To achieve a good heat transfer performance for heat pump type air conditioners, the outdoor units of the air conditioners need to perform well under both the frosting and the non-frosting conditions. This paper proposes a perforated fin whose perforated structure is capable to enhance the heat transfer and to avoid the frost blockage. The perforate position on the fin surface is figured out by analyzing the positions of the frost blockage zone and the water exclusion zone. The optimal perforated geometries are designed to enhance the heat transfer coefficient. The new designed perforated fin has two parallels of rectangle multi-perforated holes. The experimental results show that the heat transfer capacities under the non-frosting condition and the frosting condition of the designed perforated fin are 4.6% and 1.1% higher than these of wavy fins, respectively. The perforated structure has the capability to avoid the frost blockage around the enhanced structure on the fin surface.
In this paper, AQSOA-Z01, AQSOA-Z02, AQSOA-Z05 zeolites, CAU-10 and Aluminium Fumarate metal organic frameworks undergo N2 and water adsorption experiments to observe how variations of the material properties affect the water adsorption performances. The experimentally measured N2 isotherms data are used to calculate the BET surface area, pore volume and, most importantly, the pore size distribution of these adsorbent materials. The amount of water uptakes under static and dynamic conditions are measured by a thermo-gravimetric analyser, and these data are fitted with adsorption isotherms and kinetics models within acceptable uncertainties. Based on isotherms and kinetics data, the performances of adsorption cooling in terms of SCP (specific cooling capacity) and COP (coefficient of performances) are evaluated. It is shown the CAU-10 provides the highest SCP and COP as it has higher water uptake – offtake differences with fast kinetics.
By a differential capillary rise method, the surface tension was measured for a new candidate of low GWP refrigerant HFO-1123. 16 points of surface tension data with a propagated uncertainty of approximately ±0.22 mNm-1 are presented in this paper. Based on the measured data, a Van der Waals type empirical correlation was proposed for HFO-1123: = 61.02 (1-T/Tcrit)1.30 [mNm-1], where Tcrit is a critical temperature of 331.7 K measured by Higashi and Akasaka. This empirical correlation agrees with the measured surface tension data at temperatures from 267 K to 304 K.
The active magnetic bearing (AMB) has many advantages compared with the conventional bearing. It is the most widely used bearing in many machine applications; such as centrifugal compressor, air blower, and turbo molecular pump. AMB applications must be equipped with auxiliary bearings system to prevent the damage to the impellers and motor in case of system failure. The auxiliary bearing is referred to as the touchdown bearing in this study. When a failure is occurred, the active magnetic bearing cannot support the rotor stably. Touchdown bearings serve as a backup for the active magnetic bearings to support the rotor during a drop-down failure event. Therefore, a properly designed touchdown bearing system is necessary to protect the active magnetic bearing assembly and other critical machine components from direct contact with the rotor during AMB loss in power outage events. This system uses a ball bearing as a type of touchdown bearing. A finite element based 2-DOF (two-degree of freedom) flexible rotor model is used to indicate the rotor behavior. The rotor model also considers the contact force between the shaft-inner race and ball bearing force based on Un-lubricated Hertzian contact models. This study presents a dynamic rotor simulation during a drop event applied in a magnetic centrifugal compressor. This simulation is built using MATLAB with rotor speed effect and touchdown bearing design to predict the rotor behavior based on the rotor orbit and response.
The glass transition temperatures of the several kinds of materials which are considered to be effective as protective agents were measured before dry preservation experiment. The following four types of protective agents were selected to assess the dry-protective ability with Lactate Dehydrogenase (LDH); trehalose, trehalose with -Poly-L-Lysine (PLL) and trehalose with boron. The sample solutions of LDH with the various combinations of protective agents were rapidly vacuum-dried at the room temperature, followed by measuring their moisture content. After that, the dried samples were rehydration to measure the enzymatic activity by biochemical assay. The residual activity of LDH sample with trehalose was about 50% when its moisture content was 11 to 60 %. This dried-sample, however, suddenly lost its residual activity down to about 20 % when the moisture content decreased to 11 wt% or less. On the other hands, LDH samples with PLL alone and with trehalose + PLL kept their residual activities around 75 to 80 % in the wide range of moisture content. LDH samples with boron + trehalose kept their average residual activity from 69 to 74 %.
