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The work developed a system of primary low-temperature processing and storage of small-seeded grain based on a combined compression-absorption water-ammonia refrigerating machine (AWRM). An AWRM absorber with two-phase thermosiphons and air heat removal to the environment has been developed. Two designs of grain air cooling systems have been proposed – container and floor type. The proposed energysaving algorithm for the operation of the cooling system with stage-by-stage blowing of each row of the container field with cold air makes it possible to minimize the total energy consumption in the cooling system to the maximum extent due to the contribution of the air exchange system. A combined compression-absorption water-ammonia refrigeration machine allows you to refuse to use network electrical sources for 7 months of the year. Such a refrigeration machine can be made in a transport autonomous design and solve the problem of air conditioning in field conditions. To adapt to field conditions, the AWRM absorber is made with twophase thermosiphons and air heat removal to the environment. Two basic designs of grain air cooling systems are proposed - container and floor type. Both systems can solve the problems of primary refrigeration processing of grain products, and the choice of any system depends on the specific conditions of the farm: volume of products, storage location, logistics. An algorithm has been developed for the gradual supply of cold air flow through rows of containers. To find the minimum total power consumption, the method of equalizing the rate of change in electrical power on the fan and compressor depending on the grain cooling time was used. It has been shown that in the process of low-temperature processing of small-seeded grain it is possible to simultaneously dehydrate it. Increasing the quality storage period of grain to 1 year allows the farm to gain economic benefits from the difference in purchase prices. The difference in purchase prices during the harvesting period and the sowing company, for example, for rapeseed last year was 240 US dollars for each ton. Calculation of economic indicators for the development of a typical farm, taking into account market prices for work, equipment and component materials, showed that the payback of the project will be 4.9 years for construction according to the «zero» cycle and 4.4 years for existing buildings. [ABSTRACT FROM AUTHOR]

Human global anthropogenic influence forces the developers of household refrigeration equipment to reconsider their attitude towards absorption refrigeration devices (ARD). The working body of ARD consists of natural components – water-ammonia solution (WAS) with the addition of inert gas (hydrogen, helium or their mixture) and is absolutely environmentally safe – it has zero values of ozone-depleting potential and the potential of the "greenhouse" effect. Absorption refrigeration devices have a number of such unique qualities, such as: silence, high reliability and long service life, absence of vibration, magnetic and electric fields during operation; the possibility of using several sources of energy in one device – both electric and alternative; the possibility of working with low-quality energy sources, in particular, electric energy, in the range of network voltage 160...240 V. At the same time, ARDs have higher energy consumption compared to similar compression models. In this work, an attempt is made to analyze the energy characteristics in a wide range of regime parameters using the thermodynamic parameters of real ARDs obtained by various researchers. The developed method of thermodynamic calculation of a typical absorption refrigeration device, which is based on the results of experimental studies of typical real models, allows variant calculations for a wide range of operating parameters. It is shown that a decrease in the average evaporation temperature leads to an increase in heat loads on the ARD elements, i.e. freezers always have large weight and size characteristics, compared to refrigerating chambers of medium cold. The limitation of the maximum boiling temperature in the ARD generator was found, which is determined by the corrosion resistance of the wall material. It has been shown that ARDs of tropical design with a working pressure of 30 bar in the system require high energy consumption, compared to similar models for a temperate climate. [ABSTRACT FROM AUTHOR]

An analysis of the current state of technology shows the prospects for the development of alternative electric heat energy sources for the operation of absorption refrigeration devices (ARDs). It is important in today's minds that the working body of the ARDs is a water-amonia mixture with the addition of inert gas (water, helium or their mixtures) to natural refrigerants and is also absolutely environmentally friendly (maybe zero the significance of the ozone potential and the potential of the “greenhouse” effect). Before achieving the ARDs, it is necessary to maintain minimal heat among the most common types of refrigeration equipment with low cooling capacity, which in many cases means their popularity among consumers. Of particular interest may be ARDs models that use alternative, non-electric thermal energy sources in their work. A series of experimental studies were carried out at the stationary centers of the ARDs. The object was monitored by the ARDs "Kiev" AC-35. The thermal energy supplied to the ARD generator was varied in the range of 50 W to 110 W at 10 W intervals. The lower range of thermal absorption of the generator indicates the effectiveness of the ARD in terms of starting the thermosyphon that is pumped. The upper boundary of the thermal zone of the generator is surrounded by increasing temperatures and the beginning of active corrosion processes. In order to find an algorithm for supplying combined thermal energy, an experimental study of the starting modes of the ARD from a non-operating mill was carried out. The duration of the start-up period in our investigations was punctuated by the entry into stationary mode of the ARD refrigeration chamber. The principle of stationary mode was determined due to the invariability of the temperature in the refrigerating chamber. It has been proven that in order to ensure the safety of the ARD cycle, it is sufficient to use a standard car electric battery with a 70 A·hours 12 V battery. [ABSTRACT FROM AUTHOR]

