• 한국태양에너지학회 논문집
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• 제27권4호
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• pp.19-26
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• 2007

This paper concerns the study of absorption refrigeration and heat pump cycle to use sewage. Simulation analysis on the double-effect absorption refrigeration cycle with parallel and two-stage heat pump cycle has been performed. The working fluid is Lithium Bromide and water solution. The absorption refrigeration cycle use sewage as a cooling water for the absorber and condenser, and absorption refrigeration cycle does that as a chilled water for the evaporator of the first stage cycle. And the two-stage cycle consists of coupling double-effect with parallel and single effect cycle so that the first stage absorber and condenser produces heating water to evaporate refrigerant in the evaporator of the second stage. The effects of operating variables such as a absorber temperature on the coefficient of performance have been studied for absorption refrigeration and heat pump cycle.

• 대한기계학회논문집B
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• 제32권6호
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• pp.454-462
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• 2008

Since operating conditions are significantly different for heating and cooling mode operations in a $CO_2$ heat pump system, it is difficult to optimize the performance of the $CO_2$ cycle. In addition, the performance of a $CO_2$ heat pump is very sensitive to outdoor temperature and gascooler pressure. In this study, the cooling and heating performances of a variable speed $CO_2$ heat pump with a twin-rotary compressor were measured and analyzed with the variations of EEV opening and compressor frequency. As a result, the cooling and heating COPs were 2.3 and 3.0, respectively, when the EEV opening was 22%. When the optimal EEV openings for heating and cooling were 28% and 16%, the cooling and heating COPs increased by 3.3% and 3.9%, respectively, over the COPs at the EEV opening of 22%. Beside, the heating performance was more sensitive to EEV opening than the cooling performance. As the compressor speed decreased by 5 Hz, the cooling COP increased by 2%, while the heating COP decreased by 8%.

• 산업경영시스템학회지
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• 제38권1호
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• pp.143-151
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• 2015

In this paper, we investigate how the power consumption of a heat pump dryer depends on various factors in the drying process by analyzing variables that affect the power consumption. Since there are in general many variables that affect the power consumption, for a feasible analysis, we utilize the principal component analysis to reduce the number of variables (or dimensionality) to two or three. We find that the first component is correlated positively to the entrance temperature of various devices such as compressor, expander, evaporator, and the second, negatively to condenser. We then model the power consumption as a multiple regression with two and/or three transformed variables of the selected principal components. We find that fitted value from the multiple regression explains 80~90% of the observed value of the power consumption. This results can be applied to a more elaborate control of the power consumption in the heat pump dryer.

• 동력기계공학회지
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• 제13권6호
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• pp.63-69
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• 2009

The experiment was performed to check operating characteristics of fouling auto removal apparatus for multi pass type heat exchanger using ejector. The results showed as following. The ejector suction flow rate increased with the head of operating pump of ejector. Proper suction flow rate showed $7.2{\sim}10.2m^3/h$ for ball collection in case of pump head 35~50m. The head of ejector outlet pipe is below 4.1m in case of 40m, the head of operating pump of ejector to confirm ejector suction flow rate 8.4m3/h. Lattice space of ball separator is allowed 6~10.3mm in ranges of ball diameter are 15~25mm and when mass flow of cooling water is 3.0m/sec. Average of passing time of balls is 1.2~2.8sec depend on the velocity of flow and the size of balls.

• Journal of Advanced Marine Engineering and Technology
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• 제23권4호
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• pp.447-452
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• 1999

This paper describes the cycle performance of heat-pump system using R-22 and R-290. Experiments were performed in the smooth tube with inside diameter of 10.07mm and outside diameter of 12.07 mm and grooved inner tube having 75 fins with a height of 0.25mm Condensing temperatures were held constantly between 318K and 328 K while evaporating temperatures were varied from 257 K to 288 K mass velocities from 51 to $280 kg/m^2s$. From the experiments it was known that the evaporating temperature and condensing temperature had more affected by the compressor shaft power than the tube geometries. Cooling capacity of the R-22 and R-290 had similar values in the smooth and grooved inner tubes. The coefficient of performance(COP) was calculated using the compressor shaft power volumetric refrigeration capacity compression ratio and cooling capacity. The COP of the R-290 had slightly higher values than that of R-22 The major parameters affecting the heat pump cycle performance wee the refrigerant proper-ties and operating conditions rather than the geometric shapes of the heat exchanger

• 설비공학논문집
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• 제28권7호
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• pp.293-298
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• 2016

A three-dimensional (3D) numerical model of the vertical ground-coupled heat exchanger is useful for analyzing the modern ground source heat pump system. Furthermore, a detailed description of the inner side of the exchanger allows to account for the effects of the thermal capacity. Thus, both methods are included in the proposed numerical model. For the ground portion, a FDM (Finite Difference Method) scheme has been applied using the Cartesian coordinate system. Cylindrical grids are applied for the borehole portion, and the U-tube configuration is adjusted at the grid, keeping the area and distance unchanged. Two sub-models are numerically coupled at each time-step using an iterative method for convergence. The model is validated by a reference 3D model under a continuous heat injection case. The results from a periodic heat injection input show that the proposed thermal capacity model reacts more slowly to the changes, resulting in lower borehole wall temperatures, when compared with a thermal resistance model. This implies that thermal capacity effects may be important factors for system controls.