The driving range of electric vehicle can be significantly reduced if using CO2 as a refrigerant in hot climates. This paper aims to improve the performance of CO2 electric vehicle air conditioning system by using a dedicated propane mechanical subcooling, the interference between internal heat exchanger (IHX) and mechanical subcooling (MS) was discussed, since both improvements compete towards reducing the throttling losses, optimization possibilities were theoretically analyzed on several integrated system for various subcooling degrees from 3℃ to 15℃ and ambient temperatures from 25℃ to 40℃, results show that the presence of mechanical subcooling after IHX reduces its efficiency, the use of mechanical subcooling simultaneously before IHX rather yields a more efficient air conditioning system. It has been shown that compared with CO2 prototype system, the new best integrated system can improve the COP (coefficient of performance) up to a maximum of 25.72% despite the extra compression work in mechanical subcooling cycle, and the cooling capacity up to a maximum of 46.24% during the research range, thus, the driving range of EVs can be significantly extended. Furthermore, the suitable cooling capacity and propane compressor displacement required in the MS cycle are predicted. Finally, experiments were carried out to see the actual improvements achieved by MS and IHX cycle based on the theoretical results.
Heavy-duty diesel engines have been widely applied in commercial vehicles. However, escalating consumption of fossil fuels and stringent legislation of CO2 emission have raised the concern about searching for viable technologies to improve the fuel energy efficiency recently. Generally, optimization technology of engines can be categorized into two types: engine-powertrain-applied and engine-bottoming cycles. The bottoming organic Rankine cycle is an applicable combined heat and power (CHP) technology with great potential for engine waste heat recovery. The aim is to increase the fuel energy efficiency without additional fuel consumption. In this paper, a thermo-economic overview of organic Rankine cycle system integrated into engines especially for on-the-road vehicle is presented. First of all, characteristics of various engine waste heat (e.g. exhaust gas, EGR, CAC, jacket cooling water, oil circuit) are briefly analyzed; Afterwards, special attention is paid to the screening criteria of appropriate expansion machine and working fluid selection; Subsequently, an overview of various layout of organic Rankine cycle was presented; Eventually, cost-orient economic evaluation of the synthesis cycle is overviewed, which is meant for characterizing the optimum system design.
Experimental studies on the pVTx properties of the aqueous solution of ammonia were precisely conducted mainly in the liquid region. Based on these experimental results, it was experimentally confirmed that the existing range of the maximum densities was clarified in the dilute region of ammonia. Furthermore, in the vapor-liquid equilibrium states of the aqueous solution of ammonia, there exist large differences between the saturated vapor pressures, namely dew point line, and the saturated liquid pressures, namely bubble point line, and their discrepancies were thereof discussed including the influence of hydrogen bonding as same as in solid.
We investigated the energy consumption of heat source equipment in the university research facility building. The purpose is to clarify the current operation state of the heat source facility and propose a more efficient heat source facility system at the time of renewal. The survey method used BEMS data to calculate every hour of COP used by the heat pump of electric energy, inlet and outlet temperature and primary pump flow rate. As a result, the heat source efficiency of the heat pump had an the average COP=1.98 during cooling in 2016 and COP=1.98 during heating in 2016.The heat source efficiency at the time of designing the heat pump was COP=2.38 during cooling and COP=1.95 during heating. Therefore, it was revealed that the heat source efficiency average in 2016 was lower than the heat source efficiency at the time of designing the heat pump. Also, energy simulation of the target building was carried out and the energy consumption was estimated. As a result, we grasped the detailed energy consumption of the target building.
