Refrigeration Machine Research Articles

Ammonia–water absorption cycle on three-dimensional graphs – The Absorption 3D tool software

Designing of an absorption machine with ammonia–water solution as a working fluid requires the application of two-dimensional graphs showing properties of that solution. The most suitable graphs are h–ξ, s–ξ and lg p–−1/T. On the two-dimensional graph a set of isolines are presented according to third thermodynamical parameter which axis is hidden. Modern computer technology enables a dynamic creation of three-dimensional graphs. Interactive working mode strongly stimulates the user perception. Considering ammonia–water solution, three-dimensional graphs aid a comprehension study of the absorption machine properties.The computer software named Absorption 3D tool was developed and designed by the authors. The software enables a three-dimensional visualization of the processes on solution properties graphs. The purpose of the software is to support the educational process, and it is especially suitable for students and lecturers of refrigeration machine division. The software is very useful tool for engineers and scientific workers too. For educational and scientific purposes the software is available free of charge on the website scheduled.

Modelling the absorption refrigeration cycle using partially miscible working fluids by group contribution methods

The present study concerns the cycle performance modelling of a particular configuration of an absorption refrigeration machine based on phase separation as well as development of a strategy for computer aided design of absorbents. The model uses predictive methods based on the group contribution concept for the computation of the thermodynamic phase equilibria involved such as liquid–liquid and vapour–liquid as well as enthalpy–concentration diagrams. The proposed absorbents computer-aided design strategy is based on the exploration of a number of structural group combinations obtained from a selected set of functional groups, according to the chemistry laws. The model was tested on four different absorbent–refrigerant pairs reported in the literature, namely (benzyl ethyl amine–glycerol), (water–hexanoic acid), (water–2-hexanone) and (water–ethyl propionate) as well as on pairs where the absorbent compound is generated by the proposed absorbent design strategy and the refrigerant is water. The results show that quite good values of the coefficient of performance (COP) can be obtained, indicating that this cycle configuration is promising and energetically efficient, mainly due to hardware savings, i.e. absence of condenser. However, other working fluid combinations have to be tested using the proposed model.

Conventional thermodynamic and advanced exergetic analysis of a refrigeration machine using a Voorhees’ compression process

The Voorhees’ compression process is used in refrigeration as an alternative process to the two-stage vapor-compression refrigeration machines that are commercially available. This process is a combination of a compression process initially at constant total volume and then at near isentropic conditions. The compression process at constant total volume is realized with the help of injection of working fluid in the beginning of the compression process. Several factors (related to the simulation of the process and to stable operation) did not allow the wide use of this process (compressor) in the past. With today’s state of the art of compressors, automation systems and control systems, the idea of Voorhees became reality with screw and scroll compressors. However, all developments are based on data obtained from experimental research. All publications, where the concept of the Voorhees’ compression process is discussed, deal only with energetic analyses.For the first time, in addition to the detailed energetic analysis, and in order to show the limitations of the energetic analysis for such a complex process, a conventional and an advanced exergetic analysis are presented.

Cost-optimal design of an ice-storage cooling system using mixed-integer linear programming techniques under various electricity tariff schemes

The increasing costs of energy encourage the development of cost-efficient building cooling systems. Based on a thermal model of a commercial building and its cooling system, the cost-optimal design of a vapor compression system and an incorporated ice storage is determined. Special emphasis is placed on the refrigeration machine and its interaction with the thermal capacity of the building. The implementation as a mixed integer linear programming problem allows the evaluation of the optimal system operation for an entire year in approximately 50s on a desktop computer. Based on these results, the design of the optimal systems is determined for various electricity tariff schemes. Therefore, a model for variable electricity rates is introduced including costs for control reserve power. Compared to the cooling system without storage, the system including an optimally designed ice storage achieves lifetime cost reductions of approximately 8% by reducing the operational costs and the investment costs for the downsized refrigeration machine.

Performances Evaluation for a Reversed Quasi-Carnot Cycle (Refrigeration Machine) by Using the Direct Method from Finite Speed Thermodynamics

The Direct Method from Finite Speed Thermodynamics is used in order to Determine in a complete analytical format of the COP and consumed Power of a Reversed Cvasi-Carnot Cycle (Refrigeration Machine with vapor) taking into account internal irreversibility generate by: Finite Speed, Friction, Throttling and Internal Heat Loses.