In the field of refrigeration technology, resource and energy saving can be solved through the use of renewable energy sources, in particular solar energy. Absorption water-ammonia refrigerating machines (AWRM) operating on solar energy were chosen as the object of analysis. The analysis of the mode characteristics of AWRM showed that the main problems that must be solved when using them in water production systems are as follows: first, to develop AWRM structures with air cooling of heat dissipating elements; secondly, to propose a cycle that could be implemented in conditions of tropical outdoor air temperatures at the temperature level of traditional water solar collectors (80-100 °C). An analysis of the current state of energy-saving development of absorption-type refrigerating machines was performed. It has been shown that AWRM can solve the tasks of artificial cooling in the temperature range from -30 °С (longterm low-temperature storage of products of animal and plant origin) to +5...7 °С (air conditioning) using solar thermal energy. At the same time, the tasks of eliminating the adverse man-made impact of the working fluid (aqueous ammonia solution) on the environment are solved. It is promising to use cold-accumulating materials, electronic automatic control systems, which ensure minimum energy consumption during changes in operating conditions (daily temperature fluctuations of solar energy and atmospheric air) to create energy-saving schemes of AWRM. Increasing the energy efficiency of external and internal processes of heat and mass exchange in the AWRM can be achieved due to, respectively, the use of heat pipes, two-phase thermosyphons, reduction of contact thermal resistance in the heat removal and supply zones, and optimization of the steam-gas mixture circulation processes in the elements of the steam-gas circuit. [ABSTRACT FROM AUTHOR]

The article presents the results of experimental and theoretical studies of combined household refrigeration appliances that combine the functions of cooling and heating. In the process of conducting experimental studies, the possibility of operation of these devices, which contain both chambers with low temperatures (CC and LTO), and elevated ones (thermal chamber) is shown. The most rational place for removing the waste heat of dephlegmation to ensure the temperature regimes of the heating chamber has been determined. A selection of TPTS was carried out to ensure effective thermal communication between the ARA dephlegmator and the thermal chamber. A porous compressed material based on copper was used to ensure effective thermal communication between the ARA dephlegmator and the TPTS. The dependence of the effective thermal conductivity of the porous material on the degree of compression was obtained experimentally. It is shown that at the maximum degree of compression (about 8) the numerical value of the effective thermal conductivity of 166.9 W/(m·K) is achieved. Testing of the thermal modes of the unloaded thermal chamber was performed in different modes of supplying the thermal load to the ARA generator. It is shown that the TPTS, thermally connected with the dephlegmator and the thermal chamber, successfully works in the mode of thermostating the thermal chamber. The heating rate of the investigated thermal chamber was determined. In the conditions of the experiment, the daily energy consumption was determined to be 1.43 kWh, which is 6.9% less than that of a conventional refrigerator. A new energy-saving method of operation of the ARA thermosyphon generator is proposed. For partial compensation of heat losses from the lifting part, it is proposed to install an additional two-phase thermosyphon. It has been proven that this method of operation can be easily implemented and allows to save up to 7...8% of the supplied heat load. [ABSTRACT FROM AUTHOR]

