[en] The thermodynamics of a sorption refrigeration cycle has been discussed representing the cycle on a clapeyron digram. The minimum generation temperature required has been determined using the 'd-a' equation which represents the sorption equilibrium of the pair, and Gibbs free energy relation. The mathematical relation developed provides a totally new basis for determination of suitability of a particular refrigerant. (author)

[en] This paper presents an energy and exergy analysis of a domestic refrigeration system using R1234yf as a drop-in replacement for R134a. We base our analysis on a series of independent tests using two refrigerants, namely R1234yf and R134a. The test equipment consists of a fully instrumented domestic refrigeration system. A computational model is developed to work out the thermodynamic parameters such as coefficient of performance, exergy destruction ratio, exergy-based rational efficiency, component efficiency defect as well as the dimensionless exergy balance for both refrigerants. The parameters varied in the analysis were the evaporator and condenser temperatures as well as the amount of refrigerant used in the system. The results indicate that irreversibilities are mainly concentrated in the compressor, this is the case both for R1234yf and R134a. This exergy analysis proposed for evaluation of refrigerants in domestic refrigerators permitted to determine that R1234yf may not be a likely alternative to R134a. - Highlights: • An energy and exergy study of R1234yf as a drop-in replacement for R134a is presented. • A domestic refrigerator was fully instrumented. • The analysis takes into account the variation of charge of R1234yf compared with R134a. • The condenser temperature has a greater effect on the performance of refrigerator. • R1234yf is not a better alternative to R134a under the conditions assumed in this work.

[en] This paper gives a preliminary overview of our attempt at developing a hydrate-based refrigeration system based on a novel conceptual design. The system forms a closed cycle, which is more or less analogous to the conventional vapor-compression refrigeration cycle. The cycle of present interest is performed by a multiphase refrigerant, which is typically a mixture of one or two hydrate-forming substances and water. The refrigerant is required to form a hydrate at a temperature as high as ∼30 ^oC or above, desirably under a modest pressure, such that the heat released by the exothermic hydrate formation can be efficiently removed by an environmental fluid such as the atmospheric air, groundwater or river water. The hydrate slurry thus formed is depressurized to dissociate at a lower temperature, typically 5-9 ^oC, thereby absorbing heat from a space to be refrigerated. To confirm the feasibility of the above conceptual design of the hydrate-based refrigeration system, a thermodynamic analysis of the system and a simulation of its operation have been performed. Also a laboratory-scale refrigerator based on the above design was constructed and tested. The paper summarizes the results of these efforts to show the potential advantages of the hydrate-based refrigeration system over conventional ones and to give the prospects of our refrigeration-system development

[en] Highlights: • A novel dual-nozzle ejector enhanced refrigeration cycle is proposed. • The novel cycle is evaluated by using the developed mathematical model. • The results show the performances of the novel cycle could be significantly improved. • The novel cycle shows its promise in household refrigerator-freezers applications. - Abstract: In this study, a novel dual-nozzle ejector enhanced refrigeration cycle is presented for dual evaporator household refrigerator-freezers. The proposed ejector equipped with two nozzles can efficiently recover the expansion work from cycle throttling processes and enhance cycle performances. The performances of the novel cycle are evaluated by using the developed mathematical model, and then compared with that of the conventional ejector enhanced refrigeration cycle and basic vapor-compression refrigeration cycle. The simulation results show that for the given operating conditions, the coefficient of performance (COP) of the novel cycle using refrigerant R134a is improved by 22.9–50.8% compared with that of the basic vapor-compression refrigeration cycle, and the COP improvement is 10.5–30.8% larger than that of the conventional ejector enhanced refrigeration cycle. The further simulation results of the novel cycle using refrigerant R600a indicate that the cycle COP and volumetric refrigeration capacity could be significantly improved

[en] Domestic refrigerators are required to be energy efficient and environmentally safe. In this work, a slightly modified domestic refrigeration system was infused with various concentrations (0, 0.2, 0.4 and 0.6 g/L) of TiO₂ nanolubricants and R600a refrigerant with a mass charge of 40g. The average energetic characteristics of the test rig at different door openings intervals (0.5, 1, 2, 3 and 5 minutes) were evaluated. The energetic characteristics studied were coefficient of performance (COP), refrigeration capacity, power consumption and cabinet temperature recovery time. The results obtained showed that the use of nanolubricants significantly affect the energetic performance characteristics of the system. Overall, the utilization of 0.6g/L concentration of TiO₂ nanolubricant gave the best performance. The COP of the system improved by 22.39 %, while the power consumption decreased by 23.5 % when compared with pure R600a refrigerant. (paper)

[en] Cryocoolers are indispensable devices for many applications in modern technologies. New and changing demands ask for improved designs with high efficiency, low cost, extremely high reliability, and low vibrations. Pulse tube refrigeration is one of the most favoured processes. Its basic principle is explained and some typical achievements are described. Special attention is attributed to respective work at Forschungszentrum Karlsruhe where a two-stage pulse tube refrigerator for application in superconducting magnet technology is being developed. Its cooling capacitance is around 3 W at 20 K and simultaneously 50 W at 55 K when operated with a 6.5 kW compressor. The status and some of the future trends of those developments are presented. (orig.)

[en] PrNi₅ refrigerator is described. It has been cooled to 2mK. Over a period of about 6n it returned to 10mK. This system is still being developed. (J.T.)

[en] Boiling heat transfer is imperative in the refrigeration and air conditioning systems. R22 is the mostly widely used alternative refrigerant in refrigeration equipment such as domestic refrigerators and air conditioners. Though the global warming up potential of R22is relatively high, it is affirmed that it is a long alternative refrigerant in lots of countries. By addition of nano particles to the refrigerant results in improvements in the thermo-physical properties and heat transfer characteristics of the refrigerant, thereby improving the performance of the refrigeration system. The results indicate that cuo nano refrigerant works normally and safely in the refrigeration system. The results indicate that heat transfer coefficient increases with the usage of nanocuo. Thus using cuo nano refrigerant in refrigeration system is found to be feasible. Objective of this project is to study the pre and post effects of addition of NRs in refrigeration and to predict COP and power consumption reduction. (paper)

[en] A new method of refrigeration is proposed. Cooling is obtained by thermionic emission of electrons over periodic barriers in a multilayer geometry. These could be either Schottky barriers between metals and semiconductors or else barriers in a semiconductor superlattice. The same device is an efficient power generator. A complete theory is provided. copyright 1998 American Institute of Physics

[en] A brief description and a diagram are presented of equipment for subcooling of parts in the manufacture of nuclear reactor control elements. The equipment houses items of maximum dimensions of 500 mm dia x 200 mm and a maximum weight of 100 kg. The lowest achievable temperature is -196 degC while the maximum permissible temperature of an item to be cooled is 100 degC. (B.S.)