Hourly performance prediction of ammonia–water solar absorption refrigeration

Abstract This paper deals with the hourly performance investigation of solar absorption refrigeration (SAR) system with evacuated tube collector and ammonia–water (NH 3 –H 2 O) solution. The SAR system is presented to simulate the system characteristic variations using hourly atmospheric air temperature and solar radiation data for Adana province in Turkey. The evaluation is performed for the maximum temperature occurrence day on July 29. First, the variations of various parameters, such as absorption refrigeration machine efficiency, condenser capacity and heat transfer rate in the generator and absorber during the day, are calculated for different cooling capacities and generator temperatures. Later, the minimum evacuated tube collector surface area is determined. According to the obtained results, the SAR system is considerably suitable for home/office-cooling purposes between the hours 09:00 and 16:00 in the southern region of Turkey such as Adana province. The most suitable performance of the absorption cooling system is calculated for the generator temperature values equal to or higher than 110 °C. The performance coefficient of the cooling (COP cooling ) varies in the range of 0.243–0.454 while that of the heating (COP heating ) changes from 1.243 to 1.454 during the day. Evacuated tube collector area for a 3.5 kW cooling load capacity is found to be 35.95 m 2 for the region at 16:00 whereas it is 19.85 m 2 at 12:00.

Willis H carrier

Willis H Carrier, the Father of Air Conditioning, placed the science of air conditioning on a firmscientific basis in the year 1911, in his paper ‘Rational Psychrometric Formulae’ — widely known also as the ‘Magna Carta of Psychrometrics’. This paper was presented at the annual meeting of American Society of Mechanical Engineers (ASME). The centenary of this historic event happens to be the past year 2011. Amongst his many achievements are his contributions to development of the Psychrometric Chart (which remains essentially the same as the chart presentedmore than a century ago), the Law of Constant Dew-Point Depression, Dew-Point Control and the invention of the Centrifugal Refrigeration Machine.

Study of New Absorption Refrigeration Cycle Operating with Partially Miscible Fluids Pairs

In the present work a new configuration of absorption refrigeration machine based on phase separation has been studied. The main objective is to investigate the performance of this machine, using a number of binary systems (refrigerant absorbent) showing a partial miscibility and having a low critical solution temperature. A computer code has been developed for the calculation of the coefficient of performance (COP) of the machine as well as to study the influence of the operating conditions on this parameter, testing a binary mixture made of methyl diethyl amine (MDEA) as refrigerant and water as absorbent. The obtained results confirm the feasibility of this new cycle which can be regarded as a good alternative to classical cycle with no phase separation. The use of the computer code can be extended to test different working fluids for this machine, for an optimisation of the COP.

A universal method for calculating characteristics to raise efficiency of refrigerating systems

In this work, the results of heat-engineering tests of refrigerating machines are compared with the results obtained by using a mathematical model. The verification is done in two ways: by using the experimentally derived characteristics of a water-cooling refrigerating machine and comparing them with the characteristics of the built and tested systems. The mathematical model is built by applying the principles elucidated in [3, 4]. The divergence of the experimental values from the calculated (theoretical) in all numerical studies made was not greater than 10%. Satisfactory convergence of the calculated and experimental data is corroborated both at the components level and at the systems level. The program package developed making use of this model helped solve a host of practical problems associated with building of energy-efficient refrigerating machines.

Development of thermal conductive consolidated activated carbon for adsorption refrigeration

A new type consolidated composite activated carbon (AC) was developed with a host matrix of expanded natural graphite treated with sulfuric acid (ENG-TSA). Samples with different density, different grain size of AC, and different proportion of AC were produced and thermo-physical properties were evaluated. Results show that the highest effective thermal conductivity and thermal diffusivity of consolidated composite AC were 34.2 W m −1 K −1 and 3.89 × 10 −5 m 2 s −1, which were 150 times and 72 times higher, respectively, than ordinary granular AC. The permeability of adsorbents ranged between 1.24 × 10 −14 and 7.81 × 10 −10 m 2 while the density ranged between 215 and 448 kg m −3. The adsorption performance for composite AC and granular AC were evaluated by fitting experimental data with the equilibrium Dubinin–Astakhov (D–A) equations. Results show that the addition of ENG-TSA can improve the performance of adsorption refrigeration machines by increasing the concentration swing.