The expediency of using gas caps to prevent emergency situations caused by waves of increased pressure that occur in the pipeline when the pumping rate in main oil pipelines changes is investigated. It was determined that the most effective application of gas caps is the protection of short pipelines, while pressure wave smoothing systems should be installed on main pipelines. An analysis of systems with damping devices in the form of gas accumulators was carried out to find out the effectiveness of their use as a means of protecting the pipeline from emergency situations. The positive aspects of the use of gas caps are identified, which include the absence of additional devices necessary for the return injection of liquid from the gas cap to the main pipeline after a water hummer. With a sufficient volume of the gas cavity, the gas cap, as well as the safety valve, although to a lesser extent, is able to reduce the amplitude of the hydraulic shock wave, but its main effect is worsened in another way. The gas cap reduces the rate of increase in pressure in the pipeline and thus worsens the shutdown of the pumps pumping liquid into the pipeline, in other words, prevents a possible accident. However, there is currently no fully developed gas cap device ready for use at oil pumping stations. With a sufficient volume of the gas cavity, the gas cap, as well as the safety valve, although to a lesser extent, is able to reduce the amplitude of the hydraulic shock wave, but its main effect is worsened in another way. To ensure the maximum efficiency of the research results, similarity criteria were defined, which allow to present the obtained results as a criterion functional dependence. This approach allows, with a limited number of experiments, to estimate the further course of the process and the behavior of the system under study with various combinations of dimensionless parameters. A calculated example of the use of the obtained results is given, which demonstrates the choice of the volume of the gas cavity of the cap for the protection of the oil pipeline. [ABSTRACT FROM AUTHOR]

One of the ways to increase energy efficiency in refrigeration is to intensify the processes of convective heat transfer on the outer surfaces of the heat-dissipating elements of a refrigeration machine or unit. The maximum effect of the intensification of the processes of external convective heat transfer takes place in the absorption refrigeration unit (ARU). In the absorber, the supercooling of the water-ammonia solution, increased cleaning and lowering the temperature of the vapor-gas mixture entering the ARU evaporator is carried out, and in the condenser, liquid ammonia is supercooled at the inlet to the ARU evaporator. The intensification of convective heat transfer was carried out by installing a removable casing on the rear wall of the refrigerator. The casing allows you to organize a warm air vertical column and increase the speed of the air flow in the area where the heat-dissipating elements of the ARU are located. Taking into account the complexity of mathematical modeling of natural convection processes on ARU elements, experimental studies were carried out. The object of experimental research was the absorption refrigeration device "Crystal" produced by the Vasil’kovsky Refrigerator Plant. The refrigerating appliance contains a low-temperature compartment (LTC) with a volume of 11 dm3 and a refrigerating chamber (RC) with a volume of 144 dm3 . In the process of experimental studies, a decrease in the daily energy consumption of ARU was recorded by 7,6 % (casing width 150 mm) and by 21 % (casing width 170 mm). The results of the experimental studies of intensifying methods made it possible to develop new designs of a combined household appliance – an absorption refrigeration appliance with a heating chamber. The heat load was supplied from the reflux condenser to the heating chamber using a two-phase thermosyphon. Tests have shown that in the mode of compensation of heat losses of the heating chamber to the environment, the daily energy consumption of ARU for 6 hours and 12 hours of operation was 1.536 kWh and 1.564 kWh, respectively, i.e. did not exceed 1.65 kWh according to the regulatory document. [ABSTRACT FROM AUTHOR]

Copyright of Refrigeration Engineering & Technology is the property of Odesa National University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

One of the most important tasks is to further develop technologies that allow you to extract water from the air, and directly where it is needed. The most promising methods are related to the operation of autonomous artificial cold generators, which are guaranteed to provide the cooling temperature of air below the dewpoint – units for obtaining water from atmospheric air based on absorption ammonia thermal transformers (ATT), operating from low potential heat – solar energy. Taking into account the analysis of known technical solutions, the following schemes of life support systems of a residential building are proposed, on the examples of climatic conditions of Odessa region with the use of traditional and renewable energy sources. The basic scheme which is the improved technical offer of universal system of heating, cooling (conditioning) and reception of water from atmospheric air on the basis of traditional and renewable energy sources (solar collectors) is offered. To solve the problem of obtaining cold, the original design of ATT with a booster compressor after the generator was proposed, which is protected by patent documents of Ukraine. The inclusion of a booster compressor in the circuit allows to significantly expand the operating characteristics in terms of the temperature level of the heating source. So, for example, it is necessary in schemes with solar collectors with water as the heat carrier where temperature does not exceed 100 °C. It is proved that for the conditions of evaporator operation at a temperature of 5 °С the reduction of electric power in ATT systems with a booster compressor, in comparison with steam compression analogues, is 3,3 times in operation in temperate climates and 2,4 times in tropical climates. As a result of the calculation, an energy-efficient mode for the booster compressor was determined in the practical range of operating parameters of systems with solar collectors. For systems in operation in temperate climates it is: boiling point in the generator of 1,0 MPa and temperature of 80 °C. An autonomous refrigeration unit based on a pump-free absorption refrigeration unit is also proposed. The analysis of climatic conditions of the Odessa region was performed. The northernmost city – Podolsk, the city in the middle of the region – Odessa, and the city in the south – Ismail were taken into account. The analysis of the average temperature for the places revealed the best months for the formation of condensate: April-October. It was found that the city of Ismail is the most favorable for the formation of condensate and water from the atmosphere, due to the southern coordinates of the region. [ABSTRACT FROM AUTHOR]

