통신 함체 냉각용 플라스틱 재질의 열교환 소자

김내현(Nae-Hyun Kim) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.1

함체 내의 발열은 이동통신기기의 회선 처리 능력이 증가함에 따라 계속 증가하고 있다. 이 열을 적절히 외부로 방출해 주지 않으면 중계기 내의 온도가 상승하여 전자장치 오작동의 원인이 된다. 본 연구에서는 통신 함체 냉각 모듈용 알루미늄 및 플라스틱 소자의 성능에 대해 실험을 수행하고 이론 해석 결과와도 비교하였다. 알루미늄 소자는 핏치 4.5 mm의 대향류 평행 채널로 구성되고 플라스틱 소자는 핏치 2.0 mm의 직교류 및 직교 대향류 삼각 채널로 구성되었다. 한편 직교류 소자의 크기는 알루미늄 소자와 동일하고 직교대향류 소자는 알루미늄 소자보다 33% 크다. 실험 결과 플라스틱 직교대향류 소자의 전열량이 가장 크고 알루미늄 대향류 소자의 전열량이 가장 작게 나타났다. 또한 알루미늄 대향류 소자를 base 소자로 할 때 플라스틱 직교대향류 소자의 온도교환효율은 base 소자보다 평균 56% 크고 플라스틱 직교류 소자의 값보다는 평균 29% 크게 나타났다. 한편 플라스틱 직교대향류 소자와 base 소자의 압력손실은 유사하게 나타났다. 열교환 효율은 플라스틱 직교대향류 소자에서 가장 크고 플라스틱 직교류 소자에서 가장 작게 나타났다. 또한 이론 모델은 소자의 성능을 다소 과대 또는 과소 예측하였다. The heat generation rate in a telecommunications cabinet keeps increasing due to the increased usage of mobile devices. Insufficient removal of the heat increases the cabinet temperature, which results in the malfunction of the electronic devices. In this study, tests were conducted on aluminum and plastic heat exchangers for cooling a telecommunications cabinet, and the results were compared with theoretical predictions. The aluminum heat exchanger comprised counter flow parallel channels with 4.5-mm pitch, and the plastic heat exchangers comprised cross or cross-counter flow triangular channels with 2.0-mm pitch. The volume of the cross flow heat exchanger was the same as that of the aluminum heat exchanger, and the volume of the cross-counter heat exchanger was 33% larger than that of the aluminum heat exchanger. The results show that the heat transfer rate is the highest for the cross-counter heat exchanger and lowest for the aluminum one. The temperature efficiency of the cross-counter heat exchanger was 56% higher than that of the aluminum one and 20% higher than that of the cross flow heat exchanger. The pressure drop of the cross-counter heat exchanger was approximately the same as that of the aluminum one. The heat exchange efficiency was the highest for the cross-counter heat exchanger and lowest for the cross flow heat exchanger. The theoretical analysis somewhat overestimated or underestimated the data.

스택 폐열을 이용한 연료전지 자동차용 열펌프 시스템의 성능 특성에 관한 연구

전병용(Byungyong Jeon),고원빈(Wonbin Ko),박윤철(Youn Cheol Park) 대한설비공학회 2016 설비공학 논문집 Vol.28 No.8

This study was conducted to develop a heating system for a fuel cell-driven electric vehicle. The system consists of a compressor, an expansion device and three heat exchangers. A conventional air source heat exchanger is used as primary heat exchanger of the system, and an additional water source heat exchanger is used as a pre-heater to supply heat to the upstream air of the primary heat exchanger. On the other hand, the third heat exchanger consists of a water-to-refrigerant heat exchanger. The heat source of the pre-heater and the water-refrigerant heat exchanger is the waste heat from the fuel cell’s stack. In the experiment, the indoor and the outdoor air temperature were fixed, and the compressor speed, EEV opening and waste heat temperature were varied. The results indicate that the COPh of the proposed system is 3.01 when the system is operating at a 1,200 rpm compressor speed, 50% EEV opening, and 50℃ waste heat source temperature in air pre-heater operation. However, when the system uses a water-refrigerant heat exchanger, the COPh increases to up to 9.42 at the same compressor speed and waste heat source temperature with 75% EEV openings.