Recently, the installation of VRF (Variable Refrigerant Flow) heat pump systems in offices – regardless of their size and shape – has become popular in Japan. This system consists of a packaged outdoor unit and multiple indoor units connected by a refrigerant pipe. It has the advantage of fitting in easily with the any building plans because of its standardized system. Moreover, this system is energy saving and enhances user comfort, as it can be easily operated as an indoor unit. On the other hand, as there are infinite combination of indoor units of VRF systems available for the users to be chosen freely within the range of outdoor capacity, and since the indoor units can be turned on and off independently, operation conditions are not predictable. So it is very difficult to find adequate control parameters under wider load conditions. For this reason, the purpose of this paper is set to organize the control characteristics systematically. In order to evaluate VRF system, we develop a numerical simulation model based on the laws of physics. This model can easily add and delete indoor unit's elements. Therefore, we hope that this model is adequate for VRF system’s analysis. In this report we reproduce machine’s operation conditions precisely; for example, for unstable condition, we reproduce the hunting phenomenon of expansion valve and evaluate the effects of different control constants under different loads.
Drying air conditions of agricultural produce including the temperature and humidity affect the quality and appearance of the dried product. High temperature and higher humidity cause to loss of nutrient and color. Control of the latent load of drying air prior to use for drying seems more effective approach for the preservation of delicate and temperature sensitive nutrient present in agricultural produce. Desiccant drying system (DDS) removes the moisture from the drying air and makes it possible to dry at low temperature and low humidity. In present study the pertinence of DDS with two desiccant materials LiCl and Silica gel were analyzed in order to find the optimum drying conditions for wheat and rice. Results showed that in case of desiccant material LiCl, process air temperature found higher and humidity lowers, thus provided more pressure deficit and speedup drying as compared to the silica gel. The value of drying potential per watt also showed that desiccant material LiCl found more economical to use as compared to silica gel for all range of regeneration temperature. However for different type of grains, optimum ranges of regeneration temperatures is different i.e. 55-60ºC for wheat and 60-65ºC for rice.
In this study, we focused on the way of waste heat utilization to subcooling into refrigerated cabinets by cold heat of PCM (Phase Change Material) in the case of supermarket fields. On this experiment, we installed a heat exchanger into after the condenser of the refrigerated cabinet to control the subcooling degree using the PCM cold storage tank. The cold heat capacity of PCM tank water for subcooling was set assuming that it was supplied by adsorption refrigerator which was driven by the exhaust heat from gas engine and solar energy absorber. As a result, we confirmed that the power consumption decreased in the case of the refrigerated cabinet with subcooling contributed to CO2 emission reduction. Result of this experiment, the utilization of exhaust heat for subcooling by PCM was effective for energy conservation on the summer and the intermediate season. We confirmed, on the other hand, that the effect of subcooling by PCM could be disappeared when it was below 16 degree Celsius of the outside temperature.
In industrial fields, heat source over 130°C are widely needed, and for this development of industrial high-temperature heat pump systems has been promoted. For the heat release process in such the heat pump systems, the authors have studied on cooling heat transfer at supercritical pressures and condensation heat transfer at high subcritical pressures of refrigerants flowing in chevron-type plate heat exchangers (PHEs). In this study, to examine the effect of chevron angle on condensation heat transfer of refrigerants at high subcritical pressures, experiments were conducted using chevron PHEs with respective chevron angles 30°, 47.5° and 65°. In the experiments, condensation heat transfer coefficients were obtained in wide range of bulk fluid enthalpy comprising whole the saturated region, at pressures of reduced pressures from 0.65 to 0.80, and mass flow rates of 7 and 11 kg/min. The measured condensation heat transfer coefficient increased with the chevron angle. The increase rate of the condensation heat transfer coefficient against the chevron angle was compared with that of condensation heat transfer coefficient from a conventional correlation developed based on low subcritical pressures data and that of cooling heat transfer coefficient at a supercritical pressure from a previous experiment.