To work with low-potential sources of thermal energy, an algorithm for calculating the cycles of absorption water-ammonia refrigeration units (WARU) of periodic operation (PO) has been developed. The advantages of batch-type absorption refrigeration units are the simplicity of design and the possibility of using any heat and fuel as a heating source. When calculating, it is important to understand that a feature of these machines is the non-stationarity of processes. The thermodynamic calculation of the WARU PO cycle was carried out for the range of operating parameters: a) the temperature of the heating source (on the generator wall) – 65...95 °C; b) «cold» source temperature (atmospheric air temperature) – 25...45 °C. The working fluid is a water-ammonia solution (WAS). In the calculations, the maximum operating temperature in the cooling zone is 10 °C. Calculated dependences were obtained: a) maximum and minimum composition (according to WAS); b) the maximum composition in the absorber-evaporator zone; c) dependences of the maximum pressure in the system. It is shown that with an increase in the temperature of the heating source, the proportion of ammonia in the zone of the generator-absorber decreases, which makes it possible to obtain a higher potential of the absorption process during the cooling period, i.e., it is possible to increase the cooling capacity of WARU PO and the capacity for extracting water from atmospheric air. Thus, with an increase in the temperature of the heating source from 65 °С to 95 °С, the minimum temperature in the cooling zone decreases +7 °С to -17 °С. With an increase in the temperature of atmospheric air, the cooling capacity of WARU PO decreases, and this trend is especially noticeable at high proportions of ammonia in the generation zone. The assessment of the cooling capacity of WARU PO showed that it increases with increasing temperatures of the heating source, and at lower values of atmospheric air temperature this trend is more pronounced; at low ambient air temperatures, it is possible to obtain the maximum cooling capacity of WARU PO by increasing the amount of ammonia in the generation zone. A design scheme for WARU PO for operation as part of a system for obtaining water from atmospheric air is proposed. The unit is a system of two channels. To intensify the process of convective and radiant heat exchange, the surfaces of the working areas are equipped with flat ribs: two horizontal and one vertical rib are installed on the generatorabsorber, and two vertical ribs on the absorber-evaporator. In order to increase the frequency of work, it was proposed to install a protective screen made in such a way as to completely cover the generatorabsorber from solar radiation during the discharge period. To intensify the process of condensation of water from the air, a fan is installed, which together with the screen is powered by an installed thermoelectric battery. [ABSTRACT FROM AUTHOR]

For the transportation of natural gas by main pipelines at compressor stations (CS) gas pumping units (GPU) are installed, the energy carrier for which, in most cases, is the transported natural gas. 0.5 ... 1.5% of the transported gas is consumed (burned) on the GPU drive. For the current economic situation in the gas market of Ukraine, the daily reduction of operating costs in typical main gas pipelines with a decrease in gas temperature before compression in the GPU by 20 K is from 1800 to 3360 $. One of the promising ways to reduce operating losses in the main gas pipelines is the pre-cooling of compressed gas using heat-using absorption refrigeration machines (ARM), which utilize the waste heat of spent combustion products of gas pumping units. According to the developed algorithm, the supercharger was calculated for different natural gas temperatures before compression. It is shown that the use of a typical main gas pipeline for artificial cooling of the gas flow before suction will save fuel gas consumption of 79 kg/h. Thermodynamic calculation of ARM cycles of different types is performed. It is shown that despite the higher thermal coefficient in lithium bromide ARM (0.808), it is necessary to choose ammonia ARM with a thermal coefficient of 0.477, because only ammonia ARM can provide an acceptable level of cooling temperatures (258 K) of natural gas before compression. with a cooling temperature not exceeding 280 K. The design (thermal) calculation of the heat exchanger-cooler (HEC) of natural gas before compression in the supercharger is performed. The design of the heat exchanger with the coaxial arrangement of the fins on the gas flow side is calculated. The material of the ribs is aluminum. [ABSTRACT FROM AUTHOR]