A study on performance improvement of corrugated type total heat exchanger considering the structure of flow passage on surface

곽경민,배철호 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.6

Three types of flow passage structure of a total heat exchanger (perforated type, slit type, and embossed and perforated type ) are studied to enhance the heat exchange performance of a heat recovery ventilation system (total heat exchanger). The perforated type has four punched rows of 6mm holes in the flow passage channel, and the slit type has six processed rows of 40mm length. The embossed and perforated type has holes of about 1mm diameter and protrusions of about 0.2mm height on all surfaces. The heat exchange efficiency of the modified total heat exchanger was compared to that of a general total heat exchanger with a smooth surface. The Korean Standard (KS) heat recovery ventilator test condition was applied for tests. In the case of cooling operation based on a typical Reynolds number of 140 (typical air flow rate of 100 m3/hr), the perforated type, slit type, and embossed and perforated type showed temperature efficiency improvement of 1.2%, 2.5%, and 5.0%; latent efficiency improvement of 18.0%, 32.3%, and 24.5%; and enthalpy efficiency improvement of 7.9%, 11.5%, and 11.2%, respectively. The corresponding improvements of heating operation were 3.0%, 3.4%, and 4.0%; 5.0%, 6.6%, and 18.7%; 3.2%, 4.3%, and 7.7%, respectively. On the other hand, the air pressure drop throughout the modified flow passage of the total heat exchanger increased by up to 1.7% at the typical Reynolds number of 140, from the air pressure drop of the regular total heat exchanger.

통신 함체 냉각용 알루미늄과 플라스틱 열교환 소자의 성능 비교

김내현(Nae-Hyun Kim) 대한설비공학회 2017 설비공학 논문집 Vol.29 No.6

Heat generation rate in a telecommunication cabinet increases due to the continued usage of mobile devices. Insufficient removal of heat intensifies the cabinet temperature, resulting in the malfunction of electronic devices. In this study, we assessed both aluminum and plastic heat exchangers used for cooling of the telecommunication cabinet, and compared the results against theoretical predictions. The aluminum heat exchanger was composed of counter flow parallel channels of 4.5 mm pitch, and the plastic heat exchangers were composed of cross flow triangular channels of 2.0 mm pitch. Samples were made by installing two plastic heat exchangers in both series and parallel. Results showed that the heat transfer rate was highest for the series cross flow heat exchanger, and was least for the aluminum heat exchanger. The temperature efficiency of the series cross flow heat exchanger was 59% greater than that of the aluminum heat exchanger, and was 4.3% greater than that of the parallel cross flow heat exchanger. In contrast, the pressure drop of the parallel cross flow heat exchanger was significantly lower than other samples. The heat exchange efficiency was also the largest for the parallel cross flow heat exchanger. The theoretical analysis predicted the temperature efficiency to be within 3.3%, and the pressure drop within 6.1%.

Heat Transfer Enhancement for Fin-Tube Heat Exchanger Using Vortex Generators

Yoo, Seong-Yeon,Park, Dong-Seong,Chung, Min-Ho The Korean Society of Mechanical Engineers 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.1

Vortex generators are fabricated on the fin surface of a fin-tube heat exchanger to augment the convective heat transfer. In addition to horseshoe vortices formed naturally around the tube of the fin-tube heat exchanger, longitudinal vortices are artificially created on the fin surface by vortex generators. The purpose of this study is to investigate the local heat transfer phenomena in the fin-tube heat exchangers with and without vortex generators, and to evaluate the effect of vortices on the heat transfer enhancement. Naphthalene sublimation technique is employed to measure local mass transfer coefficients, then analogy equation between heat and mass transfer is used to calculate heat transfer coefficients. Experiments are performed for the model of fin -circular tube heat exchangers with and without vortex generators, and of fin-flat tube heat exchangers with and without vortex generators. Average heat transfer coefficients of finn-flat tube heat exchanger without vertex generator are much lower than those of fin-circular tube heat exchanger. On the other hand, fin-flat tube heat exchanger with vortex generators has much higher heat transfer value than conventional fin-circular tube heat exchanger At the same time, pressure losses for four types of heat exchanger is measured and compared.

