Refrigeration engineering and technology

10-12

Authors: A.V. Zimin

In the paper the technical features of binary ice screw type generators design are considered. The basic element of this type machines is a pair heat-exchanger-screw. The heat exchanger may be deformed. Screw in the process wears out. During work with the oscillation loading at a subzero temperature there are problems that result in the decline of efficiency or machines breakage. Recommendations on planning of machines of this type are given. In addition, work of screw generator is considered in a pair with the accumulator of cold. Using of accumulator reduces capital and operational costs. A properly designed heat balance of such a system will make it possible to minimize internal losses of cold. The complete chart of setting of this type is presented. The machine operation modes are analyzed.

18-24

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

Exergetic method is a universal way of thermodynamic research of various processes of energy transformation in energy technological systems, to which air conditioning system for cleanroom belongs. Implementation of exergetic analysis for energy technological system makes it possible to determine the influence of various elements of its system on its work and because of this to increase the effectiveness of work of energy technological system in general. Effectiveness of work of any air conditioning system depends on energy effectiveness of refrigeration machine, which serves it and consumes electricity for reducing the heat of supply air which enters the room. And it means that the main purpose of selection of certain refrigeration machine for air conditioning system is to reach the maximum cooling capacity with minimum energy consumption. Innovation mathematical research model of the central straight flow air conditioning system for cleanroom in order to computer estimation of its energy effectiveness by virtue of exergetic output-input ratio depending on different factors, which have influence on its work, in particular the coefficient of transformation EER of its refrigeration machine was used in this article. The dependences of exergetic output-input ratio of chosen air conditioning system for cleanroom on coefficient of transformation EER of its refrigeration machine by different parameters of outdoor and indoor air and the temperature difference between the indoor and supply air were presented. It is shown, that the chosen air conditioning system should be preferably used by higher coefficient of transformation EER of its refrigeration machine and higher difference between temperatures of indoor and supply air by various temperatures of outdoor air, that will give the opportunity to gain the highest exergetic output-input ratio , which means to gain the most advantageous economical variant of exploitation of chosen air conditioning system.

32-37

Authors: A.N. Radchenko, О.V. Ostapenko

The efficiency of waste heat transformation from gas engines in the plant forintegratedenergysupply by lithium bromideabsorption refrigerating machine was analyzed. Such gas engines are equipped with heat exchangers for producing hot water from the engine recoverable heat. The waste heat from gas engine jacket and lubricant oil cooling water, scavenge gas-air mixture and exhaust gas are used to produce hot water with the temperature of about 90 °С as heating source for absorption chiller. The analysis was made for trigeneration plant on the base of cogeneration reciprocating gas engine modules JMS 420 GE Jenbacher (electrical power output of each cogeneration gas engine 1400 kW, thermalpower output 1500 kW). This trigeneration plant was designed for combined energy supply of the factory "Sandora"–"PepsiCо Ukraine" (Nikolaev, Ukraine). The trigeneration plant, equipped with two cogeneration JMS 420 GE Jenbachergas engine modules and a single-stage absorption chiller, has been designed and assembled by "Sinapse"–"GE Energy" (Kiev) and "Khladotechnika" (Nikolaev). The absorption chiller produces chilled water for technology process cooling and conditioning of engine room intake air. The significantheat losses were revealed caused by the cogeneration gas engine modules and the lithium bromideabsorption chiller temperature regime performance discrepancy. In its turn it was caused by the increased temperature of return water from the single-stage absorption chiller of about 75 °С to the parts of the gas engine to be cooled. But in respect of the condition of engine reliable maintenance at the appropriate thermal rate the temperature of the return cooled water entering the engine cogeneration system is limited to the design value not exceeding 70 °С. If it excess, a surplus heath of return water is rejected to the atmosphere by the cooling tower. Return of excess heat to a single-stage absorption chiller is impossible because of its temperature of 75…78 °С lowered rather design temperature of the supply hot water for a single-stage absorption chiller of 90…95 °С. Fall of temperature of the supply hot water to a single-stage absorption refrigerating machine would cause considerable dropping the efficiency of transforming a gas engine recoverable heat into a cold – decrease in coefficient of performance (COP) from nominal (design) value of about 0.7 to 0.5 and lower. The results of water temperature and flow measuring showed the heat losses of 30...40 % of the heat transformed by absorption chiller into a cold.There were proposed an improved two-stream system of return water flow to the cogeneration gas engine modules that reduces the heat losses compared with traditional one-stream variant. In the two-stream system the watermass flow through cogeneration gas engine modules and absorption chiller is increased up to about 150 % compared with the base variant and the return cooled waterflow from the absorption chiller is divided into two streams.With this the temperature of the supply hot water for the absorption chiller, leaving the cogeneration gas engine modules, and the temperature of return cooled water from the absorption chiller is lowered as compared with the base one-stream system. Oneofthereturn water stream – ofthesamemassflowasinthebasevariant but at the lowered temperature–iscooled down to the required temperature of 70 °С as in thebasevariantand directed to the gas engine nodes those need cooling. The other (addition) return water stream of the50 % massflowand of increased temperature higher than 70 °С is delivered directly to the gas engine exhaust gas recovering boiler (economizer) by-passing the gas engine cooling nodes. It was shown that the two-stream system of return water flow to the cogeneration gas engine modules increases cooling capacity by approximately 25 % compared with traditional one-stream variant due to reducing the heat losses during transformation of gas engine waste heat into a cold.