Experimental studies of combined refrigeration units of absorption type (ARU) with an additional heating chamber (AHC), which provides heat and refrigeration treatment of food in the home. A two-phase evaporative thermosyphon (TPTS) is used to provide thermal communication between the heat dissipating elements of ARA (reflux condenser). It is shown that the thermal power allocated in the process of ARU tests with TPTS, fixed on the lifting line of the reflux condenser, did not exceed 7 W, and on average was 4 ... 5 W; the magnitude of the heat flux dissipated from the ARU reflux condenser by TPTS is sufficient only to maintain the temperature in the AHC at 50 °C; to maintain the DNA temperature of 70 °C and 100 °C requires additional energy consumption; the value of additional energy consumption for 70 °C is 3.5 W, and for 100 °C - 8.7 W, while the daily energy consumption of the refrigerator will increase by 4.9% and 12.3%, respectively; with full use of the heat of reflux for heating AHC, it is possible to ensure its thermal regimes in the temperature range of 50 ... 100 °C; in the case of using AHC as the working medium, there are problems with heat transfer from the TPTS condenser to the internal volume of the chamber - in this case it is necessary to maintain the temperature difference between the heating panel and air in DNA about 25 ... 35 °C and the panel size should be not less than 0.200 × 0.285 m; in the case of using water as a working medium for AHC, it is advisable to use heating panels 0.2 m high, 0.02 ... 0.03 m wide, and to intensify heat transfer processes when heating water, the heating panel must be located at the bottom of the AHC; in the case of using air in AHC, its cooling due to heat loss to the ambient air is 32 times faster than when using water at an initial temperature of 50 °C and 11 times faster at an initial temperature of 70 °C. [ABSTRACT FROM AUTHOR]

The problem of optimization of heating of oil products at drain from railway tanks at use of microwave heating is considered. It is established that microwave heating can greatly simplify the technological scheme, eliminating all processes and devices associated with the preparation of the coolant. It is determined that currently existing patents and technical solutions proposed for the use of microwave heating for heating petroleum products, suggest that microwave energy falls on the free surface of the liquid. It is claimed that the disadvantage of such schemes is the significant unevenness of heating due to the fact that the microwave energy is quickly extinguished when moving into the tank. It is noted that when heated from the surface of the liquid in the tank, the distance from the source to the drain hole is quite large, making it impossible to effectively use microwave heating. A solution to this problem is proposed, which consists in installing a microwave device inside a hollow tube, which is directly connected to the upper hatch in preparation for pumping and immersed in oil to a depth that correlates with the depth of penetration of the microwave field in a particular product. The depth of penetration of microwave energy into the investigated oil product – fuel oil is estimated, on the basis of which it is recommended to establish the distance from the radiator to the drain hole. It is argued that the simulation of microwave heating should be carried out on the basis of the differential equation of thermal conductivity, taking into account internal heat sources. A mathematical model is presented that describes the heating of the volume of highly viscous petroleum products as a process of thermal conductivity in an unlimited array under the action of microwave radiation. On the example of fuel oil, calculations were performed using the finite difference method, which showed the temperature distribution in the array at different points in time. [ABSTRACT FROM AUTHOR]