플라스틱 판형 열교환기의 성능에 영향을 미치는 인자에 관한 연구

유성연,정민호,이용문 대한설비공학회 2005 설비공학 논문집 Vol.17 No.9

Plastic plate heat exchangers have many advantages over the conventional heat exchangers such as aluminum plate heat exchangers, rotary wheel heat exchangers and heat pipe heat exchangers which have been used for ventilation heat recovery in the air-conditioning systems. In the present study, pressure drop and heat transfer characteristics of plastic plate heat exchangers are investigated for various design parameters and operating conditions which affect the performance of the plastic plate heat exchangers. In flat plate type heat exchanger, material thickness and channel height of heat exchanger are considered, and corrugate size and heat transfer area are considered in case of corrugate type heat exchanger. Pressure drop and effectiveness of the corrugate type heat exchanger increase as the corrugate size decreases.

Hardy-Cross법을 이용한 CO2 냉동기용 내부열교환기의 열전달 특성 연구

강희동,김욱중,서태범 대한설비공학회 2005 설비공학 논문집 Vol.17 No.1

The heat transfer characteristics of an internal heat exchanger for CO2 refrigeration cycle are numerically investigated. The numerical model is verified using the published experimental results for the concentric tube type internal heat exchanger. The Hardy-Cross Method gives very good agreement between the calculation and experimental results on the heat transfer rates and exit temperatures. Also, appropriate combination of heat transfer correlations is found. The operating parameters of the heat exchanger are calculated at transcritical region of CO2. The heat transfer rate of the counter flow type heat exchanger shows the 32% greater than that of the parallel flow type heat exchanger. The increase of heat exchanger length enhances the heat transfer rate. The thermodynamic characteristics and heat transfer coefficient of CO2 in the internal heat exchanger are estimated.

플라스틱 판형 열교환기의 성능에 관한 실험적 연구

유성연,정민호,김기형,이제묘 대한설비공학회 2005 설비공학 논문집 Vol.17 No.2

Aluminum plate heat exchanger, rotary wheel heat exchanger, and heat pipe heat exchanger have been used for ventilation heat recovery in the air-conditioning system. The purpose of this research is to develop high efficiency plastic plate heat exchanger which can substitute aluminum plate heat exchanger. Because thermal conductivity of plastic is quite small compared to that of aluminum, various heat transfer enhancement techniques are applied in the design of plastic plates. Five types of heat exchanger model are designed and manufactured, which are plate type, plate-fin type, turbulent promoter type, corrugate type, and dimple type. Thermal performance and pressure loss of each heat exchangers are measured in various operating conditions, and compared each other. Test results show that heat transfer performance of corrugate type, turbulent promoter type, and dimple type are increases about 43 %, 14 %, and 33 % at the equivalent fan power compared to those of plate type, respectively. On the other hand, the heat transfer performance of plate-fin type decreases 9 % because fins can not play their own role.

