Absorption Refrigeration Machine Research Articles

LPT (Local Public Transport) electric buses: innovative solutions to reduce the energy absorption of auxiliaries

The focus of the study is the analysis and sizing of the air conditioning system on board the vehicle which operates in thermal transient for the duration of the typical mission, using “fan coil” type air conditioning devices powered by a hot or cold heat vector fluid loaded into “electro-thermal” charging station and the related ground cogeneration plant (at the BUS terminus). For winter air conditioning, it was assumed that a heat transfer fluid at a temperature of 90 ° C could be stored on board. This value allows the use of water as a heat transfer fluid without pressurizing the systems, minimizing costs and supply problems, and is compatible with the characteristics of ICE cogeneration systems. For summer air conditioning, it was assumed that ice or fluid at a temperature of -20 ° C could be loaded. Also in this case it was decided to operate with a common fluid, such as a solution of water and salt (e.g. calcium chloride CaCl2). A comparative analysis of two solutions was carried out: the first involves the standard solution with BUS air conditioning system with heat pump powered by traction batteries charged by the grid and the second one analyzes the use of a high temperature Fuel Cell in a trigenerative configuration with refrigeration unit absorption fueled by the fumes of the FC. The trigeneration plant produces 100 kW of electricity via SOFC (Solid Oxide Fuel Cell) and, through an exchanger, water at 95 ° C which is stored on board the BUS for winter heating and feeds an absorption refrigeration machine that produces fluid at a temperature of -20 ° C for summer conditioning. For the two solutions, the savings of non-renewable primary energy and the reduction of GHG emissions compared to the standard solution (recharging the electric BUS from the network with on-board air conditioning powered by the traction batteries) are calculated through a WTW analysis. Consumption and emissions of electric powertrains, potentially for consumption and zero emissions, are closely linked to the methods of production and distribution of electricity.

Using absorption principles of water-ammonia mixture for energy supply of agricultural enterprises

The most promising developments in the field of energy supply for industrial enterprises are research in the field of alternative energy sources. As experience in the construction of the first geothermal power plants operating along the Kalina cycle shows, the efficiency of heat use increases sharply due to the utilization of the heat of low-potential energy sources. As such, energy sources use ground, in particular, geothermal water. In regions where there are enough geothermal sources, power plants based on the Kalina cycle can be used. The generated heat and electricity can be used for agro-industrial complexes. This is possible, as theoretical studies show, for enterprises in the field of crop production, animal husbandry and processing of agricultural products. In addition, the article describes the principles of using absorption refrigeration machines in agriculture.

Assessment of the effect of humidity of air-cooled in the absorption refrigeration machine on the operation of an energy gas turbine

Due to the fact that the construction of combined cycle plants has become the main trend in the development of the world heat power industry in the last two decades studies of the operating modes and operation of such equipment are very relevant at the moment. The aim of this work is to study the effect of chilled air in an absorption refrigeration machine on the operation of a stationary gas turbine installation. The operation of a gas turbine installation is affected by the temperature of the surrounding air due to changes in its density and humidity at different temperatures and because of the different useful work of the gas turbine. The standard adopted in the design of gas turbines is 15 °C. An increase in ambient temperature leads to a decrease in the generated power of the gas turbine. The influence of gas turbine power from ambient air can be reduced by means of cooling units for incoming air (absorption refrigeration machine (ARM)), or by modernizing the gas flow part of gas turbines and injecting water or carbon dioxide. This study is devoted to the influence of humidity of air entering the gas turbine compressor from the ARM, where it was previously cooled. It was noted that air humidity affects the efficiency of the ARM and therefore the useful power of gas turbines. The power of a gas turbine can be increased to 7-9 MW when using the ARM.

