The annual energy consumption of air conditioners has been a topic of interest in the air conditioning industry. Improving the annual performance factor (APF), which indicates the energy efficiency at rated, half-load and minimum-load cooling and heating conditions, is therefore required. To achieve this, a high efficiency compressor that operates at half-load and minimum-load conditions is necessary because compressors account for most of the energy consumption of air conditioners. For scroll compressors, it is necessary to reduce leakage loss and heating loss at half-load and minimum-load conditions with low rotational speed. To reduce these losses, it is important to supply the optimized amount of oil to each of suction chamber and compression chamber. This paper describes development of the high efficiency scroll compressor with the new oil supply structure to control the amount of oil supply to each of bearings and suction chamber and compression chamber independently. In this paper, the relationship between the efficiency of compressor and parameters such as the back pressure, the amount of oil supply to compression chamber and the amount of oil supply to suction chamber is reported. As a result, we optimized these parameters and improved APF by 0.8%.
The purpose of this study is to improve the liquid-distribution uniformity of refrigerant gas-liquid flows in parallel-flow type heat exchangers that consist of dividing/combining headers and multiple branch tubes connected to them. The test channel had a vertical header with a height of 81.5mm and 8 horizontal branch tubes connected in parallel at a pitch of 10mm. We tested the refrigerant-supplying method using a pipe with multiple outlet holes installed in the dividing header, i.e., multi-hole inner pipe. Gas-liquid distribution ratios in each branch tube were measured changing an inner diameter and outlet-hole diameters of the inner pipe. It was confirmed that the liquid-distribution uniformity was much improved with the multi-hole inner pipe. Based on the design of experiment with the orthogonal table, we evaluated quantitatively the influence of geometrical parameters of the multi-hole inner pipe on the liquid distribution characteristics. We found that the inner diameter of the inner pipe had the large influence on the maximum reaching height of liquid, while the uniformity of the liquid distribution was influenced by the outlet-hole diameter of the inner pipe. The liquid-distribution uniformity was improved by using the inner pipe with a smaller outlet-hole diameter.
In the field of the absorption chillers with LiBr/H2O as its working pair, a small amount of absorbent was mixed in the evaporator to lower the freezing point of the refrigerant and obtain lower temperature output. The purpose of this study is to develop a middle-low temperature absorption chiller that provides 1 to 3 °C chilled water by applying the above method for general hot water-driven single-effect absorption chillers. As the fundamental step of the development, this paper discusses the behavior of the cycle by cycle simulation considering dilute solution in the evaporator. We have developed a cycle simulator that includes the physical and heat transfer characteristics of the dilute solution. “2-step evaporator and absorber” was taken into consideration that is adopted to improve the cooling efficiency. This simulator also draws a Dühring diagram that helps us to understand this cycle. In conclusion, we have found that this cycle has enough margin against refrigerant freezing and solution crystallization by setting appropriate LiBr concentrations in the evaporator. These results lead us to the conclusion that an absorption chiller with 1 to 3 °C output using dilute LiBr solution has sufficient feasibility to be put into practical use.
For the low-temperature waste heat utilization, we have developed a “middle-low temperature absorption chiller” that provides 1 to 3 °C chilled water to promote waste heat utilization. This chiller has almost the same structure as a present single-stage absorption chiller and uses LiBr/H2O as its working pair. A small amount of absorbent (LiBr) is mixed in the evaporator to prevent the refrigerant from freezing. In this paper, we developed a production prototype as the practical use stage and verified the performance and behavior under the conditions of a 1 to 3 °C chilled water outlet. As a result of the experiments, the coefficient of performance (COP) was 0.71~0.73 by supplying 90 °C heat source hot water and 28 °C cooling water. The prototype operated successfully during the experiments without any problems such as refrigerant freezing or solution crystallization. We also computed the characteristics of the prototype using the cycle simulator with the same condition as the experiment. The simulation results agreed with the experimental results within ±5% for the cooling capacity and heat input and ±0.005 for the COP. Based on these results, we have put the “middle-low temperature absorption chiller” in practical use.
