Application of nano-refrigerant for boiling heat transfer enhancement employing an experimental study

Review of pool boiling enhancement with additives and nanofluids

A review on flow boiling enhancement and fabrication of enhanced microchannels of microchannel heat sinks

Role of hybrid-nanofluid in heat transfer enhancement – A review

Because air conditioning and heat pump systems contribute greatly to greenhouse gas emissions, equipment with both lower global warming potential (GWP) working fluids and a higher level of performance should be used R32 (difluoromethane) has been proposed to substitute R410A, particularly in residential air conditioning (RAC) systems This study collected the most relevant and recent researches into R32 as a refrigerant so as to assess its viability in RAC systems in both Europe and the USA, as compared to R410A and other lower GWP RAC alternatives The R32 value of GWP is 677, which is below the F-gas regulation limit in RAC equipment (750) According to ASHRAE standard 34, R32 is less flammable than hydrocarbons, and the amount of charge permitted for R32 is above the necessary level in RAC equipment It can be concluded that R32 has significantly good heat transfer characteristics and a level of performance that make it acceptable at low condensing temperatures, thereby avoiding overly high compressor discharge temperatures Its performance is very similar to that of R410A across the entire operating range, and it is therefore believed that R32 will be utilized in RAC systems in the remaining countries that prioritize lower GWP fluids but are less strict in their security regulations To replace R410A under extreme conditions, some system modifications can be conducted, or R32 mixtures with hydrofluoroolefins (HFOs) can be used Such mixtures achieve a lower performance than R32, but are acceptable replacements when considering their lower GWP compared to that of R32, and similar level of flammability Finally, other (R32-based) alternative mixtures have also been developed and their behaviours studied under a wide range of operating conditions

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Refrigerant R32 as lower GWP working fluid in residential air conditioning systems in Europe and the USA

Summary This paper proposes a three-bed three-stage adsorption cycle with a new operational strategy. The cycle consists of three adsorber/desorber heat exchangers, one evaporator, and one condenser. The two beds on the low-pressure side operate in a re-heat cycle, and another bed on the high-pressure side operates in a conventional cycle. The objectives of the current study were to evaluate the cycle at a low heat source temperature such that it can be driven by solar or waste heat and to reduce the number of heat exchangers from six beds to three beds. A simulation model was developed, and the system behavior and its performance were predicted. The performance of the proposed cycle was compared with that of a conventional six-bed three-stage adsorption cycle. The simulation results showed that the proposed cycle with the new operational strategy could operate at low heat source temperature i.e., 45 °C, and offers approximately five times higher performance in terms of SCP than the conventional cycle. Consequently, the proposed cycle is effective for use of a low-grade heat source, even with three beds.

https://www.jstage.jst.go.jp/article/tjsrae/31/4/31_14-34_OA/_pdf

A Three-Stage Adsorption Cycle with Three Silica-Gel Beds

Performance Improvement of H-Darrieus Wind Turbine with High Efficiency Vortex Structure Attachment

Numerical study on the Effect of Rectangular and Triangular Counter-Rotating Vortex Generators on the H-Rotor Wind Turbine Performance

Utilization of wasted heat instead of fuel combustion is effective to reduce primary energy consumption for mitigating global warming problem. Because wasted heat sources are not necessarily located close to areas of heat demand, one of the difficulties is that wasted heat has to be transferred from heat source side to heat demand side, which may require heat transportation over long distance. From this point we proposed and have examined new idea of heat transportation using ammonia-water as the working fluid which system is named Solution Transportation Absorption chiller, in short STA. Our previous studies of STA were mainly the experimental investigation with STA facility which cooling power was 25RT (90kW). As a result, the COP of STA was found almost same value 0.65 with the conventional absorption chiller without depending on the transportation distances. The simulation using AspenHYSYS also examined with same experimental condition. The experimental data showed good agreement with the simulation calculation. In this study, we examined the large-scale cooling power STA on simulation. The examination cooling powers were from 90 kW (25RT) to 3517 kW (1000RT). All cooling power achieved around COP 0.64 including pump power consumptions. In addition, we performed the dynamic simulation. As the results, there was no effect of pipeline size on the cooling capacities and mass flow rates. Furthermore, the stability time of the cooling capacities and mass flow rates were almost same regardless of the pipeline size and cooling capacity. In other words, STA may be achieved the same COP even though having various complex conditions compared with the conventional absorption chiller.

/pdf/simulation-analysis-of-solution-transportation-absorption-pd292x5q2w.pdf

Koji Enoki

Papers

A Three-Stage Adsorption Cycle with Three Silica-Gel Beds

Performance Improvement of H-Darrieus Wind Turbine with High Efficiency Vortex Structure Attachment

Numerical study on the Effect of Rectangular and Triangular Counter-Rotating Vortex Generators on the H-Rotor Wind Turbine Performance

Simulation Analysis of Solution Transportation Absorption Chiller with the Capacity from 25 RT to 1000 RT

Visualization and Analysis of Adsorption Kinetics by Using Image Processing Algorithm