42-47

Authors: A.S. Boychuk

Equations for alternative refrigerant R134a viscosity and thermal conductivity calculation expressed in terms of independent variables, such as temperature and density are worked out. Equation coefficients are determined by the least square technique according to the experimental data. The equations describe viscosity at temperature ranging from 248 to 439 K at a pressure up to 6,0 MPa and thermal conductivity at temperature ranging from 248 to 533 K at a pressure up to 60,9 MPa. The composed equations accuracy is quite acceptable for the engineering calculations.

53-58

Authors: P.F. Stoianov

Heat pump installation are very efficient heating and cooling systems and can significantly reduce your energy costs. The technical and economic performance of a heat pump is closely related to the characteristics of the heat source. This paper presents an overview of different heat sources for heat pumps, recommendation for designing this systems. The heat source temperature and its constancy during a year depend very strongly on the type of heat source. The heat pump performance were analyzed using ground and air temperatures for Odessa. The results of research indicate of natural temperature distribution in ground. Areas of natural temperature distribution in ground demonstrate short and long-term fluctuations of temperatures. Short-term fluctuations are influenced by weather and they exist only up to 1 m below ground surface. Long-term fluctuations (known also as seasonal fluctuations) occur in the second area (up to 8 or 20 m depending on the ground type). In deep area for every particular ground type temperature stays constant and very slowly increases with depth according to geothermal gradient, which indicates thermal impact of Earth's inner core.

65-71

Authors: S.S. Surkov, A.N. Martynyuk

Along with the crucial growth of information-technologies the communicability of the society is rapidly developing. Multiple social networks is the brightest example of this fact. All automobiles manufacturers strive to provide embedded computers with access to the Internet, but some embedded computers does not have a built-in browser. To solve the problem of applications authorization protocol OAuth was created, the aim of which is to enter Web-browser accounting data. This paper describes the implementation of the OAuth realization solution for embedded computers that do not have browser support. All social networks such as Facebook, Twitter, Google+, Foursquare, Evernote, VK provide WEB REST API which allows to create native application easily for any platform which have internet access. The communication is going through Bluetooth. As access to internet is implemented via Bluetooth protocol there won’t be technical difficulties to use the app. This method could be implemented as for iOS (headunit is needed to be MFI certified) or for Android. This paper describes the solution of implementing OAuth for headunits which without browser support.