The purpose of a heat transformer cycle is to extract heat at high temperature by utilizing waste heat at low temperature level. The heat generated during the adsorption of high-pressure water vapor raises the temperature of the external fluid to be used flowing in the adsorption reactor. However, since the heat input during preheating of the reactor and the heat removal during precooling are large, therefore, the heat capacity seems to affect the performance. In this study, first, thermodynamic analysis of the equilibrium cycle was performed to predict the amount of extracted heat from a low heat capacity reactor. The heat capacity was 20% smaller than that of the conventional reactor, and as a result, the output heat was 20% higher. Therefore, it was clarified that the decrease in heat capacity directly led to an increase in output heat. In addition to reducing the heat capacity, the effect of improving performance by heat recovery was also significant. The effect was almost the same as obtaining the upper limit of the output heat achieved by zeroing the heat capacity of the reactor. Moreover, from the viewpoint of exergy, heat recovery was important to enable high temperature extraction.
With the increase in energy consumption, energy-saving attracts lots of attention. The desiccant dehumidification system is a potential substitute for the air-conditioning system that can achieve energy saving by decreasing the energy input for latent heat. Besides, the desiccant dehumidification system can further utilize the low-temperature heat waste in the desorption process. Thus, this study has focused on the low temperatures range between 40ºC and 70ºC on the desorption process with low humidity ratios of dry air as 0.005 kg/kg. The results indicate that, with the increasing desorption temperature, the water removal amount also increases, which means the ability of dry air to capture moisture from desiccant increases with higher temperature. At the desorption temperature of 68ºC, the average moisture removal capacity reached the peak, 0.0081kg/kg. Conversely, the coefficient of performance (COP) of the desorption process presented a downward trend with increasing desorption temperature. At desorption temperature 41ºC the COP is highest at almost 0.8, then gradually dropped to around 0.51 at desorption temperature 68ºC. The optimal desorption temperature can be determined as 54ºC.
The generation of steam with high temperate was investigated when saturated humid air is flowed into the adsorption heat pump used the packed bed with 13X zeolite. As a result of experiments to measure temperature of generated steam, its maximum value was over 150 °C when humid air was preheated to 70 °C. Since the maximum temperature of steam was not drastically affected by superficial velocity of humid air, it was presented that the maximum temperature does not depend on the heat transfer between humid air and zeolite under experimental conditions in this study. Hence, the maximum temperature of steam was estimated by the relationship between the adsorption equilibrium and heat balance under the assumption that both of temperature in gas and zeolite are equal. As a result, it was revealed that the maximum temperature was possible to be estimated by this method under the condition that the temperature of humid air is high.
Water vapor adsorption on activated carbon (AC) for dehumidification purposes has gained much attention due to the abundance of benefits provided by AC. The working region limited in high water vapor relative pressure (P/P0) makes this material suitable only for removing water vapor at a highly humid region. In this study, ozone oxidation was conducted to introduce more oxygen-based functional groups on AC to attract more water molecules. Based on surface characterization results, ozone oxidation increases oxygen functional groups such as carboxylic on AC but decreases their pores. The more AC exposed to ozone, the more different properties could be observed. The increment of functional groups enhances the water vapor adsorption uptake at P/P0 ≤ 0.6, shifting the water sorption into lower P/P0.
Nanotailored microporous silica represents one of the more recent artificially prepared advanced materials used in heat transformation and conservation field after silica gel and various zeolite and zeolite-like materials. In this work, we introduce experimental findings on the energy characteristics of water adsorption on nanotailored microporous silica with 1.5 % aluminium doping in the structure. The downscaled system in this work simulates actual working conditions in a controlled environment for both heating and cooling mode. The key properties of this material lie in the regeneration temperatures 60 to 80 ℃ and COP, which reaches values around 0.6 in case of cooling and 0.7 in case of heating. In absolute values at ΔT = 15 ℃, the system reaches storing capacities of about 90 Wh and 126 Wh per adsorbent kilogram in terms of cooling and heating potential energy, respectively. An important factor of kinetic influence on system performance is discussed on a basis of constant time experiment and time-dependent energy flow breakthrough analysis. Constraining factors are found to be in parallel through the driving force of the pressure swing as well as the heat transfer through the body of the adsorption bed.