Bi-Level Optimization of the Energy Recovery System from Internal Combustion Engines of a Cruise Ship

In recent years, ship builders and owners have to face a great effort to develop new design and management methodologies that lead to a reduction in consumption and emissions during the operation of the fleet. In the present study, the optimization of an on-board energy system of a large cruise ship is performed, both in terms of energy and of the overall dimensions of the system, while respecting the environmental constraint. In the simulation, a variable number of identical Organic Rankine Cycle (ORC)/Stirling units is considered as an energy recovery system, bottoming the main internal combustion engines, possibly integrating with the installation of photovoltaic panels, solar thermal collectors, absorption refrigeration machines and thermal storages. The optimization takes into account the effective optimal management of the energy system, which is different according to the different design choices of the energy recovery system. Two typical cruises are considered (summer and winter). To reduce the computational effort for the solution of the problem, a bi-level strategy has been developed, which prescribes managing the binary choice variables expressing the existence or not of the components by means of an evolutionary algorithm, while all the remaining choice variables are obtained by a mixed-integer linear programming model of the system (MILP) algorithm. The entire procedure can be defined within the commercial software modeFRONTIER®.

Improvement to electricity generation systems by using a refrigeration machine and solar concentrator for air cooling

A process scheme of using the absorption refrigeration machine in electricity generation systems in case of application of air cooling system of the steam turbine electric generators has been developed. The proposed scheme increases thermal power plant efficiency by 0.1-0.2% according to preliminary estimates, primarily by reducing power consumption on pumps and fans drive, as well as by reducing temperature of cooling heat carrier in the period with high ambient temperatures. A feature of the proposed technology is the combination of the most efficient air-cooling scheme and the absorption plant cycle in a single power technology complex. In this refrigeration machine, the working fluid is a binary mixture, one of the components of which is called a refrigerant, and the other one is an absorbent, where the liquid absorbent can absorb the refrigerant vapor. For the first time it is proposed to use an absorption refrigerating machine as the cooling system element of steam turbine electric generators. Currently, there are advanced air-cooling systems using multi-jet cooling for turbo-generators with a capacity of 3 to 180 MW. Finally, it can be used to increase the unit capacity of power units on the thermal power plants that use air-cooled power generators.

ANALYSIS OF THE CLIMATIC FEATURES OF THE REGIONS OF THE PRIMARY APPLICATION OF THE SYSTEMS FOR PRODUCING WATER FROM THE ATMOSPHERIC AIR

The object of research is the thermal and humidity processes occurring during artificial cooling of atmospheric air to the dew point temperature in the evaporators of refrigeration machines of the compression and absorption type. This study solves the problem of finding energy efficient heat and humidity modes for cooling atmospheric air to the dew point temperature in regions with a shortage of water resources and high solar installations. It is shown that practically in all considered climatic zones with a shortage of water resources, the process of obtaining water from atmospheric air is most energetically expended in the winter period of the year, and the most energetically efficient - in the summer period. In the summer period of the year, the specific energy consumption is numerically comparable in the cooling temperature range from 5 °C to 15 °C. It is also shown that the application of the technology of night radiation will create a reserve of natural cold for additional cooling of condensers of refrigerating machines of various types during the entire period of operation. The area of practical use of the research results: compression and absorption refrigeration machines operating in systems for obtaining water from atmospheric air and taking into account seasonal changes in the thermal and humidity parameters of atmospheric air. An innovative technological product: energy-efficient systems for obtaining water from atmospheric air based on refrigeration machines of the compression and absorption type, which also work with the help of solar radiation. Scope of application of the innovative technological product: systems for supplying the population with drinking and process water, mainly in areas with a shortage of water resources.

