The operating parameters considered in this study include evaporating and condensing temperature, degree of subcooling and degree of superheating. in R744-R717 cascade refrigeration system and R744 two-stage compression refrigeration system with the range of low temperature -50℃∼-30℃. The coefficient of performance(COP) of R744-R717 cascade refrigeration system is about 16∼20% greater than that of R744 two-stage compression refrigeration system in the range of evaporation temperature of -50℃∼-30℃. R744 two-stage compression refrigeration system is unstable because its coefficient of performance changes significantly depending on the evaporating temperature and total compression work, and compression efficiency decreases. In this case, not efficient for long-term use. Whereas R744-R717 R744-R717 is a cascade refrigeration system using eco-friendly refrigerants. And this system is a high-efficiency refrigeration system that performs well even under various operating conditions. This is why it can be configured by selecting a refrigerant suitable for the high temperature side and the low temperature side.

고성능 분리막 제조기술과 더불어 새로운 분리막 다단공정 설계를 통해 용매사용량 감소 및 선택도 향상이 가능 하다. 본 연구에서는 내용매성 셀룰로스 나노분리막을 제조하여 용매에 따른 용질의 선택도 차이를 비교하였다. 제막한 셀룰 로스 막을 기반으로 비극성 용매의 선택도 평가를 진행하였으며, 비극성 용매에서 용질에 대한 음배제율이 관측되었다. 특히, 분자량이 클수록 음배제율이 높아지는 역선택도의 거동을 확인하였다. 이를 기반으로 설계한 공정에서는 기존 분획 공정 대 비 3배 이상의 용매저감이 가능한 것을 확인할 수 있었다.

In this paper, the performance characteristics of a cryogenic refrigeration system used in fields such as HMR(Home Meal Replacement) that require ultra-low temperatures of -50℃ using natural refrigerants according to the recent enforcement of the Atmosphere Environment Conservation Act were investigated. For this purpose, a 2-stage compression refrigeration system using R744(CO2) and a cascade refrigeration system using R747/R404A and R747/R717(NH3) were applied. The COP(coefficients of performance) of each refrigeration system were compared according to changes in evaporation and condensation temperature, subcooled and superheated degree. Although the coefficient of performance of the 2-stage compression refrigeration system using R744 was superior to that of the cascade refrigeration system, 2-stage refrigeration system was considered that various problems should be solved in practical terms. In addition, the COP of R744/R717 for various operating conditions showed similar results to R744/R404A, so the possibility of alternativeness could be confirmed in the cascade refrigeration system.

This Study is carried out to stabilize the system according to the change of superheat and subcooling in binary refrigeration system by applying cascade system. When the system on 1 st stage was started and the system on the other side was operated, a temperature reversal phenomenon occurred in which the temperature of the 1 st cascade outlet was temporarily lowered. This means that the condensate heat exchange on the 2 nd is not good, which can cause the compressor to overheated. In order to maintain stable system operation, the opening degree of the expansion valve is controlled to increase the refrigerant circulation amount, thereby facilitating the condensation heat exchange on the 2 nd stage system. We have found that the most suitable refrigerant circulation amount is found by stabilizing the operation of the system while lowerning the super low temperature from -65℃ to -70℃ and increasing again to -60℃.

This paper uses the informational cascades perspectives to investigate how popularity of online service deals influences consumers’ reactions when (in)congruently presented with star rating evaluations. Previous research suggested that deal popularity and star rating are two common information cues representing past consumers’ online behavior that signal about online service quality potentially influencing prospective online consumers’ judgments and decision making (Flanagin et al. 2014; Kao et al. 2016). Hence this research aims to examine the conditions under which online deal popularity and star rating can effectively influence service quality evaluation and purchase intention. Using scenario-based experiments, we show how different combinations of information cues impact on the manner in which online deal popularity is used by consumers to shape service quality expectation and purchase intention. Findings indicate that congruency effect is highly influential when high deal popularity is paired with high star rating. Specifically, an informational cascade effect is activated by high deal popularity which overrides quality cue of low star rating. Accordingly, consumers’ service quality expectation and purchase intention are increased even when a low star rating is presented simultaneously with low star rating. Findings are useful to marketing strategists and e-retailers as they devise their online strategies, promotional campaigns and website design.

The carbon capture and storage (CCS) technology from industrial flue-gas has been an important environmental issue in these days. However, membrane process has a number of breakthrough-point to commercialization in scale-up. In this work, process optimization for high purity and high CO2 recovery with lower the capture cost has been investigated. Lab-made membrane pilot process using real flue gas has been also set up to derive industrial factor.

콘덴싱 효과가 적용된 소형의 가스 온수기와 온수 보일러는 중대형 보일러보다 동일 열량에서 규격이 작고 운전효율이 높다. 이러한 소형 열원을 병렬로 연결하면 최적의 설계 열용량을 구현할수 있고 설치 공간이 절감되며 운전효율이 높다. 이를 캐스케이드 시스템이라 하며 건물의 규모와 용도를 고려한 열원 시스템 선택의 폭을 넓히고 소비자의 경제성향상과 더불어 정부의 에너지 정책에 부응하기 위해 대수 제어기등 주변 장비를 개발하여 보급하게 되었다.

