Takahiko Miyazaki

A combined power cycle using refuse incineration and LNG cold energy

The objectives of this paper are to develop a combined power generation cycle using refuse incineration and LNG cold energy, and to conduct parametric analysis to investigate the effects of key parameters on the thermal and exergy efficiencies. The combined cycle consists of an ammonia–water Rankine cycle with refuse incinerator and a LNG cold energy cycle. The combined cycle is compared with the conventional steam Rankine cycle. It was found that the thermal and the exergy efficiencies of the combined cycle were 1.53 and 1.43 times higher than those of the conventional cycle, respectively. The ammonia condensing temperature, turbine inlet and outlet pressures and overall conductance (UA) of the condenser are considered as the key parameters. The thermal and the exergy efficiencies increase with increasing the turbine inlet pressure. As the turbine outlet pressure increases, the thermal efficiency of the combined cycle decreases while the exergy efficiency increases. The present model can be applied to obtain optimum conditions of the key parameters for performance improvement of the combined cycle.

Performance Comparison of Three-Bed Adsorption Cooling System With Optimal Cycle Time Setting

This article presents the optimal cycle time and performance of two different types of silica gel–water-based three-bed adsorption chillers employing mass recovery with heating/cooling scheme. A new simulation program has been developed to analyze the effect of cycle time precisely on the performance of the systems. The particle swarm optimization (PSO) method has been used to optimize the cycle time and then the optimum performances of two chillers are compared. Sensitive analysis of cycle time has been conducted using the contour plot of specific cooling power (SCP) with driving heat source temperature at 80°C. It is found that the center point of the contour indicates the maximum SCP value and optimal cycle time, which are comparable with the quantitative values obtained for the PSO method. Both three-bed mass recovery adsorption cycles can produce effective cooling at heat source temperature as low as 50°C along with a coolant at 30°C. The optimal SCP is similar for both cycles and is greater than that of the conventional two-bed adsorption system employing the same adsorbent–refrigerant pair. Consequently, the proposed comparison method is effective and useful to identify the best performance of adsorption cycles.

Performance evaluation of hydrophilic organic polymer sorbents for desiccant air-conditioning applications

The present study provides performance evaluation of two kinds of crosslinked hydrophilic organic polymer sorbents (PS-I and PS-II) for desiccant air-conditioning applications. In this regard, optimum temperature and humidity zones are established for various air-conditioning applications which include (i) humans’ thermal comfort, (ii) animals’ thermal comfort, and (iii) postharvest storage of fruits/vegetables. Honeycomb-like desiccant blocks composed of PS-I/PS-II are assumed for numerical simulation analysis. The numerical simulation model is programmed into MATLAB which utilizes the scientific relationships of adsorption isotherms, adsorption kinetics, isosteric heat of adsorption, and thermophysical properties for each sorbent. A particular desiccant air-conditioning system design is proposed, and numerical simulation has been conducted for the performance evaluation of PS-I and PS-II. According to the results, PS-I enables higher dehumidification than PS-II at low regeneration temperature (50℃) and cycle time of 60:90 min. It is because the PS-I possesses better water vapor sorption kinetics as compared to PS-II. Although the PS-II enabled higher steady-state adsorption amount but it could not influence the overall system performance. On the other hand, the optimum performance by the PS-II is limited to relatively long cycle time and higher regeneration temperature (≥80℃). It has been concluded that the PS-I is relatively better choice for desiccant air-conditioning, and consequently can be considered for various air-conditioning applications. Furthermore, effects of mass flow rate, isosteric heat of adsorption, regeneration temperature, and cycle time on air humidity ratio and air temperature profiles have been discussed in order to highlight the performance variability of desiccant air-conditioning system.

High concentration non-imaging Fresnel lens design with flat upper surface

Concentration PV systems are emerging recently and primary lenses have been developed for concentrating solar incident. Although the authors already produced 500X dome-shaped Fresnel lens, its production process was complicated because of the shape. The objective of this study is to investigate new design method for non-imaging Fresnel with flat upper surface so that the production can be easier. The design of prisms is formulated by means of non-linear optimization to have maximum acceptance half angle with edge-ray principle. It is shown that designing more than 500X flat Fresnel lens is possible. The study also presents optimal condition of lens size requiring energy payback year to satisfy from the viewpoint of life cycle energy production and consumption.

PERFORMANCE INVESTIGATION OF ADSORPTION–COMPRESSION HYBRID REFRIGERATION SYSTEMS

An analytical investigation on the performance of adsorption–compression hybrid refrigeration systems with two different cycle configurations, cascade type and subcool type has been performed. In the former type, a cascade condenser is used which works as a condenser for mechanical compression cycle and evaporator for adsorption cycle. In the latter type, an evaporative subcooler is used which subcool the fluid of mechanical compression cycle. The refrigerants examined for the mechanical compression cycle are R134a, R152a, R1234yf and R1234ze whereas ethanol is the refrigerant for the adsorption cycle. The main feature of the proposed system is the capability to significantly reduce work input for the mechanical compressor which results up to 30% energy saving potential depending on the selection of refrigerant and system configuration. Based on the thermodynamic properties and laws the study analyzed the effect of the major design parameters such as evaporation temperature, compressor discharge pressure and desorption temperature on the system performances.

Analytical Model of a Combined Adsorption Cooling and Mechanical Vapor Compression Refrigeration System

ABSTRACT A combined adsorption and mechanical vapor compression system is a reasonable option to reduce the consumption of fossil fuels for air conditioning by utilizing waste heat. Performance predictions of combined adsorption and mechanical vapor compression systems require detailed dynamic modeling because the transitional characteristics explain the nature of the adsorption system. It is, however, desirable to simplify the model for practical use at engineering stages. Since the mechanical vapor compression system is based on the steady-state thermodynamic cycle, a semi-steady-state modeling of adsorption cycles would be functional for analysis of combined systems. In our study, the analytical solution of transient simulation for adsorption cycles was combined with a steady-state mathematical model of the mechanical vapor compression system. The performance of the combined system was analyzed based on the model developed, taking into account the cycle time of the adsorption cycle. The results show the performance characteristics as well as the energy-saving potential of the combined system.