ANALYSIS OF THE POSSIBILITY OF USING SECONDARY ENERGY RESOURCES IN FOOD INDUSTRY ENTERPRISES USING SPECIAL REFRIGERATION EQUIPMENT

Abstract. Aim. Due to the current priority given to energy conservation issues, a promising research avenue in the field of refrigeration consists in the developing of energy-saving systems based on heat-recovery absorption refrigerators. The aim of the work is to study the possibility of using a water-ammonia absorption refrigeration machine to increase the efficiency of food production facilities.Method. Based on an analysis of the initial enterprise data, the possible operating modes of the refrigeration machine were determined considering the various types of heating and cooling sources proposed in the task specification. The identification of the characteristics of single-stage and twostage absorption schemes confirmed the possibility of increasing the enterprise's efficiency through the use of secondary energy resources. Results. The choice of initial data for the design of a singlestage absorption water-ammonia refrigeration machine (AVXM) was justified on the basis of a preliminary analysis carried out to calculate the size of the degassing interval. The calculation was carried out using a ξ – i diagram for the ammonia water solution. Conclusion. Two prior conditions for the design of a high-performance absorption water-ammonia refrigeration machine were determined on the basis of an analysis of four conditions set by the customer. For operating conditions with a low degassing interval value, a scheme for an absorption water-ammonia refrigeration machine employing two-stage absorption is proposed.

Numerical study of a Solar Absorption Refrigeration Machine

In this paper, we present a numerical study of a single-stage absorption refrigeration machine, operating with a couple of water-ammonia fluids, equipped with a distillation column and associated with a solar heating system using solar collectors. The study has showed the benefit of using the distillation column which is manifested by: The decrease of the operating temperature, The improvement of the coefficient of performance, Surface reduction of the solar collectors, The improvement of the solar coefficient of performance. The solar study shows that the absorption refrigeration machine equipped with a distillation column is better suited to solar energy with significantly better performance compared to the simple absorption refrigeration machine.

Сопоставление эффективности термодинамических циклов абсорбционных бромисто-литиевых холодильных машин

The energy efficiency analysis of the actual thermodynamic cycles of lithium bromide-water absorption refrigeration machines with single- and multi-stage processes of absorption and generation and with associated mass flow is carried out. The temperature influence analysis of the heating and cooling sources on the heat coefficient is performed. Parameters of external sources that allow implementation of these thermodynamic cycles are determined. Meanwhile, for cycles with two-stage absorption and generation processes, a heating source with temperature (20 ÷ 24)°C lower in comparison with the basic single-stage cycle, and for a cycle with three-stage processes – lower by (27 ÷ 30)°C is required. It has been established that with the accepted parameters of external sources, the actual coefficient of performance is within the limits: for a single-stage, lithium bromide-water absorption refrigeration machine (LBWARM) it is 0.68 ÷ 0.74, for a two-stage LBWARM, it is 0.36 ÷ 0.39 and for a three-stage LBWARM, it is 0.24 ÷ 0.26.

COP enhancement and comparison of different absorption cooling systems

The absorption refrigeration machines represent a good alternative to compression refrigeration machines but the major problem of this type of refrigeration lies in the COP, which seems to be less efficient. Several researches are carried out to improve the performances of these machines such as the combination with the technology of the ejectors. In this work, we are interested in the three ammonia-water absorption cycles: Single effect absorption, Ejector-absorption and Combined ejector-flash tank absorption cycles. A gas-gas ejector would be installed between the generator and the condenser. We suppose that adding a flash tank between the condenser and the evaporator could help improve the entrainment ratio of the ejector. We used simulations in order to compare the performances of these three different cycles. The simulation results demonstrate that the combined ejector-flash tank absorption cycle performs better than others.

Thermo-physical properties of the nano-binary fluid (acetone–zinc bromide-ZnO) as a low temperature operating fluid for use in an absorption refrigeration machine

The current technical note is an expression for extending aspects of the previous work of Ajib and Karno [1] which related to the thermophysical properties of acetone / ZnBr2. The study covers the thermal conductivity of a solution which appears to be a promising fluid for operating vapour absorption refrigeration (VAR) systems from a low temperature source. It covers also an investigation of acetone / ZnBr2 – ZnO nanofluid including the preparation, stability, structure and properties, a zinc based nanoparticle being chosen in order to reduce chemical interactions. Furthermore, this study illustrates an extension of the log p, T diagram of the acetone zinc bromide up to 1.39 bar. The results show that the thermal conductivity drops with increasing salt concentration. With increasing nanoparticles, the density, viscosity and the thermal conductivity increase, as expected, but the heat capacity drops. Both theoretical and experimentally derived formulae for ZnO nano fluid conductivity from the literature are seen to produce good correspondence to the conductivity measured here, but in the case of the theoretical formula, the influence of particle morphology is seen to be significant. The results indicate that converting the acetone / ZnBr2 to a nanofluid provides a potential improvement of performance of this fluid in the vapour absorption refrigeration system, but that suspension stability is difficult to attain.