ANALISIS EKSPERIMEN LAJU ALIRAN VOLUME AIR TERHADAP TEMPERATUR AIR PANAS PADA HEAT RECOVERY SISTEM AC JENIS WATER CHILLER

Refrigerant in refrigeration machines will absorb heat from a room space and released the heat to the environment. The heat balancing in the system is heat released from condenser equal with heat absorbed from room space added by the heat equivalent from compressor work. Based on this heat cycle, the writer try to conduct research on using this heat rejection from condenser to heating tap water, focusing on water flow rate increased from 0.5 liter/min to 2.5 liter/min. From experiment and analysis result obtained that the maximum heat water temperature which can be reached is 47.5°C in 0.5 liter/min, with the equipment specifications are 2 HP- split air conditioning and the tank volume is 75 liters. The additional result is heating water temperature is fallen when the water flow rate is increased.

Magnetic refrigeration at room temperature – from magnetocaloric materials to a prototype

Based on the magnetocaloric effect, magnetic refrigeration at room temperature has for the past decade been a promising, environmentally friendly new energy technology predicted to have a significantly higher efficiency than the present conventional methods. However, so far only a few prototype refrigeration machines have been presented worldwide and there are still many scientific and technological challenges to be overcome. We report here on the MagCool project, which spans all the way from basic materials studies to the construction of a prototype. Emphasis has been on ceramic magnetocaloric materials, their shaping and graded composition for technological use. Modelling the performance of a permanent magnet with optimum use of the flux and relatively low weight, and designing and constructing a prototype continuous magnetic refrigeration device have also been major tasks in the project.

A study of a bubble absorber using a plate heat exchanger with NH3–H2O, NH3–LiNO3 and NH3–NaSCN

There is a continuous research effort being carried out worldwide on the development of absorption cooling systems with the objective of increasing their performance, one important area is the search for more efficient heat exchangers and alternative working fluids that can improve the performance of NH 3 –H 2 O and H 2 O–LiBr that are commonly used in commercial absorption refrigeration machines. In this work the study of a plate heat exchangers used as bubble absorbers with NH 3 –LiNO 3 and NH 3 –NaSCN as alternative working fluids is carried out. A mathematical model was developed in order to analyze the absorption process in a bubble absorber with NH 3 –H 2 O, NH 3 –LiNO 3 and NH 3 –NaSCN as working fluids using a plate heat exchanger at refrigeration conditions and low generator temperatures. The results show that NH 3 –H 2 O and NH 3 –NaSCN working fluids obtained higher absorber thermal loads and absorbed vapor mass values than NH 3 –LiNO 3 , the lower values for the latter were caused mainly by the high solution viscosity that decreases the efficiency of the absorption process. On the other hand, NH 3 –LiNO 3 obtained the highest COP value from a single effect absorption refrigeration system simulation, however, NH 3 –NaSCN obtained a higher COP than NH 3 –H 2 O; therefore NH 3 –NaSCN seems to be a good working fluid to be tested in an absorption machine. ► A bubble absorber is simulated with NH 3 –H 2 O, NH 3 –LiNO 3 and NH 3 –NaSCN working fluids. ► The analysis is realized with a plate heat exchanger at different working conditions. ► The NH3–LiNO 3 obtains lower absorption performance than NH 3 –H 2 O and NH 3 –NaSCN. ► The NH 3 –LiNO 3 has problems in the absorption process, due to the high viscosity. ► The NH 3 –NaSCN obtains better performance in an absorption cycle than NH 3 –H 2 O.

Evaluation of a seasonal storage system of solar energy for house heating using different absorption couples

In this paper, an innovative concept is presented for a long-term energy storage system for house heating, using the absorption process. The solar energy is stored during summer through desorption and the heat is released during winter through absorption. The originality of this concept is to allow the solution to reach the crystallization point, which is usually avoided in the absorption refrigeration machines. The storage capacity and efficiency of seven absorption couples, CaCl 2/H 2O, Glycerin/H 2O, KOH/H 2O, LiBr/H 2O, LiCl/H 2O, NaOH/H 2O and H 2O/NH 3, as a function of the temperature of absorption, temperature of evaporation, temperature of the solution before absorption and the presence of crystals in the storage tank have been studied in this paper. The appearance of crystals increases the storage capacity. The storage capacity increases with the temperature of evaporation and the temperature of the solution before absorption but decreases with the temperature of absorption.