This paper describes ground source heat pump (GSHP) that use direct expansion method. An underground heat exchanger consists of a copper pipe which is inserted directly into a foundation pile. We have carried out an experiment using the underground heat exchanger which inserted into the steel pipe pile. This paper describes the performance of the GSHP that use 15 sets of the foundation pile. Experimental apparatus is composed of a compressor, a four-way valve, an expansion valve, five indoor units and the underground heat exchanger. The underground heat exchanger is composed of steel pipe piles and copper pipes, and the foundation pile is filled with water. The heat exchanger is U-shaped with one and two pipes connected at the bottom part and is inserted into the foundation pile. The performance of GSHP system was evaluated by coefficient of performance (COP), which is determined by the ratio of the amount of exchanged heat to the power consumption of the compressor. From the experimental result obtained, the average COP exceeded 7 in the cooling mode. On the other hand, the average COP exceeded 5 in the heating mode. It was found that GSHP using direct expansion method which used the underground heat exchanger inserted in the foundation pile have high energy saving properties.
Two phase flow in micro channel has been of research interest recently due to its high heat and mass transfer rate, and in this study, experimental investigation is performed on the influence of wettability of the tube in slug flow. The liquid film thickness and flow behavior of water-air slug flow are investigated by using laser focus displacement meter (LFDM) and high-speed camera, respectively. Circular glass tubes with inner diameters of 0.76mm and 1mm are prepared to be hydrophilic or hydrophobic by applying surface chemical treatment (using chemical surfactant: piranha solution and toluene). The experimental results are compared and discussed to obtain the influence of wettability, and as a result, the liquid film thickness is found to be similar in hydrophobic and hydrophilic micro channels, which is compatible with theoretical analysis. However, the flow characteristics is influenced by wettability at low capillary number region, at which no liquid film exists. The critical capillary number for film deposition on the wall is influenced by the hydrophobicity of the tube, consequently, the critical capillary number is higher in a hydrophobic tube than that in hydrophilic one.
This paper analyzed life cycle costs of a ground source heat pump system used in a residence of Japan considering an advection effect of groundwater flow of eight different Darcy velocity. The required length of a single borehole heat exchanger was determined in each seven area of different heating/cooling loads to minimize the life cycle cost during 20 years through heat pump simulations. This study revealed that the effect of groundwater flow appeared when the velocity was more than 10 m/y and was almost converged when the velocity reached at 200 m/y. The cost decreased almost linearly according to the logarithms of the velocity. The velocity range was possible in steep valleys and alluvial fans of Japan. This study also showed that the costs were related mainly to the total loads, and secondarily to the groundwater flow conditions for the household system. Among seven areas, the household system was economically suitable relative to conventional air source heat pump systems in the cold areas 1 and 2 without initial cost reduction. The moderately warm areas 3 to 5 also became suitable when the initial costs would be reduced by 20 % as a common target of current R&D projects.
R32 is a refrigerant that excels in various applications and has seen wide use in recent years. However, R32 is known to have lower miscibility with refrigeration oils than do other refrigerants such as HFCs and HFOs. Moreover, when R32 is dissolved in refrigeration oils, the kinematic viscosity of the oil drops sharply. This has made it difficult to develop oils with improved miscibility with R32 that do not suffer from these drops in kinematic viscosity. Our work has shown that the addition of a new base material to POE improves miscibility with R32 while reducing the drop in kinematic viscosity that occurs when R32 is dissolved in it. Using this technology, we have developed new refrigeration oils whose critical solution temperatures were −20°C or below under R32 atmosphere. The kinematic viscosities of the new oils when R32 is dissolved in them were equal to or greater than those of POE oils currently used for R410A. In addition, the new oils have not only expanded the range of choices for POEs for R32, but also shown the possibilities for use with HFOs. In this study, we report our test methods and various characteristics of the oils under R32 and HFOs.