EXERGETIC ANALYSIS OF A SOLAR ABSORPTION MACHINE.

Absorption refrigeration machines need energy for their proper functioning. Much of this energy is lost due to energy dissipation by friction or during heat transfer under temperature difference. But thanks

EVALUATION OF THE PROSPECTS FOR PRELIMINARY COOLING OF NATURAL GAS ON MAIN PIPELINES BEFORE COMPRESSION THROUGH THE DISCHARGE OF EXHAUST HEAT OF GAS-TURBINE UNITS

For the transportation of natural gas through pipelines, gas pumping units (GPU) are installed at numerous compressor stations (CS), the energy carrier for which, in most cases, is transported natural gas. 0.5 ... 1.5 % of the volume of transported gas is consumed (burned) by the pumping unit drive. The situation with the replacement of existing equipment with modern equipment is associated with significant investments, on the one hand, and the uncertainty with the transit of Russian natural gas through gas transmission systems of Ukraine in the near future. More promising is the way to increase the efficiency of the GPU cycle through the use of circuits with preliminary cooling of the compressed gas. The aim of this research is studying the prospects for the application of technology for pre-cooling technological natural gas before compression in a gas pumping unit based on heat-using absorption refrigeration machines. To analyze the effect of pre-cooling of technological natural gas on the compressor stations of main gas pipelines, gas pumping units – GTK-10I were selected. The calculation of GPU power consumption and fuel gas consumption at various temperatures of the process gas at the inlet to the supercharger was performed. The calculation of the operating parameters of the gas pumping unit is performed and the energy and financial prospects of the technology for cooling the process gas before compression in the GPU CS are shown. For the current economic situation (July 2019) in the Ukrainian gas market, the daily decrease in operating costs in standard gas pipelines with a decrease in gas temperature before compression in the gas pumping unit by 20 K ranges from 1800 USD to 3360 USD. A scheme of a recycling plant based on absorption water-ammonia refrigeration machine (AWRM) is proposed, which in the range of initial data allows to reduce the temperature of technological natural gas before compression by 11 ... 13 ° C.

Analysis of Vapor Absorption Refrigeration Machine Performance with Different Configuration of Water Supply

Analysis of Vapor Absorption Refrigeration Machine Performance with Different Configuration of Water Supply

Study of the work and efficiency improvement of combined-cycle gas turbine plants

The purpose of the paper is to study and analyze the possibility of increasing the power output of a combined-cycle gas turbine (CCGT) unit during the period of positive ambient temperatures. The first task is to analyze the operation of a 110 MW combined-cycle power unit at various ambient temperatures and to obtain alterations in the main CCGT characteristics when the ambient temperature changes. The other task is to study the usage of an absorption refrigeration machine in a CCGT cycle to increase its energy efficiency. Calculations of the thermal scheme of a gas turbine were carried out using mathematical modeling, the steam turbine was calculated based on guidelines. The conducted studies allow to conclude that the use of an absorption refrigeration machine in the cycle of a combined-cycle plant can improve the efficiency of the unit, increasing profits from power generation, and reducing penalties for non-compliance with the load schedule.