Desiccant Air-Conditioning System for Storage of Fruits and Vegetables: Pakistan Preview

In the present study the desiccant air-conditioning system has been investigated for the on-farm storage of fruits and vegetables in Pakistan. In this regard, ideal storage zone for the studied agricultural products is established in order to ascertain the system applicability. The dehumidification performance of the silica-gel based desiccant wheel has been analysed with low regeneration temperature (50°C) by using the model of Beccali et. al. Three environmental conditions (A: highly humid, B: moderately humid & C: less humid) are considered for the analysis of desiccant air-conditioning system. The latent and sensible loads of air-conditioning are achieved by the silica-gel desiccant wheel dehumidification and Maisotsenko cycle evaporative cooling respectively. The results of the study envisaged that desiccant wheel performs higher dehumidification in climatic condition ‘A’ due to higher ambient air relative humidity as compared to the other climatic conditions. However, higher heat energy is required for its regeneration in the climatic condition ‘A’. This study concluded that the desiccant air-conditioning system can be efficiently used for on-farm storage of fruits and vegetables in Pakistan. Also, the renewable energy sources of the country like solar energy and bio-gas can be potentially harvested for the regeneration of desiccant wheel. The study further proposes the use of hybrid desiccant air-conditioning system where standalone DAC system cannot achieve the sensible load.

Study toward high-performance thermally driven air-conditioning systems

The Adsorption heat pump is a technology for cooling and heating by using hot water as a driving heat source. It will largely contribute to energy savings when it is driven by solar thermal energy or waste heat. The system is available in the market worldwide, and there are many examples of application to heat recovery in factories and to solar cooling systems. In the present system, silica gel and zeolite are popular adsorbents in combination with water refrigerant. Our study focused on activated carbon-ethanol pair for adsorption cooling system because of the potential to compete with conventional systems in terms of coefficient of performance. In addition, activated-ethanol pair can generally produce larger cooling effect by an adsorption-desorption cycle compared with that of the conventional pairs in terms of cooling effect per unit adsorbent mass. After the potential of a commercially available activated carbon with highest level specific surface area was evaluated, we developed a new activated carb...

V-cut twisted tape insert effect on heat transfer enhancement of single phase turbulent flow heat exchanger

Turbulator is recognized as a method to increase the performance of the heat exchanger. Turbulator in the form of V-cut twisted tape insert could help to increase the performance by enhancing the coefficient of the heat transfer. This paper proposes a new design of V-cut twisted tape insert (VTT) with different width ratio (w/W), which investigated on the heat transfer enhancement, in the form of Nusselt number (Nu) and friction factor (f) characteristics. Three different width ratios (w/W) 0.32; 0.38 and 0.48 are introduced in this experiment. The working fluid is the hot water in the inner tube and cold water in the annulus, the flow direction is counter-flow. The temperature inlet of hot water is kept constant at 60°C while the flow rate is in the range of Reynolds number 5400 - 17,350. The heat exchanger without insertion (plain tube) and typical twisted tape insert (TT) are examined for comparison. Results indicate that the proposed VTT increases the heat transfer, friction factor, and thermal performance of the heat exchanger. Under the similar condition, VTT provides the best performance in comparison with TT and plain tube. Decreasing width ratio (w/W) increases the heat transfer and thermal performance. However, when the heat transfer is increased, the friction factor is also increasing. The results also revealed that the use of the VTT and TT, the increase in the heat transfer and friction factor up to 97% and 3.48 times of the plain tube. The highest thermal performance is 1.4.Turbulator is recognized as a method to increase the performance of the heat exchanger. Turbulator in the form of V-cut twisted tape insert could help to increase the performance by enhancing the coefficient of the heat transfer. This paper proposes a new design of V-cut twisted tape insert (VTT) with different width ratio (w/W), which investigated on the heat transfer enhancement, in the form of Nusselt number (Nu) and friction factor (f) characteristics. Three different width ratios (w/W) 0.32; 0.38 and 0.48 are introduced in this experiment. The working fluid is the hot water in the inner tube and cold water in the annulus, the flow direction is counter-flow. The temperature inlet of hot water is kept constant at 60°C while the flow rate is in the range of Reynolds number 5400 - 17,350. The heat exchanger without insertion (plain tube) and typical twisted tape insert (TT) are examined for comparison. Results indicate that the proposed VTT increases the heat transfer, friction factor, and thermal perfor...

Influence of minimum quantity lubrication with Al2O3 nanoparticles on cutting parameters in drilling process

Machining is one of the largest and most widely used methods of production segments in industries. In this way, cutting fluids play an important role in minimizing production time, cost, and energy in various machining operations. This paper presents an experimental investigation into minimum quantity lubrication (MQL) with Al2O3 nanoparticles in drilling process of common rail as work material with DPSCM 435H code to analyze its influence on cutting parameters. Al2O3 has been selected for nanoparticles in this study due to its non-toxicity and spherical shapes for enhanced tribological attributes. Experiments were carried out for two different conditions; MQL + nanofluids (250 ml/h) and conventional cutting fluid (15 liters/min). In this work, nanofluid was prepared by adding Al2O3 nanoparticles (13 nm size) into the conventional cutting fluid in the specific proportion of 1.2 vol.%. The experiment results reveal that the performance of Al2O3 nanofluid in term surface roughness is better compared to the ...