We analyzed lipid compounds and water soluble compounds of frozen farmed scallop and bottom-cultured Japanese scallop in Mutsu Bay Aomori Japan. As a result, lipids content was higher in bottom-cultured Japanese scallop compared with farmed scallop. On the other hands, there were no difference of free amino acids in each other. Further, a comprehensive analysis was also performed by metabolome analysis using a capillary electrophoresis-time-of-flight mass spectrometer (CE-TOF/MS). 138 ionic watersoluble compounds were detected. However, no significant difference in characteristics was observed. These results suggest that there is no difference in water soluble compounds related to quality of sea food products between frozen farmed and bottom-cultured Japanese scallop.
In this study, we aimed to investigate the effect of blanching treatment on the aroma of frozen green soybeans (edamame). Frozen samples were vacuum-packed and blanched under conditions that yielded the same texture, and sensory evaluation and aroma analysis were conducted by gas chromatography-mass spectrometry-olfactometry (GC-MS/O). The results of sensory evaluation revealed no significant difference in the retronasal aroma while eating; however, the aroma of the frozen-thawed pods with unblanching immediately before eating was significantly better. Furthermore, GC-MS/O analysis detected a more green-like aroma in unblanched edamame, substantiating that blanching treatment undesirably affects the aroma of frozen edamame.
In this study, we demonstrated the superiority of a heat pump system in heating an electric vehicle over an electric heater supported with other energy-saving measures; an EV heated with a heat pump system consumed less power and enabled better mileage than one heated with an electric heater. We developed a heat pump system which had enough heating efficiency for this experiment, installed it in an EV and measured the heating capacity and the energy consumption. As for an electric heater, we calculated its power consumption based on the measured figures of the EV with the heat pump system, setting the conditions of no ventilation and low temperature respectively as energy-saving measures. We compared the following four figures: the power consumption of heating with an electric heater, heating with an electric heater plus no ventilation, heating with an electric heater plus low temperature, and heating with a heat pump system. The comparison showed that a heat pump system consumes the least energy.
We aimed to investigate the de-oiling phenomenon of yellowtail on freezing using liquid nitrogen (LN2). The yellowtail samples were frozen at -30 °C (stationary freezing, SF) or soaked in LN2 to observe the de-oiling phenomenon. The thawed samples were left on a paper plate at 25 °C for 10 h. As a result, it was observed that the LN2 frozen sample was de-oiled more than the sample of SF. The raw yellowtail was frozen in a stocker at -30 ℃and soaked in LN2. The water and oil loss were obtained on thawing under running water the frozen yellowtail and stored at 10 ℃ or 25 ℃ for 18 h. The drip loss immediately after thawing was 0.4% lower in the sample with LN2 freezing. On the other hand, the drip loss of the LN2 frozen sample was higher than the frozen sample in SF after storage at 10 °C and 25 °C. After storage at 25 °C, the water loss was 7.6%, the oil loss was 5.5% in the LN2 frozen samples, which was significantly higher. From the results, we found that the amount of drip loss, especially the outflow of lipids, increases during storage after thawing.
We investigated the odor changes in frozen horse mackerel after thawing using an electronic nose. The samples were frozen rapidly and then thawed either at 10 ℃ or 25 ℃. In samples thawed at 25 ℃, higher levels of hydrocarbon, ester, and aromatic compound odor were detected. From the results of this study, it is possible to quantify the changes in odor intensity and quality due to thawing temperature by odor contribution and similarity. This study demonstrates the usefulness of an electronic nose to evaluate the odor changes in the fish meat after thawing.
For conventional air conditioning systems, the efficiency degradation caused by sub cooling dehumidification in summer and air drying due to no humidification function in winter are two important issues in terms of energy efficiency and thermal comfort. Desiccant is considered to be one of options to humidity control with high efficiency instead of sub cooling dehumidification method adopted in conventional air conditioning systems. In this study, experiments were conducted to measure the dehumidification and humidification performance of a desiccant module consisting of a desiccant-coated heat exchanger and a novel slide type air flow switching device. Experimental results show that the desiccant module under the size of 500 (Height) x 700 (Width) x 1100 (Length) mm can satisfy 90% of the dehumidification and humidification demand (1050 g·hour-1 for summer and 750 g·hour-1 for winter) of a detached house at the floor space of 90m2, ceiling height of 2.4m, ventilation frequency of 0.7 times per hour.