Theoretical study and design of a low-grade heat-driven pilot ejector refrigeration machine operating with butane and isobutane and intended for cooling of gas transported in a gas-main pipeline

This paper describes the construction and performance of a novel combined system intended for natural gas transportation and power production, and for cooling of gas transported in a gas-main pipeline. The proposed system includes a gas turbine compressor, a combined electrogenerating plant and an ejector refrigeration unit operating with a hydrocarbon refrigerant. The combined electrogenerating plant consists of a high-temperature steam–power cycle and a low-temperature hydrocarbon vapor power cycle, which together comprise a binary vapor system. The combined system is designed for the highest possible effectiveness of power generation and could find wide application in gas-transmission systems of gas-main pipelines. Application of the proposed system would enable year-round power generation and provide cooling of natural gas during periods of high ambient temperature operation. This paper presents the main results of a theoretical study and design performance specifications of a low-grade heat-driven pilot ejector refrigeration machine operating with butane and isobutane.

DESIGN AND OPTIMIZATION OF A PERMANENT MAGNET ROTATING MACHINE FOR POWER COOLING GENERATION

Magnetic refrigeration is an innovative, revolutionary, e-cient and environmentally friendly cooling technology which is on the threshold of commercialization. The essential components of magnetic refrigeration system are the magnetic fleld generator and the magnetocaloric material. The two main goals of this paper are to design and to optimize a permanent magnet magnetic refrigeration machine for power cooling generation, where an initial conflguration is studied and based on this study two other conflgurations are presented. Both electromagnetic and thermal studies are explored. The electromagnetic design part has been accomplished by using the flnite elements method and the thermal design part has been achieved using the flnite difierence method.

Application of a compact sorption generator to solar refrigeration: Case study of Dakar (Senegal)

The feasibility of applying a low cost plate heat exchanger solid sorption reactor to solar powered refrigeration is investigated by using a validated reactor model. The proposed system is targeted at ice-making in developing countries for food preservation. The adsorption refrigeration machine modelled employs the active carbon-ammonia working pair in both two-bed and four-bed regenerative systems. Driving heat is provided from standard flat plate and evacuated tube solar collectors. The capital cost of a one-off machine with four regenerative beds which could produce up to 1000 kg of ice per day in Dakar (Senegal) is estimated at €68,000.

Sustainable development of a solar adsorption cooling machine

PurposeThe purpose of this paper is to demonstrate the possibility of the use of a solar adsorption refrigeration machine, using the pair activated carbon/ammonia within the framework of sustainability and development of rural areas.Design/methodology/approachThe limited availability of electrical grid in rural areas of Morocco makes necessary the adoption of new methods in order to provide the needs of energy services, which represent an important factor affecting the quality of life. The studies that were undertaken in this current paper investigated the sensitivity of the COP as well as the production of the cold at various refrigeration machine temperatures.FindingsIt can be recognized that the feasibility of the machine with significant production of cold in the form of ice is between 3.33 and 4.14 kg/m2 for a solar flat plate collector; and between 7.16 and 9.94 kg/m2 for solar flat plate.Originality/valueThe paper presents a model of decision‐making support for selecting the optimal conditions for the use of a solar adsorption refrigeration machine. The model optimises the quantity of cold produced and the coefficient of performance (COP) of the machine and investigates the sensitivity of the COP to the characteristic temperatures of the cycle of the machine.

Multi-objective optimization of a cooling tower assisted vapor compression refrigeration system

A cooling tower assisted vapor compression refrigeration machine has been considered for optimization with multiple criteria. Two objective functions including the total exergy destruction of the system (as a thermodynamic criterion) and the total product cost of the system (as an economic criterion), have been considered simultaneously. A thermodynamic model based on energy and exergy analyses and an economic model according to the Total Revenue Requirement (TRR) method have been developed. Three optimized systems including a single-objective thermodynamic optimized, a single-objective economic optimized and a multi-objective optimized are obtained. In the case of multi-objective optimization, an example of decision-making process for selection of the final solution from the Pareto frontier has been presented. The exergetic and economic results obtained for three optimized systems have been compared and discussed. The results have shown that the multi-objective design more acceptably satisfies generalized engineering criteria than other two single-objective optimized designs.

Comparison between two different solution-pumping methods in absorption refrigeration machines

This paper presents a pumping method in absorp-tion refrigeration where a vapour-driven pump is to replace the electricity-driven pump. The vapour pump is driven by a fraction of the generator’s hot, high-pressure, vapour mixture. The refrigerator is thus exclusively heat-powered and rendered inde-pendent of the availability of electricity as the main energy source. The design and operation of the vapour pump is presented. The results obtained by a computer simulation program show a decrease in performance (COP), which is confirmed by the data obtained from a 1 kW cooling capacity refrigerator. Peak performances occur at higher generator tem-peratures when compared to a cycle using an elec-tricity-driven pump