Numerical study on heat transfer characteristics in branch tube type ground heat exchanger

Choi, Hoon Ki,Yoo, Geun Jong,Pak, Jae Hun,Lee, Chang Hee Elsevier 2018 Renewable energy Vol.115 No.-

<P><B>Abstract</B></P> <P>A ground heat exchanger is an essential component of ground source heat pumps, which saves cooling and heating energy effectively. In this study, a branch tube type heat exchanger is suggested for a ground heat exchanger instead of commonly using the U-tube type for increasing heat transfer efficiency. The branch tube type heat exchanger has conjugate heat transfer including convective heat transfer between the walls of primary- and branch-tubes and internally circulating fluid, and conduction in the tube walls and grout. This conjugate heat transfer phenomenon is analyzed by steady 3-D numerical analysis using the finite volume method. In the analysis, temperature distribution, rate of heat transfer and pressure drop are compared for the branch tube type ground heat exchanger with 2, 4, 6, and 8 branch tubes together with a single U-tube type ground heat exchanger. Generally, the branch tube type shows better heat transfer performance compared to the U-tube type and the higher number of branch tubes give better heat transfer performance. Also, the branch tube type yields higher pressure drop than the U-tube type for the same mass flow rate of circulating fluid in the heat exchanger.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Branch tube type ground heat exchanger is proposed for enhanced heat transfer. </LI> <LI> Branch tube type ground heat exchanger has increased heat transfer area. </LI> <LI> The increased heat transfer rate is found in the out-flow region. </LI> <LI> Heat transfer rate is affected by number of branch tubes more than inlet velocity. </LI> </UL> </P>

Influence of hydrodynamic parameters in plate heat exchangers in ice slurry transport

Jiménez Pacheco Hugo Guillermo,Milon Guzmán Juan José,Miranda Ramos Lilia Mary,Delgado Sarmiento Pavel Kewin,Linares Flores Castro Antonio Erick,Leal Braga Sergio 대한설비공학회 2023 International Journal of Air-Conditioning and Refr Vol.31 No.1

Ice slurry is applied in different refrigeration and air conditioning systems, and among its main advantages is the ability to store latent heat and be pumpable as cold water. This fluid can be used for thermal storage instead of cold water or solid ice, since, at certain concentrations, it can be pumped through heat exchangers. For this technology to be widely used, the equipment must be designed considering the heat exchange characteristics. This study developed an experimental system to study the parameters that influence heat exchange, using ice slurry in a plate heat exchanger and water as a thermal load. Several situations with different flows and initial fractions of ice in ice slurry were analyzed. The input conditions of the thermal load were kept constant, the temperature, the pressure drop and the flow of the ice slurry in the heat exchanger were controlled, according to the Nusselt, Prandtl, and Reynolds coefficients. Results show that the global heat exchange coefficient increases with the increase of the initial ice fraction; the cooling capacity of the heat exchanger increases when ice slurry is used as a fluid. For flow rates greater than 0.16 kg/s and ice fractions above 11%, ice crystals are generated at the heat exchanger outlet, due to the ice slurry’s higher viscosity, at approximately 0.003 Pa at the outlet, since the pressure drop increases as the initial ice fraction increases. Results show ice slurry thermohydraulic behavior. Its use shows favorable characteristics in heat exchange. Ice slurry is applied in different refrigeration and air conditioning systems, and among its main advantages is the ability to store latent heat and be pumpable as cold water. This fluid can be used for thermal storage instead of cold water or solid ice, since, at certain concentrations, it can be pumped through heat exchangers. For this technology to be widely used, the equipment must be designed considering the heat exchange characteristics. This study developed an experimental system to study the parameters that influence heat exchange, using ice slurry in a plate heat exchanger and water as a thermal load. Several situations with different flows and initial fractions of ice in ice slurry were analyzed. The input conditions of the thermal load were kept constant, the temperature, the pressure drop and the flow of the ice slurry in the heat exchanger were controlled, according to the Nusselt , Prandtl , and Reynolds coefficients. Results show that the global heat exchange coefficient increases with the increase of the initial ice fraction; the cooling capacity of the heat exchanger increases when ice slurry is used as a fluid. For flow rates greater than 0.16 kg/s and ice fractions above 11%, ice crystals are generated at the heat exchanger outlet, due to the ice slurry’s higher viscosity, at approximately 0.003 Pa at the outlet, since the pressure drop increases as the initial ice fraction increases. Results show ice slurry thermohydraulic behavior. Its use shows favorable characteristics in heat exchange.