The effect of the freezing process and frozen storage periods on the microstructure of cooked glutinous rice has been investigated. Cooked glutinous rice (cv. Koganemochi) was frozen and stored in a household freezer (about -22 °C) during 1, 5, 10, 30 and 60-day storage periods. Its microstructure was observed by using fluorescence staining method and the morphology of ice crystals including equivalent diameter and number was analyzed. Colorimetric measurements were conducted after natural and steaming thawing on samples of each storage period. It was found that average equivalent diameter and number of ice crystals increased with storage period from 5 days, and recrystallization occurred in temperature fluctuation during freezing process and storage affected microstructure of glutinous rice. Moreover, by analyzing the distribution of ice crystals, it was found that most of them are under 10µm in each storage period. Frozen stored glutinous rice after 60 days showed darker and more unpleasant color than freshly cooked one by both thawing methods. Since the tendency of color change during the whole frozen storage was unstable, it could be assumed that the control of thawing process should not be neglected.
The effects of the freezing process and frozen storage periods on rheological parameters of freshly cooked and freeze-thawed glutinous rice have been investigated. Cooked glutinous rice (cv. Koganemochi) was frozen and stored in a household freezer at -20°C for 1, 5, 10, 30 and 60 days. After steaming and natural thawing processes, creep-recovery test (0.1N, small deformation), texture profile analysis (TPA) test (50% deformation) and the tensile testing (20N, 100% deformation) were performed on one-grain and block-shaped glutinous rice respectively by a rheometer, to measure the rheological parameters of the samples. One-grain samples showed more significant differences with freshly cooked rice in tensile testing, while blockshaped ones showed more in creep recovery tests. There were few significant differences in any fracture characteristics and viscoelastic properties between steaming and natural thawing methods for both block-shaped and one-grain samples in each storage period. The TPA results demonstrated that natural thawing method would produce softer as well as less sticky glutinous rice products during 60-day frozen storage.
Pizza dough samples were frozen and stored at different temperature (-5̊C, -15̊C, -25̊C, -35̊C and -45̊C) and for different storage periods (1 day, 15 days, 25 days and 35 days) to measure the baking characteristics of the samples in a hot air (HA) and superheated steam (SHS) oven. Baked samples were employed for the measurement of surface color and moisture content. The moisture content of the samples frozen at -5̊C significantly decreased after 15 days of frozen storage. The surface color of the SHS-dried samples changed more drastically than that of HA-dried samples. Compared with HA, the SHS baking showed the potential to give the frozen pizza dough higher thawing rate, less baking time, and faster browning ability. The combined effect of initial condensation, crust thickness and water redistribution from crumbs to crusts might have played important roles in differentiating the HA- and SHS-baked samples. Different freezing temperatures from -5 ℃ to -45 ℃ did not cause any significant difference in color.
Five Philippine durian cultivars - Puyat, Duyaya, GD69, Native, Arancillo, were subjected to consumer intensity-ranking test with 50 durian consumers as panelists to determine the correlation between the experimental measured values and the consumers' perceived intensity of the different durian quality attributes: color, texture, physicochemical properties, sugars, and organic acids content. Preference ranking test was also performed to identify the most preferred cultivar based on the five quality attributes evaluated. Results of the intensity ranking showed a good correlation between the experimental values and sensory perception on the color, texture, sweetness and overall flavor. Same trends in the degree of intensity were observed in the measurements, objective and sensory analysis. In the preference-ranking test, results revealed that Duyaya was the most preferred cultivars in terms of the color, while Arancillo was rated most preferred for the texture. In reference to the taste/flavor, the top choices were Arancillo, Duyaya, and Native. On the other hand, Puyat, GD69, and Arancillo registered the highest consumer preference in regard to aroma, although the mean rank of the former did not seem to differ with the two former cultivars. Finally, upon consideration of the overall preference, our findings suggested that Duyaya, Arancillo, and Native were more favored cultivars over Puyat and GD69.