• Journal of Advanced Marine Engineering and Technology
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• 제40권3호
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• pp.152-156
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• 2016

폐수 열원 히트펌프 시스템은 목욕탕, 공장 또는 하천수 등을 히트펌프의 열원으로 사용한다. 증발기는 폐수로부터의 오염을 완화시키기 위하여 휜이 없는 나관식(bare tube) 열교환기가 주로 사용되고 있다. 대부분의 열 저항은 관외를 흐르는 폐수측에 생성되는 파울링에 의한 것이며, 히트펌프의 성능을 급격하게 감소시킨다. 따라서 본 연구에서는 나관식 열교환기 하부에서 버블 유동층을 형성시키고 세정 볼을 사용하여 관 외측의 파울링을 저감시키는 장치를 개발하였다. 실험 조건으로, 냉수온도 $20^{\circ}C$, 폐수 온도 $40^{\circ}C$, 관 내측 유량 100L/h, 수조 내 물의 양 50L, 열교환기 면적 $0.161m^2$ 이다. 실험결과 세정 볼 없이 버블유동층만 형성한 경우에는 버블유동층이 없는 경우에 비해 파울링에 의해 생성된 열 저항이 약 56% 감소되었으며, 세정 볼의 개수 밀도가 8,000(Number of $ball/m^3$) 일 때, 파울링에 의해 생성된 열 저항은 버블유동층 및 세정 볼이 없을 때와 비교하여 약 86% 감소되었다.

• 한국지열·수열에너지학회논문집
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• 제8권1호
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• pp.13-20
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• 2012

This is an experimental study on the performance characteristics of effective heat pump in the cooling mode using a single-stage compression $CO_2$ cycle with an IHX(internal heat exchanger). The performance of a single-stage compression with IHX was investigated according to charge amount and operating condition. Moreover, the performance characteristic of cooling operating was analyzed with the length of IHX. As a result, the optimum refrigerant charge amount was 2.2 kg. The optimal system COP for compressor frequency of 30, 40, 50, and 60 Hz was 3.493, 3.228, 2.978, and 2.659, respectively. Since the system with IHX can maintain large cooling capacity regardless of operating condition, the system performance doesn't reduce considerably under unfavorable condition. When the compressor frequency was 40 Hz, the COP for a system with IHX length of 3 m and 5 m was 3.361 and 3.51, respectively. By using the IHX into a $CO_2$ cooling system, the performance and reliability improves simultaneously.

• 설비공학논문집
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• 제25권1호
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• pp.28-36
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• 2013

The aim of this study is to evaluate the performance of the GHP system with 45 cast-in-place energy piles(CEP) for a commercial building. In order to demonstrate the feasibility of a sustainable performance of the system, transient simulations were conducted over 1-year and 20-year periods, respectively. The 1-year simulation results showed that the maximum and minimum temperatures of brine returning from the CEPs were $23.91^{\circ}C$ and $6.66^{\circ}C$, which were in a range of design target temperatures. In addition, after 20 years' operation, these returning temperatures decreased to $21.24^{\circ}C$ and $3.68^{\circ}C$, and finally reached to stable state. Annual average extraction heat of cast-in-place energy piles was 94.3 MWh and injection heat was 65.7 MWh from the 20 years of simulation results. Finally, it is expected this GHP system can operate with average heating SPF of more than 3.45 for long-term.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.639-644
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• 2006

The outlet temperature of gas cooler has a great effect on the efficiency of carbon dioxide heat pump system. In order to obtain a small approach temperature difference at gas cooler, near-counter flow type heat exchanger has been proposed, and larger heat transfer area is demanded. The optimum design of gas cooler involving the analysis of trade-offs between heat transfer performance and cost is desirable. In this study, the effects of geometric parameters, such as the circuit arrangement, tube diameter, transverse tube spacing, longitudinal tube spacing and the number of tube rows and fin spacing on the performance of heat transfer were investigated using the developed model. This study suggested various simulation results for optimum designs of gas cooler.