Experimental study of thermodynamic efficiency of the absorption refrigeration machine and heat pump complex

Experimental study of thermodynamic efficiency of the absorption refrigeration machine and heat pump complex

Study of a Solar Absorption Refrigeration Machine in the Moroccan Climate

Abstract A study of a solar absorption refrigerating machine (water-ammonia) is led in the Moroccan climate, precisely in Rabat site with coordinates: latitude 34°02' North and longitude 06°48' West). A simulation program, written in FORTRAN, is performed to simulate the thermodynamic machine operations using real climate data of radiation and temperatures. The studied machine is equipped with a distillation column to purify the ammonia vapor exiting the boiler, which has a negative effect on the machine performances. The obtained results show that equipping the machine with a distillation column has a great effect in its thermodynamic performances by lowering the operating temperature of the hot source and increasing considerably the solar performance coefficient by (30%).

Modeling of the Use of Hydrocarbons in Absorption Refrigeration Machine

The present work considered the modeling of a refrigeration absorption machine with either air or water cooling at 25 and 35°C, respectively to test binary hydrocarbon mixtures as working fluids, namely n-propane and n-butane as refrigerants and n-heptane, n-octane, n-decane as absorbents.The calculations consisted of mass and heatbalancesover the main machine partsand also on the vapor-liquid phase equilibria using thermodynamics models like the NRTL and the UNIFAC for the activity coefficients predictions in the liquid phase and the viriel and Peng-Robinson equations of state for the fugacity coefficients in the vapor phase. Coefficients of performance (COP) values of of 0.632 and 0.6 were obtained for the mixtures n-C3H8/n- C10H24 and n-C4H10/n- C10H24, respectively.The results showed the great reliability of the NRTL model compared to the UNIFAC which was characterized by some limitations due to the approximations induced by the group contribution concept.Through this study one can measure how difficult is to choose the most appropriate model to calculate the enthalpies for the different involved streams.The systems achieving the best performances i.e. n-C3H8/n- C10H24 and n-C4H10/n- C10H24 are non toxic and can be regarded as competitors of Ammonia.

The mathematical modelling of the absorption refrigeration machines used in energy systems

The mathematical modelling of the absorption refrigeration machines used in energy systems

Heat and Mass Transfer of NH<sub>3</sub>-H<sub>2</sub>O Falling-Film Absorption on Horizontal Round Tube Banks

The absorption process has been confirmed as the most important process in absorption refrigeration machines in terms of improving their total efficiency. For this reason, absorber structures in general and heat and mass transfers in absorber in particular have attracted the interest of many researchers in this field. Commonly, the falling film absorber structure is the liquid mixture flows over tubes in a film mode. Mathematical model is developed for the falling film flowing on horizontal round tubes absorber derived from the mathematical model of the test volume element. The two-dimensional numerical simulation is written to solve partial differential equations predicting absorption efficiency. For evaluating the parameters which affect the coupled heat-mass transfer as NH₃-H₂O diluted solution flowing over horizontal round tubes absorb NH₃ vapor to become the higher concentration solution. The fields of velocity, temperature, concentration and thickness of the falling film solution varied by the input conditions of diluted solution and cooling water temperature flowing in the tube represented for a test volume element of the tube. The correlations which give the heat transfer coefficient and mass transfer coefficient in the absorption process in range of solution concentration ω = 28% ÷ 31%, solution mass flow rate per unit tube length Γ = 0.001 ÷ 0.015 kgm^-1s^-1, coolant temperature t_water = 28°C ÷ 38oC are set as two functions. The accuracy of numerical model and experiments are compared by the inlet, outlet the tube bundle of cooling water temperatures and absorber heat load. The absorber heat load deviation of the computing program Q_{a_cumpute and experimental result Q_{a_meas} is 4.3%. The absorber heat load deviation of simulation result Q_{a_sim} and experimental result Qa_meas} is 12.3%. The overall heat transfer coefficient k used for simulation result of absorber heat load was taken from the relationship of the heat transfer coefficient k = f(C; Г; T) = f(0.308; 0.008; 306.3) = 0.863 kWm<sup>-2</sup K^-1). The results were also evaluated with other similar studies by other authors. Based on these simulations, the theoretical studies were done for absorption refrigeration system in order to narrow the working area where the experiments later focused on. The results of this study will be the basis for subsequent application research of falling film absorbers.