凍結および解凍工程は，キンメダイをはじめとする赤色魚類の体表色の色彩変化を引き起こすことが知られているが，この色彩変化は，これらの魚の商業的価値を低下させる．本研究では，凍結解凍工程における体表色変化の原因を調べるために，キンメダイ鱗内のアスタキサンチン含量と赤色素胞の分散を測定した．凍結解凍前後の体表色をComputer Vision System を用いて数値化することにより，体表色変化は，–30 °C 下では凍結保管期間の影響を受けないことが明らかとなった．また，アスタキサンチン量は凍結解凍前後でほとんど変化しなかった．鱗内の赤色素胞の凝集と虹色素胞の損傷が，顕微鏡での観察により認められた．これらの結果より，凍結保管工程における色彩変化は，アスタキサンチンの酸化・分解だけではなく，鱗内の色素胞構造の変化にも原因があることが明らかとなった．
“Ikura,” a seasoned salmon roe product in Japan, is produced mainly from eggs of the chum salmon caught during spawning migration. Owing to the high volumes of salmon caught during peak season, appropriate storage and processing methods are essential to maintaining egg quality. We investigated the processing properties of fresh or frozen-thawed salmon eggs at different maturity levels, focusing on hardening during storage. Our results confirmed that little hardening during storage occurred in eggs in the skein state in the abdominal cavity with a low maturity level, whereas substantial hardening occurred in the individual egg grains in the peritoneal cavity. Similar results were obtained using fresh and frozen salmon eggs, and the hardening of matured salmon eggs depended on the storage time and temperature. Based on SDS-solubility and SDS-PAGE analyses, the macromolecularization of egg membrane proteins occurred during egg hardening. The frozen eggs tended to harden faster than fresh eggs, and the hardening pattern was slightly different between these eggs; these differences may be explained by various factors, such as protein polymerization and degradation. The hardening of the egg membrane progressed after salting, and this phenomenon is likely to occur during salting and aging in industrial manufacturing.
In a preliminary study to clarify the factors affecting the quality deterioration of surimi-based products, the physical properties and drip loss of five different types of commercial surimi-based products (Itatsuki-kamaboko, Chikuwa, Satsuma-age, Datemaki, and Hanpen) at different freezing conditions were evaluated. After frozen storage, the breaking strength and breaking strain of Itatsuki-kamaboko, which is a two-step-heated surimi gel without starch, decreased with frozen storage, while for the other products, which are direct-heated gels containing starch, the breaking strength and breaking strain increased. Drip loss increased after frozen storage, and the thawing drip was higher with Itatsuki-kamaboko than with other products. These changes were notable in samples subjected to slow freezing than subjected to quick freezing. Moreover, the results of physical properties and drip loss corresponded to the change in sensory characteristics. Thus, the quality change in frozen surimi-based products might be correlated to not only the freezing conditions but also the heating methods and ingredients used.
In many cases, frozen whale meat in the Japanese market is prepared before rigor mortis (pre-rigor). A serious problem for frozen whale meat is the occurrence of thaw rigor, which is the strong development of rigor mortis during thawing. To prepare frozen whale meat without thaw rigor and maintain a high meat pH, the temporal changes in adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide (NAD) contents of frozen meat stored at -2.5, -5.0, -7.5, and -10°C were investigated. The rate of decrease of ATP was higher than that of NAD at all storage temperatures. ATP nearly disappeared after holding the meat at -2.5°C for a few days; however, NAD existed yet, so pH decreased thereafter. ATP levels were maintained for a long period at a temperature of -5.0 to -10°C, resulting in the occurrence of thaw rigor. Compared to the muscles of fish such as tuna, the rates of decrease of ATP and NAD were extremely slow in whale meat.