Abstract The cascade refrigeration cycle system has been used mainly to obtain the ultra-low temperature. In this study, the effects of internal and outdoor temperatures at chamber on the heat capacity of fin-tube heat exchangers were examined. In addition, refrigerant line patterns as well as refrigerant type for cascade cycle were optimized. The results in this study show that the refrigerant line patterns have greater effect on the sensible capacity than the total capacity. Also, the condenser heat release rate for R717-R744 cycle varies the ratio of 46 % with outdoor temperature by comparing with that of 24% for R134a-R410a cycle.

In this paper, cycle performance characteristics of a cascade refrigeration system with internal heat exchanger for cascade heat exchanger using alternative freon refrigerants is presented to offer the basic design data for the operating parameters of the system. This system considered in this study is consisted of a high temperature cycle using Freon refrigerant R23, R508B and low temperature cycle using Freon refrigerants R22, R507A. The operating parameters of this system include subcooling and superheating degree, evaporating temperature, compressor efficiency, and so on. The main results were summarized as follows : The COP of cascade refrigeration system using R23/R507A is the highest results in this study. The COP of cascade refrigeration system with internal heat exchanger only in high temperature cycle is the highest value among three cycle, such as only low temperature cycle, only high temperature cycle and all the cycle

A three-staged cascade virtual impactor was designed, fabricated, and used as aerosol classifier in a dust sensor module. The dust sensor module consisted of the impactor, three commercial dust sensors, and four pumps. For the design of the impactor, three cut-off diameters of 2.5 ㎛, 2.0 ㎛, and 1.5 ㎛ were selected. Then three nozzle widths were determined from computational fluid dynamics (CFD) simulation with the three designed cut-off diameters. </br>Laboratory generated PM2.5 aerosols classified into each of three sizes, via the fabricated impactor, entered a dust sensor from which voltage signals were detected due to particle scattering by a laser diode in the sensor. The voltage signal data from the three sensors were converted to number concentrations of the dust particles utilizing correlation equations obtained from separately performed experiments. The number concentrations were in agreement with those obtained by aerodynamic particle sizer (APS).

To analyze and verify the effect of replacing thermal storage heater by a cascade cycle heat pump using midnight electricity was installed and tested at a customer's house in Wonju, Korea. The electric night storage heater is consist of 30kW electric heater and 2,700 liters of thermal storage water tank to supply hot water for warming house floor. The power for electric heater was cut off and hot water was only generated by cascade cycle heat pump. Current thermal storage water tank was not eliminated and electric heater wiring was modified. Some operation logic of the heat pump was also modified for proper operation. The required capacity of the heat pump and hot water temperature for given warming condition were estimated. The estimated capacity of heat pump was about 19kW and estimated hot water temperature for proper heating was at least 75℃.

In this paper, cycle performance analysis of cascade refrigeration system using alternative FREON refrigerants are presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooled and superheated degree, and evaporating and condensing temperature, temperature difference of cascade heat exchanger in cascade refrigeration system. The COP of cascade refrigeration system increases with the increasing subcooled degree, but there is no significant changes with the increasing superheated degree. The COP of cascade refrigeration system depends on evaporating and condensing temperatures of cascade heat exchanger. Therefore, subcooled degree, evaporating and condensing temperature of cascade heat exchanger using alternative FREON refrigerants have an effect on the COP of this system. In this paper, COP of cascade refrigeration system using R23 for low temperature system and R507A for high temperature system is higher 8 ~ 29 % than using R13 for low temperature system and R22 for high temperature system.

The cost to electricity is cheaper at night due to electric supply and demand policy in Korea. During daytime the loads are higher and extra generators are brought "on-line" to meet the demand. In the middle of night loads are lower and they need to throttle back the generators. So KEPCO (Korea Electric Power Corporation) offers "time of use" (TOU) rates to balance the grid load. The night storage heaters are generally on a separate circuit which is only switched on when the night rate is activated. Since 2000 the price of NG, kerosene and other petroleum based fuel for heating has been increased rapidly and overtook the price of electricity at last, so more and more people have chosen night storage heaters to save energy price. Currently about 900,000 customers are using electric night heaters and this causes shift of peak demand time to night in winter and increase of deficit spending. To solve this problem, replacing electric night heater by air-source heat pump has been proposed. An air-source heat pump can provide efficient heating and cooling for building, especially in a warm climate. When properly installed, an air-source heat pump can deliver one-and-a-half to three times more heat energy to a building than the electrical energy it consumes. This is possible because a heat pump moves heat rather than converting it from a fuel, like in combustion heating systems.

In this paper, cycle performance analysis of cascade refrigeration system using natural refrigerants R744 for low temperature cycle, and R290, R600, R600a, R717 for high temperature cycle are presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooled and superheated degree, and condensing and evaporating temperature, temperature difference of cascade heat exchanger in cascade refrigeration system. The COP of cascade refrigeration system increases with the increasing subcooled degree, but there is no significant changes with the increasing superheated degree. The COP of cascade refrigeration system depends on evaporating and condensing temperatures of cascade heat exchanger. The COP of cascade refrigeration system using natural refrigerants is similar to the COP using freon refrigerant (R23 / R22). Points to be considered are th security, the attached facilities for natural refrigerants than COP.