Based on the original method of calculating the thermodynamic parameters of the generator of the absorption refrigeration unit (ARU), the analysis of its operating parameters is performed taking into account the results of experimental studies of typical production analogues. The results of the theoretical study allowed us to draw the following conclusions. First, in contrast to pure substances, when operating the generator on binary mixtures, in particular, on watert-ammonia solution (WAS), the supply coefficients of the generator depend on the magnitude of the applied heat load. Thus, when increasing the heat load from 40 to 80 W, the numerical values of the supply factors are reduced by about 3 times. Second, the dependence of the specific amount of supplied heat has an optimum (minimum) in the range of heat loads from 40 to 80 W and endboiling temperatures from 145 to 170 °C. The main significant result of the calculated research can be considered the found criticality of energy efficiency and temperature of the end of vaporization (boiling) of WAS in the generator. It is shown that the operation of a typical ARU with air cooling of heat-dissipating elements at an ambient temperature of 25 °C is most effective in the temperature range of the end of boiling from 147 to 155 °C. The decrease and increase of this temperature outside the optimal range leads to an increase in the specific energy consumption during the operation of ARU, up to 9%, and in the first case it is due to unreasonably high heating of the liquid phase, and in the second – with increasing absorbent (water) in steam mixture. It is also shown that the presence of a minimum of energy consumption during the operation of the ARU generator is explained by the fact that in the studied range of mode parameters of the thermosyphon (temperature at the generator inlet from 87 to 112 °C, at the outlet from 145 to 170 °C, system pressure 9 bar, mass fraction of ammonia in WAS 0,34) the optimal ratio of the composition of the liquid and vapor phases at the output of the generator. A detailed study of the physical nature of this effect should be carried out on the basis of joint modeling of thermal and hydraulic characteristics of generators. [ABSTRACT FROM AUTHOR]

It is shown that one of the known directions of partial elimination of water deficit can be systems for obtaining water from atmospheric air, in which refrigerating machines or units provide a temperature below the dew point temperature. When choosing the types of refrigeration machines or units for these systems, the use of solar energy may be promising, in particular, solar collectors, which are widely used in the world for heating in the cold and transitional periods of the year, as well as for household and sanitary and hygienic needs. Here, absorption ammonia-water systems have great prospects, which, in contrast to lithium bromide analogs, have the ability to work with air-cooled heat dissipating elements. At the same time, the use of ammonia-water absorption refrigeration systems in systems for obtaining water from the atmosphere is difficult due to the insufficient temperature level of the solar energy source. The object of research is a modernized absorption refrigeration unit (ARU), in which additional purification of a weak ammonia-water solution (AWS) is carried out by evaporating part of the ammonia into a vapor-gas mixture. A calculation method has been developed for determining the specific thermal loads on structural elements for given parameters of the working fluid at characteristic points (input-output of elements) with the subsequent determination of the energy efficiency of the refrigerating cycle of the ARU. It has been shown that the composition of the inert gas does not affect cycle efficiency. Replacing hydrogen with helium leads only to a 2-fold increase in the amount of circulating gas, which complicates the operation of the natural circulation circuit between the absorber and the evaporators of ammonia and solution. ARU has the maximum efficiency, operating in the cooling temperature range - from -18 to +12 °С, while the temperature of the end of evaporation has a decisive influence on the energy efficiency. The results of the energy analysis of ARU made it possible to formulate a number of recommendations for developers. It is noted that the initial data necessary for calculating the evaporator of the solution can be obtained as a result of modeling the processes of heat and mass transfer in the approximation of the adiabaticity of the processes. [ABSTRACT FROM AUTHOR]

Copyright of Refrigeration Engineering & Technology is the property of Odesa National University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An important feature of the work of heat exchangers with boiling fluid is the possibility of high-frequency pressure ripples (thermoacoustic phenomena) occurring in the cooling channels. The conditions of occurrence of thermoacoustic phenomena in channels of cooling system of heat-loaded devices are analyzed. Compared to boiling with saturated flow, boiling with supercooling has a higher heat transfer efficiency and better heat transfer characteristics. Due to the high heat fluxes, the surface of the fluid cools up on the cooling surface and at large undercurrents of the liquid flow core to the saturation temperature. It is determined that under such conditions high frequency pulsations of acoustic pressure may occur. It is established that the occurrence of thermoacoustic oscillations can lead to the formation of a standing wave in the channel. Fluid bubbles, which are distributed over the surface of the tube, can be considered as harmonic oscillators. A mathematical model describing the generation of thermoacoustic oscillations in a cooling channel is presented. The assumptions of the mathematical model are the one-dimensional motion of the coolant and the sinusoidal law of change of the volume of steam bubbles. It is believed that high-amplitude oscillations result from the resonance observed when the frequency of the forced oscillations of the vapor bubbles with the natural oscillation frequency of the vapor column or their harmonics coincides. A methodic for calculating the amplitude of thermoacoustic pressure fluctuations depending on the heat flux density is developed. Conducting a computational experiment showed that it is impossible to determine the value of the amplitude of oscillations in the resonant region without taking into account dissipative phenomena. The presented method is proposed for use in the design of liquid cooling systems of heat-loaded devices, for which cooling modes assume significant undercooling of the coolant to the saturation temperature and in the event of surface boiling. [ABSTRACT FROM AUTHOR]

