refrigeration system for re-condensing of associated petroleum gas during sea transportation for LPG carrier. The structural optimization has been performed. LPG gas carriers with 266 000 m3 ethane capacity require 15 MW cascade refrigeration system for re-condensing if the temperature in the coastal LPG storage is -70°C, and the temperature for transported Ethan is maintained at -75°C. For current storage conditions the required system cooling capacity is only 1,078 MW intended for the heat gain rejection from the environment during Ethane transportation. The replacement of ozone-depleting refrigerant R22 to alternative agents: R407C, R404A, R402A, R717, R290, R1270 was estimated. The results of analysis have shown that the proposed improvements can be used to optimize the LPG carrier cascade refrigeration system.

21-26

Authors: V. V. Gorin

The paper provides the works review that includes the results of theoretical and experimental studies of condensation inside horizontal tubes. The comparison of theoretical (semi-empirical) solutions and ex-perimental data is given.

37-43

Authors: D. I. Harasym, V. Y. Labay

In modern technologies, which are related to energy transformation, namely in air conditioning systems, important places are occupied by equipment and processes, the objective estimation of value of its energy perfection can be defined only on the basis of analysis of its exergy effectiveness. Innovation mathematical research model, created by the authors, of the implemented central straight flow air conditioning system for operating cleanrooms was used, which gave opportunity to make computer estimation of its energy effectiveness by the virtue of exergetic output-input ratio depending on different factors, which have influence on its work, in particular on parameters of outdoor air ( , ). The dependence of exergetic output-input ratio of implemented central straight flow air conditioning system with recuperative air cooler and air productivity that is 4300 kg/hr for operating cleanrooms on parameters of outdoor ( , ) air by different indoor parameters ( , ) and on temperature difference between indoor and supplied air was presented. This dependence showed that the exergetic output-input ratio of the system gains its maximum by lower temperatures of outdoor air. It was shown that for providing the microclimate in operating cleanrooms the implemented central air conditioning system, with the aim of energy saving, should be used by temperature of outdoor air ≤ 35°С and by higher (as much as possible) temperature difference between indoor and supplied air ≥ 6,0°С. This will give the opportunity to get a high exergetic output-input ratio ≥ 1,93, which means to get the most economical variant of exploitation of the implemented air conditioning system. It is worth to mention that moisture content of outdoor air has no influence on exergetic output-input ratio of this air conditioning system.

48-53

Authors: D. A. Ivchenko, V. P. Zhelezny, I. V. Motovoy, K. O. Shestopalov

New experimental data for isochoric heat capacity from the two-phase region of dimethyl ether for DME (dimethyl ether), TEG (triethylene glycol) and DME/TEG solutions at weight fractions of DME 20.8%, 74.7% in temperature range from 152 to 324 К have been reported in the paper. The mean uncertainty of the experimental data does not exceed 0.45%.

58-64

Authors: V. Matukhno, Yu. Baidak, P. Tomlein

Improving of the technical level of modern distribution transformers (DT) by reducing of their weight and dimen-sions, increasing of specific power are inevitably associated with the development of method which takes into ac-count the thermal processes and technical means of intensifying the existing and new systems of their cooling. Par-ticularly important rises the question of effective cooling of small and medium power distribution transformers, which constitute the bulk of the complete switchgear in power supply systems.The result of the study is the substan-tiation of expediency for simulation results implementation of heat balance equations drawn up for the active part of the voltage distribution transformer, at the stage of its final and qualifying design. The active part is located in the transformer oil environment, and heat emission is carried out by heat transfer and convection. The heat balance mathematical model corresponds to the equivalent thermal equivalent circuit, consisting of two adjacent units with heat sinks - generalized coils and ferromagnetic core and of the third node adjacent to them - moving matter from the oil, which additionally contact with the infinite heat capacity environment. The solution of equations obtained for the mean temperatures of the winding, magnetic conductor rod and oil in function of time, allows setting of their expected values during transformer operation and especially with the uneven schedule of its loading, and to exercise grounded choice of magnetic induction in the magnetic rod and the current density in the windings according to the parameters of allowable for them heating temperatures

75-79

Authors: N. V. Zhіkhareva, M. G. Khmelniuk

The mathematical model of unsteady heat exchange space has been carried out. The heat balance of the object system is modeled by the system of ordinary inhomogeneous differential equations with nonlinear coefficients. In the developed model the transient nature of heat transfer through the structures enclosing surfaces, the intensity of solar radiation on people, equipment and lighting are taken into consideration. The climatic equipment was selected according to performed calculations which will: provide the necessary microclimate parameters in air-conditioned areas in terms of maximum heat leakage in summer and maximum heat loss in winter and ensure high power efficiency with a small thermal load in the offseason. The results of mathematical simulation allowed to determine required cooling or heat capacity on average temperatures and corresponding power consumption of the system and supplement the correct set of input data for calculating the full costs of the object microclimate, including design, equipment purchase, installation and maintenance costs over the service life of the system and allowed to estimate the system payback.