Transport refrigeration devices are an essential part of the continuous refrigeration chain and are irreplaceable for tourists, hunters and expedition workers. Modern compression and thermoelectric analogues of transport absorption refrigeration devices operate from electric power generators or from rechargeable batteries, which leads to an increase in the weight of the vehicle and, ultimately, to additional fuel costs. The relevance of the transport absorption refrigeration devices research is primarily associated with the possibility of their work with non-electric sources of thermal energy – burner devices. In the burner device 100% of the fossil fuels combustion energy is directly converted to thermal energy. At the same time the efficiency factor of modern electric energy generators does not exceed 20%. Nevertheless, for the widespread use of transport absorption refrigeration devices, it is necessary to take measures to reduce energy consumption, which will favorably affect the weight parameters of the vehicle. Due to the complexity of theoretical models constructing, the experimental method was chosen as the main research method for transport absorption refrigeration devices. The object of experimental research was the transport absorption refrigeration device "Kiev" produced by the Vasilkovsky refrigerator plant. In the burner device, due to the special ceramic catalyst element installation, gas is oxidized with atmospheric oxygen on the catalyst surface. The burner device’s design allows creating a highquality air-gas mixture and evenly distributing the flame over the catalyst entire surface. Experimental studies have shown that: a) when working with ethyl alcohol and kerosene, the necessary cooling conditions are achieved in the refrigerator; b) under equal operating conditions, the absence of a turbulizer of the combustion products flow in the generator’s ventilation channel does not allow to provide the required cooling modes. To intensify the cooling modes of the refrigerator’s heat-dissipating elements (absorber and condenser), a series of experiments were carried out with blowing using an air fan. At low ambient temperatures (16-21 ºС), the effect of external cooling is practically imperceptible – the temperatures drop in the refrigeration chamber is 0,8-1,2 ºС, at temperatures 22-26 ºС the effect reaches 2,6 ºС, and at 30-33 ºС – 5,3 ºС. [ABSTRACT FROM AUTHOR]

One of the energy saving trends in the household refrigeration equipment is associated with the intensification of convective heat transfer processes on the outer surfaces of refrigerator’s heat-dissipating elements. One of the examples is installation of an exhaust hood. The complexity of household refrigeration devices modern designs does not allow to reliably evaluate the air flow parameters in the heat dissipation zones. The most acceptable in this case is the experimental research method. The absorption refrigerator "Crystall-404-1" ASH- 155 was the object of research. This refrigerator contains a low-temperature chamber with volume of 11 dm3 and a refrigeration chamber with volume of 144 dm3. A removable exhaust hood was installed on the refrigerator’s back wall so it completely covered its surface. The width of the air channel was: 100, 150 and 170 m. During experimental studies temperatures at characteristic points of the refrigerator’s elements and refrigerated chambers, as well as ambient air temperature were measured. Moreover, the air flow rate was measured. Air velocity was recorded only in the condenser zone. The maximum flow rate was detected at the initial section of the condenser – 0,50 m/s. In the middle part of the condenser the air velocity varied from 0,38 m/s to 0,28 m/s. The experience of experimental studies made it possible to develop a new design of a combined household device – an absorption refrigeration device with a heat chamber (HC). Pilot models of absorption refrigerators with heat chambers of both the air-type and in the liquid containers form were developed. To ensure the thermal connection of the deflegmator’s lifting section with the HC, a thermosiphon 1,2 m long and 10×1 mm in diameter was used. Conducted experimental studies showed: a) exhaust hood installation in order to intensify convective heat transfer processes on the outer surfaces of the absorption refrigeration devices’ heat-dissipating elements allows reducing the daily energy consumption, while the temperatures in the refrigerated chambers are practically unchanged; b) temperature potential of the air flow in the exhaust hood upper part allows expanding the functionality of absorption refrigeration devices. For example, to provide an additional HC for heat treatment of food products, raw materials and semi-finished products in daily life. [ABSTRACT FROM AUTHOR]